Prefabrication is often put forward as a way to speed up renovations whilst cutting costs. In reality, cost reduction is often not fully achieved. Although standardization & automation at sufficiently large scale indeed have the potential to reduce costs, the process of setting up an accurate BIM model, with sufficient granularity to be used in all steps (from design to execution with the link to an as-built file and monitoring) is labour intensive. Increasing the precision tends to be postponed as far back in the process as possible. A consequence of this is that every next step which requires an additional level of precision is obliged to at least modify the existing model or, worst case, start with a new BIM model altogether. This is typically the case when Computer Numerical Control (CNC) machines are used in a computer aided manufacturing (CAM) process to produce prefabricated building elements.
Setting up a parameterised BIM model that can launch CNC production is a process that could ideally be started at the very beginning of the conception process. The recent uptake of BIM in design process has the potential of alleviating efforts in production phase. However, reality shows that BIM models used in the design phase are often too inaccurate to feed into the production process.
Postponing detailed modelling to the production phase increases the workload and thus cost, that is currently attributed to the prefabrication process. This inefficiency limits the roll out of prefab concepts to large, repetitive projects where modelling costs can be absorbed.
Existing tools and data sources should be explored to enable seamless data integration in the design process and data exchange among practitioners.
