Frontiers of Architectural Research (2013) 2, 377–386

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2095-2635 & 2013. Hhttp://dx.doi.org/1

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RESEARCH ARTICLE

Integrated design approach for improvingarchitectural forms in industrializedbuilding systems

Siva Jaganathana,n, Lenin Jawahar Nesanb, Rahinah Ibrahimc,Abdul Hakim Mohammada

aCentre for Real Estate Studies, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, MalaysiabInternational Institute for Affordable and Sustainable Housing, 609110 Sirkali, Tamilnadu, IndiacFaculty of Design and Architecture, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia

Received 26 February 2013; received in revised form 13 July 2013; accepted 19 July 2013

KEYWORDSArchitectural design;Built environment;Design management;Design model;Design strategy;Industrialized buildingsystem;Form flexibility

igher Education P0.1016/j.foar.2013

thor. Tel.: +60 19: jviewsandvision@oo.com (S. Jaganaresponsibility of

AbstractAn architectural design process is investigated to achieve form flexibility in industrializedbuilding systems (IBS), as IBS constructions do not have sufficient flexibility to develop variedarchitectural forms. The ethnography method has been used to examine the issues related to“form” flexibility in the design life cycle of IBS constructions by observing the constructions oflive experimental models. The major tasks and respective design aspects that facilitate formflexibilities in architectural design have been identified. Furthermore, an integrated life cyclemodel has been developed to effectively address the interfaces between the design tasks andeventually fulfill the needs of IBS in the design life cycle.

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1. Introduction

For achieving sustainable development in Malaysia andtransforming the construction industry to be one of the best

ress Limited Company. Production.07.003

6590367.gmail.com,than).Southeast University.

in the world, the framework of the Malaysian ConstructionIndustry Master Plan fosters the implementation of indus-trialized building systems (IBS) in building projects (CIDB,2006). However, several construction and engineering aspectsrelated to the IBS are yet to be fully realized in actualpractice. One of these aspects is “design flexibility,” which isone key aspect that governs the efficacy of IBS applications.However, this aspect has been largely neglected in bothapplications as well as literature. As stated by Hamid et al.(2008), a majority of the current IBS applications—bothin design and prefabrication—mainly support conventionalbuilding forms (e.g., rectangular and square forms). Suchmonotonous approaches can hinder an architect's ability to

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S. Jaganathan et al.378

develop flexible forms. In particular, prefabricated elementsare considered to be inflexible to changes that would benormally required over their life spans (Warszawski, 1999;Sarja and Hannus, 1996). Simultaneously, architecturaldesigns aimed toward IBS constructions should possess theattributes of manufacturing feasibility and onsite assembly.From the architectural perspective, flexibility can be definedas the ability of a unit to respond to the changes necessitatedby the client, design, and manufacturing requirements(Sarja, 1998). While architectural design ultimately dealswith the configurations, connections, shapes, and orienta-tions of the physical forms, flexibility in architectural designis predominantly related to spatial design and building“forms” (Do and Gross, 2001). As such, architects are ofteninclined to develop varied and unusual architectural forms(Saleh et al., 2003). Therefore, further investigation isrequired to improve the form flexibility in both architecturaldesign practice and construction.

To overcome this barrier, this article presents the resultsobtained from a research sponsored by the Universiti PutraMalaysia. The issue of achieving form flexibility in IBSconstructions during the design stage was investigatedbased on the premise that “it is extremely important toincorporate system thinking in the architectural designprocess to foresee and resolve complex issues during theimplementation of IBS.” As opposed to concrete and steelconstructions, timber construction was investigated in thisstudy since timber is easy to handle and timber elements(used in the experiment) could be easily fabricated.Further, timber comes from a sustainable source; therefore,timber has been fostered by the Construction IndustryDevelopment Board (CIDB), Malaysia, as an alternate mate-rial for IBS constructions (CIDB, 2003). A series of ethno-graphy methods of investigations have been proposed withregard to the construction of live timber houses. Conse-quently, the most appropriate approach for achieving anintegrated system design has been developed. This articledescribes an integrated system design model that can beused for improving the form flexibility in IBS designs. Theproposed model will help architects in understanding therelationship between building systems and their designs,and therefore, incorporate creativity and flexibility in IBSconstructions.

