• Author / Uploaded
• Sylvia Ország

• Categories
• Albañilería
• Techo
• pared
• Diseño asistido por ordenador
• Hormigón

Citation preview

MODERN CONSTRUCTION HANDBOOK ANDREWWATIS SECOND EDITIO N

~ SpringerWienNewYork

3 INTRODUCTI ON 4 MATERIALS Introduction to Second Edition 4

6

Taxonomy of material systems 8

Changes from the First Edition

4

Structure and envelope

10

Structure of this book

5

Digital tectonics

12

Parametric design

16

WALLS

82 ROOFS

Trends in facade design

84

Generic wall types

90

Trends in roof design

200 202

Metal roofs Metal

( I) Metal standing seam

206

( I) Sheet metal

92

(2) Profiled metal sheet

2 10

96

(3) Composite panels

214

Tectonics in metal

20

(2) Profiled cladding

Steel

22

(3) Composite panels

100

(4) Rainscreens

218

Aluminium

26

(4) Rainscreens

104

(5) Metal louvres

222

Copper, zinc and lead

30

(5) Mesh screens

108

(6) Louvre screens

11 2

Tectonics in glass

32

Glass

34

Glass roofs ( I) Greenhouse glazing

Glass systems

11 6

and capped systems

( I) Stick systems

120

(2) Silicone-sealed glazing

226

Tectonics in concrete

38

(2) Unitised glazing

124

and roofiights

230

Concrete

40

(3) Clamped glazing

128

(3) Bolt fixed glazing

234

(4) Bolt fixed glazing

132

(4) Bonded glass roofiights 238

Tectonics in masonry

46

(5) Glass blocks and channels 136

Masonry

48

(6) Steel windows

140

Concrete

Concrete block

50

(7) Aluminium windows

144

( I) Concealed membranes 242

(8)Timber windows

148

(2) Exposed membranes

246

(3) Planted roof

250

Stone

52

Brick

54 Concrete

Tectonics in plastics

56

( I) Cast in situ

152

Timber roofs

Plastics and composites

58

(2) Storey height precast

156

( I) Flat roof: mastic asphalt

(3) Small precast panels

160

coverings

Tectonics in timber

62

Timber

64

Fabrics and membranes

68

254

(2) Flat roof: bitumen-based Masonry loadbearing walls

164

sheet membranes

258

(3) Pitched roof: tiles

262

Masonry cavity walls Internal walls

( I) Brick

168

Plastic roofs

(2) Stone and block

In

( I) GRP roofiights

(2) GRP panels and shells 270

( I) Fixed and demountable

ri

(2) Plaster systems

74

Masonry cladding

176

(3) Wallboard systems

76

Masonry rainscreens

180

266

Fabric systems ( I) ETFE cushions

Floors

78

Plastic

Ceilings

80

( I) Plastic-based cladding

184

(2) Single membrane:

(2) Plastic rainscreens

188

cone-shaped roof

274 278

(3) Single membrane: barrel-shaped roof

Timber ( I) Timber frame

192

(2) Cladding panels

196

282

CONTENTS

5 STRUCTURE

286 ENVIRONMENT 354 FUTURE Energy and the building

Material systems for structures

6

288

I

418 REFERENCES

A future for building

Glossary of term s

496

500 501 502

envelope

356

construction

420

Authorship

Double skin facades

358

( I) Folded glazing

422

Index

362

(2) Metal solar shading: louvres

Photo credits ( I) Braced frames Reinforced concrete

292

Environmental studies for

Steel

296

envelopes

Timber

300

and mesh

428

Analysis for design (2) Portal frames

304

(3) Loadbearing boxes

( I) Solar radiation

364

(3)Triangular panels for twisted

(2) Daylight

368

facades

(3) Embodied energy

372 (4)Twisted panels with fiat glass

Reinforced concrete

308

Brick

3 12

Passive design

Glass

316

( I) Natural ventilation

(4)Trusses

320

daylight controls

378

(3) Solar power

380

(6) Precast concrete panels

(4) Solar heating

382

for facades of complex

324

for twisted facades

440

(5) Moving shading panels

448

376

(2) Solar shading and

(5) Arches and shells

geometry (6) Space grids

328

434

452

Low energymaterial systems ( I) Straw bales and hemp

Floor structures

(2) Rammed earth, cob

( I) Cast in situ /

and adobe bricks

384

(7) Glazing systems wit h integral solar shading

458

386

cast-in-place concrete

332

(3) Green oak

(8) Stick glazingfor double

(2) Precast concrete

334

and bamboo

388

(3) Steel and steel mesh

336

(4) Green walls

390

(4) Timber

338

(5) Glass

342

facades

464

(9) Shingled glazingfor facades Active design

of complex geometry

470

( I) Liquid based heating/ Stairs

cooling systems

392

( I0)Variable concrete panels for solar shading

(2) Mechanical heating/

(2) Steel

346 348

cooling systems

394

(3) Timber

350

(3) Electrical lighting

400

( I I) Str uctural facades of

(4) Glass

352

(4) Fuel and water supply

402

complex geometry

( I) Concrete

( I) Sanitation and drainage

404

(2) Fire control

406

(3) Maintenance and (4) Lifts

482

( 12) Facade with integrated

Support services

cleaning

476

408 414

furn iture

488

494

lntroduction to Second Edition

that event ually formed the basis of this book

ferent approach to construction.This book

began /5 years agowhen I was an archit ect

A view expressed in this book is that there

suggests how buildings can be designed and

working at Jean Nouvel's office in Paris,

are no fixed methods of construction;tech-

constructed wit h a limited number of mate-

developing projects for construction,typically

niques are constantly evolving, both by multi-

rial systems, much t he way buildings were

designing from the basis of small models

plying the number of components in a given

assembled before the imperatives of mass

The Modern Construction Handbook

and sketch proposals.The early design wor k

assembly in order t o perform better as well

production with its attendant need for repe-

done by others in the office was always

as searching for new ways of re-integrating

tition of ident ical components.This approach

highly aspirational, often without an estab-

and simplifying these systems.

is based on a closer tecto nic relationship between walls, roofs and structure rather

lished method of construction available to realise the designs.The aim of moving designs forward towards their construction was to bring as much of the design int ention

How does this edition vary from the First Edition? The First Edit ion of the Modern Con-

than the contemporary approach of juxtaposing systems that are manufactured quite independently of one another.More than

as possible into the finished building.This was

struction Handbook concerned itself prima-

a question of individual design choice, con-

achieved by matchingthe essential design

rily wit h setting out forms of construction

struction is an essential aspect of our culture,

ideas to forms of construction which could

in typesgrouped by their primary material.

both as a process involving a large number

be developed by the designteam to achieve

Wh ile textboo ks on construction divided

of individuals who traditionally have shown

tho se aims; ideas which were spatial,techni-

building elements int o components and

craftsmanship in their work,whether on

cal and social.The built results varied in their

assemblies rather than 'systems' based on the

sit e or in a workshop, and as an expression

technical ambition, but were always root ed

possibilities of the material used,the Modern

of the values cherished by our society.The

in these early design aspirations, built either

Construction Handbook aimed to set out

idea of individual craftsmanship is a primar y

as a 'diagram' or 'fragment' of an idealised

construction systems with a balanced and

architectural motivation which is explored in

design that was embodied both in the early

even t reatment of the different methods of

this book,with examples of where this might

design models and in conversations wit hin

constructing structures, walls and roofs and

lead in emerging archit ecture that is cur-

the office.An alt ernative approach taken

internal construction, with no system given

rent ly being developed tod ay.

on some projects wast o take one or two

more priority or described with more infor-

The simp/est evolutions in material

aspects of the primary design aspirations and

mation than any other.Essays on prefabrica-

systems can lead to quite unexpected sys-

develop only t hose to a much greater extent

tion, possible future directions for construc-

tem 'behaviour' which does not necessarily

than other components of the 'tectonic',

t ion, and their relationship to environmental

follow expected rectilinear building forms.

or parts of the construction which were

design set the agenda for Modern Construc-

The greater geometric fiexibility of t hese

considered to combine spatial,t echnical and

tion Facades and Modern Construction

'evolved' versions of contemporary material

social issues.This design process is common

Roofs, books which followed in the series.

systems allows buildings to engage more

to archit ecture that engages fully with the

This Second Edition sets out these

flexibly with our existing built environment.

possibilities of building construction:the

element s of construction in a way which

W here modernist architecture t o date has

process of building as an expression of the

explains the main principles of each con-

admired simple geomet ric forms and their

process of bringing design aspiration to life,

struction system and point s to an expres-

relatively simple interplay, material systems

rather than buildings asself-contained 'jewels'

sion of architecture based on exploring the

can be used to interact with the existing

or as visually coherent expressions of ideas

possibilities of material systems beyond the

fabric and to work wit hin it rather than

with a modest architectural basis.

cladding of structural frames. Cladding can

encourage a complete replacement of entire

Exploring forms of construction wit h

be considered as beinga 'collage' or juxta-

parts of t he built environment.This approach

other archit ects in the office led me to build

position of independent material systems,

is one which was enjoyed before the mass

up a set of sket ches of 'mat erial systems',

all manufactured in isolation of one another,

industrialisation of building production in the

since none were readily available in books,

each system seeing it self as addressing a dif-

early 20th century. In many waysthis book

MCH

4

demonstrates that the pre-industrial world

from the Walls chapter are available in an

and 'services' rather than being regarded as

of significant buildings,that formed a part of

accompanying book in the Modern Con-

fittings. Consequently, the Fittings chapter

our urban environment, can find a continu-

struction Series,called Modern Construction

from the First Edition is omitted, with materi-

ation in the world of digital fabrication and

Facades, which includes more information on

al re-allocated to the other chapters. In place

mass customisation.

detail conditions within each material system.

of Fittings is Future, showing how some of

Another accompanying book called Scratch-

the material systems could be developed in

ing the Surface, also published by Springer

new buildings.These 'future' material systems

Wien New York, sets out progressive exam-

are based on research work undertaken at

'components' identified as structure, walls,

ples of material systems in buildings of a size

our practice, Newtecnic, for consideration on

roofs and environment, following the way

and type experienced by most architects in

live projects.

contemporary buildings are designed by

general practice of modest budget and mod-

specialist consultants and constructed by

est scale.

Structure of this book This Second Edition is based on building

Qualifying commemts

specialist contractors. While the First Edition

The Roofs chapter is re-structured and

The building techniques discussed and

focussed on only material systems produced

developed to follow Modern Construction

the built examples shown are designed to

by mass production techniques, the future

Roofs, another book in the series, basing the

last for an extended period with a relatively

chapter of the Second Edition adds in sys-

classifications more firmly on systems than

high performance. Consequently; buildings

tems that could be produced by mass cus-

on types of roof covering as set out in the

for exhibitions and for temporary use are

tomisation techniques. Considerably more

First Edition of the Modern Construction

excluded. In addressing an international

information is added than that of the First

Handbook. This provides a closer link with

readership, references to national legislation,

Edition, with the addition of more materi-

the Walls chapter.

building regulations, codes of practice and

als and more systems. Within each chapter,

The Structures chapter, like the Walls and

national standards have specifically not been

material systems are grouped in terms of

Roofs chapters, has a complete set of new

included. This book explains the principles

the primary material used to construct the

drawings that explains the systems more

of accepted building techniques currently in

system, following the same order of materi-

clearly The relationship of the other building

use. Building codes throughout the world

als listed in terms of their density; from heavy

components to structure informs much of

are undergoing increased harmonisation

to light, used in the first chapter on materials.

architectural design, so this has been the basis

because of increased economic and intel-

Within each material classification, systems

of new essays in the Materials chapter.

lectual globalisation. Building components and

progress from more traditional technology

'Services' are designed increasingly to

to more recent, largely following their his-

use both 'passive'and 'active' systems and are

often used in a single building. Since build-

torical development.

referred to under the more general term of

ing codes are written to protect users of

'environment', which forms its own chapter.

buildings by providing for their health and

physical properties of each of the main

This Second Edition has been strengthened

safety; good construction practice will always

building materials explored in the book.

with the addition of information on low

uphold these codes as well as assisttheir

The first chapter sets out the essential

assemblies from many different countries are

Materials are set out in order of their density;

energy construction systems from which

advancement. The components, assemblies

from heavy to light, ranging from metals to

complete building envelopes can be manu-

and details shown in this book describe many

glass, concrete, masonry; plastics and timber.

factured.

of the building techniques used by the build-

The second chapter on Walls expands

Remaining items in the First Edition such

ing industry today; but this book does not

information of the systems set out in the

as stairs, lifts, partitions, ceilings and doors

necessarily endorse or justify their use since

First Edition from two pages per topic to

were put into a final chapter called Fittings,

techniques in building are in a continual state

four pages, in common with most of the

which was not an entirely satisfactory solu-

of change and development.

topics covered in the book. More technical

tion.The interior aspects of buildings such as

information and more detailed drawings

stairs and lifts are essential parts of structure

MCH

5

MATERIALS A taxonomy of material systems Structure and envelope Parametric design Tectonics in metal Steel Stainless steel Aluminium Copper. zinc and lead Tectonics in glass Glass Tectonics in concrete Concrete Tectonics in masonry Masonry Concrete block Stone Brick Tectonics in plastics Plastics and composites Tectonics in timber Timber Fabrics and membranes Internal walls ( I) Fixed and demountable (2) Plaster systems (3) Wallboard systems Floors Ceilings

MCH

7

Materials 0 I A taxonomy of material systems

based on the structural frame;typically

quite different headings.Whi le the system

Modern Construction Handbook,which has

either steel or concrete,with the modest,

is useful in describing a building for use by a

been refined for this Second Edit ion, has

but growing, use of timber frames as a lower

contractor;particularly with regard t o nat ion-

undergone several stages of development,

embodied energy alternative.As examples

al standards, including those for performance

based on the idea of grouping construction

of loadbearing construction are rare,the

testing, specifications do not relat e the parts

The organisation of the mater ial in the

systems by the mat erial used rather than

use of categor ies of'loadbearing'and 'non-

in a way that can be easily used at the design

by their 'function', which is one of the most

loadbearing'was not appropriat e due to t he

stage to understand generic facade assem-

widely usedconstruction-based classifica-

imbalance of the categories. Wh at emerged

blies.The approach t aken in the classification

tion systems.The mat erials-based approach

was that construction systems for the major-

system in the Modern Construction Hand-

specific to this book allows the text t o draw

ity of building construction are independent,

book was to group items in a way known to

parallels between building 'systems'that are

wit h few systems relating t o one another.

building design teams: structure, walls, roofs,

based on the same primary mat erial, since

Much of the skill of contemporary detailing

and services.

the development and use of those systems

is in knowing how to bring those systems

is informed mainly by the physical proper-

together which are fabricated or manufac-

cally, been based on a varying relationship

ties specific to each material and the way

tured in isolation of one another.

between loadbearing structure, walls and

t he material is worked, manufactured or

The linking of building systems so that

The construction of buildings has, histor i-

roofs, and this forms t he basis of classifica-

formed for use as a building material. Known

they might be able to interface more easily

tion in this book.In some buildings, walls,

classification systems create a mix between

has long been an aspiration of manufactur-

roofs and structure are a single entity as in

manufacturer-led names for systems, such as

ers, but the current sit uation is one where

medieval cathedrals, with the exception of

'structural glazing', where the glass is often

few systems co-ordinate easily wit h one

their addit ional timber roofs, used to protect

not structural at all,and 'rainscreen cladding',

another.This suggested that the taxonomy of

the structural ceiling. In framed construction

which covers almost any decorative outer

building systems in the First Edition should

the walls and roofs can be continuous over a singlesupporti ng structure,while in many

layer that has open joints. Rather than basing

be based on a robust set of genuinely dif-

classification on that of existing categories,

ferent generic typesthat would have t o be

cases of 20th century construction,walls,

the approach was to start from scratch and

identified independently of current systems

roofs and structure are quite separat e,and

t est material-based categories against one

of classification, such as those described in

are then subdivided within each category

another. In the First Edition,this evolved into

designers' specificatio ns.The structure of

t o provide a 'collage' form of construction

categories of walls, roofs, structure, environ-

architecture-based specifications identifies

where systems are overlaid in the manner of

ment and fitti ngs.Another category of mate-

components and assemblies in inter-related

a visual collage.

rials preceded this, since an understanding of

sections, where each sub-item in the assem-

Most of the primary building materials

the physical nature of materials is essential in

bly is identified independently, such as'cur-

can be used t o make loadbearing structures,

construction-led architecture.

t ain walling', which itself comprises several

where they serve as both structure and

generic external wall types set out in this

enclosure. Other uses of mat erials for walls

construction is the wide range of construc-

book.Specifications then link items such as

and roofs are non-Ioadbearing cladding.

tion systems which are non-Ioadbearing.

