A rework probability model: A quantitative assessment of rework occurrence in construction projects

Abstract

© 2015 Taylor & Francis. Statistical methods for eliciting probability distributions were used to analyse the data collected from 78 construction professionals. The empirical distributions for rework costs were found to be non-Gaussian. Theoretical probability distributions were fitted to the rework data. Non-parametric tests were used to determine the goodness-of-fit of the selected probability distributions. The results of the goodness-of-fit tests revealed that generalized Pareto distribution provided the best fit for the dataset. Single probability points for rework from 1% to 10% were calculated. It was established that rework can make a significant contribution to a project's cost overrun. The mean total rework cost as a percentage of the original contract value was found to be 5.12%. For a mean total rework cost of 5.12% the likelihood that a project exceeds is 76%. The anticipation that rework will occur, using the probabilities that are derived, can enable a quantitative risk assessment to be undertaken, which will ultimately lead to identifying alternative solutions so as to avoid rework prior to the commencement of construction work.