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Session No. 2247

Strategies for creating accurate updates of CPM construction schedules.

Todd Dunn, P.E.

Associate Professor, Rochester Institute of Technology Civil Engineering Technology

Abstract: The paper describes practical approaches that students and practitioners can use to accurately update CPM construction schedules. It describes the importance of updates, and also explores common errors made during updates, and methods for correcting them. Its purpose is to provide students and professionals involved in CPM construction scheduling the tools to create reliable and accurate schedule updates using popular application software (Primavera Systems Inc.). Detailed ‘means and methods’ employed when updating schedules are described. In particular, the paper describes the software settings and approaches for configuring the settings in an effort to achieve accurate, reliable schedule updates.

Introduction: Creating CPM (Critical Path Method) schedules for construction projects is commonplace. Construction schedules include a group of activities which must be performed in order to complete, say, a new building. Every activity in a construction schedule has an estimated time duration to complete the activity. Examples of activities might include, ‘Erect Structural Steel’ (with, for example, a ten day duration) or ‘Install brick veneer on south wall.” Critical path schedules are so-named because these time schedules highlight a subgroup of activities that lie on the critical path. The activities that lie on the critical path are important because a delay in completing any of these activities will result in a delay in completion of the project.

Schedulers and/or construction project managers should update their CPM schedules on a regular basis in an effort to compare actual progress on the job with planned progress. Owners will want to know if the project is on schedule, and the only way to provide a quantitative answer to that question is to examine each activity in the schedule and record any progress that has occurred on that activity since the last update. Once the progress is accurately recorded, the application software used to create the schedule can perform calculations that will estimate start and end dates for the remaining (incomplete) activities in the schedule. This may result in a project completion date that has changed since the last update.

Often, however, schedules are not updated regularly, in part because producing accurate updates to an on-going project is not a trivial endeavor. (Another reason regular schedule updates are sometimes ignored is that often owners and contractors loose enthusiasm and motivation for producing the updates. Part of this lethargy is due to their experience with flawed updates). In addition, the popularization of easy-to-use scheduling software has “democratized CPM schedule writing....but it has also put scheduling in the hands of many inexperienced and poorly trained

“Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition Copyright @ 2005, American Society for Engineering Education”

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Dunn, T. (2005, June), Strategies For Creating Accurate Updates Of Cpm Construction Schedules Paper presented at 2005 Annual Conference, Portland, Oregon. 10.18260/1-2--14158