'curtain walling' to their constituent materials

However;sometimeswhere different mat e-

Almost all cont emporary construction is

of glass, seals, paint finishes and so on under

rial systems are formed in the same material

An essential aspect of contemporary

MCH

8

in a building, there is still some structural

zone within the building which is an inhabit-

cific details can be created, which forms the

interdependency. Where quite different

able equivalent of the 'twin wall' or 'double

basis of an understanding of what is needed

material systems are mixed, such as in a con-

skin' facade.This has helped to inform both

to be accommodated in different geometries.

crete frame and enclosure, a different inter-

material systems,not all of which need to be

The chapter on 'future' systems adds a para-

dependency emerges, that of allowing each

sealed,as well as the environment chapter

metric component to some of the examples,

material to be expressed separately.

where passive cooling, heating and ventila-

thus highlighting the range of possibilities that

tion can be used to reduce overall energy

might exist for some of the examples shown.

The inclusion of fittings in the taxonomy

The materials chapter in this Second Edi-

of the First Edition proved difficult, with

consumption, as well as create a stronger link

smaller scale items of stairs, lifts, internal

between the built environment of the city

tion presents essays on how the tectonics

finishes and doors placed within the group.

and the building itself The materials for roads

of material systems was used historically and

The term 'internal fittings' was too restricting,

and public spaces do not form part of the

how digital tools are bringing fiexibility back

as some of these components could be used

scope of this book, of course.

into building construction, something which

externally.This was the least satisfying part of

Each generic system is described first in

was considered to be too expensive until the

the First Edition. In this Second Edition this

terms of the properties of the material, then

arrival of CAD/CAM (computer aided design

issue has been resolved by including stairs

how they are used as a material system, and

/ computer aided manufacturing), mentioned

in the structure chapter, doors in the walls

last how that material system 'behaves', or

as a development bringing change in the First

chapter, and internal finishes in the first sec-

can be made to 'behave', to form a building

Edition.This return to an almost pre-industrial

tion on materials. Lifts are now described in

by examining its detailing. Possible develop-

approach to design allows new buildings to

the environment chapter, since they are usu-

ments of some of these material systems are

develop a much closer empathy with existing

ally considered to be part of the mechanical

set out in the future chapter to show how

buildings, even if the technologies used are

systems, the layout of which is designed by

the principles can be extrapolated for use on

very different.The non-rectilinear nature of

a specialist consultant. As a result of this last

new projects.

some of the material systems allows them

decision it could be seen that the environ-

Generic systems are discussed in terms

to engage more robustly and elegantly with

ment section could include both systems

of how they are assembled, and how they

existing fabric, both pre-industrial and that of

that reduce energy consumption by the

work from a structural and/or enclosure

20th century Modernism in architecture.

use of low energy passive strategies, as well

point of view.These paragraphs on 'system

as high energy active strategies, such as

design' show how the generic example

mechanical ventilation, and lifts can be seen

works. The way the system is applied to dif-

as part of this strategy to make tall buildings

ferent geometries is explained in 'system

usable.

details'.The geometries show how the

In environmental terms, the use of sev-

system can be set out on different mathe-

eral layers of envelope and structure in a

matically-based surfaces, and how the system

single building can create a much richer set

can meet at corners and junctions.Two other

of internal spacesthan those provided by

books in the Modern Construction Series,

the single skin envelope.The outer wall can

titled Modern Construction Facades and

be made of a double skin,or even as a deep

Modern Construction Roofs, show how spe-

MCH

9

Materials 0 I Structure and envelope

Well s Cathedral ,Wells,UK

Natural History Museum, O xford, UK Architect Deane and Woodw ard

In terms of constru ction, Modern ist architec -

of the w idespread use of t he structural

N atural H istory Museum, O xford, U K A rchitect Deane and W oo dward

The use of a str uctural frame clad w it h

t ure can be considered t o be an approac h

frame in much of 20t h cent ur y Modern -

no n-loadbearing walls has led to an aesthetic

th at was not an inevit able development

ist archit ecture , th e separat ion of stru cture

typically con cerned with eithe r forming a

of 19th cent ury archit ecture but rat her a

and ext ern al wall has do minat ed, w here

'co llage' of different compo nents, or as a

respon se t o an industrialisation governe d

th e facade is redu ced t o non -loadbearing

repeated modul e of the same compon ent.

by mass production of building co mpo nents

w alls.T his approach has been a result of the

However, loadbearing constructi on can

such as steel sections for fr ames, br icks,

development of structural forms, o riginally

emb race a design approa ch of struct ural

blocks, meta l coil, timber boards and sec-

destined for large scale buildings,w hich have

and environmental integratio n: t he use of

t ions.The use of repeated , recti linear stru c-

fou nd use in much smaller scale construc -

envelope and str ucture combin ed t o create

tural bays, both in plan and elevation, can

t ions, even being used in individual houses in

space in the facade and cont inuity in gro und-

be seen as a response t o t he way the raw

co ntin enta l Euro pe.T he use of loadbearing

scape or urban context. Both loadbeari ng

products used in building are manufactured,

stru ctures for larger scale buildings resulted

and deep rainscreens are possible solutions

including the straight lines of cut t imber and

in facades with 'punched ' window openings

for th is approach .The recent introduction of

plywood used for concrete formwork.

that gave a 'massive' quality to buildings. In

computer controlled too ls has taken away

contrast, the use of t he separat e structural

the imperat ive of mass prod uctio n, offering

can be considered in te rms of it s response

frame w as able to create a visual lightness

instead possibilit ies of'mass custom isation'

t o mass production te chniques through th e

and t ransparency t hat gave greater freedom

w here many componen ts of different size

use of th e structural fr ame , Building co mpo-

t o designers. H owever,the int egrat ion of

can be produced qu ickly t o a high quality

nent s and assemb lies were used as repeated

skin and str ucture into loadbearing facades

Cons eque nt ly, architectural prod uction is no

ident ical elements in building com positions .

can also allow much greater freedom in t he

longer determined by t he need for repeat ed

Th e use of stee l o r concrete fram es led t o

design of the ext ern al envelope to suit the

rect ilinear units used in Modernist designs.In

buildin g envelopes being enclosed in non-

requirements of th e spaces immedi ately

terms of th e relationship between st ruct ure

loadbearing cladding.The use of repeated ,

behind. In the context of th e ex isting built

and ext ern al envelope, th e introduction of

rectilinear bays can be seen as a response

environm ent, a new building can almost

mass custom isat ion suggests th at systems for

to manufacture, includ ing th e straight lines

'grow' out of the adjacent existing building

both facades and structu res could become

20th century Modernist architecture

of cut t imb er and plywood used fo r co n-

using the same mat erials but with a different

mo re com plex and int erd ependent, w hile

crete formwork. Consequent ly,as a result

material system.

remaining eco nom ic by th e standards of

MCH

10

Colonia Guell,Barcelona, Spain.Architect:Antonio Gaudi

Sagrada-Familia, Barcelona, Spain.Architect:Antonio Gaudi

Sagrada-Familia,Barcelona,Spain.Architect: Antonio Gaudi

contemporary building construction.

be seen as a civic exp ression of the manual

rect ilinear structu ral frame . In the I 950s,Eero

work of many craftsmen and labo urers of the

Saarinen used loadbearing concrete in the

medieval world, w as replaced by an archit ec-

TWA Terminal at John F Kennedy Airport in

t ural expression of t he use of mass produced

New Yo rk, a building w hich int egrat es t he lan-

building components t hat were used as t he

guage of str ucture and enclosure with t hat of

A tradition of the integration of structure and envelope T he integration of structure and envelope can be seen in th e Gothic tradition:

raw mate rial for th e specialist fabrication of

partition s, counter s, desks and furniture.The

facades fo rm ing external spaces create d

entire parts in small w orkshops, rather than

furnitu re is cur ved to make it com fortable

by t he fram ing effect of flying buttresses of

that of w ork being all performed on sit e.

for t he curved human physique, linking the

medieval cat hedrals. Such structures also

Gothic Revival buildings such as the O xford

form of w hat inhabits the building to inform

commun icate a sense of the communa l

Museum are built wit h a mixture of load-

th e constr uctio n of th e building it selfThis

effort required to construct t he building:

bearing and framed co nstruction.

building can be regarded as an integration

The w alls,w hich seem t o int egrat e frame and infill wall into a single constructiona l

In t he early 20th centur y t he archit ect Antonio Gaudi saw that an advantage of

of building, int erior spaces and furnit ure t hat marked the buildings of medieval Oxford.A

ent ity, sweep inw ards at roof level t o cre-

loadbearing construction was th at individual

building designed by Eero Saarinen, t he Mil-

ate stone vaults t hat form a cont inuit y wit h

blocks of stone , bricks or concrete blocks

w aukee A rt Museum, was recently exte nded

the wa lls.Onl y a timber roof is required to

could be corbe lled inwards or outwards from

to a design by Santiago Calatrava in a struc-

protect the sto ne ceiling from the effects

t he vertical plane of t he external w all to cre-

ture that create s a loadbearing, or skelet al,

of the weat her.The t imber ro of is not a

at e a comple x vertical section as w ell as a

stru cture, rem iniscent of earlier buildings by

'concept ual' part of the masonry structure,

complex plan. Gaudi's use of brickwork was

O scar N iemeyer.Calatrava's interest in animal

but rat her a necessary addition t hat ensures

based on his own structural investigat io ns, as

skelet o ns goes one step beyond th e interest

t he constr uction provi des a weathert ight

imple mented at t he Sagrada Familia in Barce-

in the structure of Saarinen.

enclosure. Gothi c Revival buildings of th e

lona. In the years th at follow ed, the buildings

19th cent ur y,such as the O xford Museum

of Oscar Ni emeyer int egrated structure and

in England, com bine medieval methods of

skin in projects of var ying brief, fro m ho using

loadbearing co nstructio n wit h industrially

to churches to public buildings, exp loring the

manufactured iron ribs that form a vault ed

po ssibilities inherent in reinforced concret e

roof structure infilled wit h glazing.What can

rather than follo wing the imperat ives of the MCH

II

Materials 0 I Structure and envelope 2

Aerial view,Oxford, UK

Parametric modelling This need for variat ion in more complex

drawings, and that buildings can be seen as

escope and fitting the 'secondary' research

arrangements of linked spaces is tackled

mere 'built drawings' rather than being con-

spaces into it,the design allows both aspects

more comprehensively in projects by Zaha

ceived as'buildings' in the first place. Gehry

of the design to combine as a more bal-

Hadid, whose work is informed by an inter-

is less interested in loadbearing construction

anced composition.This was achieved by

est in parametric design, where spaces can

than in the built forms that can be generated

designing the spaces from the outside in, cre-

be linked by rhythm, and links achieved

from a few material systems which are liber-

ating an envelope to suit the general enclo-

through the assistance of computer soft-

ated from the constraints of mass produc-

sure of spaces, effectively wrapped around

ware, so that many more iterations can be

tion towards an eventual approach of mass

the telescope.The structure supporting the

investigated and explored than are possible

customisat ion.

telescope is set inside the building, requiring

by hand, by conventional 2D CAD, or even by conventional physical modelling. Parametric modellingprovides an interrelationship

a quite different support for the observation

Modernism and construction Modernism developed from aspects

floor.The space between the outer envelope and the inner telescope structure is inhab-

between parts of the building as well as

of architecture of the early 20th century,

ited by the circulation space serving both

the urban space surrounding it, making the

influenced by mass production techniques

t elescope and study spaces.The telescope

cityscape one of interdependence as, once

from about 1920 onwards. In contrast,the

can be considered to be designed from

again,can be found in medieval Oxford .The

approach taken by architects such as Eric

the inside out, while the study spaces are

involvement of structural engineers such as

Mendelsohn in Germany duringthe 1920s

designed from the outside in.The interstitial

Adams KaraTaylor has led to a more ambi-

considered ways of integrating different

zone between the inner and out er structure

tious engagement with loadbearing struc-

aspects of programmes informed strongly

is inhabited by the staircase which rises

tures.The office of Frank Gehry has taken

by the waythe building was constructed.

through the building. In anot her project,the

the use of parametric modelling as a tool for

The Einsteinturm in Potsdam, Germany, by

staircase itselfcould have been part of the

generat ing building forms that would not be

Eric Mendelsohn integrated the needs of a

overall building structure, but here the stair

possible in a practical sense without compu-

research cent re comprising spaces for study

is supported primarily by both inner and

ter software and its link to computer aided

and discussion, with the complimentary

out er structures on its sides.The building's

manufacturing. Gehry is concerned that

requirement for an astronomical telescope

external envelope is built from brick,cov-

archit ects produce buildings that are gener-

to be accommodated in the building.Rather

ered in render. W hile the building could have

ated by the need to be resolved in 2D as

than express the 'primary' aspect of the tel-

been formed in concrete,the construction

MCH

12

Einstein Tower, Potsdam, Germany. Architect: Erich Mendelsohn

EinsteinTower, Potsdam, Germany. Architect: Erich Mendelsohn

method of corbelling brickwork in and out

built environment.and may also depart geo-

and external facade structures creates an

of vertical plane is ideally suited as a method

metrically from its context, as in the case of

opportunity for a buffer zone between them,

to construct a form of this geometry.

Zaha Hadid's design for an extension to the

which could be used as an inhabited space

Louvre Museum in Paris.The design provides

or for circulation around the building, as was

permits this more complex approach to

continuity of material and context wit hout

mentioned in the previoustext on the Ein-

tectonicsthat was dominated in the 20th

compromising the performance of the build-

steinturm by Eric Mendelsohn.The recently

In our own time, the rise of digital tool s

century by the use of the structural frame.

ing in term s of use, organisation and spaces

completed Mercedes-Benz Museum in Stutt-

created within the building while responding

gart by UN Studio has interstitial zones used

acteristic of the construction of Modernist

to environmental imperatives of reducing

for circulation, while interstitial zones which

architecture has been the separation of

energyconsumption within the building.The

are inhabited can be seen in the Phaeno Sci-

As set out in the previous essay, a char-

structure and external envelope. where

new structure can almost be seen as 'grow-

ence Center inW olfsburg, Germany, by Zaha

the facade is reduced to non-loadbearing

ing'out of the adjacent existing building and

Hadid.

'cladding' as a result of the development of

the adjacent groundscape using the same

structural frames, originally destined for large

material but employinga different material

a loadbearing facade has obvious difficulties.