1.1. Problems in IBS attributable to designflexibility

In Malaysia, IBS was initially implemented to promote sys-tematic construction processes and minimize the number offoreign workers. However, impediments to achieving this goalhave been widely reported in literature. For instance, Hamidet al. (2008) stated that the supply and demand, economicvolume, general readiness, and social acceptability weremajor hurdles. Badir et al. (2002) stated that professionalswere not aware of the basics of IBS such as modularcoordination as well as volumetric and nonvolumetric con-struction methods. This argument was supported by manyscholars (Gibb, 1999; Davidson, 1990; Benros and Duarte,2009). Mawdesley and Long (2002) and Jaillon and Poon(2009) argued that future modifications to manufacturedbuilding components were not possible as they resulted in

less flexibility during the construction phase. Hassim et al.(2009) and Lessing et al. (2005) added that the IBS approachimpeded the creation of a customer-oriented design. Thecoordination between spatial design and dimensioning ofelements was poor and was not appropriately incorporatedinto the designing of spatial and functional space relations(Gibb, 2001). The transportation of building componentsdepends largely on the local conditions. For example, to betransportable, the component sizes should be designed inaccordance with the carriageway. In addition, incompatibleinterfaces between manufacturers, poor coordination betweenthe manufacturers and architects during an early design phase,and limited applications of building materials (i.e., mainly usingconcrete for fabricating precast beams, columns, and panelizedwall systems) are some of the pressing problems that mar IBSconstructions (Thanoon et al., 2003). Tam et al. (2007)suggested a lean construction approach to deliver betterstandardized products. However, the consequent constructiondefects were difficult to conceal, possibly leading to structuralfailures and water leakages. All these impediments adverselyimpact the design creativity in IBS, resulting in monotonous andaesthetics-deprived buildings.

In the past, conventional building construction has beenadopted in the Malaysian housing sector (IEM, 2003). Conse-quently, the CIDB, Malaysia, has promoted IBS technologies sothat prefabricated building components are utilized to themaximum possible extent in the construction industry. Asstated by Junid (1986); Padrid (1997); Trikha (1999); Lessinget al. (2005) and Tam et al. (2007), it is a known fact that IBSintegrates the manufacturing and construction processes thatinvolve mass production, where the building components areprefabricated to optimize the majority of onsite constructionactivities and workmanship, reduce material wastage, reducethe time required, and reduce the overall cost of the project.IBS can also create engineering benefits for the constructionindustry since it mainly encourages the production of standar-dized buildings rather than varied ones. Studies have notinvestigated the manner in which IBS can be incorporated inthe development of architectural design to meet contempor-ary design changes such as “form flexibility” (Howes, 2002).On the other hand, architects are unaware of envisioning theincorporation of IBS building components in the architecturaldesign process. The lack of an IBS data repository andinadequate knowledge of IBS among architects has resultedin redundant design flaws during detailed construction doc-umentations, which has further delayed projects (Kamaret al., 2009). Moreover, the IBS approach has created anegative perception among the architects and customersbecause of the following factors: it hinders flexibility; it onlyallows internal flexibility in the layout; it creates jointingproblems; it promotes monotonously manufactured buildingcomponents; it creates repetition in standardized buildingcomponents and it does not allow varied forms that can yieldcreative architectural designs. In spite of these defects, theexisting IBS construction practices need to be revitalized inthe minds of the designers such that they can efficientlyincorporate “system thinking” in the architectural designprocess. A systematic approach often limits the freedom ofdesigners, notably architects.

Besides the standardization of building components, IBSshould be able to develop compatible systems that canintegrate building components with the spatial design.

379Integrated design approach for improving architectural forms in industrialized building systems

In addition, varied forms and efficient design solutions arepossible when system thinking is applied at an early phase ofthe architectural design process (Gann and Senker, 1993). Incurrent practices, the industrialized construction, manufac-turing, and assembly processes are involved only after thedesign process is completed (Walch, 2001). To improve andenhance the potential outcomes of IBS, an approach invol-ving system thinking, as emphasized by the above men-tioned literature, should be integrated with form flexibilityduring the architectural design process.

O

2. Research methodology

In this article, we have investigated the issue of creating variedarchitectural “forms” during the iterative architectural designprocess. This research adopted the approach of an experi-mental case study to examine the issues involved in the designlife cycle of IBS. For investigating the issues pertaining tomanufacturing and assembly, a couple of new timber houseswere fabricated as the fabrication of timber materials is ofteneasier than that using other building materials. In addition,timber as a construction material has not been sufficientlyinvestigated with regard to IBS constructions as compared tothe other widely used elements that can be prefabricated,such as steel and cast-in-situ and precast concrete (Warsza-wski, 1999). According to a survey conducted by the CIDB,Malaysia, the use of timber in IBS constructions is almostnegligible (Majid et al., 2010). Therefore, this research canalso provide the construction industry with practical standardsthat can define the use of timber as an alternate sustainablematerial in IBS constructions.

