Re-engineering through pre-assembly: client expectations and drivers

Pre-assembly is an important facet of the strategy to re-engineer construction. It can be categorized as: modular building; volumetric pre-assembly, non-volumetric pre-assembly and component manufacture/subassembly. This paper presents the results of an interview survey of major construction clients about their expectations from and drivers for pre-assembly on their projects. In particular, time, cost, quality and productivity benefits through minimization of on-site operations and duration, less congestion on site, improved health and safety along with greater and more predictable quality are identified. To get the best out of pre-assembly, clients acknowledge that they must be able to freeze the design early, provide reasonable lead times and provide time for presite prototyping. Clients' past experience has been mixed, with some citing tangible benefits, but others experiencing poor-quality products and a limited and disjointed supply chain - these mitigate against efforts to increase pre-assembly as part of the re-engineering mantra. Typically, clients accepted that suppliers should be involved early, but in practice many do not re-engineer the process and leave key decisions too late in the process to maximize benefits. More than half wanted to see an increase in the use of pre-assembly on their projects, but the supply chain must refocus to consider the client's perspective and capitalize on this opportunity. Whilst pre-assembly is not new and many have published on the subject, the perspective of clients has not been adequately covered. Pre-assembly may be well understood by manufacturers, contractors and even some designers, but unless the client decision-makers understand its benefits and limitations, then their misunderstandings and prejudices will continue to be a barrier to further development.