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BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)INTRODUCTION - Basic Concepts1.5 Basic Concepts1.5.1 Definition of Terms1.5.2 Examples of DfMA ElementsThe list below outlines some examples of DfMAelements that are commonly used inconstruction projects. This is by no means acomprehensive list and elements should bedeveloped for specific project needs.Assembly(1) Verb – the act of construction of a buildingthrough the combining and securing ofmanufactured components on site,generally in a planned, tested and carefullycontrolled sequence.(2) Noun – an item formed by aggregating orcombining different components orelements in part (Sub-Assembly) or in full(Assembly).Cross Laminated Timber (CLT)Manufactured from wood harvested fromsustainably managed forests and fabricated bybinding layers of timber at 90 degrees withstructural adhesives to produce a solid timberpanel. Can be used as either structural or nonstructural components in buildings.AssetA finished building or other structure.Integrated Prefabricated M&EMechanical, electrical and distribution itemsprefabricated either as linear lengths, flatassemblies or integrated within volumetricmodules.ComponentManufactured individual building elementincluding prefabricated elements e.g. precaststaircases, refuse chutes, structural memberssuch as columns, reinforcement cages etc.Precast & Prefabricated ElementsElements that are manufactured in a controlledenvironment and are generally of better qualitythan in-situ elements e.g. staircases, facades,refuse chutes, parapets etc.ManufacturingThe production of a building element(components, assemblies or modules) in acommoditised manner, typically in a factoryenvironment located remotely to theconstruction site.Prefabricated Bathroom Unit (PBU)A bathroom unit fabricated and preassembledoff-site complete with finishes, sanitary fittings,bathroom cabinets, concealed pipework,conduits and ceiling before delivering andinstalling in position on site.ModuleSimilar to an assembly but typically selfcontained, volumetric and room sized orenclosing usable space. Often standardized inform and/or volume.Prefabricated Pre-Finished VolumetricConstruction (PPVC)Assembly of whole rooms, modules orapartment units complete with internal finishesand fixtures that are prefabricated off-site andinstalled on site to form modular apartments.PartsIndividual objects used in the construction of abuilding.4

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)INTRODUCTION - Basic ConceptsComponentsIntegratedComponentsFully IntegratedComponentsStructural(e.g. precast facade)PBUPPVCArchitectural(e.g. drywall)M&E(e.g. flexible sprinklerdropper)Integrated PrecastComponentsIntegrated Prefab M&EExamples of components, integrated and fully integrated components(Image source: BCA)5Assets

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - Process Overview2GETTING STARTED2.1 Process OverviewThe DfMA approach, coupled with the use ofBIM, can potentially make the industry becomemore integrated and productive at every stageof the project delivery – from design toconstruction and ultimately in operation.Throughout the detailed design stage, themodels can be developed with increasing levelsof sophistication in terms of geometry and data.As the components are better understood,further validation of the detailed design ispossible versus the strategic brief with vastlyimproved levels of stakeholder certainty to aidthe decision making process.2.1.1 Developing the DfMA StrategyDuring the initial design stage, the DfMAstrategy should be developed incorporating theuse of BIM to facilitate the process. The strategyshould respond to the following: Sector (e.g. housing, healthcare,infrastructure etc.) Availability of known products orsuppliers; Likely degree of repeatability; Site/logical constraints; Project scale/value etc.In the pre-construction phase, virtual buildingand prototyping exercises could be carried outusing the digital models. The outcomes of thevirtual prototyping can be used to carry out thereal-world prototyping including training theoperators, to refine the construction approach,test feasibility and maximise efficiency on site.This can take place in a safe, controlledenvironment and can be used to plan everyaspect of manufacture, logistics and assemblylong before the actual works start on site.2.1.2 Step-by-Step ProcessIn the early concept design stage, DfMAelements can be identified and represented inthe BIM model by ‘placeholder’ objects whichare data rich but have limited geometry. Thesecan be used to rapidly generate models to yieldthe estimated cost and procurementinformation etc. Scenarios and alternativeoptions may be tested to optimise the projectbrief, assumptions and project drivers. Theseplaceholders could also be used to identify thetype of specialist to be involved to develop aDfMA solution.Real 3D models could also be produced from thedigital models e.g. via 3D printing. Lessonslearnt from prototyping can be incorporatedback into the BIM model.During the construction process, componentscan be tracked via serialization/QR coding orother means through each step of themanufacturing, packing, logistics and deliveryprocess (see Section 3.5). The data that isinputted into the BIM model can also be used tomanage marshalling of the components and thelogistics of the site assembly process tominimise risk of delays.As the concept design is developed, the buildingcomponents could be advanced and refined inparallel. Early contractor involvement andsupply chain engagement at this stage can helpto validate the emerging concept designs interms of the delivery of the project throughDfMA and the adoption of standard solutions.6