Two units of prefabricated timber houses were designedand constructed at Seremban—situated in the state ofNegeri Sembilan, Malaysia—as experimental samples. Thesehouses looked like 'Malay' traditional chalets (see Fig. 1) inwhich an independent square was connected to a semi-covered timber deck. Each square accommodated func-tional spaces such as a living room, dining room, kitchen,master bedroom, and service facilities. Each unit wasdesigned such that the functional spaces fit in an area of36 m2 to meet the criteria of modular coordination. More-over, dimensional coordination was set to follow the aspectsof the standardization of components and simplifying pre-fabrication issues such as the availability of timber sections,transportability, onsite labor involvement, easy assembly toavoid component damage, and maintaining precision inconstruction. The prefabricated components were alsoused as infill for nonstructural components. The spatial

Fig. 1 Prefabricated Timber House Units constructed atSeremban, Malaysia.

dimensions were determined according to the size, span,repetitions, and ease of assembly of the building compo-nents, regardless of their spatial designations and spatialrelations. On the other hand, pyramid roof houses wereconstructed using bespoke timber elements that werepartially assembled onsite.

2.1. Ethnography data collection method

In the experimental case study, the design and constructionprocesses were determined using the ethnography method,because this method has the potential to play a valuablerole in design-related research and can effectively delineatethe design process. According to Spradley (1979), ethnographyis usually applied in social settings to study people's behaviorsand culture. Since this study primarily involves people andtheir decision-making attributes during the iterative designprocess, ethnography is used as a feasible technique toobserve the implications of manufacturing and assemblyprocesses involved in the design life cycle of prefabricatedtimber buildings. Conducting ethnography requires the for-mulation of a set of open-ended research questions (Atkinsonet al., 1999). This requires the identification of the nature ofthe required data, data location, and the informant. As statedby Spradley (1979), this study revolves around three maincomponents of ethnography: the key informants (KI) as thepeople, a prefabrication process as the culture, and aprefabricated timber building as the context. Prior to fabri-cating the model houses, a miniature model house (see Fig. 2)was developed to guide the construction of the actual houses.With the aid of these miniature models, the aforesaid threecomponents were represented by a team comprising timberand prefabrication experts who were the KI, five industrialdesigners (ID) who were the facilitators, and one observer(O) who was present right throughout the project—from thecognitive stage until the construction process. The KI acted asthe source whose knowledge and expertise were documentedthroughout the prefabrication process of the miniature mod-els. The data were obtained through videotaped interviews,archival documents, and photographs. The ethnography datacollection method helped the researcher to identify varioustasks and aspects involved in the designing, manufacturing,and assembling of the prefabricated timber houses. During theethnographic data collection, the KI contributed to the

ID ID

KI

Fig. 2 Key informants (KI), industrial designer (ID) and obser-ver (O) during the ethnography of making the prefabricatedtimber house miniature.

S. Jaganathan et al.380

construction of the prefabricated timber houses throughouttheir development process with all suitable technical inputs.Their inputs were incorporated in the following aspects: thedesign; the selection of timber species; the fabrication andsizing of elements and components; and making decisionsregarding the methods of construction, manufacturing, andassembly.

In addition, this study revealed certain overlaps thatexisted when performing various design tasks that requireinterdependent design decisions. Consequently, these inter-dependent tasks led to the proposed integrated designmodel that can assist designers in incorporating IBS in thedesign process, as discussed later in this article.

3. The implication of design tasks and designaspects in the prefabrication of timber housing

There is no common formula or software tool that can beused to analyze the ethnography data, except transcribingthe conversations between the participants and the KI(Gibbs, 2007). The ethnography data were analyzed in aqualitative and descriptive manner, where the data col-lected at various stages of the tasks and subjective designaspects of the prefabrication process were sorted out in achronological order.

As stated earlier in this article, several engineeringfactors such as standardization, inflexible joints, logistics,and rigidity, which are unique to IBS building processes andconsequently limiting the application of IBS in different

Table 1 The design aspects involved in prefabrication.

