Evaluating the impact of cost waste causes in residential buildings construction total cost

Cost increase is one of important factors that always have a negative effect on project success. Cost increase is divided in two parts: cost overrun and cost waste. Cost overrun is the difference between the actual and estimated cost of project and money waste is the cost that paid for non-value-added activities that are no positive effect on project process. This paper has researched on cost waste causes in building construction. In addition to the articles in-depth review, by semi-structured interview with experts and thematic analysis, this paper has identified 3 main causes that are reworks, material waste and labor inaction. But the uniqueness of this paper is related to the numerical calculation of the impact of these cause on total cost. Total cost is cost of building production without costs related to permits and land price. Required data were collected from 130 project manager by using a questionnaire containing four questions. The answer of three questions in questionnaire were Yes or No and just one last question requires estimation of the project manager. As a result, according to criteria codification, the efficient questionnaire was provided. Lasso regression Model were used that according to the type of data and the possibility of error in estimating was fully compatible with the problem. Finally, among three causes, rework were obtained as the most important cause and If there is any loss in the case of presenting three causes in project, costs waste was estimated 3.12% of the total cost.