CPM Best Practices: Updates to a Construction Schedule

A Critical Path Method (CPM) scheduler acts as an accountant of time and explains if the project is ahead or behind schedule.

An accurate updated CPM schedule is a powerful tool in documenting the history of the construction project and forecasting the remaining activities to reaching certain interim and/or completion milestones. Most construction projects have a specification requirement to provide monthly updated schedules and narratives that coincide with the end of the month pay period. The CPM scheduling consultant or person in charge of updating the schedule should take the information from the previous updated schedule and use that data to gauge the status of the current update period.

7 Tips to Success

1. The Bar Chart Mark-up

To kickoff an update, a good practice is to take a bar chart of all remaining activities, from the previous updated schedule, and mark up the bar chart with the current status by documenting actual starts and/or finish dates, remaining durations along with adjusting the schedule to show known expected start or finish dates. The scheduler should gather update information from the project manager and superintendent for each major contractor involved and document their input for the update period and forecast for the next update period. One step often skipped is asking for and documenting any known schedule changes and/or impacts and incorporate the impact into the update and logically tie it to the tasks it is impacting. This step will help to document a history of how the project evolved and how to mitigate impacts and provide an As-Built histogram.

2. Walk the Site

After gathering the update information, the scheduler should walk the site (if available) and verify the accuracy of the update information and that the schedule update reflects the true field conditions of the project. Depending on the simplicity or size of the project, some updates can be performed without site visits as long as the source of update information is accurate. After verifying the schedule update information, the scheduler will enter the update information into the previous updated schedule and rename the new update to a new file name to retain a monthly history and for comparison purposes. A new data date is entered and the schedule is calculated relative to the new current data date.

3. Note The Variances

Once the new schedule update is calculated, the scheduler should review the new schedule update against the latest baseline schedule and/or the previous updated schedule and note major variances. The critical path should be checked to make sure it accurately reflects the true status of the field conditions and let the project manager know if the project is ahead or behind schedule. The scheduler should then issue a preliminary version of the updated bar chart schedule to the project manager and/or superintendent to review and comment on the current projected status. If there are no comments or changes, the scheduler is ready to start writing the narrative.

4. Put It In A Conversation

The narrative is a written summary of what happened the previous update period and the anticipated progress for the upcoming period. A well written narrative will be a helpful tool to communicate to all the parties the current status, any known problem areas and possibly a solution to mitigate impacts.

Items to include in a narrative are:

Executive summary of the status of the project relative to key milestone dates
Discussion of major activities started and/or completed
Discussion of anticipated major activities that will see progress in the next update period
Listing of known impacts or issues affecting the project and possible solutions to mitigate their impacts
Describe the critical path from data date to key milestones
Mention any major slippages or gains from the previous update
Describe major logic changes from the previous update including added/or deleted activities and revised logic.

5. Show A Picture

Along with the narrative, the specification should list which reports and bar chart formats to submit with the updated schedule.

The bar chart columns/items to include should be:

Activity ID/#
Activity Description
Original Duration
Remaining Duration
Percent Complete
Early Start
Early Finish
Total Float

In the graphic portion of the bar chart, it is helpful to include the Act# and description next to the activity bar and also to include notes next to the activity bar to describe and document important details affecting a certain task.

6. Make It Logical

The organization of the bar chart should flow and help describe what is happening on the project. The grouping of activities depends on the size and complexity of the project. A sample of a simple grouping would be divided by area/level, responsibility and then flow by early start.

Adding the logic ties may result in a mess, in the graphic area, and in that case, you may want to add a 9th column for either predecessor ties or successor ties to help a person follow the logic.

7. Go Forward

After issuing the official updated schedule, the project management team should refer to the current updated schedule in all meetings and try to maintain or beat the early dates in the update. It is up to management to enforce the adherence of the current plan and execute to the plan. “Plan your work and work your plan”.