Calculation of "normal"construction time for building construction projects whilst considering uncertainties

Construction time has a major influence both on the cost-efficient execution of construction works and on the overall project outcome achieved by the client. Clients would do themselves a disservice if they specified short or extremely short construction periods for their projects. The same applies to time made available for project preparation, particularly for the design and tender stages. Any project that is poorly planned, tendered, and executed under time pressure will adversely affect actual construction work but also the building's use and possible reuse. Cost, time and quality targets are at risk due to the resulting disruptions to the construction process. Productivity is adversely affected not only by unduly short but also exceedingly long construction times. Short or very short construction times have a major influence on the efficient and effective utilization of production factors, including elementary (workforce, materials, equipment and machinery) and discretionary factors (project manager, site manager, technicians, etc.). This paper outlines the basic correlation between construction time, labor consumption rates and productivity as well as construction cost. Furthermore, it sets out to determine the influence of construction time on costing and, consequently, on the construction process. A practical example demonstrates how normal construction time can be calculated for reinforced concrete works based on uncertain input parameters. In addition, the benefits of specifying normal construction time for clients and contractors are outlined.