PRODUCT DESIGN FOR IMPROVED MATERIAL FLOW—A MULTI-STOREY ... · PDF filePRODUCT DESIGN...

PRODUCT DESIGN FOR IMPROVED MATERIALFLOW—A MULTI-STOREY TIMBER HOUSING

PROJECT

Anders Björnfot1 and Lars Stehn2

ABSTRACT

Understanding of construction has evolved to include a deeper understanding of its mechanics; in ad-dition to traditional on-site work involving the manufacturing of building products—industrial con-struction. One of the most important aspects of any industrial process is flow of materials andresources. Using empirical data from a unique multi-storey timber housing project, this paper aims atbuilding a better understanding of how product design affects flow of materials in housingconstruction.

Even though a high degree of prefabrication was used in the project, the amount of complementarysite work caused delays, complaints, and a slow learning cycle. A standardization process was used toshift product ‘know-how’ from person to product, resulting in increased flow and a reduction of errors.Prefabrication was not the sole solution to the encountered problems, but the controlled and orderedenvironment in prefabrication provided solutions at early stages.

Instead of working towards solving the main production issues, the management was insteadobserved working with minor changes (first-aid solutions) to control flow. If industrialized multi-storey timber housing construction is to be successful, product design decisions should be thoughtthrough, thoroughly, from start to finish using standardization as a guiding star.

KEY WORDS

Assembly, Logistics, Multi-Storey Timber housing, Prefabrication, Standardization.

INTRODUCTION

The understanding of construction has evolved toinclude more than on-site, traditional constructionwork. Construction now includes a deeper under-standing of its mechanics, in addition to on-sitework, involving the manufacturing of products—referred to as industrialized construction (orsimply industrial depending on the context used).The activities involved in manufacturing and on-site assembly are in theory structured under theterms factory and construction physics (Bertelsen,2004). This new understanding has providedterms to describe and control processes and opera-tions in order to bring a construction product tolife, e.g., waste management, work structuring,industrial operations, etc. One of the most impor-

tant aspects of any industrial process is flow ofmaterials and resources (Bertelsen and Koskela,2004).

The design of building products (floors, walls,etc.) has an important impact on flow, evidentfrom one of the main construction issues—lack oftolerance consideration from early design, tomanufacturing, and construction site work (Tsaoet al., 2004). Solving flow issues already at theproduct design stage was in Björnfot and Stehn(2004) argued as the main path towards leannessin housing construction. Using empirical datafrom a unique multi-storey timber housing pro-ject, this paper aims at building a better under-standing of how product design affects the flow ofmaterials in construction. Since this paper con-tains the early stages of the case study, no quanti-

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1 Tech. Lic., Div. of Structural Engineering - Timber Structures, Luleå University of Technology, 97187 Luleå,Sweden, Phone +46 920 492067, FAX +46 920 491091, [email protected]

2 Prof., Div. of Structural Engineering - Timber Structures, Luleå University of Technology, 97187 Luleå,Sweden, Phone +46 920 491976, FAX +46 920 491091, [email protected]

fiable aspects of flow have been collected.Instead, the aim is to explain the observed eventsin a lean construction context. The purpose of thispaper is to analyze current practice of productdesign in a Swedish multi-storey housing project,and to discuss product design strategies forimproved flow. Of interest in this paper is there-fore to identify processes, or activities, where lackof flow is a problem, and also to propose solutionsto these problems.

CONSTRUCTION THEORY ANDTERMINOLOGY

Understanding of construction has with the onsetof lean construction evolved into two ways ofthinking; factory and construction physics(Bertelsen, 2004). Factory physics is an under-standing of construction as a controlled andordered system where construction products aremanufactured under factory conditions andassembled on-site using industrial operations.Construction viewed from site dynamics is farfrom such a controlled and ordered system. Con-struction has in recent literature been denoted ascomplex and chaotic, e.g., uncertainty in produc-tion labour productivity (Radosavljevic andHorner, 2002), project network fragmentation(Dubois and Gadde, 2002), etc. These construc-tion ‘peculiarities’ are well known issues in con-struction research today. Construction physics isthe understanding of these specific dynamics. Inthis paper, construction physics is used to denotework and activities performed to maximize valueand remove waste on the construction site. Figure1 illustrates construction and factory physic, andtheir relation to the main construction phases; thisway of understanding construction is in accor-dance with the ‘Transformation-Flow-Valuetheory’ (e.g., Bertelsen, 2002). The decouplingpoint (DP), see also Naim and Barlow (2003), sig-nifies a change in thinking for the completion of aconstruction project, i.e., this is where the charac-teristics of construction changes from factory tosite based production; the further downstream theDP is pushed, the less amount of work is per-formed on site while the factory productionincrease in importance. Consequently, increasingthe amount of industrialization in a construction

project is achieved by manufacturing more underfactory conditions, and/or using industryoperations and tools for on-site work.

