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21 Buildings

J Rodin BSc, CEng, FICE, FIStructE,MConsEBuilding Design Partnership

Contents

21.1 Background 21/3

21.2 General management 21/3

21.3 Brief 21/3

21.4 The site 21/9

21.5 Landscape 21/9

21.6 Town planning 21/11

21.7 Public utility 21/11

21.8 Feasibility 21/11

21.9 Cost 21/11

21.10 Internal environment 21/1221.10.1 Thermal environment 21/1221.10.2 Air-conditioning 21/1221.10.3 Accommodation of building services 21/1321.10.4 Heating/cooling generation 21/1421.10.5 Thermal insulation 21/1721.10.6 Lighting 21/1721.10.7 Noise 21/20

21.11 Water supply, drainage and public health 21/2121.11.1 Water supply 21/2121.11.2 Put installations 21/2121.11.3 Water treatment 21/2121.11.4 Drainage 21/2121.11.5 Public health 21/21

21.12 Lifts, escalators and passenger conveyors 21/22

21.13 Energy 21/22

21.14 Building Regulations 21/2421.14.1 Procedures 21/2421.14.2 Appeals procedure 21/2421.14.3 Approved Documents and mandatory

requirements 21/2421.14.4 Structure 21/2621.14.5 Fire spread 21/2621.14.6 Other Approved Documents 21/27

21.15 Building security and control 21/27

21.16 Materials 21/2821.16.1 Concrete 21/2821.16.2 Steel 21/2821.16.3 Brick and masonry 21/2921.16.4 Timber 21/29

21.17 Walls, roofs and finishes 21/2921.17.1 External finishes, materials and

weathering 21/2921.17.2 Floor, ceiling and wall finishes

(internal) 21/3021.17.3 Roofs 21/3021.17.4 Partitions 21/31

21.18 Interior design and space planning 21/31

21.19 Structure 21/3221.19.1 Structural behaviour 21/3221.19.2 Robustness 21/3321.19.3 Wind effects on buildings 21/3321.19.4 Movement 21/3421.19.5 Structural arrangement 21/3421.19.6 Resistance to vertical load 21/3421.19.7 Resistance to horizontal load 21/3521.19.8 Multistorey construction 21/35

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21.20 Tall buildings 21/3721.20.1 Frames in bending 21/3921.20.2 Braced frames 21/3921.20.3 Shear walls and cores 21/3921.20.4 Combined systems 21/3921.20.5 Vertical movement 21/4021.20.6 Lateral movement and dynamic effects 21/4021.20.7 Additional considerations 21/42

21.21 Special structures 21/42

21.22 Foundations 21/42

References 21/44

Bibliography 21/44

The design of the total building including its internal andexternal environment has traditionally been the responsibility ofthe architect but this is now so complex a task that, except forthe simplest of buildings, a multidisciplinary involvement isnecessary whereby engineering, surveying and other specialistskills are integrated with those of the architect to achieveconsistent quality throughout the project.

Internal form and environment will be determined by thefunctional requirements of the occupying organization, thespace needed to meet these functional requirements and therequired comfort levels in regard to such items as noise,temperature, humidity and lighting. The external form andenvironment will be determined by the characteristics of the siteand adjacent buildings. Influencing all aspects will be theconstraints arising from time and cost, town planning andbuilding regulations.

21.1 Background

Architects look to the civil and structural engineer for a positivecontribution to the building design; from concept to comple-tion, with understanding of the basic objectives of the projectand with sensitivity and inspiration in their realization. Thetechnical and economic solution to a predetermined problem,on its own, is no longer sufficient. The primary responsibility ofthe civil and structural engineer will be to ensure the safety andrigidity of the building but, with the architect, he can make acreative contribution to the building form, the spaces within itand its impact, visually and psychologically.

The potential freedom of building layout and expressionwhich stemmed from the development of the structural frametook a surprisingly long time to be understood and put intopractice. Framing techniques were available from the midnineteenth century but, in the main, they were used simply tosupport buildings of predetermined form and style into whichthe required functions had to fit. It was not until a few leaders ofarchitectural thought and practice adopted a more rationalapproach to design that the potential of the structural frame wasgrasped and put to good effect. For those who understood andwanted it, there was now much greater freedom of internalplanning and external expression; and for the rationalists, formcould more easily follow function.

The design of the Bauhaus building in Dessau by its founderWalter Gropius was a turning point in bringing logic into thedesign of buildings. It was the first major building to derive itsform not from the irrational imposition of style, symmetry andproportion, but from the requirements of function and struc-ture. Its character came from intrinsic materials and designdetail, not from applied decoration; its subtlety of form andspace from an ordered solution to the planning problems, notfrom some preconceived design formula or style. It was a majordemonstration of a rational design approach founded upon theworking out of solutions from first principles. The architecturalfeatures of the Bauhaus building became popular among pro-gressive architects: assymetry, rectangular forms, lightness ofthe external wall, space and precision, all, in a way, reflections ofthe contradictory combination of freedom and disciplineafforded by the sensible use of structure.

For form to follow function became the natural starting pointfor design; indeed, it seemed strange that it could ever have beenthought otherwise. Later experience showed that a too-rigidadherence to this principle leads to a too-'tailored' buildingunable to respond to changing need and that a loose-fit ap-proach is advantageous. The introduction of the structuralframe allows building expression to be whatever is wanted andacceptable. Structure and building services may be expressed or

hidden. Height is no longer a problem if it is acceptable to theplanners and is economically viable. Almost any clear span isachievable. In short, the constraints are no longer technical;given the resources, design options are now almost limitless.

The more significant question has become: How is thistechnical freedom to be applied? Buildings are for people, toprovide them with shelter, comfort, spiritual uplift and psycho-logical support, and to accommodate the sophisticated pro-cesses that are part of modern life. Changing expectations ofpeople and social relationships have become major determi-nants of the volume and nature of building. Communicationsystems of all types have changed remarkably. Science-basedindustries of unimagined complexity now exist requiringextreme levels of environmental control. These changes have ledto the need for completely new types of building.

The design and construction itself is complex, requiring greatskills of co-ordination and management. Functional require-ments in many building projects are now so diverse thatspecialist input and understanding are required to establish thebrief before building design can commence. Building materials,methods and forms of contract are diverse and changing, as arethe constraints of cost and time, town planning and buildingregulation. The finished building itself is complex and highlyserviced; and it often requires sophisticated building control andsecurity systems to ensure satisfactory and safe performance.Cost in use, maintenance and energy consumption, have becomeas important considerations as first cost.

The diversity and depth of these aspects of building designand construction cannot be covered in a single chapter of a bookdevoted primarily to civil engineering practice. What follows isan introduction to the subject, to help the civil and structuralengineer see his contribution better in the context of buildingdesign and construction as a whole.

References are in the main to UK practice but most aspectsare, in principle, applicable generally.

21.2 General management

The procedures for handling large-scale building projects asopposed to civil engineering projects are complicated by thelarger number of individual professional parties involved and bythe large amount of legislation on permissions and approvals.The handling of such projects in the UK has been studied by theRoyal Institute of British Architects (RIBA).1 A similar publi-cation relating to US practice has been produced by theAmerican Institute of Architects.2

The overall procedures for the organization of buildingprojects are covered in another publication produced by theRIBA.3 Table 21.1, taken from that publication, shows thetwelve discrete stages into which the project can be divided andbriefly indicates the contents of each stage and the partiesdirectly involved. Full details of the work required from each ofthe several professions and contractors at each stage are shownin separate diagrams. For example the detailed breakdown ofStage C, Outline Proposals, is shown in Table 21.2 in whichcolumn 5 details the input required from the civil and structuralengineer.

21.3 Brief

Buildings are either purpose-built for a particular user or arespeculative. In either case, the first step is to compile an agreedbrief setting out the basic requirements of the project covering:

Usual terminology

BRIEFING

SKETCH PLANS

People directlyinvolved

All client interests,architect.

Clients' representatives,architects, engineers,and quantity surveyoraccording to nature ofproject.

All client interests,architects, engineers,quantity surveyor andspecialists as required

All client interests,architects, engineers,quantity surveyor andspecialists and allstatutory and otherapproving authorities.

Tasks to be done

Set up client organization forbriefing.

Consider requirements, appointarchitect.

Carry out studies of userrequirements, site conditions,planning, design, and cost, etc. asnecessary to reach decisions.

Develop the brief further.Carry out studies on user

requirements, technical problems,planning, design and costs, asnecessary to reach decisions.

Final development of the brief, fulldesign of the project by architect,preliminary design by engineers,preparation of cost plan and fullexplanatory report. Submission ofproposals for all approvals.

Purpose of work anddecisions to be reached

To prepare general outline ofrequirement and plan futureaction.

To provide the client with anappraisal and recommendation inorder that he may determine theform in which the project is toproceed, ensuring that it isfeasible, functionally, technicallyand financially.

To determine general approach tolayout, design and construction inorder to obtain approval of clienton outline proposals andaccompanying report.

To complete the brief anddecide on particularproposals, including planningarrangement appearance,constructional method, outlinespecification, and cost, and toobtain all approvals.

Stage

(1) INCEPTION

(2) FEASIBILITY

(3) OUTLINE

PROPOSALS

(4) SCHEME DESIGN

Brief should not be modified after this point.

WORKINGDRAWINGS

Architects, quantitysurveyor, engineers andspecialists, contractor(if appointed).

Full design of every part andcomponent by collaboration of allconcerned.

Complete cost checking of designs.

To obtain final decision onevery matter related todesign, specification,construction and cost.

(5) DETAIL DESIGN

Table 21.1 Outline plan of work. (After Royal Institute of British Architects (1973) Plan of work. RIBA, London).

