Shorter project lead times in construction

Abstract: The manufacturing industry has made an extensive journey through the last century when it comes to increasing productivity. Results in the construction industry end up far behind manufacturing and do not show anywhere near the same efficiency increase, improved quality or decreased costs. There are a lot of potential savings in the form of activities that consumes resources without creating value for the end customer, also called waste. Waste in combination with uncertainty and variability in task duration forces the project duration to be longer than necessary. The purpose of this study is to investigate the opportunity to shorten the lead time of a construction project and investigate how construction companies can work continuously towards shorter project lead times. The purpose has been fulfilled through a time study performed at four projects managed by one of the leading construction developers of residential buildings in Scandinavia. Waste and variability were mapped in the interior phase. The measured time for each activity was categorized either as; value adding time (VT), necessary but non-value adding time (NNVT) and non-value adding time (NVT). The results showed that mounting consists of 48 % VT, 28 % NNVT and 24 % NVT, while material handling consists of 0 % VT, 75 % NNVT and 25 % NVT. The results further showed large variability in task duration between the projects. Theory from lean, logistics and scheduling were combined to form three different scenarios for shortening project lead times. The first scenario describes how to work with removing waste from the process. The second scenario describes how to reduce variability and thus be able to reduce buffers in the time plan. The last scenario describes how support processes, for example material handling, can be removed from the critical path, in order to reduce project lead times. A proposal for a general approach for continuously working with decreasing project lead times is also presented. Central aspects for shortening project lead times were concluded to be the takt time, variability and risk. The proposed approach involves a combination of the three scenarios, where their impact on each other is considered.