The integration of skin and structure into

scale buildings. In contrast, the use of digital

system. The material system can be chosen

The conventional 'layered'approach of clad-

tools and mass customisation methods can

or developedto suit the design needs of

ding applied to structural forms in Modernist

be used to create a partial or full integration

the spaces immediately behindthe external

construction has the advantage of superim-

of skin and structure as loadbearing facades.

envelope.

posing wat erproofing,thermal insulation and

This revived loadbearing approach can allow

W it hin building designs. spaces can be

vapour barriers to form a sequential wall

a much greater control of the design of the

created in an outward direction from the

build-up. In loadbearing facades it is more

envelope to suit the requirements of the

internal spaces of the building.W here spaces

difficultto integrate these different func-

spaces immediately behind, rather than using

are required to have a high level of techni-

tions into a single structural wall. However,

the repeated bays of structural frames built

cal performance, or specific light conditions

allowing lines of structure to deviate from

using established methods of mass produc-

that are to be created, this can be achieved

the rectilinear rather than beingusedto suit

tion.ln this loadbearing-based approach.

without immediate referenceto the external

primarily rectilinear facade cladding. allows

the choice of material used may be taken

envelope but rather to the building structure.

structure to interact with non-rectilinear

from the immediate physical context of the

An interstitial zone between internal spaces

spaces within buildings. Current Modernist MCH

13

Materials 0 I Structure and envelope 3

.. '

~

.-

..-

..-

..--

.-

.-

..-

~ II

-

::I Paramet ric mode l of a twisted tower

architecture responds to the needs of mass

of the mass production of identical compo-

ing forms have been seen in both twi sted

production,a set of design imperatives of

nents towards a new period of craftsmanship

and folded geometries.

repeatability and a rectilinearapproach based

as a result of mass customisation.

on mass production rather than the possibili-

A design approach of designing inwards

Twisted building forms achieve geometric complexity by using curves,typically across

ties provided by digital tool s of design and

from the facade of the building, and outwards

a surface of constant curvature in order

production available wit h mass customisation.

from the internal spaces of the building, could

to make it easierto build in a construction

allow structure to create interstitial space

market that is used to mass production tech-

The renewed interest in the structural design of the externalloadbearing wall cre-

between inside and outside.This approach

niques of building construction. Geometric

ates at once a new design vocabulary for

can also create environmental 'buffer' spaces,

complexity can also be achieved wit h folds,

architecture and a return to an expression of

which are not maintained at the internal tem-

where conventional flat surfaces, which are

the joy of making buildings, as demonstrated

perature of the building but serve as a buffer

straightforward to build, can be formed into

in individual craftsmanship,an approach that

between inside and outside temperature

unconventional facade forms. The recent

can be seen to have been shared widely in

conditions.These spaceswould not require

examples are those by Sant iago Calatrava,

construction before early prefabrication tech-

the same amount of tempered air;but would

Frank Gehry and UN Studio in twisted forms,

niques were introduced in the 1920s.This

provide an opportunity for natural vent ila-

and OM A, Zaha Hadid and LABArchit ecture

approach to design is informed by a balance

tion,all key to reducing carbon dioxide emis-

in folded forms.The approach of folded and

of the specific useof the material system,

sions in buildings. From the point of view of

twisted building forms is a way of introduc-

used to form the building, wit h the sequence

construction, this approach is more complex

ing complex geometr y while maintaining contemporary principles of'repeatability' in

of movement around the building and the

than 20th century construction, but could be

spaces created within.The expression of

achieved with digital tools for design and fab-

order to makethem economicto build using

construction and circulation as'designed'

rication,the to ols of mass customisation.The

a conventional approachto construction. In

elements harnessed to the 'objective' design

possibility of mass customisation of compo-

t his sensethe approach of tw isted and folded

requirements of spatial organisation related

nents allows a departure from the repeated

forms is an intermediary one between the

to programme and site context, can be

rectilinear component so that components

rectilinear repetition of Modernist construc-

a powerful partnership of principles.This

can be more geometrically complex, either as

tion and the emerging construction methods

approach could allow construction to move

individual components or as complete build-

described here.The current approach to

on from 20th century industrial imperatives

ing assemblies. Recent developments in build-

folded and twisted facades requires geomet-

MCH

14

·. -

Computer generated construction system models

ric discipline in order to maintain the repeat-

construction as an additional driving factor.

factured and used in a system in addition to

ability of components, mainly facade panels,

This may be digital, as wit h the possibilities

their essential physical properties.This book

used in conventional construction techniques.

for invention that the t ools bring, or may be

also sets out the construction systems essen-

With the greater introduction of digital fabri-

used for the continued cladding of structural

tial to contemporary architectural produc-

cation tools,the need to maintain a geomet-

frames.This leads the design into a direct

tion, categorised in terms of envelope, struc-

ric discipline will slowly disappear; perhaps

connection with traditional loadbearing con-

ture and environment.The book begins with

making design choices more dependent on

struction, but moving it forward with chang-

a setting out of materials and how they are

the principles of design performance impera-

ing methods of industrial production. Digital

used as material systems and ends with pro-

tive in buildings such as the Einsteinturm dis-

tools allow the performance of a design to

posals for new material systems as an extrap-

cussed in the lastessay. Greater freedom of

be explored and optimised,and be devel-

olation of what is possible in the present and how it could be used in the future.

design from digital tool s will provide greater

oped in order for an individual or a t eam

control and greater responsibility from the

to tackle the fabrication of the component

designer to usethe technology wisely.

which has not been made in a particular way before. Alt ernat ively. a design may usehistori-

Design methodology Current architectural design has a prefer-

cal models, either to endorse the construction methods of existing buildings,to mix old

ence for rectilinear spaces linked in a spatial

and new to create something new, or even

organisation which is also primarily rectilinear;

to advance what is already constructed by

though dependent upon site conditions,

physically adjusting it by using the same mate-

based around the useof rectilinear structural

rial but a different material system.

frames.The design generated is then given

The Modern Construction Handbook

an outward facade expression of materials

sets out these construction techniques, both

formed wit h openingsor wraps as an inter-

traditionally-based and contemporary. all of

face between the internal arrangement of

which evolved during the industrialisation

the building at its immediate site context.

of the 19th century. Essential to this use of

An alternat ive design methodology is to add the use of material systems to that mix:

material systems is an understanding of the physical characteristics of materials as manu-

MCH

15

Materials 0 I Parametric design

Parametrically modelled glazed structural facade

The use of parametric design in architecture

open jointed rainscreens and solar shading

ing is typical or dimensionally constant in the

has been centred around the use of soft-

screens set forward of a wat erproofed back-

external walls.The relationship of inner and

ware that was originally developed for other

ing wall. Rainscreen facade panels comprise

outer skin varies, 50 a set of' rules'is set out

industries. Its primary use in architecture has

a pattern of repeated tri angular panels in a

in the system drawings,then applied t o t he

been t o generate digital models for build-

pinwheel grid,where a set of five triangular

'kit of parts' drawings and the setti ng out

ing structures and external envelope which

panels forms a shape identical in propor-

drawings.

have a complex geometryThe word 'com-

tion to the smallest triangle from which it is

plex' is used t o denote geometries which

formed. In projects such as these,facades are

inner and outer layers are set out in a loose-

are not rectilinear; and therefore cannot be

described in a way that can communicate to

fit relationship between inner and outer skin.

described by plans and sections which can

contractors the nature of a complex three

In projects where forms are either facet-

be extruded in a straight line through the

dimensional form on paper. Elevations of

ted or curved t o create an architecture of

form of the building. Building designs which

such buildings are set out as unfolded or

complex geometry. the means of contro lling

At Federation Square for example, the

do not conform to the rectilinear forms

'developed' facades from a 3D digital model.

the geometry of the building become more

characteristic of Modernism are difficult to

This describesthe scope of the facades and

crucial. In single skin buildings where the

describe as 2D plans, sections and elevations

the t ot al material needed as'kit of parts'

building has a complex form,the exact fit of

in a way which can be communicated to

drawings resemblingthat of anAirfix model

the different components during construc-

thosewho will construct the building. Even

kit. In addition, 2D details describe the 'sys-

tion is critical during construction. In devel-

2D plans, while still a useful t ool, still cannot

tem' as a wall method that could be used

oping such building forms and implement ing

be used to establishthe edge of the external

t o describe how the facades go to gether;

them,the forms need to establish criteria

envelope if the external wall is not vertical,

regardless of its actual application around the

which are fixed, such as floor areaof the

as the position of that wall applies only at

building.Drawings specifically for the facade

different spaces comprising the building,sit e

the horizontal planeat which the plan is set,

systems are needed since the facade con-

constraints, and criteria which are not fixed.

typically at floor level for a form of complex

struction method is devised individually for

Some building designs for complex forms

geometry.Typically. glazing is set above the

such projects. Details of facade conditions at

evolve as a result of more information being

floor level, where plans are typically drawn,

edges, corners, interfaces and junctions with

known about the building, allowing more

but any dimensions on the plan at this point

other parts of the building construction are

of the design to be fixed. Consequently. the

are set at a level difficult to establish on sit e

prepared in the tradit ional way

different criteria of the design can be set

in buildings of complex geometry

Drawings describing the design of com-

as'parameters'which can be related as a

A well-known example of complex

plex geometry of the external envelope are

matrix in the form of a spreadsheet.The

geometry using flat facadesthat do not

of different types:'kit of parts' drawings,'sys-

spreadsheet can be linked to the process

conform to the rectilinear forms of most

tem' drawings, details and setting-out draw-

of modelling the building forms digitally in a

contemporary archit ecture is Federation

ings.This method differs significantly from

parametric design software.Working para-

Square in Melbourne,Australia.The external

the traditional approach of plans, sections,

metrically allows the design to establish what

walls were designed in the form of'wraps'of

elevations,typical details and so on,as noth-

is'fixed' and what will be 'variable' in the

MCH

16

Detailed images of construction system from the same parametricmodel

design development.This approach allows

different requirements can be put into the

to the design of individual buildings, the

a digital design method to evolve. In facade

model at the beginning, with changes in the

possibilities are being seen more widely in

design,the behaviour of the model as a set

digital model showing the corresponding

both fieldsof architectural design and urban

of surfaces can be understood by number;

effect between them all. Facade design of

design.Whe re buildings have been designed

size,geometry and so on.The relationship of

complex forms is often driven by a desire to

asa 'collage' of components which are jux-

the parameters in the design allows the dig-

optimise the construction; often by simplify-

taposed or stacked to gether in a loose-fit

ital model to evolve through an engineering-

ing it by providing as simple a solution as

manner;more contemporary architectural

based method of iteratio n,rather than start

possible without losing t he strength of vision

design is basing itself on a greater integration

the digital design model again each time

or strength of archit ectural expression in

of structure, envelope,environment. space

a new option is explored.This approach

the design. Even in higher budget projects,

and light as ingredient s in a richer mix.

requires some discipline and clarity in the

the need to omit unnecessary complexity

design approach at the outset. which often

of construction and diversity in panel size is

of design allows buildings t o become bet-

makes the parametric design met hod more

important to both reduce costs and attract

ter constructed at the scale of the window,

suit ed t o design development than initial

the most highly qualified companies to work

the bay,the wall, the building and the street

design research. However;parametric plug-

on the project.

to form a continuit y.Where the provision

ins are becoming available for early stage

The possibilities of parametrically-based

This greater level of interdependency

of buildings, roads, natural landscape and

design go beyond the need for evolving a

services infrastructure are considered quite

approach is gaining influence throughout the

single digital model for the main components

separat ely in our industrialised society. the

design process.

of building structure and external envelope.

re-integration of these essential components

With more and more parts of the design

of our cities could eventually become part

design software,ensuring that the parametric

In facade design, where the parametric approach is becoming a primary to ol

forming a single model, the use of a building

of linked parametric models.The interde-

in architecture,the aims vary during the

information model or 'BIM' that sets out all

pendency of building,street. and the natural

different stages of design development.

the components required to make a build-

landscape that was a criticalgenerator ofthe

Outcomes of parametric design can range

ing, is becoming a reality.Whe reas large scale

built forms of the pre-industr ial world, where

from establishing a rationalised or optimised

manufacturing of aircraft, cars, boats and so

the use of energy for both transportation

geometry. reducing the number of panel

on have already usedthis working method

within towns and cities and the responseto

types, restricting the facade assembly so that

for some years, the use of BIMs in building

the built environment played much bigger

it conforms only to the design limits imposed

design is just becoming the norm in higher

roles in the generation of urban form.

by the material systems or facade systems

profile projects. Building information models

An essential aspect of parametric design

being used, ensuring that the floor plates

are now becoming parametric, with the pos-

with digital models is to establish what is

provide a fixed t ot al amount of floor area,

sibility of introducing complex geometry into

import ant in the design and what is much

or ensuring that the relationship with the

the process.

less important; understanding what design

primary supporting structure is maintained without exceeding maximum spans.All these

W hile this approach is aimed primarily

'problem' is being set. and what might be the

at bringing greater control and knowledge

ways of exploring that design.This approach

MCH

17

Materials 0 I Parametric design 2

Parametrically modelled lapped glazed panel covered facade

Embodied energy and digital design

allows buildings to become a much more

parallel, for these choices are as important

closely dependent set of spaces, and building

as the internal organisation of the building,

construction becominga closer expression

the spatial arrangement and relationship to

Two trends in buildingconstruction

of the ideas of space, light and form con-

the site.This brings the choice of materials

which are driving change in architectural

structed within the constraints of a particular

andthe way they are used, or 'tectonics' back

design are concerns about the environment,

material system.A parametric approach will

to the centre of architectural design, rather

and the introduction of computer controlled

also allow much greater int erdependency of

than material and construction-related issues

manufacturing.The effect of building con-

buildings working together as part of a single

being chosen as standard construction meth-

struction on the environment has been of

'organism'- the urban environment of build-

ods afterwards.The result of involving issues

concern since at least the I960s.The effect

ings, streets and public spaces. It is perhaps

of mat erials and construction at a later stage

in building construction is a growing aware-

in the design of public space, and the elimi-

is that the forms of construction used can

ness of the energy required to construct

nation of residual or ill-defined space that

become no more than an outer 'clothing'

buildings, or'embodied energy', and secondly

could be the next major use of parametric

that is deemed appropriate t o the site con-

the energy required t o operate the building

design in digital models.

text and the brief.that it should somehow

when in use.The embodied energy part of

behave well in an architectural sense.The

the equation is concerned wit h both the

limitation of this approach is that the outer

amount of energy needed t o manufacture

Parametric working method

skin has little t o do with the structure and

the materials,transport them t o site,then

parametric design is the ability to develop

envelope mat erials behind it, often forming

install them on sit e.This interest has favoured

different parts of the building design in

the outer rainscreen or covering of a con-

the use of timber,which absorbs C02 dur-

parallel rather than working sequentially

struction systemthat is based on procure-

ing its growth and can be re-planted when cut down for useas a building material.

An essential aspect of working with

from outline design, scheme design, detailed

ment expediency rather than design. Conse-

design and so on. Rather than viewing design

quently. there is a need for material systems

as a series of stages to complete and move

to be involved at early stages of the design

ding' mater ial to an envelope constructed of

on from without significantly changing or

process. Construction methods used for

quite different materials.The idea of'c1adding'

informing what has already been accom-

these essential parts of building design are

buildings involves increasing the number of

However,much timber is used as a'clad-

plished in the design,the design of a building

set out as material systems in the chapters

layers, and has led to a desireto reduce all

is tackled not as something developing as

of this book;each described from a com-

the different requirements of construction

a result of a series of decisions which influ-

mon platform of how the principle mat erial

by making the external walls loadbear-

encethe next decision in turn (from primary

is used to form a system for wall,roof or

ing rather than being cladding panels to a

concerns to secondary concerns and so

structure,and how these might be applied

structural frame.This interest is linked to a

on) but rather of material systems which

to specific strategies of environmental design.

preference for reduced amounts of glazing in

interact and influence one another. A mate-

many building types, where structural frames

rial system for structure,walls, roofs and

were enclosed in highly transparent enve-

environmental design can be developed in

lopes.W hile high levels of glazing encourage

MCH

18

Detailedimages of a glazing systembased on a voronoi pattern

increased levels of natural daylight in build-

become primary tools to reduce energy

material systems shown in this book are

ings,they also admit solargain and provide

consumption for heatingand cooling build-

set out in more detail in the accompanying

poor thermal insulation in all climates.The

ings.This has resulted in the re-introduction

books Modern Construction Facades and

preference for loadbearing construction

of opening windows and of cross ventilat ion

Modern Construction Roofs. From a design

is in some ways a return to pre-industrial

in buildings.

perspective,rather than production of infor-

forms of construction.This interest in a 'leaner' higherperforming construction is

mation for tender or for construction, a 3D

Material systems

model andthe controlled manipulation of that model in relationto the constraints of

possible wit h computer controlled manu-

This Second Edition is aimed as a guide

facturing tools that are linked to drawings

to using material syst ems in contemporary

the material systems such as glass sizes or

and 3D models produced by the design

buildings, with material systems shown as

bending constraints on panels, is as valid as

team.Although in practice it is manufactur-

views of 3D models in order to understand

a 2D section through a building of constant

ers who provide the final drawings for CNC

how they fit together spatially rather than

section. Drawings can show the 'kit of parts'

machines,this is largely a requirement based

treat them as 2D sections.This is because

required to describe the scope of the build-

on how buildings are procured rather than

traditional vert ical and horizontal drawn sec-

ing, which is essential to understanding and

an imperative of the design process. Conse-

tions assume most systems are continuous

setting out how much material is required to

quently, designers can produce a full set of

through their length,that they are extruded

construct the building. From these drawings,

drawings for manufacturers to make a much

in a linear direction either side of the section

the embodied energy required to construct the building can be calculated.

wider range of components than has been

taken. This method of representation also

the case wit h mass production.This link of

assumes that a drawn section, both vertical

The systems of modern construction

design directly to construction, rather than

and horizontal, is a typical condition. W hile

set out in this book suggest a gradual move

re-interpretinga design as a set of drawings

plan, section and elevation explain the over-

forward to methods of production based

that in turn 'get built' is forging a much closer

all scope of the design,junctions of the sepa-

on mass customisation techniques that are

link between design and construction. In

rate planes represented in these drawings

evolving in manufacturing, as well as show-

common with the re-introduction of load-

are rarely resolved in these drawings, leaving

ing how current mass produced material

bearing construction, the use of computer

some coordination issues to be resolved at a

systems can be modified and'diverted' to

controlled mass customisation tools is bring-

later stage. Expressing information as images

the end of producing an architecture rooted

ingthe design of buildings much closerto

from a 3D model allows the system's behav-

in the construction techniques that makeit

the process of constructing them, a privilege

iour to be understood from a geometrical

possible.

enjoyed in the pre-industrial world of con-

point of view of how the components,

struction prior to around 1920.The second

assemblies or panels are set out.

essential aspect of environmental concern

Traditional detail drawings can show

is of the energy consumed by the building

how to describe assemblies in a way which

in use. Natural vent ilation,thermal mass and

is useful when progressing from design ideas

associated issues of night-time cooling have

to a design ready for construction, andthe MCH

19

Materials 0 I Tectonics in metal

Olympic Stadium, Tokyo, Japan. Architect: KenzoTange

Guggenheim Museum Bilbao, Spain.Architect: FrankGehry

Architectural interest in metals in the early

striking form of construction that was char-

industrial world can be seen in the writings

acteristic of later 19th century construction.

of Jean-Baptiste Rondelet, an admirer of

Olympic Stadium,Tokyo, Japan. Archit ect: Kenzo Tange

industrial Britain in the early 19th century.