Usual terminologyPeople directlyinvolved

Tasks to be donePurpose of work anddecisions to be reached

Stage

Any further change in location, size, shape, or cost after this time will result in abortive work.

SITE OPERATIONS

Architects, engineers andspecialists, contractor(if appointed).

Architects, quantitysurveyor, contractor (ifappointed).

Architects, quantitysurveyor, engineers,contractor, client.

Contractor,subcontractors.

Architects, engineers,contractors,subcontractors,quantity surveyor,client.

Architects, engineers,contractor, quantitysurveyor, client

Architects, engineers,quantity surveyor,contractor, client.

Preparation of final productioninformation, i.e. drawings,schedules and specifications.

Preparation of bills ofquantities and tenderdocuments.

Action as recommended inparas 7-14 inclusive ofSelective tendering*

Action in accordance with paras5-10 inclusive of Projectmanagement*

Action in accordance withparas 11-14 inclusive ofProject management*

Action in accordance withparas 15-18 inclusive ofProject management*

Analysis of job records. Inspectionsof completed building. Studies ofbuilding in use.

To prepare production informationand make final detailed decisionsto carry out work.

To prepare and complete allinformation and arrangements forobtaining tender.

Action as recommended inparas 7-14 inclusive ofSelective tendering*

Action in accordance withparas 5-10 inclusive ofProject management*

Action in accordance withparas 11-14 inclusive ofProject management*

Action in accordance withparas 15-18 inclusive ofProject management*

To analyse the management,construction andperformance of the project.

(6) PRODUCTIONINFORMATION

(7) BILLS OFQUANTITIES

(8) TENDERACTION

(9) PROJECTPLANNING

(10) OPERATIONSONSITE

(11) COMPLETION

(12) FEEDBACK

*Publication of National Joint Consultative Council of Architects, Quantity Surveyors and Builders.

Table 21.1 (continued)

Col. 8Remarks

Col. 7Contractor(if appointed}

function

Col. 6Engineer,mechanical andelectrical, functions

Col. 5Engineer,civil and structural,functions

Col. 4Quantity surveyorfunction

Col. 3Architectdesign function

CpI. 2Architectmanagement function

Col. 1Client function

ITEMS FOR AGENDA FOR

MEETING:(1) State objectives and

provide information:(a) brief as far as

developed;(b) site plans and

other site data;(c) restate cost limits

or cost range,based on client'sbrief;

(d) timetable; and(e) agree dimensional

method.(2) Determine priorities.(3) Define roles and

responsibilities ofteam members andmethods communi-cation and reporting

(4) Define method ofwork, tenderprocedure andcontractarrangements.

(5) Agree drawingtechniques.

(6) Agree systems ofcost and engineeringchecks on design.

(7) Agree type of bill ofquantities.

(8) Agree check list ofactions to be taken.

(9) Agree programmingand progressingtechniques.

(1) Contribute tomeeting, note itemson agenda in col.8.

(2) Carry out studiesrelevant to stageC, e.g visit site andinvestigate:

(a) ground conditions,access andavailability ofservices forconstruction;

(b) local laboursituation; and

(c) local sub-contractors andsuppliers to assessquality reliability,production potent-ial and price level,etc.

(3) Advise architect onfindings and alsoon:

(a) approximate timesfor construction ofalternativemethods; and

(b) effect ofconstruction timeson cost, etc.

(1) Contribute tomeeting: note itemson agenda in col.8.

(2) Carry out initialstudies relevant tostage C, e.g.:

(a) environmentalconditions, userand servicesrequirements,appraise M and Eloadings on anarea or cube basis;and

(b) consider possibletypes of installa-tion and analysecapital andrunning costs,possible sizes andeffects of majorservicesinstallations, mainservices supplyrequirements.

(3) Advise architect ondesign implicationsof studies made,e.g.:

(a) factors whichwould influenceefficiency, and costof engineeringelements, i.e. siteutilization,

(1) Contribute tomeeting: note itemson agenda in col.8.

(2) Carry out studiesrelevant to stageC, e.g.:

(a) site surveys, soilinvestigation; and

(b) completequestionnaires onstructural and civilrequirements.

(3) Advise architecton, for example:

(a) types of structure;(b) methods of

building;(c) types of

foundation; and(d) roads, drainage,

water supply, etc.

(1) Contribute tomeeting: note itemson agenda in col.8.

(2) Carry out studiesrelevant to stageC, e.g.:

(a) Obtain allsignificant detailsof client's require-ments relevant tocost and contractinformation on siteproblems, etc.; and

(b) re-examine,supplement andconfirm costinformationassembled in stageB.

(3) Outline designimplications ofcost range orcost limit.

(1) Contribute tomeeting: note itemson agenda in col.8.

(2) Carry out studiesrelevant to stageC, e.g.:

(a) study publishedanalyses of similarprojects, visit ifpossible;

(b) study circulationand spaceassociationproblems; and

(c) try out detailplanning solutionsand study effect ofplanning and othercontrols.

(3) In consultationwith teamassimilateinformationobtained in action2, and producediagrammaticanalyses, discussproblems.

(1) Organize designteam. Call meetingto discuss directiveprepared in stageB, action 9 (col. 2):establishresponsibilities,prepare plan ofwork andtimetable for stageC. (See col. 8 foritems for agendafor meeting.)

(2) Elicit allinformation rele-vant to stage C byquestionnaire,discussion, visits,observations, userstudies, etc. Initiatestudies byconsultants andclient as required.Maintain andcoordinate pro-gress throughoutthis stage.

(1) Contribute tomeeting: note itemson agenda incol. 8.

(2) Provide all furtherinformationrequired byarchitect. Assist asrequired in allstudies carried outby members ofdesign team.Initiate andconclude accordingto timetable, anystudies that arerequired withinown organizations.Make decisions onall matterssubmitted fordecision relevantto stage C.

Table 21.2 Stage C: Outline proposals - plan of work for design team operation(To determine general approach to layout, design and construction, in order to obtain authoritative approval of the client on the outline proposals and accompanying report.)

CoL 8Remarks

CoL 7Contractor(if appointed)

function

Col 6Engineer,mechanical andelectrical, functions

CoLSEngineer,civil and structural,functions

CoL 4Quantity surveyorfunction

CoL 3Architectdesign function

CoL 2Architectmanagement function

CoL 1Client function

(4) Collaborate inpreparation ofoutline scheme:continue to adviseon time and costimplications ofalternative designsor methods.Record details ofproposals andassumptions.

(5) Provide quantitysurveyor withinformationaffecting pricelevels, for outlinecost plan andagree quantitysurveyorproposals.

building aspectand grouping,optimumconstructionparameters, etc.;

(b) possible servicessolutions andramifications ofthem; and

(c) regulations andviews of statutoryauthorities.

(4) Collaborate inpreparation ofoutline scheme,check that servicesdecisions remainvalid; recorddetails ofalternative plansand assumptions.

(5) Provide quantitysurveyor with costrange informationfor outline costplan, and agreequantity surveyorproposals:interpret agreedstandards byillustration.

(4) Collaborate inpreparation ofoutline scheme,prepare notes andsketches, consideralternatives, agreedecision on generalapproach, andrecord details ofalternative plansand assumptions.

(5) Provide quantitysurveyor withinformation foroutline cost plan,with sketches onwhich to baseestimate, and agreequantity surveyorproposals

(4) Collaborate inpreparation ofoutline scheme.Prepare quick coststudies ofalternativestructural andservices solutions,and advise oneconomic aspectsof solutions.

(5) Confirm cost limitor give firmestimate basedupon userrequirements andoutline designs andproposals. Prepareoutline cost plan inconsultation withteam, either from

(4) Try out variousgeneral solutions;discuss with team;modify asnecessary, anddecide on onegeneral approach.Prepare outlinescheme, indicating,for example,critical dimensions,main spacelocations and usesand pass to team.

(5) Assist quantitysurveyor inpreparation ofoutline cost plan;discuss and decideon cost ranges formain elements, andmethod ofpresentation ofestimate to client.

Table 21.2 (continued)

CoL 8Remarks

Col. 7Contractor(if appointed)

function

CoL 6Engineer,mechanical andelectrical, functions

Col. 5Engineer,civil and structural,functions

Col. 4Quantity surveyorfunction

Col. 3Architectdesign function

Col. 2Architectmanagement function

CoL 1Client function

The report includes:(a) the brief as far as it

has been developed;(b) an explanation of

the major designdecisions; and

(c) firm estimate withoutline cost plan.

(6) Compile dossier ofbasic costinformation agreedwith quantitysurveyor andarchitect.

(7) Contribute topreparation ofreport.

(6) Compile dossier ofessential datacollected in actions(2) to (5) above.

(7) Contribute topreparation ofreport.

(6) Compile dossier ofessential datacollected in actions(2) to (5) above.

(7) Contribute topreparation ofreport.

comparison ofrequirements withanalytical costs ofprevious projectsor fromapproximatequantities based onassumedspecification.

(6) Record basis ofestimate tocontribute todesign dossiers.

(7) Contribute topreparation ofreport.

(6) Contribute todesign dossiers,assemble allsketches and noterelevantassumptions.

(7) Contribute topreparation ofreport.

(6) Compile dossiersprovided by teammembers on final(or alternative)sketch designs,recording allassumptions, andissue to allmembers of theteam.

(7) Prepare report ascoordinatedversion of allmembers' reports,including fullydeveloped brief.

(8) Receive architect's (8) Present report toreport; consider, client; discuss anddiscuss and decide obtain decisionsoutstanding issues. and furtherGive instructions instructions,for further action.