Design tasks Design aspects

Selection ofappropriatebuilding system

Space requirementsDimensional co-ordination with spatial lModularization of functional space (i.e,proportions)Dimensional co-ordination between builelements and components

Constructability Represent modularizationStandardization and repetitionRepetition in elements and componentsAssembly-able jointing

Manufacturing Construction application (structural andstructural)Workability (ease of planning, ease of bboring finish, ease of turning and turningease of nailing)Applicable jointing systemDurability and decay

Assembly Necessary assembly detailsLayers and sequenceCross section sizeStraightness for levelingFlexible joints for conduitsTrim and finish for aesthetics

types of buildings, were identified during the ethnographydata collection process. However, it was observed that formflexibility was one of the major factors that limited theapplication of IBS in creating varied buildings. Because theIBS building process fosters precision engineering, andtherefore, predominantly involves limitations in manufac-turing and assembly processes, it was relatively difficult toachieve form flexibility. Initially, the ethnography team wasnot fully aware of the design tasks and design aspectsneeded to be considered at the conceptualizing stage.During the course of the ethnography process, it wasobserved that space planning was critical to achieve theowner's requirements in the development of spatial designand form generation. The ethnographer (observer, O) iden-tified this volumetric design of additive and subtractivedesign processes could not be effectively coordinated withthe design of IBS elements and components to conform totheir offsite building processes. Volumetric design involvesmodularizing the space in coordination with building mod-ules, including building elements/components. In addition,the lack of awareness regarding IBS processes requiredmaking major alterations in the modules such that theycould conform to the prefabrication characteristics andassembly elements/components, thereby facilitating suc-cessful offsite construction. These types of iterative adjust-ments and changes, caused by improper design decisionspertaining to temporal aspects in the design (such as space),had to be investigated to maintain the form.

The temporal aspects of space design included issues suchas functional relativity, social factors (comfort and privacy),

Effect on Form

ayoutXYZ

ding

Need to foresee coordination betweenfunctional space in connection with spatial anddimensional relationships to represent thedesign system

Design must incorporate modularization toease constructability

non

oring andfinish and

The manufacturing process of the elementsmust involve instructions from manufacturersin order to achieve flawless production.

Assembly of prefabricated timber componentsconsequently led to changes during theassembly.

381Integrated design approach for improving architectural forms in industrialized building systems

massing, facade constraints (i.e., windows, shading devices,and protrusions), and building services. These factors wereexplicitly coordinated mainly with the physical buildingelements and components. However, during standardization,the temporal aspects of the form generation were repre-sented by dimensions. As per the ethnography, in the IBSbuilding process, dimensional coordination contradicted withthe space and modularization of elements/components. Animplicit volumetric approach yielded an effective “form” soas to meet the needs of modular coordination. The relation-ships between spatial (functional space)/temporal aspectsand dimensional coordination were revealed at every stageof the prefabrication process throughout the ethnogr-aphy study.

Based on the design iteration, the ethnographer (obser-ver, O) observed and derived a series of design tasks, asshown in Table 1. These tasks included the selection of anappropriate building system, constructability, manufactur-ing, and assembly. The process of prefabrication, asobserved through the ethnographic study, was consideredto be a significant source that enabled better decisions inthe architectural design.

Analyses of the ethnography data led to the identification ofthe most significant linkages between the design tasks andsubjective design aspects for creating flexible “forms” indesigning timber IBS buildings. One of the critical issuesobserved during the architectural design process was achievingflexible “forms” during an early design phase and continuallymaintaining the same form throughout the fabrication process.In accordance with the requirements of prefabrication, thedimensions should be standardized. Further, when changesoccur, these dimensions should be continually controlled inconnection with the design of architectural elements such asfunctional spaces, designs of openings (i.e., windows anddoors), structural elements, roofing, and aesthetics. Themorphological expressions of such detailing can be labeledas “form.”

In the early design phase, the KI emphasized that “theprime focus of prefabrication should be the consideration ofthe dimensional coordination among the spatial and buildingelements.” The coordination should evolve whilst consider-ing adaptable design changes pertaining to the spatialrelations and architectural elements (i.e., spaces, openingsfor light and ventilation, service shafts, projective andrecessive elements in the façade, and structural and con-struction detailing). Simultaneously, it should enable theprediction of standardizations during the iterative designprocess. Therefore, to enable the architects to exhibit theircreativity and morphing abilities, they must preconceivethe constraints pertaining to the design life cycle of IBS.