Stadium of 1964, designed by Kenzo Tange,

His book Traite theorique et pratique de

comprises st eel tension cables in a catenary

l'art de batir discussed architecture from

form, support ed by concrete masts at each

the point of view as comprising a mixture of

end.The complete tent-like structure is used

the visual and the technical rather than the

to support a metal skin,which would typi-

prevailing values of the time of Renaissance

cally be used on a rigid substrate.The metal

architecture, which were primarily of art and

roof skin is actually a series of metal plates

symbolism. He also taught stereotomy, that

welded to gether to form a sealed surface.

is, the art of cutting stones to form complex

W elded metal roofs have been used in more

shapes such as arches and vaults,which is

recent projects for large-scale roofs, but few

enjoying a revival wit h an interest in complex

combine the possibilities of a continuous,

geometry in contemporary archit ecture.As

welded metal surface with that of a skeletal

a construction textbook , the Traite theorique

or tent-like structure that can form a metal

set out many of the components needed

cable structure. Even the cable structure is

for a complete metal construction, such as

made from short lengths bolted together to

prefabricated market buildings, showing an

form a structure that can support the metal

approach towards an integrated assembly

roof plates without an intermediary material.

that follows on from his passion for stereot-

The metal structure and skin is not a'mini-

omy.The metal castings securing the bases

mal' structure, but is certainly one where

of the supporti ng arches illustrate both the

thesetwo components are interdependent.

need for the continuity of material needed

The all-metal roof structure and skin is held

to fix the archesto their bases as well as

in place by a reinforced concrete structure

the elegance associated with their use.The

beneath,whose form echoes that of the

drawings in Rondelet's books are both a

metal structure rather than contrasting visu-

'kit of parts'showing what components are

ally with it.

needed as well as a 3D representation of the assembly of key components.This inter-

MCH

20

In the 20th century, the Tokyo Olympic

More recently. moving structures such as the sail-like canopy at Milwaukee Museum of

est in the physical modelling of junctions

Art, designed by Santiago Calatrava,take for-

rather than in reducing them only t o 2D

ward the visually dynamic qualities of metal

views helps to explainthe more complex

construction.This canopy is used t o provide

nature of t he construction, whose design

solar shading, and moves in order t o provide

approach is embraced rather than simplified.

different experiences of light. Here a folding

The combination of rolled members, castings

structure with a building performing differ-

and connecting brackets creates a visually

ent functions and forming different spaces

Milwaukee Museum of Art. Architect:Santiago Calatrava,

Guggenheim Museum Bilbao, Spain. Architect: Frank Gehry

through moving, is possible because of the

well suited to metal frames, where standard

relative lightness and flexibility of metal,

rolled sections are joined wit h plates or

allowing the possibility of moving parts to be

nodes.The technical success of the system

used to form part of the structural frames

lies partly in creating a limited number of

of buildings. In the Guggenheim Museum

node t ypes which can provide a visually

in Bilbao by Frank Gehry,the architectural

rich construction with a small number of

form of the building is generated as a form

node types or bracket sizes.The use of a

of complex geometry, enabled by the pos-

limited 'kit of parts' can provide a visually rich

sibilities of metal construction, and working

structure and enclosure that can respond

with techniques associated with modelling

to particular design requirements such as

in metal rather than conceivingthis innova-

positioning of openings or links with adjacent

tive form of construction from 20 draw-

structures without needing to be aligned to

ings.ln this sense, the buildings described

a rectilinear grid.

here follow on in the tradition of the Traite

More recently, designs for metal frames

theorique of Rondelet, combining the con-

to support cladding systems have begun to

vention of describing elements in 20 while

use identical polygons which might be twist-

designing in a 30 modelling environment.

ed or pulled out of plane in their geometry

The examples described demonstrate

Milwaukee Museum of Art. Architect: Santiago Calatrava,

and which produce complex shaped surfaces

the ability of metals to form building enclo-

when joined together. In addition, the 'cold

sures of complex form in a single material

bending' of metal panels to cladding systems

where structure and skin are a visible part of

can create more complex forms for enclo-

the architectural design. In more rectilinear

sures from flat sheetor profiled sheetwit h-

building designs, steel frames can be used

out the need for any special manufacturing.

which do not necessarily produce a rec-

This can combine the benefits of more com-

tangulargrid of cladding panels across their

plex steel frames that are straightforward

surface. Federation Square in Melbourne,

to construct with metal wall systems that

Australia, designed by Lab Architecture uses

are usually more associated with rectilinear

a triangularspace frame as a point of depar-

forms wit hout changing the way such enclo-

ture from which to create a structure which

sures are constructed. However; for all these

gently departs from this principle, creating

examples of tectonics in metal, the designer

junctions which form moment connections

is obliged to set out the construction of the

rather than the pin joints associated with

structure and enclosure in a more detailed

triangulated frames.This approach allowed a

waythan that expected for more generic

range of glass panels to be added which are

forms of construction,just as Jean-Baptiste

still based on a triangulargrid.This method

Rondelet set out examples from hisTraite

of startingwith regularforms of construc-

theorique, completed in 1817.

tion and working with their geometry is MCH

21

Materials 0 I Steel

Federation Square, Melboume,Australia.Architect: LAB Architecture Studio

Steel is an iron-based metal alloyed with small amou nts of other elements , the most

Guggenheim Museum, Bilbao, Spain..Architect: Frank Gehry

making it less susceptible to shock damage. (The Eiffel Tower; in Paris, was one of the

impo rtant being carbon .The three main

last large structures to be constructed in

forms of steel used in th e building industr y

wrought iro n). By the end of the 19t h cen-

are sections,sheets and castings. Stee l sec-

tury.both materials had been superseded by

t ions are currently formed using a ro lling

steel. Stee l was first prod uced aro und 1740,

pro cess. It can be extruded to form complex

but was not available in large quant ities unt il

sections, but th is curre nt ly has only limited

Bessemer invented his converter in 1856.

applicat ions due t o th e high pr essure need-

Thi s device introduced a method of blasting

ed to extrude st eel.Aluminium is a much

air into th e furn ace (hence blast furn ace) t o

soft er materi al, making it easier t o extr ude.

burn away t he impu rities th at inhibite d th e

Even w hen alumi nium is alloyed wit h ot her

extraction of a purer iron . By 1840, standard

materi als such as bro nze, the extrudable size

shapes in wrought iron, mainly ro lled flat sec-

of sections dro ps dramatically Extrusions in

ti ons, t ees and angles were available wh ich

steel cannot exceed shapes th at fit into a

could be fabricate d int o structural compo-

circle approximate ly 150mm (6") in diameter.

nents w hich are then assembled by rivet ing

This is too small for structural sections, but

them together. By 1880,the rolling of steel

the ir smooth appearance makes them suit-

I-sections had become wi despread, leading

able for components such as stiffeners in

the way to th is material event ually replacing

curtai n wa lling (to provide a fin t hat is visu-

wrought iron as a material of choice .

ally mo re refined th an an I-sectio n or a t ee). C urrently.it is still far easier t o roll steel secti ons than to extrude th em. Historically, cast iro n and wro ught iron

Guggenheim Museum, Bilbao, Spain..Architect: Frank Gehry

MCH

22

Production process of raw material There are several steps in the manu-

were the forerunner s of stee l. Cast iron,

facture of steel. First, iron is refined from

a brittle material w it h high compressive

ores containing iron oxide .The iron ox ide

st rength, came into general use as a build-

is heated in a blast furna ce until it is mol -

ing mater ial at th e end of th e 18th cent ury.

t en, using carbon as a reducin g agent.T he

w hile wro ught iron was develop ed some 50

mo lte n materia l is po ured into moulds to

years later. Wrought iron is a mo re ducti le

prod uce pig iro n. It is then re-heate d to

mate rial and has greater tensile strengt h,

remove impur ities, including carbon, to make

Federation Square, Melbourne,Australia. Architect: LAB Architecture St udio

cast iron th at has a carbon content of 2.4

· High st rength in both ten sion and

per cent t o 4 per cent. Stee l is produc ed

com pression.

by reducing the carbon cont ent to approx i-

• High stiffness.High rigidity in both t ension

mately

0.2 per

cent, w it h mate rials such as

and compression.

manganese and silicon added to halt the

· Its appearance is smo ot h in sheet form ;

oxidation proce ss and stabilize the carbon

rougher of t exture in roll ed sections and

content. It can be pou red w hen molten to

castings, even wit h paint applied.

make castings o r formed into ingots to be

• Lighter th an an equivalent structural mem-

rolled into sheets or sections.

ber in reinforced concrete . · High duct ilit y,deforming long before it fails.

Properties and data

· High impact resistance.

The main prop er t ies of structural carbon

· High heat conducto r.

steels are as follow s:

• High electrical conductor.

lAC Headquarter s, NewYork. USA.Architect: Frank Gehry

· Thermal expansion approx imat ely half th at Density: Mild steel = 7850 kg/m3 (490 Ib/ft 3)

of aluminium. · Suscept ible to cont inuous rusting, excluding w eat hering steels.

D esign strength: A pp rox imat e ran ge 275 N/mm2 to 800 N/mm2

· Low fire resistance.

(5.7 x 106 to 1.6 x 107 Ibf/ft 2) Young 's modulus = 205 kN/mm 2 (4.2 x 109 Ibf/ft 2)

made in th ree types called 'grades' increas-

Coefficient of thermal expansio n

ing in design strength from 275N/mm2 t o

= 12 x 10-6 K-I

(6.7 x 10- 6 OF-I )

Thermal conductivity =

o

45 W /m

(26 BTU/hr.ft.0F) Specific he at capacity=

Material selection Hot ro lled structural mild steels are

400N/mm 2 (5.7 x 106 Ibf/ft 2 t o 8.3 x 106 Ibf/ft 2 ), vary ing slight ly in different regions

C

of th e world. High strength steels can reach

480 J/kg

o

C

(0.I I

BTU/lbOF)

design strengths of 800N/mm 2

(1 7.6 x

106 Ibf/ft 2). Since th e Young's Modulu s is

..... .....

II ...

constant for all the se ty pes, th e strength of For compariso n w it h oth er materials, steels

mater ial increases but th e st iffness remains

have th e follo win g general properties:

constant. Steel also increases in cost with

The Barcelona Fish, Barcelona,Spain.Architect: Frank Gehry MCH

23

Fisher Center for the Performing Arts, Bard College,

Federation Square, Melbourne, Australia. Architect: LAB Architecture Studio

Hudson Valley, New York. Architect: Frank Gehry

higher levels of strength, both in the cost of

and castings. Steel can also be sawn and

This can be done by either encasing the

the raw material and in the working of the

drilled. An essential characteristic of steel-

material in concrete, by enclosing it in a fire

material. In addition, as strength increases in

work is that it will continue to rust if a sur-

resistant board, or by coating it in intumes-

the material, welding becomes more difficult

face protection is not provided. When drilling

cent paint. A spray-applied coating that yields

and consequently more specialized. In some

or cutting the material, the newly exposed

a very rough, fibrous surface appearance is

high strength steels,which undergo heating

surface requires protection, which is par-

often used where the steel frame is con-

and quenching during their manufacture, the

ticularly important if the material has been

cealed behind finish materials.

effects of welding could potentially undo the

factory coated prior to drilling and cutting.

work of manufacture if sufficient care is not

The economic protection is galvanising, a zinc

taken. Standard rolled sections are manufac-

coating that is corrosion resistant, applied to

Coatings Many factory applied proprietary sys-

tured in the low to medium strength grades

the steel in a hot dip bath or as a flame spray

tems are available for coating steel; the most

but higher strength steels are made mostly in

Galvanising occurs after fabrication of steel

common types are thick organic coatings

the form of plate, due to lower demand for

components to cover all the welding and

and powder coating. PVDF (polyvinylidene

their use. Consequently, compound shapes

drilling.This process can cause distortion of

di-fiuoride, also called PVF2 in Europe), is

for structural components, such as beams

smaller steel components, so may not suit all

sometimes used, and is discussed further in

and columns, must be specially fabricated.

types of fabrication. The appearance of galva-

the section on aluminium. Organic coat-

Cold worked mild steels are used for

nising when new is a mottled shiny grey,turn-

ings provide high levels of protection against

much smaller scale structural components

ing to a dull grey with weathering as the zinc

corrosion but have a distinctive orange peel

such as lightweight structural framing in metal

oxidizes. Its visual appearance is often not

texture. They are applied to steel coil, from

framed housing and low-rise commercial

suitable for exposed structural steelwork or

which sheet is cut, during manufacture.These

buildings, used mainly in the USA, and dry-

cladding in buildings, where paint coatings are

finishes have methods of touching up surfaces

wall partitioning. Cold-formed steel sections

more common. Flame sprayed aluminium can

that become exposed or are damaged dur-

are made from structural carbon steel to

be used as an alternative to galvanising. Paint

ing installation, but colour matching remains

form sheets or strips approximately l.5mm

can be applied by hand on site or in a factory

an important consideration in successful re-

(1/ 16in) thick. Complex sections are formed

as part of a proprietary finish. Care must be

touching.

by folding and pressing,rather than rolling

taken to ensure that touching up on site of

which is the case with hot formed sections.

visible components is done in controlled con-

Working with the material

ditions that ensure the finish both matches

Sections and sheets can be curved to

and blends into the surrounding coating.

small radii. Bolting and welding are the most common methods of joining sections, sheets

MCH

24

When used as primary structure in a building, steelwork requires fire protection.

Recycling Steel can be recycled at reasonable cost, and requires much less energy than the original production process.

Federation Square, Melbourne,Australia.Architect:LABArchitecture Studio

Stainless steel

Dancing House Prague, Czech Republic .Architect: FrankGehry

Stainless steel has the following general

variety of rolling techniques from smooth to

properties:

textured, in an appearance from matt to pol-

contains between approximaately I I to 25

• Highly resistant to corrosion and usually

ished. In addition, the sheetcan be coloured

per cent chromium,together with nickel

requires no further coatings.

as part of the manufacturing process.

in some types,giving it properties that are

· Higher fire resistance than carbon steels.

Stainless steel is an alloy of steel which

distinct from carbon steels, the main one

• A risk of bimetallic corrosion at the junc-

being a high resistance to corrosion without

tion of stainless steel and carbon steel when

the need for an additional coating. Since the

they are used together.

material is considerably more expensive than

Separation at junction is usually required,

the traditional pattern of fabrication for

carbon steels, stainless steel is most com-

such as a nylon or neoprene spacer.

carbon steel members except that more

Working wrth the material The fabrication of stainless steel follows

monly used in small building components and

use is made of pressing and bending to form

in cladding panels where durability is a prime

suitable shapes. Fabrication of stainless steel

Material selection

concern.

Although the material develops a thin

should be kept entirely separate from that of carbon steel to ensure that the processes

Properties and data

oxide layer that protects it from further

of cutting and grinding do not cause impreg-

Density

corrosion, different grades of stainless steel

nation of carbon steel particles onto the

are available to suitthe severity of exposure

stainless surface, which can lead to rusting.

= 7850 to 8000 kg/m 3 (490 to

500 Ib/ft 3) Young's Modulus : In the longitudinal direction 190-200kN/mm 2

=

from polluted urbanto maritime to rural

Fabricated elements should seek to eliminate

environments.A limited range of standard

standing seams or edges where water can

sections is available and usually in small

collect, in order to avoid crevassing corro-

(3.9 x 109 to 4.1 x 109 Ibf/ft2)

sizes only. The need for a high degree of

sion. Stainless steel has high ductility which

In the transverse direction 195-205 kN/mm 2

fabrication of members can make construc-

gives the material excellent resistance to

tion time slower than that for carbon steel

impact loading.