Table 21.1 (continued)

(1) Purpose, function and scope including limitations of costand time; proposed activities and organization includingnumbers and types of people concerned, internal and exter-nal service requirements, particular systems such as docu-ment retrieval, special functional requirements such assecurity.

(2) Design factors and required standards covering internal andexternal environment; spatial requirements, organizationalrelationships and required groupings affecting layout.

(3) Internal and external traffic and required access for pedes-trians, vehicles and materials.

(4) Factors affecting type of construction, expansion, alter-ation, change of use, life.

(5) Phasing required.(6) Special sensitivities or critical functions.

Of primary importance is the building use and the associatedschedule of basic accommodation including the number andnature of the intended occupants. By adding allowances forcirculation, services, plant, toilet and ancillary accommodation,a close assessment of the gross floor area can be made andthereby the size of building determined. By considering therelationships between the different activities, the optimumgrouping of the spaces provided for them can be analysed inpreparation for their translation into a physical plan to suit theparticular site.

A user client may have special requirements: most buildingsare expected to have a useful life of 60 to 100 years, but in somecases, a more limited life span may be envisaged dictating a lightform of construction which can be demolished and replacedeasily and cheaply. Alternatively, a client may require a robustbuilding shell of long life in which internal adaptation can becarried out to suit a later, and perhaps unknown, alternativeuse. Substantial mechanical and electrical service requirements,as occur in hospitals and some specialist laboratories andfactories, may dominate the design leading, perhaps, to theincorporation of near-storey-height service floors alternatingwith the functional floors.

21.4 The site

Early site appraisal is vital. Suitability for the purpose intendedrequires consultation with various planning authorities to con-firm zoning and land use definition. Access for vehicles, peopleand goods must be checked and the availability of publictransport and future road or transport links determined.Increasingly, good access to major international air and railtermini or proximity to the national road network is a prerequi-site of a site.

Subsoil deficiencies and underground service easements maypresent difficulties in development. Investigation of old mineralworkings (e.g. brick clay, salt, sand and gravel extraction), coal-mines, shafts and wells should be undertaken, particularly ifsuch work is known to have occurred in the vicinity. Evidence offilling should be investigated and dated. A subsoil survey shouldbe recommended to the client (together with a cost estimate)early in the life of the project to identify the underlyingconditions which may ultimately influence the building location,arrangement and cost.

The local climate requires early checking: high wind speedswill involve special stiffening; atmospheric pollution or salt-laden coastal winds will require the selection of suitablematerials and careful detailing of exposed building elements.Excessive external noise from major roads, railways or airportsmay necessitate soundproofing in the building or sound screen-ing between the building and the noise source.

Confined city sites introduce problems such as: (1) deliveryand storage of building materials and components; (2) the threatof restrictions or stoppages arising from local objection toconstruction noise; and (3) protection of adjoining propertywhich may need underpinning and should be surveyed fordilapidations before work commences on site.

21.5 Landscape

The landscape is the setting to which new developments mustrelate, therefore its consideration is vital at the outset of eachproject. Landscape and civil engineering bear a close affinity,due to a mutual and direct concern with land form and naturalresources. All but the most cosmetic landscape treatmentinvolves civil engineering considerations. Landscape consider-ations include feasibility studies, environmental assessments,public inquiries, erosion control, reclamation, restoration, con-servation, transportation, industry, commerce, natural heritageand the landscape related to all types of buildings both exteriorand interior.

The quality of the landscape is now an essential constituent ofthe planning consent process. Early site appraisal should includean analysis of the landscape or urban space. Among the factorsto be considered are geology, topography, soil, microclimate,drainage, land use, artefacts, vegetation and visual analysis. Theeffects of the interaction of these factors should be considered inrelation to the development. A skilful appraisal will lead to theestablishment of sound principles, which will enhance the lessfavourable aspects of the site whilst conserving the best.

On a yet broader scale, a full environmental assessmentleading to designs which cause the least damage socially, aes-thetically and to our natural resources, would extend to a largeteam including other specialists.

Reclamation of abandoned industrial and domestic waste-land is an area in the re-creation of the environment whereengineering and landscape are inseparably combined. Suchoperations can restore the form of the landscape, provide newsites for housing, industry and recreation, and create newhabitats, from wetlands to woodlands.

There are numerous factors concerning planning and designwhich will be important to the landscape architect, the civilengineer and the architect. These factors include planning forvehicles, finished levels and materials, economic cut-and-fill andthe integration between the hard paved areas of the scheme andits immediate environment. Close collaboration between theprofessions is therefore needed to achieve an economic andsympathetic design.

As part of the site investigations, soil tests should be taken toassess biological qualities and should include horizon depth, soiltype, texture, moisture content and pH. It is advisable to obtaina chemical analysis from an approved laboratory to assessdeficiencies.

Planning the site operations to achieve the best resultsinvolves many decisions related to the landscape. Vegetationand topsoil are delicate natural resources which are easilydamaged by thoughtless construction techniques. Their valuemust be assessed at the outset by a specialist, and if consideredof value they should be protected carefully and retained. Topsoilmust not be mishandled, as compaction and poor storage canrender it useless as a growing medium. Drainage and gradingshould also be considered regarding any vegetation to beretained.

Working areas should be kept to a minimum in order to leavethe maximum undisturbed area and avoid the replacement orrestoration of topsoil and subsoil. Excavation, compaction,

changes in water table and in finished level within the rootspread of trees, should be avoided. The canopy will suffer inproportion to the amount of root damage sustained and simi-larly the stability, appearance and life expectancy of the tree willalso be affected. On no account should the level of soil adjacentto the trunk be changed. Where trenching is unavoidable withinthe root spread, hand digging and retention of roots will beadvantageous.

Where trees are an important feature close to buildings, roadsor drainage foundations should be designed to withstand theeffects of root growth or moisture movement.

The structural requirements and economic viability ofplanted areas within the building which are conceived as roofgardens, terraces or interior gardens, must be considered earlyin the design process together with the client's understanding ofthe long-term maintenance commitment. In addition, drainage,access and the sequence of construction are significant factors.The growing medium and planting should either be installed asthe very last of the building operations, or adequately isolatedand protected from further construction activities. All planting,but especially interior planting, can be affected adversely andeven destroyed by subsequent operations such as the repair offaulty tanking, the installation of lighting and irrigation or thegrinding of materials such as marble and terrazzo. It is clear,therefore, that where planting is part of a design concept it needscareful integration into the building process.

Management of the landscape in the long term is essential andshould be discussed at the earliest opportunity, preferably whenthe brief is being formulated to ensure the wellbeing of the newlycreated environment and that a succession of planting is pro-vided for the future.

Figure 21.1 and the accompanying text describe the carefulintegration of an important headquarter building within abeautiful parkland setting. The aim was to provide a head-quarters which would give high quality conditions for work,training and recreation. The new building was planned to haveminimal impact upon the local environment, and to ensure thatits landscaped surroundings would enhance working conditions.At the same time it had to cater for the latest demands ofinformation technology, ensuring that the layout and fabric ofthe building were flexible enough to accept inevitable futurechange.

While the briefing process was underway, surveys were car-ried out on site conditions, tree planting and acoustic aspects ofthe location. It was seen as vital to respond to the exceptionalnatural quality of the site, and to the architectural qualities ofthe two main existing buildings there - the listed Fulshaw Hall,and Harefield House.

The form of the new headquarters evolved from these con-siderations as a low-lying building, tucked into the landscape ona slope of land across the lake from Fulshaw Hall. Car parkingis provided discreetly to the south. The three-storey construc-tion, pitched roofs, and brick and slate materials of the buildinghelp further to establish it as a worthy neighbour to the hall.

The plan provides outer and inner bands of office space,linked at intervals to create enclosed courtyards. Its externalappearance is of a series of linked pavilions, sweeping round in agentle curve that focuses upon the hall itself. The western end ofthe building surmounts a landscaped terrace facing the entrancefrom the A34 road.

Inside, circulation is provided by a pedestrian mall on themiddle level of the inner band, facing the park. Vertical access isvia stair towers at back and front. All the offices are fitted outwith a raised floor to accommodate all cabling and air handlingneeds. The offices are 12 m wide along the bands, and 15 m widealong the links, so providing a good level of natural light. Theplanning module is a highly flexible 1.5m allowing practicallyany type of interior fit-out. Uplighters bounce light off an

Figure 21.1 Integration of building and landscape, (a) Plan of theFulshaw Hall site; (b) disposition of spaces

A34toAlderley Edge

Siteboundary

Entrance

A34toWilmslow

(1) Fulshaw Hall(2) Coach House(3) Fulshaw Hall North Lodge(4) Fulshaw Hall South Lodge(5) Harefield South Lodge(6) Lloyd House(7) Harefield

acoustically treated structural ceiling, providing glare-free con-ditions and easy replanning of working spaces.

A 100Om2 computer suite is provided, together with diningroom, coffee lounge and kitchens. Although the main spaces areleft open, cellular offices may be provided as required through-out the plan.

21.6 Town planning

Most development and construction work is governed by theTown and Country Planning Act 1971. Section 22 of the Actdefines development as: 'the carrying out of building, engineer-ing, mining or other operations or the making of any materialchange of use of buildings or other land'. With some exceptions(mostly under the General Development Orders 1977 and 1981)permission to undertake any development is required from thelocal planning authority.

Other planning powers are concerned with individual build-ings listed as of special architectural or historic interest (whereconsent is required for any works of demolition or alteration),conservation areas, advertisements, caravan sites, tree preser-vation, national parks and the countryside.