Lately, industrialization as a concept has beenaddressed in construction research (e.g., Crowley,1998; Stehn and Bergström, 2002; Björnfot andStehn, 2004). The importance of prefabricationand pre-assembly for industrialized constructionis described in literature (e.g., Gibb, 2001; Ballardand Arbulu, 2004). Tools used to manage workunder factory physics are well developed in themanufacturing industry; one example is Enter-prise Resource Planning (ERP) tools. In Swedensuch tools are being developed for use in manu-facturing of timber frame housing (Bergström andStehn, 2004). Following the introduction of leanthinking in construction, tools for industrial sitework are more frequently discussed in construc-tion literature; the Last Planner system (Ballard,2000), and work structuring principles (Tsao etal., 2004) are but two good examples.

Work structuring and tools for industrial sitework, as well as industrialization involving pre-fabrication and pre-assembly, aim at the core oflean construction, namely value generation,removal of waste, and improved flow. The seventraditional wastes of construction (overproduc-tion, correction, material movement, processing,inventory, waiting, and motion) and the 8th waste(make-do) are given in Koskela (2004). During aconstruction project, many participants areinvolved expecting value generation; tenants’desire satisfying living quarters, contractorsdesire return on investments, etc. Value is there-fore hard to measure in absolute terms; value forone participant is not necessarily of any value foranother. The relationship between value, waste,and flow is by the authors summarized as; if anactivity, product design, or process hinders flow,then in some sense it provides less value whilegenerating waste. Waste can be identified bylocating flow bottlenecks. Flow charts can be usedto identify waste and flow bottlenecks, e.g.,improvement of a house-building supply chain(Naim and Barlow, 2003), and study of a moduleproduction system (Arbulu and Ballard, 2004). Aflow chart is in this paper used to study the multi-storey housing project.

CONSTRUCTION PRODUCTGENERATION

As the materials are transformed into buildingproducts, the value of the product grows. Whenthe product achieves its final place in the structureand is ready for end customer use, the product hasattained its maximum value. Figure 2 illustrates ageneral example of how value is generated in a

Proceedings IGLC-13, July 2005, Sydney, Australia

298 Product design for improved material flow—a multi-storey timber housing project

Figure 1: Understanding of construction as a combinationof factory and construction physics.

multi-storey timber structure. Each productinvolves the use of upstream products, e.g., rawmaterial (timber, plaster, etc.) convey no directvalue to the structure by itself, but is in the form ofelements (processed raw material), required fordownstream products. The highest order of prod-uct value in construction is volumes (ready-to-useliving space). In this paper, this scenario is calledthe ‘product value chain’, where value generatedis comparable to both streamlining processes(process value) (Starbek and Menart, 2000) andvalue generated for the end costumer by custom-ization (Naim and Barlow, 2003). A Swedishstudy of the domestic housing industry indicated ahigher return of asset for volume-product compa-nies compared to traditional element companies(Bergström and Stehn, 2004). If return of asset isconsidered a value for a company, then volumesclearly provide Swedish manufacturers with ahigher value than element or module production,as illustrated by Figure 2.

Element and module manufacturers produceproducts in factories, which are then transportedto, and assembled on, site. Volumes are producedthrough element manufacturing, which are thenassembled to three-dimensional volumes com-plete with installations, surface finishing, doors,wardrobes, etc. The volumes are then transportedto the construction site, assembled, and remainingfixed equipment is added. Housing constructionusing volumes is thus highly dependant on thefactory side of construction, which in Figure 1would push the DP downstream. The design andvalue generation for each structural component inhousing construction can be described using theterminology of Figure 2. Figure 1 can then be usedto describe how industrialized the production isand what form of improvements would providemost value for its completion—factory or con-struction.