=

(4.0 x 109 to 4.2 x 109 Ibf/ft2)

applications. For example, plate is folded to

Coefficient of thermal expansion

form angles and tubes,and hollow sections

=I 3 x I0- 6 to 17 x I 0-6 K-I (7.2 x 10-6 to 9.4 x 10- 6 OF-I)

are formed by bending and seam welding.As wit h carbon steels, the high strengths types, which have been heat-treated,are more difficultto weld, as the process can undo the heat strengthening. Different finishes are available which are achieved by using a MCH

25

Materials

0I

Alum inium

St Paul's Place car park,Sheffield, UK Architect Allies & Morrison

St Paul's Place car park,Sheffield, UK.Architect:Allies & Morrison

Aluminium was first produced in 1825,and

steel, aluminium is a material that can be

by the late 19th cent ury a method had been

extruded, rolled and cast into complex

found to mass produce the material by the

shapes: plates, sheets, extrusions and castings,

electrolysis of alumina and cryolite.

Properties and data Production process of raw material

The main properties of aluminium alloys are as follows:

Aluminium is madefrom bauxite, which

ImperialWar Museum North, Manchester, UK, Architect: St udio Daniel Libeskind

is essentially an hydrated alumina, or alu-

Densit y = 2700 kg/m3

minium oxide, Mined bauxite is treated

( 169 Ib/ft 3)

chemically to remove impurities and obtain

Design strength

alumina,which is aluminium oxide.This is then reduced to aluminium by electrolysis,

Heat treate d = 270 N/mm2 (5.6 x I0 6 Ibf/ft 2) for extrusions

Becausealuminium has a very high melting

and 235 N/mm2 (4.9 x 106 Ibf/ft 2) for

point (2450°C) it cannot be electrolysed on

plate

its own,and so it is dissolved in molten cryolite.A high electric current is passed through

Fully softened= 105 N/mm 2 (2, I x 10 6 Ibf/ft 2) for plate

the alumina-cryolite mixture at around

Young's Modu lus = 70 kN /mm 2

IOOO°e, and the molten aluminium is tapped

109 Ibf/ft2)

off,Aluminium alloys are either formed directly, followed by continuous casting, or

Coefficient of t hermal expansion = 23 x 10-6 K- I ( 12.8 x 10-6 O F-I)

are cast into solid ingots.The metal is t hen

Thermal conductivity =

cast into ingots which form the basis for

200W/m oC

producing aluminium alloys. Pure aluminium

( I 16 BTU/hr.ft,0F)

istoo soft for structural use and is therefore

Specific heat capacit y = 880 J/kg C (0.2 1

combined with other metals to form alloys

BTU/lb OF)

to increase its strength and hardness,though reducing its ductility. Magnesium, silicon and manganese are the most common additives, Aluminium alloys make strong, lightweight structural components. In common with MCH

26

o

( 1.4 x

Selfridges. Birmingham,UK.Architect: Future Systems

For comparison with other materials, aluminium alloys have the following general properties:

Material selection Pure aluminium and its alloys are in two broad groups:the non heat-treated alloys. also called fully softened alloys. whose

· Lightness, weighing about a third that of

strength is produced from being cold

steel.

worked. andthe heat-treated alloys whose

· High t ensile strength. similar to that of steel.

strength is produced by heat treatment.The

· High impact resistance. (compared to steel)

non heat-treated types are generally not as

· High corrosion resistance, but alu-

strong. but have better corrosive resistance.

minium requires protective coating in very

Structural useof aluminium alloys is

polluted or severe atmospheric conditions.

limited by two significant disadvantages: they

· Coatings are not applied solely for appear-

are more expensive t o manufacture than

ance.

steel andthey deform more easily under

· High heat conduction.

load.Aluminium alloys are more elastic than

· High electrical conduction.

steel.restricting their useto components

· Poor stiffness.

and assemblies where this is not a constraint.

· Low resistance to soft impact, but absorbs

Since the Young's Modulus of aluminium is

impact energy which localises damage.

one third that of steel, buckling is an impor-

(Whereas a soft.or low level impact, such as

tant issue in its structural use.The potential

a kick, would not damage a steel panel. it will

of this material as a full structural material

dent one in aluminium.

in buildings is beginning to be recognised.

· A high impact, such as a car reversing into

The Media Centre at Lord's Cricket Ground,

a panel. would cause a large steel panel to

London.England. is a recent notable example

buckle across its entire height and length, but

becauseof the full structural use of aluminium

one made of aluminium will again dent only

in a large-scale building frame.

around the impact area). · Thermal expansion approximately twice that of steel. · Poor fire resistance.

Working with the material On exposureto the atmosphere. aluminium forms a protective coating of aluminium oxide. Under adverse conditions.the oxide film can break down locally, but it usu-

MCH

27

Materials 0 I Aluminium

Iris Dome at EXPO 2000 in Hanover, Germany

OitaStadium, Japan. Architect:Kisho Kurokawa & Associates ally reforms to a greaterthickness preventing

treatment in the other alloy types.Since

and applying an electrical current,creating an

further attack.Aluminium can be exposed to

the design strength of the fully softened

oxide layer integral wit h the underlying metal.

the weather; in non-polluted environments

alloys is halfthat of the heat-treated types,

The anodic film is porous and must be sealed.

and awayfrom maritime conditions, without

the section sizes used in welded aluminium

This is done by immersing the anodised alu-

the need for additional treatment provided

structures can often be similar to that of

minium in boilingwat er or steam.The ano-

the surface is maintained. Over time, it loses

comparable steel structures, but wit h con-

dised coating can be dyed; the sealing then assists its colour-fastness. Anodising should

its initial bright appearance and assumes a

siderably less weight.The design strength of

dull grey sheen. Aluminium should be cleaned

the heat-treated alloys, which is similar to the

be carried out after welding.The process of

regularly to avoid pits forming in the material

bottom end of the design strength of steel,

welding would otherwise break down the

surface. However; one way to avoid this isto

can be exploited in extrusions, which require

anodising process at heat-affected locations.

anodise or paint the material with a propri-

no welding in their manufacture. Extrusions

Broken-down anodising could result in weld

etary coating.

can be usedto form complex profiles, such

impurities that would impair its structural

as those needed in window sections or walk-

effectiveness.

Aluminium is susceptible to electrolytic corrosion in contact with certain materi-

way decking, and be much lighterthan an

Aluminium's natural finish, often referred

als such as copper:Therefore direct contact

equivalent member in steel.The material can

to as mill finish, can be worked to produce

wit h copper and copper-rich alloys, such as

also be cast to form complex shapes that are

a polished, ground or brush-grained finish.

brass and bronze is avoided and the material

more economic in large quantities than an

Etching gives a matt and non-directional finish

should be used in a way that water does not

equivalentfabricated component.

with no direct refiections.Anodising gener-

fiow onto it from copper: However; water fiowing from aluminium to copper or lead is not harmful.There is no corrosive action

Anodising Anodising produces a fine translucent

ally follows these processes, which increases durability and enhances long-term appearance. Brightening is not suitable for architec-

between aluminium and zinc or zinc coat-

film over the surface of aluminium.The ano-

tural alloys which are only 99.5% aluminium

ings and galvanised surfaces. Some timber

dising process results in the replacement, by

because the brightening is not uniform.

preservatives contain compounds harmful

electrochemical means, of the metal's natu-

Chemical brightening on other alloys dis-

to aluminium. Untreated timber affects the

rally formed oxide film by a dense chemi-

solves and fiattens surface irregularities found

material to a much lesser extent.

cally resistant artificial film many times the

in extruded or sheetaluminium surfaces, and

thickness of its natural equivalent.This film

produces a mirror finish with a very high

Aluminium can be cut and drilled, riveted, bolted, screwed and glued.The material can

is extremely hard, gives added protection

refiectivity It can be anodised without dulling

also be welded. However; welding is usually

against abrasion,and reduces the adhesion

the surface.

done using the fully softened alloys, since

of dirt particles.Anodising is carried out by

this process can undo the work of the heat

immersing the aluminium in an electrolyte

MCH

28

Luigi Colani designs

Coatings Aluminium can be coated in a wide range of colours through the use of pro-

Recycling Aluminium is one of the easiest and cheapest materials to recycle. The conversion

prietary processes. Plastic coatings provide

of scrap backto high-grade metal requires

a durable paint surface; polyester powder

only about 5% of the energy needed to make

coating is one of the most common finishes.

the same amount of metal from bauxite.

Plastic coatings are dip-coated, sprayed or electrophoretically deposited underwater.The electrostatically applied finish ensures that an even coat is built-up on the metal.These paints fade and losetheir shine with time, though the change is slow and even. PVDF (polyvinylidene di-fluoride),also called PVF2 in Europe, and powder coatings are most commonly used. PVDF is a spray-applied finish, which is highly resistant

The Lightbox,Woking. UK.Architect: Marks Barfield Architects

to fading in sunlight, making it very suitable for external use where colour stability is an important consideration such as in wall cladding. Powder coating is applied in an electrolytic process that provides a softer. and less expensive coating than PVDF. It is not as resistant to fading in sunlight, but is a harder finish and less expensive, making it suitable for both an economic external finish and excellent for internal use.All these finishes have methods of touching up surfaces that become exposed or are damaged during installation or use, but colour matching remains an important consideration.

The Public.West Bromwich.UK,Architect:W ill Alsop

MCH

29

Materials aI Copper, zinc and lead

Copper cladding in use

Properties and data

(65.4 BTU/hr.ft.OF) Lead: = 35W/mK

Density :

(20.2 BTU/hr.ft.OF)

Copper = 8900 kg/m3 (560 Ib/ft 3) Zinc = 7 140 kg/m3 (445 Ib/ft 3)

Specific heat :

Lead = I I,340 kg/m3 (705 Ib/ft 3)

(0.093 BTU/lb OF)

o

Copper: = 390 j/kg C o

Zinc: = 385 j/kg C Tensile st rength:

(0.092 BTU/lb OF)

Copper = 2 16- 355 N/mm2 (4.5 x 105 to 1.0 x 106 Ibf/ft 2)

Lead: = 388 j/kg C

o

(0.093 BTU/lb OF)

Zinc = 139-216 N/mm2 (3.8 x 105 to 5.9 x 105 Ibf/ft 2) Lead = 15-18 N/mm2

Material selection

(3. 1x 105 to 3.8 x 105 Ibf/ft 2)

zinc and lead are the most widely used met-

Apart from steel and aluminium, copper, als in the building industryThese metals are

Copper claddingin use

You ng's Modulus : Copper = I 17-132 kN/mm2 (2.4 x 109 to 2.8 x 109 Ibflft2) Zinc = I 10 kN/mm2 (pure) (2.3 x 109 Ibf/ft 2) Lead = 15-18 kN/mm2 (3. 1 x 10 8 to 3.8 x 108 Ibf/ft 2)

produced as sheets of up to approximately one metre (3ft 3in) wide sections and castings. All three metals have excellent weatherresisting properties, however, they are susceptible t o attack by pollutants such as acids. Their use is restricted to non-structural metals and alloys, because none has the strength or rigidity of steel,or the combinat ion of

Coefficient of thermal expansion :

strength and lightness of aluminium.They are

Copper = 17 x 10- 6 K- I across grain (9.5 x 10- 6 OF-I ) Zinc =23 to 40 x 10-6 K-I (across

generally used as cladding materials for walls

grain) ( I2.8 x I0-6 to 22.5 x I0-6 0F- I) Lead 29.5 x 10-6 K- I (across grain)

wiring.

( I 6.5 x I0-6 0F- I)

Working wit h these materials

and roofs. Copper is also used extensively for water supply pipework and in electrical

Copper is stro ng in tension,tough and

MCH

30

Thermal conductivity :

ductile, but is not as malleable as lead.The

Copper: = 300 W/mK

material has a shiny red/yellow colour when

( 173 BTU/hr.ft.OF)

new, slowly developing a protective sulphate

Zinc: = 113 W/mK

layer on its surface when exposed to the

Zinc cladding in use

Copper cladding in use

atmosphere.This patina has a characteristic

Zinc is a durable material, although it is more

can be cut,drilled, nailed, welded in a proc-

green colour which has a fairly consistent

brittle than copper. It is manufactured as a

ess called leadburning,and soldered with

colour and texture. Copper is available with

white coloured metal, but when exposed

hand power tool s. Due to its lackof rigidity,

a pre-weathered, or pre-patinated finish

to the atmosphere a carbonate is slowly

lead sheet is most commonly jointed by

which is chemically induced.This finish varies

formed which produces a protective coating

dressing it over rounded timber battens or

slightly from naturally weathered cladding.

that isgrey-white in colour. The material has

rolls.W here standing seams are used, they

Well maintained copper cladding, which has

a linearthermal expansionthat is similar to

often incorporate a steel angle to keepthe

oxidised atmospherically, will lastfrom 30 to

lead and higherthan copper.

line of the joint straight and vert ical. Lead is

50 years.

Zinc can be cut,drilled,nailed, welded

There is a variety of copper types avail-

and soldered wit h hand power tool s, mak-

alloyed with tin to form solders for jointing and sealing.

able, each of which is suitable for a particular

ing it reasonably versat ile for use on site. Its

task. For instance, deoxidised copper is suita-

rigidity makes it well suited to standing seam

ble for welding, while fire-refined tough-pitch

joints. W ell maintained zinc cladding can last

copper; with its tougher resistance to cor-

for between 30 and 50 years. Zinc is liable

other;rainwater running from one to the

rosion, is used for cladding. Otherwise, both

to attack from copper alloys, so that rainwa-

other can cause corrosion by electrolysis.

have similar properties. Copper forms a high

ter running off copper should be avoided.

Run off from copper and zincwill attackcast

proportion of metal in alloys such as bronze,

Apart from its use in alloys, zinc is used as a

iron, mild steel, galvanised steel and alumini-

which is primarily a mixture of copper and

protective coating to steel, applied through a

um. In addition, copper will attack zinc. Lead

tin. Brass is primarily a mixture of copper

process of galvanising and sherardising

is much more resilient and does not attack

and zinc,and aluminium bronze is primarily

Lead

is an extremely durable,ductile

Electrolytic action W hen different metals are near each

other metals wit h the exception of alu-

a mixture of copper and aluminium. Cop-

and malleable material, making it extremely

minium when used in marine environments.

per can be cut,drilled, nailed, welded and

useful for roof coverings and flashings in

W hen roofs or walls are made from either copper or zinc, typically other metals are not

soldered with hand power tools, making it

traditional roof construction. However; while

versat ile for site-intensive work.W hen used

its relative softness allows lead to be formed

usually used in adjacent components, such as

as cladding,joints between sheets are made

into complex shapes, its lackof rigidity

gutters and flashings,where wat er run off is

by foldingthe edges together.This method

means that a supporting material must be

likely to occur.

takes advantage of the fact that copper can

provided beneath it.Timber boards are most

be bent alongan edgefairly easily, but is rigid

commonly used for this. Lead has low resist-

enough to remain folded.

ance to creep.

Zinc

sheetfor cladding is made from

On exposure to the atmosphere,a pro-

either commercial zinc orfrom an alloy of

tective coating of lead carbonate is slowly

zincwith small amounts of copper and tita-

formed on its surface.This gives weathered

nium added.The properties ofthe two types

lead a dull grey appearance . Lead is a poi-

are similar;but zinc alloy has better tensile

sonous material, leading to increased aware-

strength and resistance to creep, which is

ness of the dangers of water run off from

long-term plastic deformation under load.

lead cladding reaching the water supply. Lead

MCH

31

Materials 0 I Tectonics in glass

Paris Metro station canopy, Paris, France.Architect: Hector Guimard

An essential use of glass in buildings is

Paris Metro station canopy, Paris, France.Architect: Hector Guimard

opportunities for designers to use large

ing importance of thermal insulation and a

glazed panels in facades. However, since

reduction in the energy consumed to temper

most glazing is made in double glazed units,

the internal environment of buildings, the use

glass panels do not often achieve these sizes

of singleglazing with thin supporti ng frames

due primarily to issues of deflection under

without thermal breaks, is no longer used

wind load and the dead weight of the glass.

in most new buildings except where, for

A 3000mm wide double glazed unit, storey

example, the spaces enclosed by the glass are

height, weighs around 6S0kg, making it diffi-

considered to be external and serve only as

cult to lift into place using conventional lifting

canopies, or in the outer screens to double

systems for glazed units and even more dif-

facades. In these semi external applications,

ficult to consider moving it around by hand.

the visual lightness afforded by lightweight

Double glazed unit s of half their size can be

steel supporting structures can still echo t he

difficultt o manhandle on site. In addition to

glazed structures of t he early 20th century,

the weight of glass, its size is an important

such as the canopies to Metro stations in

consideration when designing wit h the mate-

Paris by Hector Guimard.Theses canopies

rial. The six metre by three metre sheets,

have glass panels which have no support

called 'jumbo' sheets, are required to be cut

on the outer edges,allowingthe supporting

economically to avoid waste.This makes glass

metal structure to take precedence.This pref-

economic for the ISOOmm wide panels pre-

erence for the expression of the supporting

ferred in office buildings, but does not restrict

structure at the visual expense of the glass

their cutting to rectilinear panels.Triangular

has been a theme in glass tectonics through

panels can also be economic if cut without

the 20th century In the Guimard canopies,

significant waste, as can other shapes which

covers for lights to illuminat e the entrance

frt the jumbo sheet format.