County and district planning authorities prepare structure(broad policy) and local plans against which applications forplanning permission are judged. If planning permission isrefused or conditions are imposed upon the permission, theapplicant has the right of appeal to the Secretary of State for theEnvironment, and such appeals may be heard at a local publicinquiry.' Early consultation with the local planning authority (thedistrict or borough council) is recommended when advice will begiven on the need to obtain planning permission, the scale offees charged and the adopted planning policies which should betaken into account.

In some cases the local authority may provide access to grantsavailable for special types of development. These include dere-lict land grant for approved ground restoration works andurban development grants for joint public/private sector fund-ing of approved inner areas projects. In addition, most authori-ties offer grant, loan, site and premises assistance to encourageeconomic development in their area.

Major civil engineering projects such as oil refineries, powerstations, radioactive toxic and dangerous waste treatment anddisposal, iron and steelworks, asbestos extraction, chemicalplants, motorways, ports and airports are all listed in an EECDirective as likely to require an environmental impact assess-ment.

Further details of the planning legislation will be found in awork by Telling.4

21.7 Public utility

Once an outline brief exists and a site is under consideration thevarious public utility organizations (PO, gas, electricity, waterauthorities) should be consulted to determine the availability oftheir various services.

21.8 Feasibility

The compatibility of brief and site with the external constraintsin their varying forms logically leads to the preparation of afeasibility study. This is normally the first design exercise andprovides the design team with an opportunity to explore theproblem, propose solutions, cost the alternatives and identifyoptions for the client. Presentation of a preferred option with

objective data supporting the preference completes the firststage and forms the basis for the final design.

21.9 Cost

Cost is an important factor at all stages of the design process.Alternative design solutions or materials must be consideredcarefully to ensure that cost is within budget, that money isallocated in a balanced way to best suit the client's needs andthat, throughout the project, good value is obtained for themoney spent. The most significant decisions affecting cost occurin the concept and outline planning stage.

Of first importance is the economic use of space in theproposed building. Although the basic range of accommodationis fixed, considerable additional space is required for circulationand access, stores, plant rooms and toilet facilities. This ad-ditional space, sometimes called 'balance area', can vary consi-derably according to the layout adopted and should be kept tothe minimum by efficient planning of staircases and serviceducts, grouping of toilet facilities and a restriction on the area ofcirculation routes. The economic planform will also aim atreducing the ratio of external wall area to total floor area thussaving expensive wall materials and reducing heat losses (orgains) and, hence, minimising the installation and running costsof the heating, ventilation or air-conditioning systems. Thereduction of storey heights to a minimum will have similar costbenefits but could affect significantly the building's futureadaptability.

It is usual to prepare a cost plan for the project in elementalform. Initially it is a cost estimate based on the preferred schemeand structural system together with a specification covering themain building elements. In the long term it forms a coststructure for monitoring the cost effect of changes and thedetailed development of the design. The cost plan should statewhether it provides for price inflation to tender stage or buildingcompletion, or is based upon rates current at date of estimate.

Major elements should be kept in reasonable balance, e.g. theuse of an expensive cladding material could leave too littlemoney for the remainder of the work resulting in a visuallypleasing but operationally unsuccessful building. The cost planis an excellent means of checking the balance between thedifferent elements of structure, finishes and services though therelative percentages of the overall cost will vary from case tocase according to the type of building and its user requirements.

While the capital construction cost of a building is of primaryimportance, other costs will also be significant and could affectdesign. The annual running cost is one such item and servicesinstallations, particularly, should be considered in terms ofoperational as well as initial cost. Similarly, the use of anexpensive but hardwearing material may be justified in terms ofsubsequently reduced outlay on cleaning or maintenance. Dis-counting techniques and, possibly, tax considerations are neces-sary to make true cost assessments of such comparisons.

The total cost of a building project will also include expendi-ture on land, borrowed capital and the fitting out of thecompleted building, compensation to adjoining owners andother associated costs as well as legal and design consultant'sfees and expenses. In some cases, the earlier a development canbe occupied the better the cost advantage to the client. Theconstruction method and programme are then significant andmay affect the design form. It is often possible to assess thefinancial advantage of early completion and by comparativefinancial analysis to justify additional construction cost toshorten the construction period. Similarly, value engineeringcan be applied to ensure that optimum arrangements areadopted to meet the client's objectives.

21.10 Internal environment

21.10.1 Thermal environment

The required comfort conditions and tolerances are determinedby the intended function of the space concerned.

Thermal comfort depends on a complex of inter-relatedfactors: air temperature, ventilation rates, relative humidity andmean radiant temperature of the enclosing space. Mean radianttemperature is generally a function of enclosure construction,although the form of heating can have an influence. All otherfactors are determined by the air-conditioning system. Manyattempts have been made to devise indices which will representin one figure the composite effect of the different variables, suchas equivalent temperature (Teq) and corrected effective tempera-ture (CET). The former incorporates three of the basic vari-ables: (1) air temperature; (2) mean radiant temperature; and (3)rate of air movement; the CET adds relative humidity. For thepurpose of design calculations, however, the generally acceptedindex is resultant temperature, which is the mean of the airtemperature and the mean radiant temperature.

Internal design temperatures for air-conditioned buildings inthis country are usually of the order of 20° C in winter and 22° Cin the summer; relative humidity values are usually kept withinlimits depending upon the spaces served, the types of system,condensation considerations and the enclosure construction.Glass area and type, especially large single glazed windows, hasan appreciable effect on mean radiant temperature and alsorestricts the permitted humidity level in cold weather.

21.10.1.1 Site and climate

Internal thermal control will also be influenced by externalseasonal temperatures, relative humidity, wind velocities anddirection, air quality (industrial smoke pollution, etc.), solarorientation and latitude and relation of the site to surroundinglocality and adjacent buildings.

In other than air-conditioned buildings, external temperaturerelated to occupancy levels and internal heat gains determine theamount of external ventilation air to be introduced. Wherewindows can be opened, however, occupant behaviour tends tobe the dominant influence. In air-conditioned buildings ventila-tion air quantity can be related to external temperature andrelative humidity, but this is dependent on the type of air-conditioning system. In warm summer conditions, the amountof ventilation air has a direct effect on refrigeration loads, but atother times of the year, cool outside air can be introducedbeneficially to offset internal heat gains.

Excessive infiltration through openings such as doors, win-dow gaps, etc. can reduce performance seriously and increaseoperating costs; satisfactory sealing is necessary as are effectivemeasures to reduce the stack effect (flow of air up stair and liftareas) which grows in significance with increasing buildingheight.

Solar penetration into the building is determined by latitudeand season and the resulting heat gain can be serious. Methodsof control include internal or external louvres and blinds, specialheat-absorbing and reflecting glasses, small glass areas andvarious forms of external shading structure.

21.10.1.2 Building function and form

Thermal design is affected by the energy-producing elementswithin the building: human, mechanical and electrical. Buildingconfiguration, size and proportion and construction of thebuilding shell influence the adaptability and capacity of thesystem to cope with external environmental changes. The pro-portion between interior space which is independent of external

effects and perimeter space which is not, is important. Externalconditions penetrate a building to approximately 6m: thisperimeter zone will require a system which can quickly adapt torapid variations in the heating or cooling loads. In contrast,load changes in interior spaces are usually less rapid andrepresent a predominantly cooling requirement.

21.10.2 Air-conditioning

Natural ventilation has certain potential drawbacks: (1) noiseinfiltration through open windows; (2) overheating during sum-mer due to solar and internal heat gains; (3) excessive infil-tration of outside air resulting in uncontrollable internal airmovement; and (4) ineffective ventilation beyond about 5 mfrom the perimeter with attendant overheating.

Mechanical ventilation solves only a few of these problems.Noise and outside air infiltration are reduced as windows areopened less frequently. Increased air movement during warmerweather can alleviate discomfort to some degree.

Overheating and high humidity can, however, occur due tothe inability of the system to supply air at the correct thermalcondition. This inability is overcome by the inclusion of refriger-ation, thereby changing the system from mechanical ventilationto air-conditioning.

Air-conditioning provides a controlled internal thermal en-vironment which is largely independent of the external con-ditions or of any changes in the internal load conditions.Planning and configuration of the building will be influenced bythe provision of air-conditioning. Deep space can be createdwith the knowledge that a satisfactory internal thermal environ-ment will be achieved. Similarly, nonopening windows avoidinfiltration problems which are accentuated with increasedbuilding height.

Moisture control and filtration of the incoming air areintegral parts of full air-conditioning giving a cleaner, healthierand more comfortable atmosphere compared with ventilationby natural methods. Redecorating costs and absenteeism maybe reduced and working efficiency increased.

21.10.2.1 Air-conditioning systems

Many types of air-conditioning systems are available and can beclassified into three basic groups: (1) 'centralized'; (2) 'decentra-lized'; and (3) 'self-contained' systems; some solutions arecombinations of these three.

Centralized systems. Centralized systems are:

(1) Systems where air is processed at a central plant anddistributed for use without further treatment:(a) single-duct all-air systems using high-, medium- or low-

velocity distribution;(b) double-duct all-air systems using high-, medium- or low-

velocity distribution with local terminal mixing units(referred to as dual-duct systems).

(2) Systems where air is processed at a central plant, but withfinal heat addition or subtraction at the point of use:(a) single-duct all-air reheat/recool systems, using high-,

medium- or low-velocity air distribution with associatedheating and/or cooling water distribution;

(b) perimeter induction air/water systems using high-,medium- or low-velocity primary air distribution withsecondary heating and/or cooling water distribution ona two-, three- or four-pipe principle.

