The design process has a significant impact on the performance and profitability of a housing project. Therefore, decisions made during the design process should take into consideration knowledge and experience from other processes in previously accomplished projects, specifically from the production phase. How to capture and use production experience in housing has not gained enough interest, possibly leading to suboptimal improvements during the construction process. This motivates research on how onsite production experience from similar previous projects can be captured and used to improve constructability without risking customer values. Based on the concept of constructability, 'design for manufacturing and assembly' and the theory of waste, the method 'design for construction' (DFC) has been developed. The four-step model complements the conventional construction process, and consists of the following steps: (1) specify customer values and similar previous projects; (2) identify onsite waste and cost drivers in previous projects; (3) develop criteria to evaluate constructability; and (4) evaluate constructability of the design. The DFC method is exemplified and tested through a case study, in which it was shown that the method facilitated identification of all problems that were considered in the investigated project. The method also highlighted other project obstacles that potentially could have been solved to improve constructability.

Abstract:For some years an intense debate regarding the building costs has been ongoing in Sweden and reducing construction costs is highly prioritised among the construction companies. At the same time, passive houses have started to appear on the Swedish market and so far the construction costs for these have been higher compared to tradition1al houses. It is therefore important to investigate the construction methods to find out where to focus and where to improve the process so the energy performance can be increased while at the same time construction costs can be reduced. Based on an interview study with construction site managers, seven key areas could be identified which were different compared to traditional housing; system design, building documents, construction planning, working methods, quality control, leadership and attitudes. Projects that were successfully accomplished from an economical and productivity point of view had been planned with special focus on these aspects. In the less successful projects, the importance of the understanding of the concept had been ignored and underestimated which led to additional time consuming activities which could be described as waste of time. There is a need to find alternative production methods which prioritize the product quality in an integrated and efficient manner.