Within this context, most of the buildings designed forprefabrication might have impeded product manufacturing,logistic supply, and assembly process; this, in turn, wouldhave required iterative revisions in the architectural design,and therefore, delayed the coordination process to meetthe necessary standardizable dimensions. For instance, therecurring changes/flaws recognized during the manufactur-ing process would eventually affect the elements connectedduring their assembly. For instance, certain variations in thedesign of a wall panel can affect the roof dimensions. Thesignificance of the design iterations is to foresee design-induced flaws and avoid them before beginning the

manufacturing and assembly processes. During the study,iterative design revisions were made in the architecturaldetailing such that the design elements could conform tothe desirable form with customizable flexibility. Duringthe initial stage of the prefabrication process, the designtasks need to be synchronized with the relevant designknowledge.

3.1. Selection of appropriate building system

For addressing the design task of the “selection of anappropriate building system,” the investigation team—com-prising the aforesaid KI, ID, and O—brainstormed; subse-quently, from the ethnographic study, the pertinence ofbuilding systems and their types in designing prefabricatedbuildings were determined. The dimensional aspects of eachspace should be ascertained in connection with the designof various elements and components of the buildings.Therefore, the concept of spatial design is closely linkedto “form” as it yields appropriate design decisions withregard to building elements and components. The majorconstraints, as revealed by the experimental model, whenaddressing the issues of building systems in an architecturaldesign include the following aspects:

�

The dimensions of the prefabricated elements and com-ponents should be designed such that they conform to thespatial layout. For example, a multitude of spatial con-nections between the spaces and their orientations shouldmeet the standardizable dimensions. The space con-straints should be volumetrically designed (i.e., symme-try, dimensional proportions, and dimensional gradation)to meet the standardization requirements.

�

Dimensional coordination is nothing but a modular sys-tem in which the functions are designed with certainlimitations. This is applied not only to the horizontalelements but also to all the vertical and volumetricelements/components of the building (e.g., the toiletpod). Therefore, the design approach should be volu-metric (e.g., form) rather than only spatial.

3.2. Constructability

The design aspects related to “constructability” wereidentified when a set of prefabricated elements and com-ponents were developed for manufacturing and assembly. Tofacilitate constructability, the KI emphasized “repetitions”in the design of the building elements/components. Subse-quently, both the experimental miniature model and theactual building model proved the need for designing repe-titive elements/components and their influences on thedimensional coordination between the spatial spaces andvertical elements were demonstrated. Therefore, con-structability warrants the need to integrate the designs ofspaces and elements for achieving a desirable “form.” Itwas also observed that constructability influences thedesign decisions in relation to architectural design features.A fragmented design process causes variations in the ele-ments due to the lack of inputs from the manufacturing andassembly processes. In addition, the design separationbetween the spaces and elements/components does not

S. Jaganathan et al.382

meet the requirements of the manufacturer. The process ofdesigning elements and components should not be finalizeduntil the prefabrication aspects meet the manufacturingrequirements, such as the availability of timber of therequired size, strength, durability, treatability, and otherworking properties (i.e., ease of planning; ease of boringand boring finish; ease of turning and turning finish; andconvenient nailing, application, and jointing systems).These properties are designed in conjunction with themanufacturing indices.

In particular, the following design constraints hinderedthe constructability aspect:

�

The size of cross sections (timber sizes) needed to befixed in accordance with the design and manufacturabil-ity of the elements and components.

�

Uniformity in the size of the elements/components shouldbe improved proportionately such that standardization andrepetition can be facilitated, and therefore, wastages canbe reduced.

�

Aesthetic design (design style) with varied dimensionshaving repetition, symmetry, and rhythm should abide bythe principle of proportion to maintain dimensionalrelativity. The volumetric design approach should involvespace modularization.

3.3. Manufacturing

Although the manufacturing process is not part of the designprocess, significant issues were identified that could be usedfor anticipating design-induced flaws during onsite assemblyand their impact on prefabricated elements/components. Inparticular, certain issues pertaining to the methods involvedin timber procurement, transportation, packaging, andonsite assembly were considered, consequently leading toiterative modifications in the design. The iterative designprocess yielded the manufacturing specifications required tomake assemble-able elements and components. The speci-fications include the following:

�

Awareness regarding the wood species to be used forvarious prefabricated elements/components is critical.The working properties offered by various species includ-ing ease of planning, ease of boring and boring finish,ease of turning and turning finish, and ease of nailingshould be considered. This will assist architects indistinguishing between their structural and nonstructuralapplications (for example, floor, wall, roof, and otherstructural applications). If the species selection is notconsidered in the early design phase, the resultantmanufacturing imprecision can damage the joints ofthe elements/components and result in disparate formsand sizes.

�

The utilization of composite techniques regarding mixingand matching materials (for example, jointing interfacesbetween steel and timber) is critical for fabricatingflexible joints. In addition, inappropriate manufacturingdetailing (including tolerance) and the lack of knowledgein manufacturing can lead to structural failures.