Decentralized systems. Decentralized systems are:

(1) Systems where a liquid medium is distributed from a central

point to units which condition air locally: some such systemsalso have a supplementary primary air supply from a centralplant to the unit or space:(a) room fan coil unit air/water system with two-, three- or

four-pipe water distribution and local outside air con-nections;

(b) as for (a) but with supplementary primary air fromcentral plant;

(c) localized zone air-handling unit all-air systems withassociated heating/cooling water distributions and withlow-velocity air distribution to conditioned spaces fromthe units;

(d) radiant ceiling systems supplied with heating/coolingwater distribution and supplemented with separatesingle-duct all-air system.

Self-contained systems. Self-contained systems are systemswhere self-contained air-conditioners process and supply air atthe point of use.

Each system has merits and limitations. The simpler low-velocity all-air single-duct systems require a large amount ofduct space and are not a practical solution where a large numberof zones of varying use are to be served. In these cases a systemwhich can respond to these variations is required. One of thefollowing systems would be appropriate. Double-duct all-airsystems mix air from separate hot and cold distribution ductsusing ceiling- or sill-mounted terminal mixing boxes. Thissystem is very adaptable, but the combination of two supplyducts plus a return air duct requires considerable service space,even when using high- and medium-velocity distribution.

The induction unit discharges primary air supplied from thecentral plant through high-pressure nozzles and this induces airfrom the space into the unit which then mixes with the primaryair before discharging back to the space; temperature control isachieved by a heating/cooling coil. Space is saved because theair is distributed at high velocity. The basic difference betweentwo-, three- and four-pipe associated water distribution systemsis that the latter two can provide, at the point of use, thesimultaneous facility for either heating or cooling, while thetwo-pipe system is restricted at any one time to one or the other.

Fan coil systems incorporate a heating/cooling coil and acirculating fan. Primary air can be ducted direct to the unitsfrom a central system or discharged to the space independentlyor alternatively, each unit can draw in air direct from outside.

Radiant heating/cooling ceilings, when used with a supple-mentary air system, can provide an effective environmentalthough their adaptability to meet rapid fluctuations in heatingand cooling loads is limited.

Self-contained packaged air-conditioning units are usuallyrestricted to smaller specialized projects.

21.10.2.2 Air-conditioning - distribution and integration

Considerable duct distribution space is required and air outletsand extracts are often incorporated in the detailing of lightfittings and suspended ceilings. From the earliest stages, there-fore, the air-conditioning system should be integrated into thetotal planning and detail design process of both the buildingelements and the structure.

Perimeter units can be served from a network of air ducts orwater pipes concentrated in zones near the outer wall, within theunder-sill or ceiling void for horizontal piping or ducts andwithin structural column enclosures for vertical distribution.Alternatively, the perimeter area may be served from the centralcore with ducts and pipes accommodated above a false ceiling,within a structural hollow floor or beneath a raised floor.

In areas where little flexibility for changing use is required, atotally integrated solution using the structure to accommodate

air and water distribution may produce some economies includ-ing reduced storey height. Where a high degree of flexibility isrequired as, for example, in open-plan buildings, ceiling distri-bution on a modular basis for interior zones and sill or ceilingdistribution for the perimeter becomes essential and a falseceiling is required, the ceiling space being used to accommodatethe ducts and pipes.

The above systems can be described as fully ducted. There aretwo other basic air-supply and exhaust methods using theceiling space as a large duct or plenum:

(1) Negative plenum: air is extracted into the plenum throughoutlets in the false ceiling which are usually part of the lightfittings. Air supply is ducted to diffusers or slots incorpor-ated in the ceiling design.

(2) Positive plenum: the plenum is used as the supply duct, airbeing forced through ports in the false ceiling. Extracted airis ducted from terminals usually incorporated in the lightfittings.

When the air is exhausted through the light fittings it cools and,hence, increases the efficiency of the light source: it also removesexcess heat (arising from high light levels) which can be trans-ferred for use elsewhere, e.g. the perimeter area, but is morecommonly vented to the exterior. The outlets require carefuldesign coupled with adequate ceiling height, 4 to 5 m if possible,to prevent downdraughts.

The completely ducted system has fewer thermal problems,but occupies more space and is more expensive. The plenumsystems substantially reduce duct requirements, but are lessefficient; they also require careful control of temperature toprevent condensation and, sometimes, the incorporation ofinsulation on the underside of the structural floor to confine theplenum effects to the storey intended.

21.10.3 Accommodation of building services

Services can occupy 15% or more of the volume of a buildingand their distribution through the building is critical to itsperformance and flexibility. The organizing of space for servicesis thus of vital importance both in the strategic planning anddetail design stages of the building. The servicing systems maybe given direct expression or be entirely hidden within theoverall form and finishes of the building.

The strategic planning of the services installations involvesthe optimization of the location and size of plant room spacesand the distribution systems linking them with the buildingareas being serviced, coupled with their integration with thestructural and architectural elements. Frequently, there is pres-sure on the design team to minimize the space occupied by theservices as the result of planning height restrictions or ongrounds of economics. This can prove a false economy as suchan approach can affect significantly future flexibility in the useof the building.

Plant rooms should be positioned as close as possible to thecentre of gravity of the areas they serve to keep maximum ductsizes to a minimum and should be readily accessible to connect-ing ductwork without impediment from adjacent structure. Theimpact of weight, noise or vibration on adjacent elements orbuilding functions should be considered. In general, service runsshould not be more than 25 m from the point of origin and,vertically, plant rooms should not serve floors more than tenstoreys away. Plant rooms should be sensibly proportionedavoiding L-shapes and long thin spaces. Clear height generallyhas to be to the underside of structural beams and if possible theplant room space should be column-free.

Frequently several plant rooms are required covering thefollowing items.

(1) Boilers and refrigerators: commonly referred to as theenergy centre.

(2) Air handling: fans, heating and cooling coils and filters.(3) Water: storage tanks.(4) Sprinklers: storage tanks.(5) Cooling towers: serving the cooling plant.(6) Lifts: motors, winding gear or pumps.(7) Electrical: switchroom or substation or standby generator.(8) Telecommunications: telephone and data transmission

equipment.

Some of these items must not be incorporated in the same plantspace. Examples are water and electricity, refrigerationmachines (chillers) and boilers to avoid toxic fumes fromrefrigerator gas coming into contact with boiler flames.

Access for installations, repair and maintenance must beincorporated and construction problems including speed shouldbe taken into account in the siting of these elements especiallywhen the installation of plant is on the critical path to comple-tion.

In air-conditioned buildings, the air intake must be separatedfrom the air discharge. The top of the building is often thepreferred location for the air-handling plant particularly with allair systems involving recirculated air. In very large buildings, anumber of air-handling plant rooms distributed through thebuilding provide greater flexibility and less inroad into usablebuilding volume.

The combined plant room area typically ranges from 4 to15% of total floor area depending upon building type. Someplant area requirements are as follows:

(%)Hospitals/laboratories 9-15Swimming pools/ice rinks 5-12Shopping centres 5-8Theatres/concert halls 9-11Air-conditioned speculative offices 6-9Residential/hotels 4^5Factories/warehouses 3—4

Special cases can lead to even greater plant areas when environ-mental control is required to extremely fine limits, e.g. inpharmaceutical or semiconductor production facilities.

The incorporation of the horizontal services within the ceilingand floor construction is a vital element in the efficient design ofthe building particularly when overall floor depth is critical.Many different arrangements have been developed around bothsteel and concrete structural elements with the objectives ofkeeping floor depth to a minimum yet providing easy access andflexibility for future change. Some typical arrangements andcorresponding floor depths are shown in Figure 21.2. In somecases complete storeys may be given over to services distribu-tion.

The location of the plant rooms and the location of pipe andduct runs can have a critical impact on structural arrangementand detail. The co-ordination of structural penetrations is animportant task for the structural engineer and timely receipt ofrelevant information from the services engineers is vital. Incertain cases, duct and plant room walls may be subjected topositive or negative pressure which the structural engineer mayneed to take into account. Enclosure materials and constructionwould need to be appropriately airtight.

Modern office design has to cater for widespread use of thecomputer. Space for cabling and easy access for modification orextension are essential ingredients for good design catering forboth immediate and long-term requirements. At the same time,increased space is needed for air ducting to deal with the higherheat loads generated. The growing impact of this heat-generat-

ing equipment on the total heat load that has to be dealt with bythe air-conditioning system is illustrated in Figure 21.3. Figures21.4 (a)-(c) show diagrammatically three methods used for theincorporation of air-conditioning and cabling in the present-dayelectronic office.

Figure 21.4(a) shows a conventional-sandwich ceiling andraised floor. In this arrangement, which is favoured by mostspeculative developers, the air supply and removal and thegeneral lighting are incorporated in the space between thestructure and a suspended ceiling. All cable services are in theelevated floor usually between 75 and 150mm deep. In somecases, cables are run Jn hollow cells in the structural floor deck.This arrangement separates service systems cleanly but costsmore.

Figure 21.4(b) shows a total ceiling servicing using 'stalac-tites'. In this arrangement, a little more depth is added to theceiling space and facilities provided for easy and frequent accessso that heavy cabling can be accommodated in the ceiling space.The cabling is brought to the workstation down partitions,columns or free standing 'power poles'. This is the lowest costoption but is not much used in new design outside the high-technology industries. However, the increasing shift back tocellular offices coupled with the arrival of slimmer, more flex-ible, data cabling could make this solution more acceptable.

Figure 21.4(c) shows the total floor servicing using 'stalag-mites'. In this arrangement, all the services and cabling areincorporated in the floor void. Uplighting is bounced off theceiling helping to provide glare-free background lighting forvisual display unit (VDU) working, and is augmented whererequired by task lighting. Air can be supplied, under occupants'control, through desks and removed through heat-producingequipment and light fittings. Partitions sit between the heavyfloor and the solid ceiling giving better sound insulation. Theexposed structural ceiling acts favourably as a heat sink helpingto even-out internal temperatures. Removal of a small propor-tion of overhead stale air can be effected through uplighter unitsor in voids at walls or around structural columns.

