Demystifying the cost barriers to offsite construction in the UK

Offsite construction has long been reported as an effective alternative to conventional construction, with wide-ranging benefits. However, a wider take-up has been inhibited by perceived cost barriers which are insufficiently studied. Such cost barriers are addressed, drawing on an examination of the cost performance of four types of construction method: pre-cast concrete cross-wall panel, in-situ reinforced concrete (RC) frame, steel frame and timber frame. Data were collected for 20 medium to high rise residential buildings of eight projects by a leading UK housebuilder over a five-year period (2004-08). In all cases, detailed cost comparisons were completed for build method selection. Cross-wall was found to be consistently cheaper than RC frame or steel frame by 11% to 32% in the projects. The process of developing and innovating cross-wall technology led to sustained cost savings up to 25% from its first use. Cross-wall construction also improved cost effectiveness of 20-storey high rise buildings over other solutions. Cost engineering means for achieving cost reduction and effectiveness are identified, which included efficiency learning, technological innovation, multinational partnering, and 'in-house' build management. The results prove the logic of the experience curve in improving the cost efficiency of offsite construction, and should encourage offsite construction in the future.