In this paper a floor structure is used as a caseexample. The floor structure is a module built-upfrom multiple elements and sub-assemblies, inte-grating many technical systems—i.e., joists orslabs for load-carrying, ducts and cables forinstallations. If the floor structure is manufacturedas a module, then the demand on manufacturing ishigh (the DP moving downstream). If the floorstructure is manufactured as sub-assemblies then

the on-site assembly process will increase inimportance (the DP moving upstream).

CASE STUDY: MULTI-STOREY TIMBERHOUSING PROJECT

A multi-storey timber housing project is studied,Figure 3. An interesting aspect in this case study isthe material and structural system choice, massivetimber elements in both floors and walls, Figure 4.Before 1995, multi-storey timber structures wereprohibited due to restrictive Swedish fire regula-tions. Consequently, there is presently a lack oftimber construction knowledge among Swedishcontractors, consultants, engineers, and archi-tects. The uniqueness of the case is further ampli-fied as product development and experiencefeedback has progressed hand-in-hand with actualconstruction.

The multi-storey timber housing projectinvolves five buildings of six floors each (a totalof 95 apartments over 8.600 m2 [≈ 93.000 sq.feet]). The case study involves the construction ofthe first three houses (numbered 1 to 3 in Figure3). The project is a design-build project where themain contractor procures suppliers, consultantsand other contractors. Practical experience wasobtained from personnel responsible for design

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Anders Björnfot and Lars Stehn 299

Figure 2: Product value generation in multi-storey timber housing construction.

Figure 3: Illustration of the buildings.

Figure 4: Cross-laminated massive timber slab.

and handling, i.e., interviews with constructionworkers, site supervisor, project management,and manufacturer personnel. Other data used wasdocumentation from manufacturing and assem-bly. The main interest during the interviews werecollecting experience of floor structure handlingand assembly; what are the main problemsencountered using the current design of the floorstructure, and how can the design be improved toease flow?

CASE STUDY RESULTS

The floor structure, Figure 5, consists of load-car-rying system (massive timber slabs, and T-joists),floor (slabs are used as finished floor surface), andsub-ceiling (a three layer cross-work of timberbeams, insulation, and two layers ofplasterboards). The product design and materialflow results are summarized in a flow chart,Figure 6. The flow chart, illustrates work doneunder factory conditions and construction sitework. Length of flow arrows is just a form of illus-tration and has no relation to any measure. Valuegenerated (compare with Figure 2) is evident byfollowing the flow (arrows) from Timber to Fin-ished Floor (raw material to module). The DP forthis project is identified as the state when the floorstructure arrives ready to be assembled on theconstruction site.

MANUFACTURING

The manufacturer is one of northern Sweden’slargest sawmills and one of Europe’s leading andmost modern glulam producers. For the manufac-turer, the current project is a breakthrough for anew technique and a new way of thinking con-cerning construction using massive timber ele-ments. Due to the low use of massive timberelements, it is only recently they upgraded theirfactory production to include a higher degree ofautomation. The decision to move towards moreautomation was by the manufacturer crucial tosecure delivery for the current project. The con-tractor project manager stated; “the manufactureradvertised an undeveloped product, not ready for



Figure 5: Floor structure drawing.

Figure 6: The floor structure flow chart. Processes are described in Table 1.

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Process Activity

Make MT

Cut 1

Formelement

Cut 2

Formceiling

Formmodule

Assembly

Finishceiling

Table 1: Description of the processes used in the floor structure flow chart (Figure 10).

Massive timber elements (width: 1200 mm [≈ four feet]), arefabricated using three to five glued cross-laminates. Thefabrication process is similar to the manufacturer’s fabrication ofglulam, which is well known and used within the company for along period of time.

Using a CNC machine, the elements are provided dimensionsaccording to drawings, and sockets for installations andsanitary areas are cut. Tolerance problems emanating from thisstage are reported as uncommon.

Glulam beams are glued to the massive timber elementsforming beams with T-shaped cross-sections supporting themassive timber elements. The formed elements are then gluedtogether two and two forming elements up to a width of 2400mm [≈ eight feet].

Holes and notches are cut into the beams for installations. Thiswork is currently performed by hand using handheld machinery.Hand-work is prone to human error, and tolerance errors havebeen reported from this stage.

A cross-work of timber is formed to support and make room forthe sub-ceiling. “Blocks” of timber are added to support themodules in transportation.

Plasterboards are added to the pre-cut elements, while drainsand ducts are added by specialised installation contractors. Alayer of insulation is added before the ceiling is assembled,producing a module ready for shipping and on-site assembly.