21.10.4 Heating/cooling generationArrangements for the heating and cooling generating plant willdepend on a number of general and localized factors: (1)availability, suitability, and economic costs associated with theutilization of fuel and power; (2) resources peculiar to the site;and (3) utilization of recoverable energy associated with theheating and cooling systems installed within the building.

Fuel and power considerations are complex and include adetailed appraisal of operating and capital costs for various fuelalternatives (coal, gas and oil) and power. Boiler plants incor-porating combined dual-firing burners suitable for gas (town ornatural) and oil can offer attractive capital and operating costcharacteristics combined with greater flexibility.

Heat-recovery systems have been gaining popularity. A com-mon arrangement is to utilize low-grade heat being rejectedfrom refrigeration machines. Another is to transfer heatextracted from the interior of deeply planned areas, which haveto be cooled, to spaces requiring a heating load, such asperimeter zones, during winter and certain mid-season periods.

On larger specialized projects, total energy is finding anapplication. This is based on the concept that the total energyrequirement, in all its forms, can be provided from a single fuelsource. These systems incorporate electrical generation withheat being produced as a byproduct. Refrigeration, which canbe met by either electricity or heat, is usually a complementarypart of such an integrated energy system.

Floorceilingconstruction

Description

Services implications

Typical applications

Typical floor to floor height

Solid concrete slab-powerfloated finish

Cast-in electrical conduitsSurface fixed lightingLighting position fixedPerimeter power, data, telecom

trunkingPerimeter mechanical systems

typically radiators orconvectors, visible pipework

Heated and naturally ventilatedoffice (simple), hotel bedrooms,multiple housing anddormitories

2.7m

Solid concrete slab, sc reededfinish

No access false ceilingSurface fixed lightingLight position may be altered

by stripping out and replacingfalse ceiling

Screed can accommodate flushfloor but unlikely to haveelectrical trunking as analternative to perimetertrunking

Perimeter mechanical systemsVisible pipework

Heated and naturally ventilatedoffice (simple)

3.0m

Solid concrete slab, screededfinish

Limited access false ceilingrecessed light fittings

Light position may be alteredby local modification of falseceiling

Ceiling zone can accommodatepipework runs that serveperimeter mechanical systems(concealed pipework)

Flush floor trunking possible(and likely) with floor screed

Most naturally ventilated andheated buildings with a 'simple'services content

3.3m

Solid concrete slab, screededfinish

Full access false ceilingrecessed light fittings

Changes to ceiling layout easyservice zone sufficient size forair ducts serving air/waterair-conditioning systems - butnot all-air systems

Perimeter terminal units for400 mm void

Some ceiling-mounted terminalunits (such as, fan coils) for500 mm void

No space for duct crossoversAverage-quality office,

refurbished officeall areas with an averageservicing requirement

3.6 m

Service void and ceiling as for (d)Structure change from concrete

slab to steel frame metal deck,small raised floor

Changes to ceiling layout easilyaccommodated

False floor allows easy locationrelocation/addition to electricalservices and outlets

All-air systems possible withlarge terminal units instructural zone between beams

Large duct crossovers possiblewithin structural zone

Minimal perimeter systemshigh-quality office; areas withaverage to high servicescontent

3.9m

As for (e) false floor depthincreased

Increase in depth of false floorallows pipework to be locatedin the floor zone

Flexibility due to ease ofaddition of piped services

Allows flexible location ofcomputer rooms

Easy to upgrade coolingcapacity on floors for tenantswith high floor heat loads

High-quality office with highinformation technology contentoffice where frequent internalreplanning/changes occur

4.2m

False floor depth increased,services removed from ceilingzone-transferred to floor zone

Increase in depth of false floorallows pipework ductwork andelectrical services to be located

Allows flexible location of allservices

High-quality office with highinformation technology contentoffice where frequent internalreplanning/changes occur

3.9m

Figure 21.2 Options for horizontal service distribution showingincreasing size and complexity of service zone planning assophistication increases provision. (After Architect's Journalist, 9,p.62 (1986))

Figure 21.4 Incorporation of air-conditioning and cabling in theelectronic office, (a) Conventional sandwich; (b) stalactites; (c)stalacmites

Stalagmites

StalactitesConventional sandwich

Figure 21.3 Trend in office space internal heat gains fromequipment lighting and occupancy

High-technologyspaces100 plus W/m2

High 50 W/m2

Average 25 W/m2

Low 10 W/m2

Lighting 20 W/m2

Occupation 10 W/m2

Lighting

Occupancy

Equipment

Inte

rnal

load

ings

(W/m

2)

Equip

men

t loa

ds

Present

21.10.5 Thermal insulation

The object of thermal insulation, together with heating, is toobtain, irrespective of the prevailing weather conditions, a near-constant internal temperature determined by requirements ofhuman comfort and satisfactory conditions for manufacturingprocesses or storage of goods. Adequate insulation is needed toavoid excessive expenditure on heating plant and fuel. Theinsulation and heating of buildings for human occupation arenormally designed to maintain a temperature of 16 to 210Caccording to use when the outside temperature is -I0C. Goodthermal insulating materials generally are those which entrapair, such as lightweight concrete, wood-wool slabs, glass ormineral fibre wool.

Calculation of the thermal transmittance, or U value, of awall, floor or roof is carried out by adding together the thermalresistances of the materials and surface coefficients and takingthe reciprocal of the answer to provide the thermal transmit-tance of the composite construction:

U=\/R (21.1)

*-** + ** + $ + $«*' + *• + ** <2L2)

where R is the total thermal resistance of the structure, R^ is thesurface resistance of the inner face, R&2 is the surface resistanceof the outer face, /?a is the resistance of the air cavity if present,Rh is the resistance of unit material such as hollow block whereresistance per unit thickness does not apply and L/K is theresistance of one layer of material or thermal conductivity K andthickness L.

To evaluate the total heat loss from a room or building thethermal transmittance of the walls, windows, floor and ceilingmust be calculated and allowance made for the losses involvedin heating-up the ventilating air and the structure when heatingis intermittent.

Structural members penetrating the full thickness of a wallproduce 'cold bridges', locally reducing the thermal resistanceand internal surface temperatures, with consequent added riskof condensation. In such cases the cold bridge should be reducedin width or eliminated by appropriate insulation.

Ureaformaldehyde foam is sometimes used to fill the cavity incavity-wall construction resulting in an almost 80% reduction inheat loss through the walls. Double glazing, as well as reducingheat loss, has advantages in increasing the temperature on theinside window surface and may improve internal comfort con-ditions.

Condensation problems have increased due to new methodsof building, standards of heating and control of ventilation, andchanging family habits which have led to intermittent heatingcoupled with the generation of more moisture inside the dwell-ing. Old buildings, particularly domestic ones, usually had openfires and flues and windows were generally less well-fittingresulting in natural, if draughty, ventilation which got rid ofmoisture-laden air and avoided condensation on cold walls andwindows. Condensation in modern buildings can be avoided byadequate combination of insulation, heating and ventilation.

The amount of moisture which air can hold, increases withthe temperature and when it can hold no more water it is said tobe saturated and the relative humidity is 100%. The temperatureat which air with any particular moisture content is saturated iscalled the dewpoint and if that air falls on a surface which iscolder than the dewpoint, condensation will occur. Anotherobject of thermal insulation, in conjunction with heating andventilation, is to ensure that the inside surfaces of walls, floors,ceilings, roof and, if possible, windows, are kept above thedewpoint.

Moisture-laden air can pass through a porous wall or roofconstruction and condense inside where it meets a temperaturebelow the dewpoint. Figure 21.5,5 shows the relationshipbetween the local material temperature and dewpoint throughthe cross-section of varying arrangements of a composite exter-nal wall, for given internal and external air temperatures andmoisture contents. By appropriate positioning of a vapourbarrier and combination of materials forming the wall, the localdewpoint can be kept above the local temperature and conden-sation avoided. Temperature drops across the section are deter-mined by the proportional thermal resistances of the materials,surfaces and airgap; dewpoints are obtained by first determiningthe local vapour pressures from the proportional vapour resis-tances and then converting these to their respective dewpointtemperatures.

21.10.5.1 Estimation of condensation risk

At any point where the computed temperature is lower than thecomputed dewpoint temperature, condensation can occur in theconditions assumed. In the worked example, liquid may form ina position where, clearly, it can reduce the effectiveness ofinsulation and it is likely also to put the nearby timber at risk ofrot. As in illustration of the effect of structural detailing, Figure21.5(b) shows the construction reversed and free from risk in thesame surrounding conditions. Slight modifications shown inFigure 21.5(c) and (d) are sufficient, however, to limit thepotential risk by using materials that modify the vapour pres-sure gradient.

21.10.6 Lighting

Three types of lighting are used: (1) daylight; (2) daylightintegrated with electric lighting; and (3) electric lighting. Gooddaylighting is more than the provision simply of large windows.Optimum size, shape and position of windows is a function notonly of the required lighting levels, but also of the resulting eyeadaptation conditions, sky glare and external view. In addition,heat loss or solar gain, ventilation, noise transmission, privacyand the shading effects of adjacent buildings, present or future,must be taken into account. Side-lit rooms often appear badlyilluminated because of the contrast between the areas adjacentto and those remote from the windows, even though workingillumination levels may be adequate throughout.