�

As much as possible, lightweight elements/componentsshould be designed such that jointing can be flexibly

achieved and the material can be easily handled, whichcan expedite both transportation and onsite assembly.

By using the aforesaid aspects, modular systems suitablefor fabricating standardized jointing, demountable systems,and standardized assemblies can be developed. By applyingthese aspects along with the other tasks can yield damage-free elements and components. These aspects are beneficialto improve the constructability of IBS buildings and theyalso play a vital role in form flexibility.

3.4. Assembly

As stated in the literature, the significance of the prefab-rication process lies in the reduction in a majority of onsiteconstruction activities that can lead to time optimization,labor reduction, cost-saving, and reduction in constructionwastages. Assembly activities play a major role in designingtrimmed elements, and therefore, reduce the requiredonsite construction works. A smart jointing system usingcranes and related technical know-how should be consid-ered in the design. Understanding the onsite assemblyprocess during the experimental modeling (including thefloors, walls, and roofs) can enable the anticipation ofassembly detailing including element plumpness, concealingand fastening the finished materials, as well as mechanicaland electrical requirements such as cladding, paneling,calking, trimming, and sheathing. The same should be consi-dered during the design process to effectively conceive theassembly process. Fig. 3 shows the sequential assemblyactivities undertaken for each layer of the elements/components of the timber building.

Design variations in terms of dimensional incompatibilitycaused problems in the upcoming layers involved in theassembly sequence and element/component detailing. Thedesign was iteratively amended during the onsite assemblyas the technical know-how of the assembly process was notadequately included in the design process. Such subjectiveand intricate assembly changes were minutely investigatedduring the experimental modeling and the following aspectswere formulated:

�

The selection of appropriate species and cross section forachieving assemblable construction is highly critical.

�

Leveling for tolerance and tangential movements shouldbe considered.

�

The building service requirements (including mechanicaland electrical) should be easily concealable for smoothlyinstalling and maintaining the building services.

�

Weight is the most critical factor as it determines themanual or automated applications in the assemblyprocess. The lifting process should be hassle-free andshould involve lesser number of scaffoldings.

�

The quality of the factory-produced trimmed productsshould be retained, because it promotes damage-freeelements and enhances their aesthetics.

�

The design must afford adequate flexibility, easy jointingsystems, and assembly sequences (i.e., connectors,hinges, rebates, interlocker, sliding tracks, calking, andclips/anchors for installations) to carry out the assemblyprocess safely and quickly.

Fig. 3 The assembly method adopted in the miniature model of the prefabricated timber house.

383Integrated design approach for improving architectural forms in industrialized building systems

were derived from the ethnography of the experimental

The aforesaid tasks and respective aspects (constraints)

model. The designers—besides their conventional designwisdom—should consider these tasks when developing pre-fabricated building elements/components for IBS buildings.

4. Integrated design tasks for improvingforms in IBS

In design practice, the evolution of the “building form” is aniterative process such that all the aspects of the designrequirements are entirely met in the architectural designprocess. As documented in the ethnography data, this researchidentified various tasks and aspects that are interdependent oneach other. To avoid recurring changes and amendments, theconcept of manufacturing and assembly should be inculcated inthe early design phase. This is one of the feasible solutions thatthis research has proposed in designing flexible forms.

The ethnography of the experimental model was the keysource of data required in developing the proposed model ofthe design life cycle for IBS, which focuses mainly on “defrag-mentation” of the elements/components. The life cycle tasks

derived from the experimental model included the following:feasible translation of design into prefabrication, design ofbuilding elements and components, design of the dynamics andtolerance of the embedded joints, manufacturing/productiondesign aspects for elements and components, and variousdesign aspects of the assembly process. The purpose of thismodel is to bridge the gap between the design developmentsand construction documentation in which the manufacturingaspects, construction logistics, assembly aspects, and selectionof material properties can be adopted. The integration of thesetasks and aspects facilitates resolving the manufacturing pro-blems and optimizing the design. The life cycle tasks and otherconstraints that should be predicted along the process of designdevelopment are shown in Fig. 4. In addition, the proposedmodel facilitates the interdependency between the tasks,eventually enabling the fulfillment of the requirements of IBSin the design life cycle.