The modules are assembled straight from trailers, using a towercrane. The modules are joined to walls using steel-plates andnails or screws. After assembly the ceiling is cut lose from thefloor. Tolerance errors discovered at this stage was identified asrelated to human errors in detailed design or fabrication.

On site the sub-ceiling is complemented; A layer of timber isattached, cables for sprinkler and electricity are added byinstallation contractors, and then insulation and two layers ofplasterboards are added. All work is performed from below. Atthis stage, installation tolerance issues have been the mainconcern.

use in a construction project. They were in beliefthey were contracted as suppliers only, when theyhad clearly been contracted with overall respon-sibility for their products (manufacturing toassembly).”

The manufacturing process has been constantlystreamlined during the project. Today, manufac-turing of the floor structure is performed in asemi-automatic process using computer aidedmachinery, and classic construction work, Figure7. The manufacturing processes (Make MT toForm Module) are described in Figure 6 and Table1. Timber required for manufacturing of elementsand T-joists are brought straight from the manu-facturers own sawmill and stored at the factory.The installation work is performed by a con-tracted installation crew. Cutting and notching theelements is done in a computer aided machine(Cut 1). The manufacturer factory supervisorstated; “the CNC machine provides the slabs withmeasures according to provided drawings. Toler-ance mistakes are mainly due to errors in thedetailed design stage.”

Assembly problems related to manufacturinghas been most common during assembly of thefirst house, the manufacturer factory supervisorstated; “at the start of house one, we had problemswith efficient manufacturing of the floor struc-tures, since it’s a new product for us and we didn’thave a fully developed manufacturing process.”These errors are mostly related to the massivetimber elements having the wrong dimensions,therefore requiring extra cutting work on site,resulting in assembly delays. The numbers oferrors related to manufacturing were substantiallyreduced for house two and three, as shown in aregister of construction site faults maintained bythe contractor site supervisor.

Another common error related to manufactur-ing is the cuts and notches used for complemen-tary site work on installations—a general

consensus among the site workers are; “the cutsand notches are much too small for reasonablework rate, and low tolerances on notches makes itvery difficult for us to uphold the strict demandson fire and sound insulation. It is not uncommonthat the ducts and pipes assembled at the factoryare placed up to a few decimetres from theirintended place.” Feedback between site workersand factory workers have solved many of theseissues, though there are still, as of house three,complaints regarding installation work on site.

LOGISTICS AND HANDLING

The assembly of the floor structure for a wholefloor is performed in two stages during twosequential days. Approximately half the floor isassembled in each stage. The manufacturer isresponsible for transporting the floor structuremodules to the construction site. The modules foreach assembly stage were supplied just-in-timeusing one truck and trailer; the transports werepulled from the factory by the assembly schedule.This has been carefully organised in detaileddesign to minimize transportation, the manufac-turer factory supervisor stated “we have workedwith a limit for the height of the modules to ensurethey can be delivered to the site on one truck andtrailer. This is the main reason why not more partsof the sub-ceiling are integrated already at thefactory.” The off-loading was supervised by fourworkers and a tower crane, one worker connectsthe modules on the truck (using straps as shown inTable 1—Form Module) and the remaining threeassemble the modules. “The transportations andoff-loading of modules has worked as intended forall three houses” is a general consensus among allinvolved parties. Though, the straps used to off-load the modules are problematic, since thesehave to be removed and the holes must becarefully insulated to cover sound and firedemands.

At the beginning of this project (house 1), noneof the contractor work crew was familiar workingwith massive timber floor structures integratingstructural system and sub-ceiling. The only know-how of the system was in the hand of the manufac-turer’s personnel. Therefore, the manufacturerfactory supervisor was initially forced to spendtime teaching the work crew how to handle thenew system. The supervisor spent a total of sixweeks (three assembly cycles) on site transferringhis knowledge to the work crew. This enabledfeedback of notches, tolerances, connectors, etc.to be brought back directly to manufacturing. Allconstruction site personnel agreed that “the man-ufacturer factory supervisor’s role was criticalfor the success of this project. Without his aid we



Figure 7: Use of handheld machinery

would still be standing out there trying to under-stand the drawings.”