32

In wall construction, where glass is used

ing structure being almost a container for t he

in most quantity in most buildings,the mate-

exquisitely formed lamp covers.The use of

rial is fixed either along its edges or at point s.

glass and metal is finely balanced both t echni-

The use of edge restraint results in a frame

cally and visually,though the richness of the

behind all glass edges, but point fixed glazing

forms were only gradually accepted as being

allows the material to become visually domi-

of architectural merit.

nant,allowing it to be seen almost as a con-

Glass is manufactured in sheets of float

MC H

laminat e glass at this size, providing more

in double glazed units.With the increas-

have a form of their own, with the support-

Bilbao Metro entrance, Bilbao,Spain.Architect: Foster & Partners

Paris Metro station canopy, Paris, France.Architect: Hector Guimard

tinuous plane of glass rather than as an infill-

glass approximately 6000mm x 3000mm,

ing material. The glazed screen in the Dancing

which is typically much larger than can be

House by Frank Gehry in Prague, completed

used as single sheets in buildings. Some

in I996.This contrasts with the use of glass at

glass manufacturers are ableto temper and

Federation Square by Lab Architecture, com-

187 - 195 Oxford Street,London, UK.Architect: Future Systems

Swiss ReTower, London, UK.Architect: Foster& Partners

pleted in 2003, where the supporting frames

reducetheir U-value andto reduce solar

dominate as the language of the tectonic,

gain.This makes double glazed units increas-

with the glass as an infill material. An advan-

ingly energyefficient. and the introduction

tage of the framed approach is economy, as

of argon gas into the void between the glass

the double glazed units can be fitted directly

panels further increases their thermal per-

to the supporting frame. Bolt fixed glazing

formance.When used in curtain walling,the

requires the glass to be drilled before any

framing is typically much poorer in thermal

tempering is done, making it expensive to

performance, bringing the U-value from a

use, though recent examples use bolt fixings

typical 1.1 W /m2K up to a typical 2.0W/m2K,

that are bonded to one face of the glass, or

depending on the framing type.The thermal

drilled through only one sheet of the double

break in curtain wall systems is a structural

glazed unit.An alternative approach isto

component at present. so finding a much

clamp the glass by passing plates through the

higherperformingthermal break is not with-

joints between the units. Consequently, the

out its difficulties. In very cold climates, triple

design and position of the clamps becomes a

glazed units are being introduced, though

primary issue in the design of the system as

there is still a limited condensation risk at the

the visual impact of a surface covered with

edges of the unit where the perimeter spac-

small clamps creates a kind of'point cloud'

er conducts greater amounts of heat energy.

of fixings across the surface of the glass wall

A development over the past 10years has

or roof

been in the introduction of so-called 'super

The curving of glass has undergone some

neutral'glasses in double glazed units which

development. at leastin the quality of pro-

have high solar control performance com-

duction,in recent years. Specialist companies

bined with higherlevels of transparency than

around Europe now offer single curved glass

was formerly the case with so-called 'body

panels in both tempered and laminated glass.

tinted' glasses. Superneutral glasses have

Some companies around the world will now

a colour which is visually not as strong as

provide double curved panels, as used at the

the older generation of body tinted types,

Nordpark Cable Railway in lnnsbruck, Austria,

though these are still available. Superneutrals

which form a durable and reflective surface

allow more daylight transmission than their

finish for canopy enclosures.The ability of

forerunners, but in locations where there is

glass to be curved, coated andtempered is

considerable exposure to the effects of the

making it more of a sculptural material again,

sun an additional outer screen of solar shad-

following in the tradition of the Guimard

ing panels might be used.

Metro entrances. The useof glass in double glazed units

Dancing House Prague, Czech Republic Architect: Frank Gehry

A recent development in glass design has been the introduction of all-glass structures,

allows the encapsulated inner faces of the

where glass components are connected

glass to have coatings applied to them to

together by silicone bonds.The silicone

Dancing House Prague,Czech Republic Architect: FrankGehry

MCH

33

Materials 0 I Glass

Federation Square, Melbourne, Australia, Architect: LAB Architecture Studio

Federation Square, Melbourne, Australia. Architect: LAB Archit ecture Studio

Nordpark Cable Railway.lnnsbruck .Architect:Zaha HadidArchitects

serves as both adhesive and sealant, provid-

ment across the extent of the walls. Some

ing weathertight enclosures.The scale of use

projects, particularly for glazed roofs, have

to date has been modest, with single storey

used a large number of glass panel sizes in

conservatories,walkways,canopies and glass

order to suitthe structural geometry of the

floors as the primary examples of their use.

roof form, but these are typically quantified in

Mostapplications have additional mechanical

detail by the design team in order to control

fixings to overcome concernsabout the long

cost.

term durability of all-glass structures, but this

A recent alternative to the curving of

varies from projectto project. An alternative

glass as part of the manufacturing process

to the all-glass structure is the cladding of

has been to 'cold bend' glass sheets on site,

conventional structures or walls in opaque

typically as part of a stick (site assembly

rainscreens.This method uses screen printed

based) glazing system.The amountsto which

glass which istypically silicone bonded to a

the glass can be pushed at the corners to

backing frame ,then hooked on, or fixed back

take up a curved form across its surface is

to, a carrierframe behind.This use of glass

limited, but curves in glazed walls and roofs

as an external rainscreen allows the void

are often modest, making the idea of cold

between the glass and the external face of

bending more attractive to contractors.

the backing wall to have lighting, creating a glow to an otherwise opaque or utilitarian facade, with the benefit of creating some lighting for safety of users around the building.

The manufacture of float glass is the first stageof production. Float glass is made by

One of the main changes in the use of glass in facades and roofs is a gradual move

Federation Square, Melbourne, Australia. Architect: LAB Architecture Studio

Production process of raw material

pouring molten glass onto a bath of molten tin.The glass floats on top and is drawn offas

away from entirely rectilinear glass panels to

it solidifies. It is available in thicknesses ranging

those that deviate slightly from it.These can

from 2mm to 25mm (I/8in to Iin).

rangefrom parallelogram shapesto triangular

Most float glass has a green tint caused by

to diamond patterns in glazed facades, but

small amounts of iron oxide in the glass.Add-

all are based on the need for repeatability

ing different oxides to the mix during the

of glass unitsize in order to make the glass

manufacturing stage can alter the tint of the

economic to manufacture. In addition, glazed

glass.

walls are required to move in relation to their supporting structure, and must be able to move from one panel to the next.This further encourages the panels to be of the same size in order to ensure that the movements have a consistent 'behaviour' of moveMCH

34

Properties and data

Density: Float glass = 2520 kg/m 3 (158 Ib/ft3) Tensile strength: Float glass = 35-55N /mm 2 (7.4 x 107 Ibf/ft2)

Nordpark Cable Railway. Innsbruck .Architect:Zaha HadidArchitects

Compressive strength:

=

3800--4670 N/mm2

Glass block sizes for external walls:

Float glass ( 1.0 x 107 to 1.2 x 107 Ibflft 2)

(8in x 8in x 4in thick (imperial)

Young's Modulus:

146 x 146mm (nominal 6in x 6in)

Float glass 70 kN/mm 2 ( 1.4 x 109 Ibf/ft 2)

197 x 197mm (nominal 8in x 8in)

Coefficient of thermal expansion 23 x 10- 6 K-I (12.8 x I0- 6 F-I)

Typical thickness 98mm (nominal 4in x 8in)

=

=

Thermal conductivity

=

0

190 x 190 x IOOmm thick (metr ic)

197 x 95mm (nominal 8in x 4in)

Glass block sizes for internal partitions

0.7-1.1 W /m C (0.4 BTU/hr.ft.OF)

120 x 120 x 40mm (nominal 6 x 6 x I

Specific heat capacity

3/4in)

o

=

820-995 J/kg C

and

(0.19 - 0.24 BTU/lb OF)

200 x 200 x 50mm (nominal 8 x 8 x 2in).

Approximate and easily available maximum

The characteristics common to

glass sheet sizes

different glass types are:

I) Float glass

·Variable tensile strength.

Maximum size 3180 x 6000mm ( 125in x

· It is proneto fracture resulting

235in)

from tiny cracks or imperfections.

for thicknesses from 2mm to over 25mm

Cityof Arts and Sciences, Valencia, Spain.Architect: Santiago Calatrava

Oriente Station Lisbon, Portugal Architect:SantiagoCalatrava

·Variable impact resistance. · Non-corrosive.

2) Clear toughened glass

· Non-combustible.

Maximum size 4200 x 2000mm (165in x

· High heat conduction.

80in) for thicknesses from 6mm to 12mm

· Low thermal expansion.

The City of Arts and Sciences inValencia,Spain Architect:Santiago Calatrava

3) Laminated glass Maximum size 3180x4200mm ( 125in x I 65in) for thicknesses from 4.4mm to

Material selection Heat soaked glass is made by re-heat-

9.8mm (31 16in x 3/8in)

ing float glass then cooling it quickly, which

4) Rough castwired glass

putsthe surface of the glass into compres-

Maximum size 3700 x 1840mm

sion and removes impurities such as nickel

( 145in x 72in) for thickness 7mm ( I14in)

sulphide.W hen broken,fully toughened glass

5) Polished wired glass

disintegrates into tiny, comparatively harm-

Maximum size 3300x I830mm

less, pieces. Its strength, measured in terms

( 130in x 72in),thickness 6mm ( I14in)

of impact resistance, is up to five timesthat

6) Body tinted float glass

of float glass.The tougheningprocess can

Maximum size 2540 x 4600mm ( I OOin x

produce minor distortions in the glass, usually

180in) for thicknesses from 6mm to 12mm

caused by roller marks. Heat soaked glass is

City of Arts and Sciences ,Valencia,Spain Architect:Santiago Calatrava

MCH

35

Materials 0 I Glass

Oscar Niemeyer Museum, Curitiba, Brazil. Architect: Oscar Niemeyer

Lyon-Satolas TGVStation, Lyon, France.) Architect: Santiago Calatrava

a partiallytoughened glass for usewhere full

to the rise in temperature to provide a

toughening is not required or as part of a

degree of insulation against radiant heat.

laminated glass construction.

Variable or switchable transmission glass is a new form of treated glass.Though

Laminated glass

Nordpark Cable Railway, Innsbruck .Architect: Zaha Hadid Architects

is made by bonding

two or more sheets of glass together with a

expensive,it aims to reduce internal heat loss

film of plastic in between, called the interlayer.

from inside as well as to reduce solargain. It

The interlayercan be clear or translucent,

is able to change its own thermal and light

and is available in a wide range of colours to

transmission performance by means of an

create effects of colour in the glass that are

electrical signal. In many applications, it turn s

translucent in a way which is different from

from transparent to an opaque whit e when

the screen printing of glass. When broken,

an electric signal is introduced.Applications

laminated glass staystogether in a single

include glazed partitions in office buildings.

piece due to this bondingbetween the lay-

, ""

Glass blocks can

be solid or hollow.

ers. This makes it very useful for glazed roofs

Solid blocks are used as paving for floors.The

and for glazed screens which are set forward

hollow type is used for walls and consists

of glazed facades. However, after the initial

of two half-bricks fused together to give a

impact, laminated glass will eventually fall

smooth appearance on both faces.

away as dangerous fragments of glass, so it is

Glass can be mounted in double- and

required to be replaced as soon as possible,

triple-glazed unitsto provide greaterther-

with the floor areabeneath the broken pan-

mal insulation and sound insulation than is

els typically being secured to avoid the risk

achieved by an equivalent single sheet of

of injury to those below. Combiningseveral

glass. An insulated unit can be a mix of float,

laminates together in one sheetcan make

laminated or other glasses.To improve ther-

anti-vandal and even bullet resistant glass.

mal performance, the air gap between the

Wired glass

is made by sandwiching a

layers can be evacuated to create a vacuum

steel wire mesh between two layers of glass,

or be replaced wit h a low conductivity gas

which are then rolled flat.The wire holdsthe

such asargon.The maximum size of double

glass together for a period of time during a

glazed units is determined by the maximum

fire and so prevents the passage of smoke

sizes of glass types used. However, the size

from one sideto the other.The roughcast

of unit is usually determined by windloading

product can be polished to provide a more

rather than maximum glass sizes.

transparent finish.Wired glasses cannot be toughened and are not regarded as safety products.

Fire resistant glass is formed by glass Metropolitan Cathedral, Brasilia, Brazil. Architect: Oscar Niemeyer

MCH

36

Worl-

I

CD

~

CD -


= Vert ical sectio n I : I0, Base upstand, Junction w ith adjacent mat erial

Vert ical sectio n 1:5 through roofiight showing t ypical details

CD

System design The method of silicone bonding glass to

be extremely difficult to fabricate, The rec-

in glazed curtain walling to provide visually

tangularroofiight shown is bonded together

smooth glass facades with no visible cap-

without a supporting structure; the glass pro-

pings, The use of silicone sealed roofiights

vides its own support. The fiat monopitch

can be taken a step further to become a full

roofiight is bonded to a frameto provide

bond without the need for the mechanical

a small roofiight from one double glazed

restraint of pressure plates, In silicone bond-

roofiight, with laminated glass sheets used to

ed roofiights, the glass is glued to a support-

fonm a surface which can be walked upon.

ing frame, The glue is also the extemal seal.

Similar to a glass fioor used inside a building,

This technique is useful for small roofiights,

it must also take heavier traffic loadings and

where cappings would be very difficultto

be weathertight.

238

The generic conical roofiight shown has

upon, where the roofiight is an extemal glass

a lightweight steel frame used to support

floor,

double glazed unitsthat fonm a roofiight.

The generic conical roofiight shown has

MCH

both vertically and horizontally, which would

aluminium framing is well developed for use

fabricate, and in roofiights which are walked

3-D Details showing glassto glass junctio ns

cover caps that would have to be curved

The structural frame comprises box sections

curved double glazed units bonded to an

set vertically, held in place by thin tube sec-

aluminium frame, Silicone bonding avoids

tions running horizontally to fonm a circle,

3-D view of glass beam with central steel support beam

3-D view of underside of glass beam and ste el suppo rt beam 111111111111111111111111111111111111111111111111111111111111111111111

~ ' /-

Vertical section I: IO. Support systems for roofii ght

" " 0"'1

3-D det ail of st eel support beam

"v' The glass panels are supported on steel fi at sections which are welded to the horizontally set tube section. The glass is levelled on

is constructed without a supporting frame.

blocks set onto the horizontal fiat section,

Mechanical restraint is provided at the

and the si licone is applied to the joint. At the

comers in t he fonm of pressure plate clips.

base, the horizontal metal section projects

The double glazed units at the corners are

out to fonm a fiash ing over the upstand in

fabricated with a recessed groove on the

which the roofi ight is set. An additional inner

two sides of the panel fonming the corner

metal upstand can be provided with another

in order to receive the clip. An alternative

si licone seal ifthere is risk of future flooding

method is to fix the metal clip to the outside

from blocked rainwater outlets, for example.

of t he glass at the comer. This avoidsthe

The waterproof membrane for the roof slab

need for special ly made comer pieces but it

is continued up the upstand and is bonded

does fonm a visible fixing. The modest size of

to the base of the horizontal section that

this roofiightallows the horizontally-set glass

supports t he glass. This provides a complete

to span from side to side with no additional

"

@ ~

" "

top of the wate rproof membrane. The generic rectangu lar roofi ightshown

"

@

". '1

Vertical sectio n I : IO. Junctio n with adjacent w all

~ @

@ Ire:::

~

1

0

~ ~~

re:::

seal from the glass to the roof membrane,

support. The comers of the roofl ightare

with the metal flashing providing both a pro-

stiffened by short lengths of pressure plate

tection to this seal and a means of conceal-

which holdthe glass in place. The glass has a

ing the closed cell thenmal insulation set on

specially shaped groove in the depth of the

@

Vertical sectio n I: IO. Bracket support

MCH

239

Roo~03 Glass roofs 4: bonded glass rooflights

I

0 .