4.1. Design translation feasibility

The design translation feasibility is a knowledge-basedassessment system used to achieve constructability in IBS

ManufacturingFeasibility

Form/ Spatial Design

Defragmenting Elements and Components

Design Translation Feasibility

Tolerance DesignAssembly process

Onsite Assembly

System (i.e., standardization,modularization)

Possible design flaws prediction

Optimization through design (i.e., material, cost)

Floor, wall & roof elements and components

Machine tolerance

Assembly tolerance

Elements selection (Timber species)Elements standardization (i.e., stud)

Elements assemblyPrefab indicator for assembly

Transportation

Design complied with the assembly needs

Joints for self-scaffolding

Manual handling

Easy assembly

Fig. 4 Integrated design life cycle of IBS.

S. Jaganathan et al.384

constructions. This assists in anticipating recurrent designmodifications, and subsequently, making better decisions onappropriate “building systems.” It also helps in translatingthe implicit design decisions into defragmented elements/components for prefabrication, while considering otheraspects that are interdependent in the early design phasesuch as those in the manufacturing and assembly processes.The following aspects should be considered in achieving thefeasibility of design translation and reducing the recurrenceof design revisions that is normally required in the con-struction of IBS buildings.

�

Modularization should be achieved by handling issues such asspace, form features (geometry), dimensions, and buildingelements/components. Modular coordination should con-sider manufacturing and assembly requirements, availabilityof material, transportability, and constructability. As there isno single and perfect prescribed modular application, anappropriate system can be achieved only by following the“mix and match” method with regard to space and buildingstandards by deploying ratio/divisibility, proportion, andstandardization. Finally, the resultant set proportions andset standardization can form the benchmarks in the form ofmodules that should be adopted throughout the buildingdevelopment process.

�

The standards will contribute toward defragmentingvarious building elements/components including thefloors, walls, and roofs so that they are manufacturableand assemble-able (for example, panel walls and stan-dardized bespoke elements, modular roof trusses, mod-ular rafters, and purlins).

�

Repetition should also be featured in standardization sothat flexible architectural forms can be designed havingdifferent architectural styles, patterns, rhythms, andharmonies. For example, featured repetitions in timberIBS constructions include window/panel wall awnings,projections, sunshades, balconies, as well as decorativeprotrusions in the floors, walls, and roofs.

The ethnography results from the models designed byJunid (1986); Trikha (1999); Lessing et al. (2005) and Tam

et al. (2007) demonstrated the importance of the feasibilityof design translation and demonstrated the use of thearchitectural design process to resolve issues related tothe manufacturing and assembly processes. Task interde-pendencies unveil and curtail abrupt design changes, whichare normal occurrences during manufacturing and onsiteassembly of building elements/components. Besides, thisapproach results in balanced composition (i.e., symmetry)and modular designs.

4.2. Defragmenting building elements/components

Defragmentation yields an adequate number of element detailsthat should be matched with the manufacturing requirements.They are normally expressed in terms of modularity, symmetry,proportional ratio, and identifiable pattern. Defragmentationexamines the feasibility of using design features to fully achievethe manufacturing and assembly requirements. It synergizestask interdependency and fuses design development withconstruction documentation to obtain comprehensive jointingand assembly methods for various building elements andcomponents. The defragmentation process developed duringthe ethnography of the timber model yielded exclusive con-struction documentation that supported flawless manufacturingand assembly processes. In implementing the defragmentationprocess, the following aspects should be considered:

�

Modularization should be incorporated both in the spatialdesign and elements/components.

�

Support the evolution of modularized design patterns inspatial designs in relation to architectural features (i.e.,symmetry).

�

The elements/components that can be defragmentedshould be designed for various jointing systems, whichwill simplify both onsite assembly and deconstruction.

�

IBS design standards should be used to achieve element/component defragmentation, and therefore, supportmanufacturing and mobility.

385Integrated design approach for improving architectural forms in industrialized building systems

4.3. Tolerance

Tolerance refers to the behavior of material under changesand structural reactions. In assembly elements, tolerancecan be used to control joint damages such as leakages,fissures, and failure to withstand expansions and contrac-tions. Prior consideration of tolerances can help reducingmanufacturing errors and simplify jointing requirements,and therefore, assist in the structure's response to tangen-tial movements induced by weather, wind, and structuraldynamics. The tolerance design should be addressed inconjunction with the other interdependent tasks such asmanufacturing so that manufacturing flaws can be avoidedduring the later stages. The following aspects should beapplied in tolerance design for both jointing and makingsystemic patterns for the façade.

�

Identify and design suitable jointing systems with recom-mended tolerances (for instance, from 3 mm to 5 mm).

