The impact of change orders on mechanical construction labour efficiency

Change orders impact many areas of a construction project. However, the impacts that change orders have on labour efficiency are much harder to quantify than other impacts and therefore are a significant risk to contractors. Little research has been completed in the past quantifying these impacts, so disputes are common between owners and contractors regarding the actual cost of change. This study used data from 43 projects to develop a linear regression model that predicts the impact of change orders on labour efficiency. The input factors needed for the model are (1) total actual project hours, (2) total estimated change hours, (3) impact classification, and (4) timing of change. The model calculates the labour loss in efficiency for a particular project so that owners and contractors will better understand the true impact of change on labour efficiency. The research is limited to the mechanical trade, but does include specific work in plumbing, HVAC, process piping, and fire protection.