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - Process OverviewFollowing completion of the project, the BIMmodel represents a data-rich digital version ofthe building that can be used for facilitymanagement. This could include tracking thescheduled maintenance of MEP items ornecessary replacement of plant etc. Thecomplete history and location of everycomponent used in the construction can berecorded for future use and learning.Key BIM actions for the DfMA approach at the various stages(Image source: BCA)7

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - Project Strategy2.2 Project Strategy3. Agree on BIM Execution PlanThe BIM Execution Plan will outline thestructure of the BIM modelling activities on theproject. It will provide details of therelationships between the various partiesinvolved in the project and the BIM model, thesoftware platform that will be used, and theoutputs that will be generated at each stage.The software platforms that are to be used onthe project will depend on a number of factorsand should be part of the BIM strategy.Different software platforms may also be usedto perform different tasks as well as enablesharing and coordination of models as part ofthe Digital Delivery Strategy of the project. Atemplate BIM execution plan has been ov.sg/media/586149/Essential-Guide-BEP.pdf.2.2.1 Project ConsiderationsThere are a number of considerations thatshould be made at the very earliest stage of theproject that will help optimise BIM and DfMAintegration in the project. These should beincluded as part of the development of a projectDigital Delivery or BIM strategy.1. Define Project BIM StrategyIt is important to develop a Digital Delivery orBIM strategy for the project that specifies thelevel of resolution and the types of data thatneed to be built into the BIM model at eachdesign stage. This should be developed inaccordance with the project brief and to achievespecific client objectives e.g. costing, sales andmarketing, programming of site works.2. Understand Whole Life Function of the BIMModelData sets that are inputted into a parametricBIM model can be used over the whole life spanof the building, for more effective and efficientfacility operation and management. It istherefore important to ensure that the data setsused are relevant to the facility managementand operation teams and that they are appliedin order to develop an understanding of the useof the asset and generate accurate as builtinformation.4. EarlyInvolvementofConstructionSpecialistsTo fully realise the potential for constructionefficiencies through DfMA, it is important tohave specialist construction knowledge as partof the design team from the early stages. Thismay be part of the services of the main designconsultant on the project or it could be providedby a separate construction consultant.Alternatively, early involvement of theContractor and Specialist Subcontractors wouldenable the design team to tap on theirexperience and expertise in developingproposals for off-site fabrication and on-siteassembly. This early input can also help inensuring the cost-effectiveness of proposals,e.g. through identifying efficient mould sizesand shapes for precast elements or advising onmaterial selection for finishes.8

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - Project StrategyThe system design is developed throughprototyping and realised on site in the firstprojects, with analysis and lessons learned ateach phase.2.2.2 Process Shifts Through BIMAs BIM and DfMA practices become moresophisticated, the design process will start togenerate substantial quantities of usable dataand construction knowledge and inputs will beincorporated into the models at an earlier stage.The workflow below shows the potential for ashift in the way that construction projects aredesigned and procured.The parametric components in the BIM modelcan be used to generate outputs to inform theconstruction process including training andvirtual building simulations (see Section 3.5).The BIM model is also used to manageoperations over the life cycle of the assetincluding life cycle costs. The system becomesmore efficient, more effective and moreintuitive with multiple deployments over aframework of projects rather than onestandalone project.BIM facilitates lessons learned to be rapidlyincorporated between projects. Instead ofindividual projects acting as “standalone” orbespoke projects with minimal relationship withsubsequent projects, the BIM model can act asa test-bed for a first, product based “system”comprising traditional construction elementsand parametric prefabricated components,assembled in an efficient way.9

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - Project StrategyProcess shifts through BIM(Image source: Bryden Wood)10