ASSEMBLY AND COMPLEMENTARY WORK

The structural assembly of each floor was per-formed during a nine day assembly cycle. Themodules were fastened on the walls using steel-plates with nails or screws, Figure 8. Handheldmachinery (most common; nail guns) was usedfor the fastening operations. Screwing was, whenpossible, preferred over nail guns by the siteworkers due to safety reasons and noise. With thefloor structure assembled, complementary sub-ceiling work was performed; adding the third andlast layer of timber to the sub-ceiling cross-work,followed by electricity and the sprinkler system(Table 1—Finish Ceiling). Then, missing insula-tion and plasterboards were complemented.

In assembly, the drawings have been difficult tounderstand, as was also the case in logistics andhandling. The expertise of the manufacturer fac-tory supervisor helped solve many of the issueswith the assembly cycle. During early assembly,the fit between factory and on-site assembledinstallations was an issue. Direct feedbackbetween site workers and the manufacturer fac-tory supervisor solved many miss-fits in installa-tion work, Figure 9. One of the most problematicassembly operations was the connection betweenfloor modules and walls. These operations werecommonly complained upon, it is by the siteworkers often stated that “a smarter way of fas-tening the modules is a must; the way we have towork now is simply not possible in the long run.”Even though the assembly process has been con-tinuously improved from house one to three, theassembly schedule has remained mostlyuntouched. It was agreed on that assembly couldbe made faster, but the site workers expressed aneed to have plenty of time for assembly work dueto the rigorous demands on connection work stillremaining.

The complementary work on the sub-ceiling ispointed out as an important issue, both from awork environment, and a technical perspective.Complementary work on installations is problem-atic, as one site worker expressed; “there is verylittle space to work in and the tolerances allowedare minimal, best would be if complementarywork on installations could be minimized by pre-fabrication.” Often asked for by the site crew is

pre-assembled plasterboards. No reason for notintegrating plasterboards in factories was givenby the interviewees. Assembly of plasterboards infactories would circumvent another issue, storageon site. For this project the plasterboards for bothwalls and sub-ceiling are stored at their place ofuse within the houses. Due to limited space, theplasterboards are often a hindrance when per-forming complementary work.

DISCUSSION AND CONCLUSIONS

As shown in Figure 6, lean construction theoryinvolving factory and construction physics wassuccessfully used to describe the observed pro-duction events. Due to a general lack of timberconstruction knowledge among Swedish con-struction participants (Björnfot and Stehn, 2004),Swedish multi-storey timber housing projects areoften prone to flow bottlenecks and waste genera-tion. This project is no exception. Even though ahigh degree of prefabrication was used (modules),the high amount of complementary site workcaused delays, complaints, and a slow learningcycle. These issues stress the importance of con-struction physics considerations in prefabricationdecisions. In this project, it is clear that the designof the floor structure had a large impact on mate-rial (and resource) flow. Table 2 presents exam-ples of product design observations obtained fromthe case study, highlighting the importance ofcareful product design.

It should be noted that neither of these per-formed actions had any major impact on the flowchart structure (Figure 6), i.e., the relation(amount of work) between factory and construc-tion physics is unchanged. Even with the per-formed actions, the main issue related to the sub-ceiling remain, i.e., complementary work frombelow. The performed actions instead served as ameans to remove waste resulting in improved

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Figure 8: Typical floor-to-wall connection Figure 9: Complementary site work on installationsin sub-ceiling.

flow within, and between, processes (in Figure 6this improvement is not quantifiable). More fun-damental actions are required to fully benefit fromthe prefabrication. Table 3 proposes solutions totwo of the main identified product design issuesand their expected impact on flow.

The Finish Ceiling solution would induce amajor change in the floor structure flow chart;division of the floor structure into floor and sub-ceiling, Figure 10 (the processes before Cut 2 areomitted for visibility). In contrast to the flow chartused in this project (Figure 6), the empirical datasuggests a flow chart where the DP is moved evenfurther downstream, indicating more work underfactory conditions and assembly being the onlyremaining site activity. While moving work fromthe site to factories would ease assembly, manu-facturing and logistics would instead be intro-duced with an increased workload. Prefabricatingmore is not the sole solution to all problems in thisproject. But compared to the variability of siteproduction (Bertelsen, 2002), a holistic productdesign where more of the product completion isperformed in factories would provide a controlled



Problem Performed Action Improvement in Flow

Cut 1

Even using CNC, poor designdocuments lead to elementsdelivered to site with wrongdimensions.

More attention was given tomanufacturing and tolerancesalready at the detailed design stage.