At one time, daylighting appeared cheap and its real cost wentunquestioned. The present position is different: modern lightsources cost less and are more efficient while the true cost ofdaylight is recognized in terms of added cost in construction,maintenance, heat loss or gain and, in urban areas, the inef-ficient use of the available site area. Simultaneously, theexpected standards have increased in both quantity and qualityand, in modern buildings, daylighting would not be relied uponas the sole source of light even during periods of good outdoorlight.

By introducing electric lighting of a colour to blend withdaylight it is possible to provide adequate illumination over thewhole working area without a sense of deprivation of daylight.Moreover, such arrangements - known as permanent supple-mentary artificial lighting of interiors (PSALI) - can be appliedwithout visual discomfort over areas much greater than can belit by daylight alone, irrespective of the prevailing outdoor light;its added cost must be weighed against the direct and indirectcosts of higher ceilings and bigger windows, reduced floor spacefor lightwells, and/or restricted useful depth of rooms.

The current quest for saving energy has stimulated researchinto methods of securing greater penetration of daylight intobuildings. One such method involves the use of carefullymachined acrylic prisms sandwiched between sheets of glass

Figure 21.5 Prevention of condensation in wall cavities. (AfterBuilding Research Establishment (1979) Thermal, visual andacoustic requirements in buildings. Digest No. 91 (2nd edn). BRE,Watford)

attached to the exterior of the building as a form of shading. Theprisms redirect the Sun's rays parallel to the ceilings within thebuilding whilst blocking sky glare. The ceilings are speciallyshaped to divert the parallel beams and provide the uniformillumination on the working plane. Another approach usesheliostats to direct the Sun's rays into a hollow square acrylicpipe which, using the principle of total internal reflection in amanner similar to fibre optics, can feed light down the risers of a

building to illuminate the inside. This method has the advantagethat as daylight fades, artificial light sources can irradiate thesame piping.

The use of external automatic sunblinds has had limitedacceptance, mainly due to high costs both initial and subse-quent. Inevitably, the continued operation of electro-mechani-cal devices such as these, subject to external forces, is difficult.More promising is the development of special glasses similar to

0.05 mm polythene 38 mm mineral wool 38 mm foamed polystyrene

Dewpointtemperature

Structuraltemperature

12mm softwood38 mm mineral wool

Cavity

114 mm masonry12 mm rendering

Condensedwater

Insid

e

inside

inside

Insid

e

the familiar photochromic but whose light transmission may bevaried reliably by the application of an electrical potential.

Quality of the electric light is as important as quantity anddesign should take into account: (1) brightness and colourpatterns; (2) directional lighting where appropriate; (3) controlof direct or reflected glare from light sources; (4) colour render-ing; and (5) prevention of excessive contrast between adjacentareas.

The most common light sources are tungsten lamps andfluorescent tubes with a growing acceptance of high-pressuredischarge lamps. Tungsten lamps are common in domestic anddecorative installations, but are inefficient in their light outputand are generally uneconomic for the lighting levels required inmost modern buildings. However, at a time when the newcompact-source fluorescent lamps seemed likely to oust tung-sten lamps even in the home, a specialized form - the low-voltage reflector tungsten halogen lamp - is growing in popular-ity, especially for display purposes. Their small size, longer life,improved efficacy and excellent colour rendition compared withstandard tungsten lamps have tended to outweigh high capitalcost and the inconvenience of the stepdown transformers andheavy cabling.

Fluorescent tubes are the most commonly used, but can takeup considerable amounts of ceiling space. High pressure dis-charge lamps provide similar benefits of efficiency and long life,but more closely approach a point source, permitting greaterfreedom in ceiling design. The ability to accommodate aneconomic light fitting will depend upon the planning andstructural grids. When these are not appropriate to the lightfitting, the lighting system will be expensive in itself and mayalso cause extra cost in removing the unwanted heat.

The light fittings have to be spaced carefully to provideadequate lighting levels over the whole working plane. Due tothe physical discomfort which can be caused by the brightness ofthe light source, careful attention must be given to the preven-tion of direct or reflected glare. Glare standards exist for mosttypes of working environments and the glare characteristics oflamp fittings and control diffusers are readily available.

The rationale behind such lighting layouts has always beenthe ensurance of a high degree of uniformity so that any locationof the working plane will be served adequately. The basicinhumanity of such schemes, together with the absurdity oflighting circulation spaces to the same level as the task, hasresulted in the growing popularity of uplighting where thelighting plane is illuminated indirectly by light bounced off areflecting surface, usually the ceiling. As in most spheres of life,high quality is difficult to reconcile with efficiency and the cost ofa superior working environment is increased consumption,typically 16 W/m2 for 400 lux on the desk. Possibly the greatestsingle factor behind the popularity of uplighting is the expan-sion of the use of VDUs and word processors where, unlikemost other forms of lighting, a correctly designed indirectscheme can limit tiring and distracting reflections from thescreen.

The varying colour qualities and corresponding luminanceefficiencies of the available light sources have an importantbearing, not only on the visual environment, but also on thedegree of heating or air-conditioning that may be required. Thecolour appearance of a light source is always cause for muchsubjective judgement and prejudice. Daylight cannot be used asa reference value since its spectral composition shifts through-out the day. Indeed, what is wrong with light sources, the puristsinsist, is that their colour appearance does not noticeablychange. Fluorescent tubes can now be had in a bewilderingrange of phosphors equally able to imitate tungsten lamps orcold north light. The triphosphor tubes now make it possible tohave both excellent colour rendition and high efficacy. The mostpromising light source for commercial interiors is the high-

pressure sodium lamp, which is able to better the fluorescenttube on most counts. However, its colour appearance even inthe de luxe form remains controversial.

In some buildings, the energy for lighting can be a substantialpart of the total required for all purposes. Since most of thatprovided for light appears as heat the possibility exists of usingthis as a major, and perhaps the only, source of internal heating;alternatively, the extra heat load may prove an embarrassmentto the air-conditioning system. In either case the lighting mustbe treated as an integral part of the total environmental design.

Having selected the most efficient light source and used it inthe most effective luminaire, the remaining part of the energyequation is control of the running hours. In many situations,people switch lighting on but never off so the advent of remotecontrols providing automatic switching is beneficial. Generally,such controllers operate either on a time basis or in response tosome local stimulus. Their switching programmes may be heldin their memories for as much as a year ahead with all holidaysand weekends catered for. The instructions in the form of codesare transmitted along dedicated hard wiring or even over thesupply cables themselves to the luminaires which are equippedwith decoders enabling them to respond to one or severalinstructions. Local overriders often in the form of hand-heldinfra-red transmitters enable the central instructions to bemodified. Less extensive forms of automatic lighting controltake the form of presence detectors which switch off after apreset period, as the result of high daylight levels, or in theabsence of people. The detecting principle may be either acous-tic or infra-red.

21.10.6,1 Lighting for various categories of building

Speculative offices. Such buildings are generally leased withoutlighting fittings to avoid inhibiting either the letting pattern orthe tenant's partition layout. Where lighting fittings are sup-plied, the preference is often for surface-mounted hot-cathodefluorescent tube units with prismatic light controllers. Lightinglevels are currently in the region of 400 lux.

Offices: purpose design. In keeping with the design standardsrecommended in the Chartered Institute of Building ServicesEngineers (CIBSE) code for interior lighting,6 average levels of500 to 750 lux are usual, depending on the task. Such levelsusing combinations of light controllers with 'batwing' andasymmetric distributions may be had for as low as 10 W/m2 butat the cost of inflexible and regimented workstation layouts. It isnow possible to simulate lighting effects by means of models andartificial skies but this is best used where the budget will permitthe purchase of purpose-designed luminaires. Much interest isbeing focused on the introduction of high-frequency controlgear for fluorescent tubes which, for example, would reduce theloss on a 1500 mm tube from 13 to 5 W with gains in freedomfrom flicker and with silent operation.

Offices: burolandschaft. The gentle modulation of light andshadow produced by uplighting is particularly apt for this formof office. Using either metal halide or high-pressure sodiumdischarge lamps, uplighting brings good colour rendition, highefficacy, low maintenance and lack of glare, either direct orreflected. It saves the cost of a discrete lighting circuit sinceuplighting is usually fed from the small power points installed inthe floor. The design process involved in an uplighting scheme isstill unfamiliar to many, being task-related rather than building-related, and this unfamiliarity has tended to limit its moregeneral acceptance.

Hospitals. The difficulties of reconciling the lighting needs in

wards of patients who may either be lying supine or sitting up intheir beds has led to separate systems being installed. In thelatter case, wall-mounted units are preferred and these are oftenincorporated into continuous horizontal trunking runs whichmay contain other services such as oxygen, sound broadcasting,nurse call systems, etc. The former requirement is met byfluorescent fittings generally of the suspended pattern. There aremany specialized considerations, such as operating theatres andanaesthetics rooms where totally enclosed, noise-proof fluor-escent fittings sealed into the ceiling structure provide generalillumination whilst shadowless operating-table lighting fittingsincorporating tungsten light sources produce intensities up to10 000 lux in the operating area.

Housing. Whilst tungsten fittings are still the norm for thehome, the advent of compact fluorescent lamps with theirsignificant economic advantages and tungsten-like colourappearance may change this. More sophisticated forms oflighting control, such as touch dimmers and infra-red switching,are now available and are beginning to be installed.

Schools. Cost considerations usually dictate surface-mountedfluorescent fittings with prismatic light controllers with levels inthe region of 600 lux. In rooms where the seating has a fixedorientation, directional fittings may be used.

