Factors Affecting Upstream Production Rate and Causing Reworks in Downstream Activities due to Activities Overlapping

Overlapping (or fast tracking) is a schedule compression technique in which phases or activities normally performed in sequence are performed in parallel, PMI, [1]. Rework has both direct and indirect effects on the performance of construction projects. The direct effect of the impact of rework are: additional time for rework, additional costs of rework, additional materials spent on rework and control next waste, additional labor for rework, difficulty of managing resources. To reduce the impact of reworks there is a need to understand their basic reason for their existence or set of conditions that stimulate their occurrence in a building process. This paper aims to identify the top important changes that affecting upstream production rate and causing reworks in downstream activities. These changes were identified through three stages. The first stage twenty three changes which causing reworks in downstream activities were collected from past literature review and were divided into three major categories: designer, contractor and owner changes. One hundred effective interviews were conducted and their results are employed. The second stage, the twenty three changes were then ranked from the most significant to the less significant. The third stage, the 80/20 rule applied to the changes identified to get the eight most important changes that represented about 25% of the causes. The result shows the top important eight factors which were considered as the factors affecting upstream production rate and causing reworks in downstream activities as follows: 1) Lack of coordination and poor communication, 2) The contractor instruction to modify a design, 3) Non-compliance with specification, 4) The owner instruction to modify a design, 5) Incomplete design at the time of tender, 6) Poor planning and coordination of resources, 7) Errors made in the contract documentation and 8) Lack of experience and knowledge of the design and construction process.