Reduced extra site work spentmanually cutting, or re-orderingelements due to size issues.

Cut 2

Handwork using standard handheldmachinery is prone to human errorsand mistakes, which are especiallyevident in complementary site work.

Site installation workers have beenin close contact with factoryinstallation workers andmanufacturer factory supervisor.

Reduced amount of site workcorrecting installation placementerrors. Has also reduced the timespent adding insulation or plasterrelated to the corrections.

Assembly

The drawings are difficult tocomprehend, and the amount ofplates and fasteners used causebad work conditions and partsmissing in assembly.

In the design stage the number ofsteel-plates and fasteners requiredfor assembly was significantlyreduced.

Reduced the amount of work inuncomfortable positions, andreduced the amount of emergencyorders on missing parts.

Table 2: Examples of performed product design actions for improved flow.

Problem Proposed Solution Expected Improvement

Assembly

An easy way of off-loading modulesis sought. The straps causeunnecessary complementary sitework. The steel-plates used forassembly should be even morereduced, and placed at locationwhere work can be performedefficiently.

Fasten the steel-plates to themodules already at the factory, andfind an innovative way to connectthese to walls on the site. The steel-plates can also be designed toserve a purpose in off-loading ofmodules.

Prefabricating and findinginnovative connections wouldsignificantly reduce re-work on site.Possible problems encountered arerelated to transportation, storage,and handling of elements containingjutting steel-plates.

FinishCeiling

This is the main project issue.Working conditions oncomplementary sub-ceiling workcan be described as awful. Limitingor totally removing work from belowis a strong wish among siteworkers.

Divide the floor-structure in twoparts; floor and sub-ceiling. If thesub-ceiling is assembled first, thisenables work to be performed fromabove. This would also enable thewhole sub-ceiling to beprefabricated.

Working from above is a preferredworking position and providesincreased quality in complementarywork if required. Problems arerelated to manufacturing, which maybe difficult handle due to reducedstability.

Table 3: Examples of remaining product design issues and proposed solutions.

Figure 10:The proposed revised floor structure flow chart.

and ordered environment with opportunities tosolve site waste generation issues already at anearly stage.

Each problem identified, and each proposedsolution, is a standardization process to continu-ously improve the floor structure by removal ofwaste and improvement of flow. Continuousimprovements are an important part of lean think-ing, and are usually integrated with innovationstrategies (Knuf, 2000). All encountered prob-lems can be identified as traditional constructionwastes; the main waste in this project being cor-rections. Each action to solve these problemsserves as a driver to shift product knowledge frompractitioners to product. This shift of knowledgeis important in standardization processes;buildability/constructability is a good example ofwhere standardization serves as a driver for siteproductivity (Björnfot and Stehn, 2004). The ini-tiator for the shift of knowledge in this project wasthe manufacturer factory supervisor. Know-howtransferred to the construction site workers even-tually resulted in an understanding of handlingand assembly. The manufacturer site supervisorwas the coordinator continuously improving thework and design of the floor structure, while theconstruction site workers provided input for thestandardization of the product and process,Table 2. The proposed innovations (Table 3) weremainly provided by the project management andthe manufacturer factory supervisor. Figure 11illustrates the participants’ roles in product devel-opment for this project. In each row, the relativearea of each process (standardization, continuousimprovements, and innovation) illustrates theamount of work performed by the participants. Abetter developed floor structure design wouldhave allowed the management to give more atten-tion to finding innovative solutions, instead ofdeveloping first-aid solutions to make it work atall.

Concluding this paper, the results highlight theimportance of the DP for industrialized construc-tion. Failure to utilize a holistic process view inprefabrication often ends up with problems, i.e.unnecessary complementary site work where theadvantages of prefabrication are lost. The projecthas to live with the initial prefabrication deci-sion—changing a prefabrication strategy on the

run is often difficult due to long lead times(Koskela, 2003). The main observations in thiscase study are summarized as;

• Think holistic. The substantial complemen-tary site work in this project is a result of poorproduct design decisions in early designphases. As a result, the main advantages ofprefabrication (control and order) are lost.Product design decisions should be thoughtthrough, thoroughly, from start to finish. Inthis project first-aid solutions was employedto improve flow but the main issues stillpersisted.