Industrial buildings. When ceiling heights are below about 4 m,fluorescent fittings are still the most-used light source. Abovethis, high-pressure mercury or sodium discharge lamps in reflec-tor fittings are used with a wide range of distribution curves,both symmetrical and asymmetrical. The colour rendition ofmercury fluorescent, mercury halide or high-pressure sodiumlight sources are satisfactory, but care has to be exercised inmachine shops because of stroboscopic effects.

Car parks. The majority of multideck car parks use barefluorescent tubes in fittings with moisture-proof lampholdersand glassfibre or PVC-coated bodies. In the larger open carparks, increasing use is being made of high mast lighting.

Museums and art galleries. The lighting of museums and artgalleries should be designed principally to meet the require-ments of conservation, display and specialized study. Apartfrom atmospheric pollution, the main destructive agents will bethe ultraviolet and infra-red content of light. Natural light is theworst offender with discharge sources such as fluorescent tubes,with high-pressure sources coming second. All three requirecareful filtering before they can be used to illuminate anyexhibits containing organic materials or pigments.

Even tungsten halogen sources are suspect because of ultra-violet energy. The usual formula is a blend of tungsten displayfittings giving a restrained average illumination plus fluorescenttubes with ultraviolet filtering. Deterioration of organicmaterials is a product of the intensity of the harmful wavebandsand the length of exposure. The use of presence detectors -which ensure that exhibits are only illuminated for the periodwhen there are people to see them - would be of value.

21.10.7 Noise

The control of noise requires consideration of its nature, sourceand mode of transmission. Typically, the main problems are: (1)reduction of noise to an acceptable level for efficient working;and (2) effective noise barriers for privacy. Problems of soundinsulation and sound absorption are involved.

The main source of external noise is air or road traffic;penetration is reduced by double glazing (cavity preferably notless than 200mm), minimum window area and heavy wall

construction. In extreme cases, windows must be kept perma-nently closed and the building air-conditioned.

Internally, structural walls and floors are generally of suffi-cient mass to provide effective barriers against airborne soundbut impact sound is not reduced by mass alone and a resilientmaterial must be added to provide adequate total sound insula-tion. The lighter building elements, such as suspended ceilingsor demountable partitions, do not provide good sound insula-tion. Continuity of sound insulation, where it is required, isimportant; a sound-insulating wall would need to extendthrough the void above a suspended ceiling, for example, unlessthe ceiling is itself a good sound insulator.

The use of sound-absorbing surface materials and shapes iseffective in reducing the ambient noise level and may be sosuccessful in burolandschaft offices that a degree of manufac-tured ambient sound may be needed to mask and, hence, reducethe disturbance from local intermittent noise.

Appropriate planning and detailing of the building is vital tothe elimination of noise problems and the establishment ofprivacy. Wherever possible, areas requiring low noise levelsshould be divorced from noisy areas such as plant rooms,loading bays and lift motor rooms. Many items of mechanicaland electrical equipment produce airborne noise which can passalong air-conditioning or ventilation ducts which then requiresilencer units. Equipment located in occupied rooms must beselected with appropriate low noise characteristics; in certaincases, especially on high-pressure systems, secondary silencerunits are required. Rotating or reciprocating plant should beisolated from the structure to prevent structure-borne noise orvibrations. The increase in plant noise within buildings isincreasingly a factor in modern design, requiring specialistadvice.

Rooms with a high level of sound within them do not requiresuch a good standard of insulation from adjoining rooms ofsimilar level, but low-tolerance rooms will require a highstandard. Figure 21.6 gives an indication of sound reductionlevels for different room tolerances.

Figure 21.6 Sound reduction levels for various room tolerances.(After Parkins, Humphreys and Cowell (1979) Acoustics, noise andbuilding (4th edn). Faber and Faber)

The sound reduction of dense walls varies with the soundfrequency and with the weight of wall. At 550 Hz, the soundreduction is as follows:

Weight (kg/m2) 3 6 12 25 50 100 200 400 800 1000Sound reduction (dB) 20 24 28 32 36 40 44 49 54 55

For a cavity wall, a reduction value corresponding to thecombined weight of the two leaves is used and to this is addedthe additional assistance provided by the cavity which varieswith its width as follows:

Noise source

High level

Noise receiving room

Low tolerance

Medium toleranceAverage level

High toleranceLow level

Air space (mm) 30 40 50 60 80-100 150 200Added sound reduction (dB) 6 8 9 10 12 10 6

If the wall contains a door, the equivalent resistance is anintermediate value between those for the wall and door, depen-dent upon the relative decibel values and areas. For a brick wallof say 46 dB and door of 20 dB and the wall 10 times the area ofthe door, the equivalent sound reduction values (obtained fromcharts, e.g. Neufert7) is 3OdB. The full insulation value isobtained only if all holes, e.g. for services, are sealed; even verysmall openings such as keyholes and open joints representserious sound leaks and must be taken into account in the designif good insulation is to be achieved.

21.11 Water supply, drainage andpublic health

21.11.1 Water supply

Potable water supplies are generally supplied from the localwater undertaking's mains, the local water companies beingrequired under the Water Act, 1945 and EEC directives tosupply consumers with a potable supply. The conditions arebased on the Model Water Byelaws of 1982, the purpose ofwhich is to prevent waste, undue consumption, misuse andcontamination. Water charges may be based on rateable value,assessed annual consumption or on metered consumption.

In the UK, storage provision for cold water for purposesother than drinking is normal and is provided for convenience inthe event of mains failure. British Standard Code of Practice 310schedules the amount of water storage required based uponoccupancy (or number of fittings) and building type. Waterstorage is ideally located at roof level and below the availablemains head to minimize operating and maintenance costs and toavoid pumping. A major revision to the various existing waterservices codes of practice is BS 6700.

It is increasingly found that water mains have insufficienthead to deliver water to the upper levels of buildings without theaid of supplementary boosting. The method of boosting shouldtake into account the location of storage, the possible need forany intermediate storage, pressure limitations or requirementsin the distribution system, routing, quantities and usage ofwater. The two most common methods are direct centrifugalpumps serving high-level storage tanks or pneumatic pressurecylinders to boost the available mains pressure; the latter avoidsthe need for, but does not preclude, the use of high-level storagetanks. Break-cisterns are often required at ground level tocushion demand and very high buildings require break-pressurecisterns restricting gravity drops to about 30 m.

The distribution pipework generally separates cold- and hot-water service feeds and is preferably arranged to provide hotand cold water to the fitments at equal pressures. The routingshould take into consideration maintenance, the requirementsfor draining down, protection against back siphonage andinsulation against freezing and condensation.

Most large buildings have extended hot-water distributionsystems served by a central heating plant which generally alsoprovides the space heating. A central plant offers economies ofscale and uses less fuel than a system of dispersed boilers. Theboiler water is kept separate, the hot-water supply being heatedby means of heat-exchange coils in calorifiers located in proxi-mity to the outlets being served. Deadlegs need to be avoidedwherever possible. Intermediate calorifiers can be located to actas break-pressure cisterns.

21.11.2 Fire installations

Water for fire-fighting purposes in buildings is separated from

general water usage and is required for the hose reels, wet risersand sprinklers.

Consultations with the local fire authorities are required toensure that storage and system duties are met. A number ofpackaged pumping units are available on the market for hy-draulic hose reel installations. Wet risers are a fire authorityrequirement in tall and large-volume buildings. Sprinklers maybe a requirement of the local fire authority or the buildingowner's insurance company. In the UK, most installations arerequired to comply with the 29th edition of the Fire Officers'Committee Rules* which have very specific water flow/pressurerequirements and can involve large bulk water-storage require-ments, dependent upon the fire risk hazard category. Specialistadvice should be sought on these installations.

21.11.3 Water treatment

The growth of the electronics and pharmaceutical industries hasexpanded the need for water-quality levels far in excess of thosesupplied by the statutory authorities and special advice shouldbe sought. In hospitals, additional chemical treatment may berequired to reduce the rise of disease transmission through thewater system.

21.11.4 Drainage

The aim of a well-designed building drainage, sanitation andrainwater installation is to convey foul waste and rainwaterefficiently to the sewer or outfall without nuisance or risk tohealth and self-cleansing. The layout should be as simple anddirect as possible and in accordance with the requirements of BSCode of Practice 8301:1985 'Building drainage', BS 572:1978Sanitary pipework, and BS Code of Practice 6367:1985 'Drain-age of roofs and paved areas'.

21.11.4.1 Design considerations

The practice of combining soil and rainwater pipes within abuilding is extremely unwise and the connection of the twosystems, even with a combined sewer system, should be locatedexternally, preferably at the last manhole before discharging tothe sewer. Soil and waste stacks should be as vertical as possiblewith the minimum number of offsets. Particular care should betaken with discharges from kitchens, laboratories and disposalunits. Separate systems should be provided for activities involv-ing chemical and radioactive effluents. Ventilation pipes arerequired to maintain a balanced air pressure throughout thesoils and waste system. All access locations for rodding shouldbe reviewed in design and located to enable easy maintenance.Ground-floor fittings should be discharged direct to drains andseparate from upper-floor fittings. Consideration should begiven to draining basement levels via pumps to reduce the risk offlooding in the event of sewer back-up. In selecting pipeworkmaterials, consideration should be given to such items as noise,fixings, condensation and material damage in addition to thegeneral material performance criteria.

All sanitary appliances need to be trapped to prevent sewerand drain smells entering the building. Precautions are requiredto prevent the seals being broken by siphonic action or plugpressure generated within an adjoining stack. Traps can beprotected against these dangers by design or by the incorpora-tion of secondary venting immediately behind the trap. Gener-ally, the provision of sanitary appliances should accord with BS6465:1984, Part 1.

21.11.5 Public health

The importance of providing a wholesome drinking water