�

Fabricate grooves and inlays in the joints and createarchitectural design patterns to improve the façade (forinstance, joints between panel walls, floors and walls,and marking sills should be provided with such grooves).

The inclusion of the aforesaid aspects of tolerance in thedesign process can yield flexible jointing systems andimprove the façade's aesthetics with higher precision.

4.4. Manufacturing physical elements/components

It is a transition phase between the design and assemblyprocesses, where the manufacturing aspects are applied tomanufacture building elements and components off the site.The inclusion of manufacturing issues into the design lifecycle of IBS can help in predicting design-induced construc-tion problems prior to production and onsite assembly. Themanufacturing issues include cutting types, fastening meth-ods (boring and nailing), durable assembly, selection ofpermissible cross sections (dimensions), and assembly prop-erties (location and edges). The following design aspectsrelated to issues including sequence, onsite assembly mark-ings, and transportability should be considered.

�

The designers must coordinate with the manufacturers tohave an appreciation and understanding of the manufac-turing process prior to the completion of the design.

�

Manufacturers’ inputs in deriving the design specificationsfor the elements/components should be sought for achiev-ing standardization, onsite assembly, and transportability.

�

Suitable jointing systems—addressing both mountableand demountable issues—should be developed.

4.5. Assembly

Assembly relates to the design of architectonic entities inwhich the jointing systems are fabricated for assemblingthe building elements/components. The requirements ofthe assembly process that should be considered during thedesign process include the following: easy transportability

and simplified man-handling, easy assembly using the leastnumber of scaffoldings, requirement of minimal final finish-ing and trimming touches, and aesthetics of the element/components. The aspects required to achieve workability(i.e., feasibility) and improved performance (i.e., time andspeed) in assembly design should include the following:

�

The design of the building elements/components shouldincorporate the features required for onsite assembly.

�

The joints should be designed to simplify the assemblyprocess, deconstruction, and transportation.

�

To enjoy engineering optimization, the design shouldconsider to incorporate the use of construction equip-ments on the site.

�

Trimming and finishing touches are the most critical tasksthat should be considered in the jointing system so thatthe aesthetics of the building can be improved and thejoints can be devoid of leakages and failures.

The aforesaid aspects should be addressed in conjunctionwith the other interdependent tasks to meet the strategicrequirements of the assembly process. Applying these aspectsin the early design phase improves form flexibility.

5. Limitation of the model

The integrated life cycle design for IBS constructions wasdeveloped using tropical timber material. Although most ofthe design tasks and the respective strategies were derivedfrom the case study of live timber construction pursued inSeremban (Malaysia), they could be applied in the case ofconcrete and steel materials, too. However, the applicationof this model using other materials such as concrete andsteel requires further investigations. Consequently, besidessome additions and omissions, certain additional tasks andaspects might evolve. The findings of the integrated designlife cycle model, including the process interdependencies,should be further validated before they are widely applied.As a result of this model, the architectonic aspects ofseveral assembly joints were developed. The architectonicforms were specifically designed and developed for timberand were later patented; these patents are pending withthe World Intellectual Patent Office (WIPO), EuropeanPatent Office (EPO), Australian Patent Office (APO), andMalaysian Patent Office (MYPO).

6. Conclusion

Conducting research on the use of timber in IBS construc-tions is the first of its kind in Malaysia. Literature review hasshown that few scholarly works have investigated theincorporation of manufacturability that facilitates creativityin design. The ethnography of the Seremban timber housemodel significantly contributed toward formulating varioustasks and aspects that enunciate the integration of IBS intothe design life cycle. The ethnography process led to thegeneration of documentation for the entire model develop-ment process, and subsequently, the construction process,which led to the categorization of tasks and respectiveaspects. It also led to the identification of both explicit and

S. Jaganathan et al.386

implicit processes during prefabrication. The integratedmodel, as described in this article, focuses on the core taskof defragmentation and other interdependent tasks; thismodel exhibited improved form flexibility. The interfaces ofall the stakeholders involved in the design showed improvedcommunication and better design outcomes, therebyachieving the core benefits of the IBS. The findings of theintegrated design life cycle model including the processinterdependencies should be further validated before theyare widely applied using other construction material includ-ing concrete and steel.

Acknowledgement

This research was partly sponsored by Universiti PutraMalaysia. The authors acknowledge the significant contribu-tions received from the Centre for Real Estate Studies,Universiti Teknologi Malaysia, in successfully completingthis article. Gratitude is also expressed toward Ms. DanieleRambaldini, whose constructive suggestions greatly contrib-uted to develop the ethnography model.

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