• Standardized thinking. In this project eachmodule could have varying dimensions, re-sulting in unnecessary lead times in fabrica-tion and errors in assembly. The findingsindicate that prefabrication without a ‘stan-dardized way of thinking’ (more related tomass customization than mass production) isprone to issues; obvious from the manage-ments’ decision to add part of the sub-ceilingto the floor, without realizing the amount ofadded work in site assembly.

The above points are not new to the constructioncommunity; still failure to utilize these facts is alltoo often documented. In this project the manage-ment, responsible for setting fundamentalchanges into motion, was instead observed asworking with minor changes (first-aid solutions)to control flow. The main reasons for this are mostlikely related to a combination of using a rela-tively new product, participants not used to work-ing together, and a paced time-to-finish withouttime for any changes during production. But theseconditions are apparently more of a rule than anexception in construction.

ACKNOWLEDGEMENTS

We acknowledge all interviewees, the openaccess to documentation, and the financial sup-port by the ‘Development Fund of the SwedishConstruction Industry’ and ‘The Kempe ResearchFoundation’.

REFERENCES

Ballard, G. (2000). “The Last Planner System ofProduction Control.” Doctoral Thesis, Uni-versity of Birmingham, Birmingham, UK.

Ballard, G. and Arbulu, R. (2004). “Making Pre-fabrication Lean.” Proceedings of the 12thannual conference of the Int. Group for LeanConstruction, Elsinore, Denmark.

Bergström, M. and Stehn, L. (2004). “Benefitsand Disadvantages of ERP in IndustrialisedTimber Frame Housing in Sweden.” Submit-

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Figure 11: The manufacture’s and site personnel’s roles inthe floor structure development process.

ted for publication in Constr. Mgmt. andEcon., 2004.

Bertelsen, S. (2002). “Bridging the Gaps—Towards a Comprehensive Understanding ofLean Construction.” Proceedings of the 10th

annual conference of the Int. Group for LeanConstruction, Gramado, Brazil.

Bertelsen, S. (2004). “Lean Construction: Whereare we and how to proceed?” Lean Construc-tion Journal, 1(1) 46–69.

Bertelsen, S. and Koskela, L. (2004). “Construc-tion beyond Lean: A New Understanding ofConstruction Management.” Proceedings ofthe 12th annual conference of the Int. Groupfor Lean Construction, Elsinore, Denmark.

Björnfot, A. and Stehn, L. (2004). “Industrializa-tion of Construction—A Lean ModularApproach.” Proceedings of the 12th annualconference of the Int. Group for Lean Con-struction, Elsinore, Denmark.

Crowley, A. (1998). “Construction as a Manufac-turing Process: Lessons from the AutomotiveIndustry.” Computers and Structures, 67(5)389–400.

Dubois, A. and Gadde, L-E. (2002). “The Con-struction Industry as a Loosely CoupledSystem.” Construction Management and Eco-nomics. 20(7) 621–631.

Gibb, A. (2001). “Standardization and Pre-assem-bly—Distinguishing Myth from RealityUsing Case Study Research.” ConstructionManagement and Information. 19(3) 8pp.

Koskela, L. (2004). “Making-Do—The EightCategory of Waste.” Proceedings of the 12th

annual conference of the Int. Group for LeanConstruction, Elsinore, Denmark.

Koskela, L. (2003). “Is Structural Change the Pri-mary Solution to the Problems of Construc-tion?” Building Research & Information,31(2) 85–96.

Knuf, J. (2000). “Benchmarking the Lean Enter-prise: Organizational Learning at Work”Journal of Management in Engineering, 16(4)58–71.

Naim, M. and Barlow, J. (2003). “An InnovativeSupply Chain Strategy for Customized Hous-ing.” Construction Management and Econom-ics. 21(6) 593–602.

Radosavljevic, M. and Horner, W. (2002). “TheEvidence of Complex Variability in Construc-tion Labour Productivity.” Construction Man-agement and Economics. 20(1) 3–12.

Starbek, M. and Menart, D. (2000). “The Optimi-zation of Material Flow in Production.”International Journal of Machine Tools &Manufacture. 40(9) 1299–1310.

Stehn, L. and Bergström, M. (2002). “IntegratedDesign and Production of Multi-StoreyTimber Frame Houses.” International. Jour-nal of Production Economics, 77(3), 259–269.

Tsao, C., Tommelein, I., Swanlund, E., andHowell, G. (2004). “Work Structuring toAchieve Integrated Product-Process Design.”Construction Engineering and Management.130(6) 780–789.



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