-

-

--

---,

o l:D

0)

0)

8)

I

0)

I

aJU3

11 r-

r

0)

1°

Vertical section I:10 through bonded glass roof light showing typical details

0

I

1"",

f-

0) 0)

CD

CD

o Vertical section 1:5. Typical comer detail

0)

Horizontal section 1:5. Typical comer detail

Vertical section 1:5. Bonded glass to glass connection

Vertical section I:5. Typical connection to roof

double glazed unit, to which the pressure

decking is in development and will no doubt

upon the individual design. Here steel plate

platesare fixed. Comer joints have an outer

become much more common over the next

is used to provide a beam instead of lami-

comer piece of folded aluminium which is

10years.

nated glass, a steel flat is welded to the top

silicone bonded either to the face of the

The glass used is laminated, in common

of the beamto fonm a T-section that gives

adjacent glass units, or is folded at 90° to

wit h other rooflights, both to avoid the pos-

enough bearing for the glass deck. The ends

bond it to the side of the unit. Glass-to-glass

sibility of any falling objects from penetrating

of the glass beams are supported by a metal

joints between horizontally-set units have a

the glass on impact, as well as preventing

shoe support, made from either mild steel

silicone seal wit h an aluminium angle set on

damaged glass from falling immediately into

or aluminium. Stainless steel is used where

the inside face to provide a second seal.

the space below. The glass is set into a series

conrosion is an essential consideration of the

of extruded aluminium anglesto which it is

design. The metal shoe is bolted backto the

bonded on its underside. A gap between the

supporting structure or reinforced concrete

System details

frame and the top of the glass is sealed wit h

floor slab. The gap between the edge of the

accessible roof decks have been in use over

silicone of a different type. An additional

glass deck and the adjacent roof finish mate-

the past 10years. Previously used only

condensation channel is set below the glass

rial is madewith a silicone seal.

inside buildings for walkways and stairs, they

to catch any water that penetrates the sili-

are now beingused as fully waterproofed

cone seal, or any water that passes through

external decks, manufactured as proprietary

a damaged joint.

Rooflights fonmed as nominally flat,

systems. Single glazing is used, since double

The details here show altematives for

glazed units are difficult to use asa result of

both steel beam and glass beam supports to

solar gain around the edge of the unit, where

the glass panels. A typical rooflight is shown

the glass is exposed to the outside, but is

with glass panels 2400mm x 1200mm in size.

supported on its underside, allowing heat to

The supporting structure has a glass beam

enter but not to escape. W here blackcol-

set in the centre, spanning the full length of

oured edge 'frittiog' is used, the situation is

6000mm. Its depth is approximately 600mm,

made difficult. However, double glazed roof

but the beam depth will vary depending

MCH

240

3-D cutaway of t ypical com er detail

3-D cutaway of t ypical rooflight assembly

3-D cutaway of t ypical junction w ith roo f

ED

3-D detail of connection between glass beam and concret e w all

3-D det ail of junction betw een glassand steel support beams

3-D view looking up at int erior finish at edge of glassbeam and concrete base

Details I Silicone bon d 2. Mild steel support frame 3. Single glazed laminated glass panel 4. Silicone seal 5. Concrete base 6. Insulated metal panel 7. Folded metal flashing

8. Reinforced concrete support frame 9. Folded almunium protective cover 10. Steel aluminium support shoe I I . Structura l glass beam

3-D view of junction at edge of glassbeam and steel support

MCH

24 1

Roofs 03 Concrete I: co ncealed mem brane

3-D overview of a concrete roof w ith a concealed membrane

Det ails I. W aterproof membrane 2. The rmal insulation 3. Co ncrete de ck 4. Paving slabs 5. Smoo th pebbles 6. Parapet cop ing 7. Rainwater o ut let 8. Slot dra in 9. O pen ing for overf ow

System design Bitumen hastraditionally been used as a

dimensional stability andtensile strength.

of the building. An outer protective layer

wat erproof layer, applied while hot in liquid

This reinforcement often allows the mate-

is added for vulnerable locations such asat

fonm onto a concrete roof slab. As it cools it

rial to be folded through 90°, making its use

gutters and at upstands.

hardens, fonming an impervious membrane,

considerably easier, where angle fillets are

but will soften again if heated by the effects

not required.

of solar radiation. For this reason, in order to

With the development of much thinner

System details Concealed membrane roofs are typi-

keep the material cool, bitumen membranes

membranes in thenmoplastics and elastom-

cally in 'inverted' roof configuration with

are concealed by smooth pebbles or pav-

ers, together wit h their competitive costs,

either open joints or sealed joints in the

ing slabs, usually wit h thenmal insulation set

there have been considerable efforts made

top layer that coversthe thenmal insulation,

between the bitumen andthe pebbles or

by manufacturers over the past 20 years to

usually paving. In the open joint version, the

paving. Traditional bitumen roofs are usually

makethe bitumen layers thinner,to reduce

membrane, bonded to the concrete slab, is

laid in two layers, with an overall thickness

the material required while enhancing its

covered by a protection layer, with closed

of around 25mm. One of the limitingfac-

properties of strength and flexibility. This has

cell, rigidthenmal insulation set on top . A

tors with bitumen is foldingthe material at

been achieved by replacing the thick two-

polyesterfilter sheet is set on top, wit h pav-

a comer or edge. W hen the material tums

layer method wit h a mixture of thin layers,

ing or smooth pebble ballast on top to hold

through a right angle from the horizontal

still applied in hot liquid fonm on site, but

the insulation in place as well as to walk on.

roof to a vertical parapetwall, it can pass

reinforced wit h an elastomeric sheet, usually

Pebbles are 20mm - 40mm diameter, while

through a maximum of 45° in a single fold.

bedded between the layers. This is typically

paving slabs are around 600 x 600mm in

For this reason 45°angle fillets are used to

two layers, each 3mm thick with reinforcing

size and 30 mm - 40mm deep. In the sealed

make a 90° tum from roof to wall.

layers bedded into the material. This allows

joint configuration, the bitumen membrane

the bitumen to accommodate both small

with its protection layer has a drainage layer

are concealed beneath roof finishes are typi-

amounts of movement at these junctions, as

on top, onto which is laida minimum 65mm

cally a combination of bitumen-based sheet

well as the sharp fold in the material, which

sand/cement screed, usually reinforced or

mixed wit h synthetic rubber to give flex-

creates a weakness in the membrane which

made sufficiently thick to avoid cracking both

ibility combined with a reinforcement to give

might otherwise be damaged duringthe life

in the screed and the sealed paving above.

Modem bitumen-based membranes that

MCH

242

CD

CD -- --c.!F - -' -CD

CD

Ve rtical section I:10. Rainwater o utlet

3-D detail of rainwate r outlet

CD 3-D view of parapet and rainwater out let

-,

--

--'

:

,, J

.

CD '(

Vertical section I: I0 , Parapet and rainwater o utlet

MC H

243

Roofs 03 Concrete I: concealed membrane

3-D detail of concrete upstand

Persistence W orks, Sheffield, UK. Architect: Fielden Clegg Bradley Studios

Vertical section I: IO. Concrete upstand

Paving slabs or blocks are bonded to the

bitumen based material, or increasingly, a

screed with mortar and grouted.

rubber-based strip.

Expansion joints between concrete Vertical section I: IO. Junction of extemal wall and roof slab

slabs of widths between around IOmm to

as possible with the adjacent areas of roof

50mm are fonmed by stopping the material

to allow water to drain freely from the roof.

each side of the joint and setting a rubber-

The reinforcing membrane is sometimes

based strip that dips into the gap between

folded down into the gap, separat ed from

the slabs, linking the membranes into a

the membrane below wit h a foam backing

continuous seal. The joint is protected and

rod. It can be difficultto drain water from

reinforced with an additional layer, either

this groove at the edge of the slab unless

fiat and bonded on one side only, or fonmed

water at this lower level can discharge into a

as a folded, S-shaped cover that folds back

rainwater outlet.

over itself, held in place by an additional

CD- - - Vertical section I:IO. two-way drain outlet

MCH

244

The top of the joint is finished as level

In fonming parapet upstands, an essen-

protection sheet on top . The gap between

tial requirement is t o keep the waterproof

the membrane, dipped into the joint, and

membrane as well protected from the

the reinforcement cover is filled with a foam

effects of the sun as elsewhere on the roof.

backing rod or tube, as used in the glass

For this reason, thenmal insulation is applied

joints of bolt fixed glazing. The material used

to the inside face of the parapet, even if

for the reinforcement is either the same

this has no direct benefitto the passage of

CD

CD

3-D detail of ballustrade w it hin ro of system

3-D detail of roo f parapet

/)-_ _----'.c=-=..::"--_

CD Vert ical sect ion I : IO. Expansion joint in concrete slab

3-D det ail of ex pansion joint in concret e slab

heat th rou gh t he building. Th e membrane

of the waterproofing layer. T he base of the

is t umed through a full 90° as shown in th e

rainw ater outlet is fixed to the concrete slab.

drawings. but an angle fillet is required by

The w at erpro of membrane is dressed dow n

so me manufacturers t o limit t he angle of

int o t he top of the rainwater outlet and the

any fo ld to 45°. A reinforcing strip is usually

upper part of the rainwater outlet is bolted

added where a 90° fold is made.

down onto the part already fixed and sealed.

Plint hs which are fomned as short col-

CD Vert ical section I : IO. Parapet detail

The geotextile sheet is wrapped around t he

umns for the support of roof-mounted

outl et to avoid dirt and debris being washed

mechanical equipm ent or balustrades are

int o t he rainwat er drainage system.

wate rproofed in a similar way to a parapet upstand. The membrane is fold ed up t hrou gh 90° fro m the roo f level and is

J.

-·,, 0-

fomned t o cover the complete plinth . Th e themnal insulation extends across the complete plinth to prevent a themnal brid ge through the roof constructi on.

CD

CD

Rainwat er outl ets are set at t he level of t he wate rpro of membrane . drained at both

Ve rt ical section I : IO. Base of balustrade

the level of the sealed paving and t he level

MCH

245

Roofs 03- - - - - - - - Concrete 2: exposed membrane

3-D overv iew of concrete roof with an exposed memb rane

System design wide range of exposed membrane materials

with ballast to the concrete deck beneath.

for flat roofs which are not visible from

Exposed membranes have been used

available to suit different budgets and indi-

Developments in these materials have led to

below, but this has changed in recent years

vidual roof designs.

them being used on timber decks and pro-

as membranes are produced in increasingly smooth and regularfinishes. Because of their

Polymer-based membranes have the main advantage of an abilityto be cut and

filed metal decks in addition to the concrete decks discussed here. Both thermoplastic

lightweightnature, they are often used in

formed to complex shapes, allowing them

and EPDM membranes can be welded

conjunction with lightweightroofs such as

to take up shapes precisely. sometimes pre-

together to form a continuous waterproof

profiled metal deck and timber. This section

formed in the factory before being delivered

sheet. While both material types were glued,

considers their use in concrete construction,

to site. Single layermembranes are very

there is an increasing use of hot air welding

though the same principles of waterproofing

practical on roofs with a large number of

methods, which avoidthe need for flame

can be applied to these other materials.

penetrations, typically in commercial build-

techniques or adhesive bonding methods

ings where mechanical ventilation equip-

that can be both slow and can damage adja-

ment is regularly being modified or replaced

cent work duringtheir application. In hot air

The introduction of polymer-based membranes provided economic waterproofing materials that are more flexiblethan their

duringthe lifetime of a building. Single layer

welding, a jet of heated air is used to soften

bitumen-based predecessors. The increased

membranes are made from either elasto-

the materials and weld them together,

flexibility of the new sheet materials allowed

meric materials, typically EPDM, or from

applied from a range of tools that are either

for greater amounts of movement between

thermoplastic materials, typically plasticised

hand held or fully automated, depending on

adjoining components and assemblies, allow-

PVC (PVC-P). Elastomeric materials are

the application.

ingthe detailing of junctionsto be relatively

very popular in the US while thermoplastics

straightforward in forming a reliable weath-

are preferred in Europe. EPDM (ethylene

fibre sheetor polyesterfabric. These lay-

ertight roof membrane. As a result of these

propylene diene monomer) is a flexible and

ers are bonded into the material. The glass

developments, polymer modifications were

elastic material that has the appearance of a

fibre provides dimensional stability, making

also made in the earliergeneration bitumen-

synthetic rubber. EPDM is manufactured in

it more stable for bondingto the substrate.

based materials to makethem more flexible,

the limited colours of black, grey and white.

The woven polyesterfabric, used in tent

in order to compete with the polymer-based

Both elastomers and thermoplastics can

sheet materials. As a result there is now a

MCH

246

be mechanically fixed, bonded or secured

Membranes are reinforced with glass

membrane structures, has hightensile strength to resist wind loads.

Details I.Waterproof membrane 2. Thenmal Insulation

3. Concrete deck 4. Paving slabs 5. Smooth pebbles 6. Parapet coping 7. Rainwater outlet 8. Opening for overflow 9. Balustrade 10. Pipe or duct I I. Extemal wall 12. Rooflight

Tenerife Concert Hall, Spain. Architect: Santiago Calatrava.

(( r:

tiIf( (-r-n

.J.J.J .JJ~'~'.J.JJ

Vertical section I:10. Pipe penetration

3-D detail of pipe pentration.

@

'0 I

,

.-: _) .J :-- :,; ~-

r

r

~

_J

.J .J j

- r '-;

-- .J

-

)

r') '-

J

,

.J

- :J

Vertical section I: I0 Junction of extemal wall and roof slab

3-D detail of junction between roof slab and extemal wall.

MCH

247

....----Roofs 03- - - - - - - Concrete 2: exposed memb rane

Vertical section I: IO. Rainwate r outlet (ballust ed met hod)

3-D detail of rainw ater out let w ithin exposed membrane roo f

Verti cal section I: IO. Rainwat er outlet (bonded metho d

place. The pressure plates are fixed by bolt s

systems still bond the membrane at points

membrane is a concrete deck with a vapour

A typical build-up for a single layer

at centres along their length to the substrat e

only rather than across the entire surface of

barrier set on top, with thermal insulation

below.

the membrane, but this is dependent upon

above that, sealed on top with a single layer membrane. PVC-P membranes are typically

the wind load and the proprietary system

System details

used.

I.Smm - 3.0mm thick, while EPDM mem-

Membranes can also be secured by

Bonded membranes have a visually

branes are typically I.Omm - l.5mm thick.

point fixings rather than by pressure plates.

smooth appearance, making them suit able

SO-7Smm diameter rigid plastic discs are

where the roof surface is seen from points

used to hold the build-up in place. These are

around the building. This fixing method still

The mechanically fixed method is suit ed to applications with high wind uplift forces, as bonded systems tend to be limited by

set at centres to suit the design wind loads.

requires mechanical fixing at the edges, and

the bonding strength of the vapour barrier

The closed cell rigid insulation istypically

around openings such as rooflights.

to which the membrane is itself bonded

made in panel sizes of 1200mm x 2400mm

through the thermal insulation layer, which

in thicknesses from 2Smm to IOOmm.

is typically made from expanded polystyrene

Membranes can be bonded or mechanically fixed to parapet upstands. The fixing

In the bonded fixing method the

method that is used on the main area of

board. The vapour barrier is loose laid on

exposed membrane of the vapour barrier

roof is usually continued on these vertical

the concrete deck and thermal insulation is

is usually bitumen-based and is bonded to

areas. W ith mechanical fixing t he pressure

then mechanically fixed through this barrier

the deck.Joints betw een the vapour bar-

plate can be fixed either to the upstand

to the deck beneath. The spacing of the fas-

rier sheet s are lapped t o avoid any risk of

or to the flat roof area. The pressure plate

teners varieswith the design wind loads. A

vapour passing through the roof structure

forms a junction between the membrane

separating layer of glass fibre sheet is usually

from inside the building. The thermal insula-

sheet forming the upstand andthe mem-

laid onto the insulation with an outer single

tion is then bonded t o the vapour barrier.

brane sheet of the roof Intermediate pres-

layer membrane. The membrane is mechani-

Insulation can also be mechanically fixed

sure plates are applied horizontally on the

cally fixed wit h pressure plate bars, similar to

with pressure plates to the concrete deck

upstand when its height exceeds around

tho se used in glazed curtain walling systems

beneath. The membrane is then bonded

SOOmm, depending on the specific material

to hold t he glass in place. Bars form strips of

to the insulation with a continuous layer of

used.

pressure plate to hold the roof build-up in

bonding adhesive on its underside. Some

MC H

248

Canary Wharf underground stat ion, London, UK. Architect: Foster and Partners

...--

0 "

-

(2)'

_,-

I

_l~~--,,-,l_

Vertical section I:IO. Upstand for balustrade

3-D detail of upstand

I

I

(

.... I"""'-- I - I

-,-

I

@ Y)

3-D detail of low parapet

CD

-

I

Vertical section I:IO. Low parapet

MCH

249

Roofs 03 Concrete 3: planted roof

Vertical section I:IO. Heavy planting. Rainwater outlet. 3-D detail of rainwater oult et in heavily planted roof

@

3-D detail of pipe penetration in heavily planted roof

3-D detail of cill junction in heavily planted roof

on a roof accessible to building users, but are seen from vantage points around the building. Light planted roofs have plants and Vertical section I:IO. Heavy planting. Pipepenetration.

flowers that require little maintenance and

System design Concrete decksused for planted areas

do not usually have an irrigation system to supply wat er at controlled times, relying on

can be waterproofed with either a con-

rainwater and modest amounts of wat ering

cealed membrane or an exposed membrane

during maintenance at specific times of the

asdiscussed in the previous sections. Planted

year. These lightweight planted roofs suit

roofs are of two types: light planted and

a lightweight deck, such as a thin concrete

heavy planted. Unlike other concrete roof

shell, although profiled metal decksare

types, planted roofs are not always insulated

commonly used as substrates. Maintenance

asthey often form the roof of underground

access is provided by the pebble strips at the

structures such as car parks, providing a

roof edges or by individual paving slabs that

planted roof at ground level.

avoid the need to walk across the planting.