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - BIM Outcomes & Model Progression2.3 BIM Outcomes & Model ProgressionAn example of a possible structure for dataextraction and usage is as follows. This isintended to show the underlying data whichchanges and grows over the course of thedevelopment of the BIM model. The modelgeometry may not differ substantially betweenstages - the difference lies in the extent andaccuracy of the embedded data.2.3.1 BIM OutcomesA key aspect of planning the BIM process for aproject is understanding the desired BIMoutcomes that are planned for each stage ofwork and the benefits that are expected to beachieved. This should be based on the client’sown goals and business requirements and maybe weighted in order of importance. Definingthe desired BIM outcomes early on will enableidentification of requirements for dataextraction from the BIM model. Definingincorporation of DfMA approaches as a desiredBIM outcome will facilitate the adoption ofthese at the relevant project stage.Stage 1: Project Brief DevelopmentThe BIM strategy for the project is established.Desired BIM outcomes are identified and dataextraction requirements for subsequent stagesare agreed on.Stage 2: Concept Design DevelopmentIntended to ensure that the design andspecification are consistent with the client briefin terms of function, cost and sustainability. Themodel can show information such as massing(overall volume), space allocation (e.g. roomsizes) and site location (e.g. northings andeastings).2.3.2 Data ExtractionAt pre-determined intervals over the projectlifecycle, data will need to be extracted from theBIM model. This data can be used for signing offby clients to ensure that the modeldevelopment is appropriate for each stage,while providing valuable information about thedesign. The data can help make more informeddecisions about different DfMA constructionsolutions.Stage 3: Detailed Design DevelopmentIntended to enable identification of contractors,procurement routes and supply chain. Accuratedata will be included and visually represented.The model will represent the technical solution.Extracted data can be used for differentpurposes depending on the defined attributesfor each stage. As more data attributes areadded to the model the level of detail increases.The required attributes are based on thedesired BIM outcomes and are decided by theclient in collaboration with the author of theproject BIM strategy at the start of the project.Stage 4: Pre-ConstructionIntended to confirm that the developed designfully conforms to the client brief and to allowcalculation and approval of the project agreedmaximum price. The model is highly accurate,incorporates information from the supply chainand can be used for prototyping, first runstudies and planning construction activities.11

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - BIM Outcomes & Model ProgressionStage 5: ConstructionIntended to enable construction to take place inline with the project brief requirements. Themodel incorporates all amendments andlessons learned resulting from previous stages.The model is extremely accurate and can beused for construction.2.3.3 BIM Design Object LibrariesThere are various sources for pre-designed BIMobjects that already contain data attributes(although these may or may not be populated,and data sets may need to be altered to meetprojectspecificrequirements).Somemanufacturers can provide BIM objects for theirproducts either through their website or onrequest. These pre-modelled elements canprovide further efficiencies to the process.Stage 6: Post CompletionIntended to represent the as-built assetincluding all installed systems, along withoperational data sets to show how the asset isused. The model represents the building in use,including feedback information from BuildingManagementSystemsandfacilitymanagement. The model is up-to-date andaccurate at handover and will continue evolvingover time to reflect the status of the buildingsystems.BIM objects to form facade of PPVC module(Image source: P&T Consultants)12

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)GETTING STARTED - BIM Outcomes & Model ProgressionModel development and data required at the various stages(Image source: Bryden Wood)13

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)PROCESS - Stage 1: Project Brief Development3PROCESS3.1 Stage 1: Project Brief DevelopmentA successful design incorporating BIM andDfMA to best advantage starts with an accuratebriefing process. On projects where the brief isnot recorded formally, thoroughly andprecisely, designs tend to veer away from theclient’s actual requirements. A clear brief allowsthe design to be checked continuously as itevolves. It also allows users and otherstakeholders to make their own individualcontributions to the design and specification oftheir own working environments.2. Brief Compliance PlanAlong with the Briefing Execution Plan, a BriefCompliance Plan can be developed to allow theclient to assess whether the original brief isbeing met. This forms the basis of the projectdesign management process, the aim being toeliminate unwanted design changes and costoverruns by “getting it right first time”. Oneelement of this Plan may be the establishmentof assessment criteria for each design stage toconfirm the degree of brief compliance ofemerging proposals and allow sign off toproceed to the next stage.1. Briefing Execution PlanThe structure and hierarchy of the clientrequirements should be established during aseries of early workshops. Based on this aBriefing Execution Plan can be developed. Thepurpose of the Plan is to establish what aspectof the client’s requirements need to bearticulated at each stage for the design toprogress smoothly. To deliver a quality solution,it is essential to identify as early as possible thedetails (technical, organisational, etc.) that willhave a big impact on the design. The Plan alsorecords who the stakeholders are, whatinformation they should provide at each stageand what information they will need toapprove.The Plan may also include objective milestones(e.g. design cannot proceed unless complianceis at 90%).14

BIM Essential Guide – Design for Manufacturing and Assembly (DfMA)PROCESS - Stage 1: Project Brief Development3. Initial Design ConsiderationsAt the commencement of the design stage,attention should be given to aspects that willimprove the efficiency of the design andfacilitate the adoption of DfMA solutions. Theseaspects may include the adoption of standardgridsdriven

DfMA stands for Design for Manufacturing and Assembly. It stresses the importance of design for ease of manufacturing and assembling of components that will form the final product. The DfMA approach when applied in the building and construction arena, requires a change in the relat