The construction industry is based on craftsmanship. Quality control and assurance procedures applied in manufacturing cannot usually be readily applied in construction, where there are higher degrees of uniqueness in each project. One category of companies, industrialized housebuilders, is attempting to bridge some of the gaps between construction and manufacturing. These companies prefabricate building modules for later assembly at the building site. Since they are wholly responsible for large parts of the building process, these companies have greater opportunities to control and improve quality in a more consistent way than ordinary construction companies. Thus, it could be hypothesized that the frequency and severity of defects should be lower in industrialized housing than in ordinary construction. The aim of the study presented here is to examine this hypothesis by measuring and characterizing defects in industrialized housing. The design and manufacturing processes at two Swedish timber module prefabrication firms has been analysed through interviews, site visits and document reviews. Quality audits from three phases of the building process were compiled, analysed and categorized to provide statistical measures of defects in industrialized housing. The results show that the case study companies are better in terms of product quality than conventional housing.Building defects, offsite production, quality management, industrialized housing, modular construction,

PurposeSeveral off‐site manufacturing companies in Sweden have attempted to apply lean management to improve process effectiveness and efficiency. A state of continuous improvement is a key goal of lean management, as described in, e.g. Likers 4P model. The aim of this study is to test a method to measure the degree to which lean management principles have been adopted by companies that base their production on off‐site manufacturing, as a prerequisite for a sustainable approach to continuous improvement.Design/methodology/approachA survey is applied as research method, using a questionnaire based on the authors' perceptions of best practices corresponding to each lean management principle. Two questionnaires were distributed to both management and factory production personnel in two off‐site manufacturing firms in Sweden.FindingsThe Likert scores regarding the degree to which lean principles have been applied in the two studied companies showed similar patterns (and similar differences between the management and production personnel's responses), indicating that the results can be generalised within an off‐site construction context. The study shows that continuous improvements must emerge and evolve simultaneously with a focus on processes, people and long‐term thinking.Research limitations/implicationsIn order to obtain more generalised and detailed results a more extensive survey covering several companies, as well as more detailed case studies and more questions regarding each principle, are needed. A multivariate analysis will also scan the material for further dependences.Originality/valueThe paper highlights several aspects that are important for management to be aware of when aiming for continuous improvements in off‐site manufacturing.

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