Light planted roofs have resilient plants

Heavy planted roofs permit a wide

that require little or no irrigation, and that

variety of plants, shrubs and trees to grow

Vertical section I:IO. Heavy planting. Cill

will grow in a thin layer of soil or organic

on a concrete roof deck. Due to the size

junction.

growing medium. They are not usually used

and intensity of the plantingthey require an

MCH

250

3-D overview of concrete roof with heavy planting

3-D detail of parapetjunction in heavily planted roof Vertical section I: 10. Heavy planting. Low parapet.

automated irrigation system, usually from pipes set into the soil that provide a trickle

drainage it is estimated by manufacturers of proprietary systems that 50% to 90% of rain-

water feed t o the soil at specific times which

fall is retained in planted roofs, but this varies

may vary duringthe course of the year.

considerably with local climate conditions

Heavy planted roofs require regularmainte-

and rainwater drainage provision.

nance, provided by paved paths or by areas of grass. Both light planted and heavy planted

System details

Details

8. Vapour barrier

I. Light vegetation

9. Concrete deck

2. Heavy vegetat ion

10. Smooth gravel

3. Soil/growing medium

II . Coping

4. FiIter sheet

12. Pipe/ duct

5. Drainage layer

I 3. Supply pipe

6. Waterproofing layer

14. Rainwater outlet

7. Thenmal insulation

15. Wall cladding

Both light planted and heavy planted

roofs have drainage layers beneath the

roofs have a similar build-up, comprising typ-

growing medium that hold wat er and

ically a top layer of planting, with a growing

release it backto the plants when required.

medium or soil beneath. A filter layer is set

This allowsthe soil depth to be much less

underneath, and below this, a drainage layer

than that which would be required for

and moisture mat. Beneath this lowest layer

older landscaping methods, where the soil

is set thermal insulation if required. Although

was expected to hold all the water. The

planted roofs provide a limited amount of

reduced depth of soil allows planting to be

thermal insulation from the soil, in practice

considered for concrete roof structures that

this is reduced due to the varying amounts

would require no significant strengthening to

of wat er held wit hin the soil. A root barrier

receive the added weight of soil. In terms of

is set beneath the insulation to protect the

Laban Centre, London, UK. Architect: Herzog and de Meuron

MCH

251

Ro o~03----------'"

Concrete

3: planted roof

-@'- -

Section I:IO. Light planting. Rainwater outlet

3-D detail of rainwater outlet in lightly planted roof

Section I:10, Light planting. Low parapetjunction

3-D detail of low parapet in lightly planted roof

wat erproof membrane, that is the bottom

age layer. The mat is made from a durable

drainage layer to provide greater water stor-

layer, bonded to the concrete roof deck.

fibre that retains moisture and nutrients as

age. The soil depth, in excess of 150mm,

The root barrier is sometimes bonded to

well as serving as protection to the root

requires an automatic irrigation systemto

the waterproofing layer, usually when the

barrier beneath. It is not used in inverted

provide a reliable water supply coverage of the complete roof

complete build-up is a single proprietary sys-

roof configurations. In inverted roofs, a root

tem. To prevent the passage of organic mat-

barrier is set immediately below the insula-

ter and fine particles into the water drainage

tion to protect the waterproof membrane

ples apply to planted roofs as discussed in

system, a filter sheet is set undemeath the

fonnning the lowest layer. This layer prevents

the previous sections. The waterproofing

planting. This sheet is lapped up the sides of

planting roots from damaging the water-

extends a minimum of 150mm above the

the planting,where it meets an upstand, to

proofing. In wannn roof construction, the

level of the planting, providing a continuity

the level of the planting.

wat erproof membrane is set on top of the

from the roof membrane to the fiashing at

The drainage layer beneath the filter

At upstands and eaves the same princi-

thennnal insulation, positioning the insulation

the top of the upstand or to the adjacent

sheet retains wat er that drains through

within the building envelope. A vapour bar-

wall construction. Upstands for parapets

the planting. W at er is retained in profiled

rier is set between the thennnal insulation

and door sills, highwalls and roofiights are

troughs in a typically polystyrene egg-crate

and the concrete deck. In this configuration a

fonnned by extending the waterproof filter

shaped tray that releases wat er back to the

moisture mat is set between the wat erproof

sheet and root barrier up to a minimum of

planting. This method also perfonnns satis-

membrane and the drainage layer above.

150mm above the level of the soil or grow-

factorily on sloping concrete roofs. Excess

The soil depth in light planted roofs

ing medium. The visible membranes and

wat er is drained away through gaps between

ranges from 50mm to around 150mm.

sheets are concealed wit h thennnal insulat ion,

the drainage trays. The egg-crate fonnn allows

W ater is stored in the growing medium and

and typically either paving tumed on edge, as per the paving used for adjacent access

aerat ion, pennnitting the soil to absorb the

drainage layer, making it efficient in mild,

water stored here. In drier months, water

temperate climates. Lightplanted roofs can

paving, or a metal sheet to match that of

diffuses up through the soil to the plant

be grown on both nominally fiat roofs and

the parapetcoping where a metal coping is

roots. A moisture mat is often set under this

on sloping roofs with a pitch up to 25° to

used.

layer to catch wat er that runs off the drain-

30°. Heavy planted roofs have a deeper

MCH

252

3-D overview of concrete roof wit h light (sedum) planting

CD I

-- - 0 ,

r

f

Section I: 10. Light planting. Rooflight upst and

3-D detail of ro oflight upstand in light ly planted roof

@

(J

I'

, r

{

,

(

Section I : 10, Light planting. Pipe penetration .

3-D detail of pipe penetration in lightly planted roof

Section I:I0. Light plant ing. t wo- way outlet

3-D detail of t wo- w ay outlet in lightly planted roof

MCH

253

Roofs 03 Timber roofs 2: fiat roof: bitumen-based sheet

3-D overview showing typical flat t imber roof construct ion with insulation between roof joists.

-- - - ,L

Section I :IO. Flat roof w it h insulation between joi sts

(!) -- -

CD

'0' ,

6

3-D overview showi ng typical flat timber roof construction w ith rigid insulat ion above roof structure

0 '

System design

Section I : 10. Flat roof w it h rigid insulation above roof structure

@

Flat timber roofs are described as being

tion, on the wanrn (in winter) side of the

tion. In the wanrn roof configuration, thenrnal

insulation, with a dry wall or intemal lining

insulation is set on top of the timber deck,

board set below this. In both wanrn and cold

which is protected by a wat erproof layer set

roofs, the vapour barrier avoids the passage

onto its upper face. A vapour barrier is set

of damp air up into the thenrnal insulation

between the thenrnal insulation and the tim-

where interstitial condensation can fonrn that

ber deck. The roof build-up is not required

might damage the intemal construction of

to be vent ilated as the timber structure is

the roof.

maintained at near intemaltemperature

Section I : IO. Low parapet w all w it h drain outlet

MCH

254

A vapour barrier is set beneath the insula-

in either 'warm' roof or 'cold' roof configura-

In a mastic asphalt waterproofed wanrn

conditions. In the cold roof configuration the

roof. thenrnal insulation is set on top of the

wat erproof layer is set directly onto the tim-

timber deck, with an asphalt layer on top of

ber deck. Thenrnal insulation is set beneath

this. A separation layer is set between the

the timber deck, in the voids between the

asphalt andthe thenrnal insulation. A vapour

timber joists and air is allowed to circulate

barrier is set between the thenrnal insulation

in the void to provide ventilation that avoids

and the timber deck. In the mastic asphalt

the possibility of rot fonrning in the timber.

cold roof configuration, the asphalt is set

r

0 .------, ,----,

0)

CD CD

CD (2)

~

® 0)

(2)

(2)

CD

CD CD ®

(2)

0

J~

CD

ly

X

Section I: 10. Balustrade detail

®

Section I:10. Expansion joint

Section I: 10. Low parapet wall

Details I. Bitumen based sheet

2. Plywood sheet 3. Rigid thermal insulation 4. Vapour barrier 5. Softwood joists 6. Dry lining/drywall intemal finish 7. Metal Flashing 8. Timber upstand 9. Extemal Wall 10. Angle fillet I I. Proprietry skirt flashing 12. Rainwater outlet 13. Paving bonded to bitumen

3-D view of expansion joint in typical timber flat roof construction

directly onto the timber deck, wit h a separat -

greater strength, flexibility, a higher melting

ing layer beneath the asphalt.

point and UV resistance. However, the use

Mastic asphalt, usedto form a continu-

of this material is set to continue, mainly

ous wat erproof covering on flat or sloping

a concealed membrane, but its use as an

roofs, has polymer additives in some types

exposed membrane is discussed here since

to provide stability at the relatively high

this application is much more common in

temperatures experienced when exposed

timber constnuction. Mastic asphalt is laid on

to the effects of the sun, aswell as providing

rigid substrates, typically reinforced concrete

flexibility ofthe material at low temperatures,

decks, but its use as an exposed membrane

which allows it to take up movements in the

on a timber deck is set to continue, particu-

substrate. Asphalt is applied in a hot liquid

larly as a result of additives which make the

form on site, allowing it to form a homoge-

material more flexible than was previously

neous material at complex junctions such as

the case.

at upstands, roof penetrations and changes in

based sheet

In warm roof constnuction, a protective

level. It was used more commonly 25 years

surface is usually applied to all exposed areas

ago, and its popularity is being challenged by

wit h a solar reflective paint, stone chippings

single layer sheet membranes, which have

or thin paving slabs which are bedded into

Private residence, London, UK. Archit ect: Lynch Architects MCH

255

Roofs 03 Timber roofs 2: fiat roof: bit umen-based sheet

3-D view of drain outlet in t imber roof

3-D section t hrough roo f show ing pipe penetrat ion and step. Timber roo f w it h low parapet and layer of shingle

CD

I

Section I: IO. Pipe panetratio n and step in roof

MC H

256

I

,

3-D detail showing step in roof construction

3-D detail showing pipe penetration through roof

cally fixed and sealed, or bonded, to the duct

the asphalt surface with a proprietary adhe-

Trims to verges and eaves are formed

sive. A single layer of IOmm - 14mm stone

with a GRP or aluminium trim in order to

or pipe creating the penetration. An addi-

chippings is used as permanent surface pro-

support the bottom edge of the asphalt.

tional secondary seal, formed typically wit h

tection for asphalt. The chippings are usually

Some installations use no trim at all, but the

either EPDM or metal sheet, forms a second-

bonded to the asphalt after the asphalt has

edge becomes vulnerable to damage and can

ary seal to this penetration.

cooled, with a bitumen solution to provide

result in a visually uneven appearance. W hen

only a limited bond. This allows the chip-

the asphaltedge is terminated by a gutter, a

ated within the timber deck since asphalt can

pings to be removed easily at a later date for

metal flashing can be set under the bottom

be laidto suit a complex geometry without

repair and maintenance work

of the asphalt.

the need for joints in the material. W here

Verges can be formed by creating an

System details

Gutters can be formed t o any shape cre-

the gutter is formed as a parapet gutter at

asphalt upstand, built to a height of around

the base ofthe tiled roof, the asphalt is car-

SOmm to suit the expected flow from the

ried up over the tilting fillet of the tiled roof.

set vertically, or at a steep slope, the mate-

roof. An altemative detail is to stop the

Rainwater outlets are formed by setting the

rial is laid in three coats. The first coat is very

asphalt at the edge of the roof andterminate

out let at the level of the structural deck. The

At upstands, where the asphalt is usually

thin in order to key in the substrate, then

in a metal strip so that the asphalt cannot be

asphalt is stepped down with 45° folds down

two further separate coats are applied to

seen from below, but in practice it can be

into the rainwater outlet, and the metal grat-

give an overall thickness of around 20mm. In

difficult to achieve a reliable seal between the

ing and cover is fixed down onto this. The

forming an upstand, sheat hing felt is fixed to

asphalt and the metal trim.

sheathing felt extends up t o the edge of the

the substrate, often a separate upstand fixed

Penetrations through an asphalt covered

to the roof, as mentioned earlier. Expanded

roof are formed by extendingthe asphalt

metal lathing, typically at 150mm centres,

up by ISOmm to create a collar round the

primed in bitumen, is fixed to the face of

material. The top of the asphalt collar has an

the sheathing layer, which provides a 'key'

apron flashing around it to protect the top

to which the asphalt will bond. W here the

of the asphalt. An altemative method of seal-

upstand is formed in lightweight concrete

ing a roof penetration is to form a complete

block, the surface is faced with either a sand

upstand around the penetration which can

cement render, or metal laths and sheathing

be insulated to the top of the opening. An

felt is used as described.

insulated metal panel can then be mechani-

rainwater outlet.

MCH

25 7

Roofs

03- - - - - - - - - - - - - - - - - -

Timber roofs I: fl at roofs: mast ic asp ha lt coverings

® @

@ (3) 3-D view of step in roo f

CD

® Sectio n I: I O. 2 w ay drain outlet

CD

®

CD Section I : IO. Step in roof

® System design This section discusses flat t imber roofs

® 3-D view showi ng ridge in mastic roof

CD

Section I : 10. Eaves

MCH

258

applied to concrete decks are usually laid in hot liquid form and are reinfo rced to suit the

that use the common combination of bitu-

specific condit ions of fold s and joints occur-

men sheet -based membrane as a w at er-

ring within th e struct ural deck In this section

proofing layer in a warm ro of. Alt hough

t he mat erial is considered as an exposed

oth er membrane mat erials are used on

and visible material o n a relatively lightweight

flat t imber roofs as bot h w arm and cold

deck

roofs , ty pically formed in elastomeric and

Bit umen sheet membranes are eco-

t hermo plastic memb ranes, th eir applica-

nom ic, and are often used w ith t imber ro of

tion is discussed in the earlier sectio n on

decks, w hich t ogether provide an economic

expose d membrane s in concrete roo fs. The

roof design for relatively small-scale applica-

princip les of detailing in that section can be

t ions, or designs wit h a comple x geometry

similarly applied to timber roofs. Bit umen-

of low pitched roofs, as is often used in

based sheet can also be used in 'inverte d

hou sing and in schoo l buildings. Bitumen-

roof, or concealed membrane configuration

based membrane s have develop ed over the

as described in th at earlier section w here

past 25 years t o compete with the newer

the detailing is similar, but bitumen-based

elastom eric and thermoplastic materials by

sheet is generally less ro bust th an the mem -

increasing t heir flexibility and making t hem

branes described in that section . Memb ranes

th inner, requiring less materi al, w hich helps

l >-, ,

CD I

•

I

I

'17'\'

------ 0-- ~--

,~

o

, ,~

@

® Section I:IO. Low parapet wall

®

u

3-D view of low parapet wall

~.

J

-

CD, ,

-' (])-

, _'

,

I

1

' _'_'_1 __

o

-

I

0

I

I

CD 1_1_1_'0 __ 1_1 __ '_1_,

o

-