How to Schedule your Construction Projects using the Critical Path Method (CPM)

A detailed and accurate schedule should be developed for your projects by using the CPM method.

The Critical path method (CPM) scheduling is a process for building a Construction project schedule and analyzing it to determine the most critical tasks affecting the scheduled completion date.

Let’s look at this example of a custom house that I completed. As you see from the drawing and 3D rendering, the house is 1,800 Square feet, one story, and a three-car garage. 

I start to develop a rough draft of the Schedule. I obtain the activities for the schedule from my construction takeoff and estimate. (Figure 3)

The Takeoff is a list of activities that are necessary to complete the project. I feel that it is important that the Project Manager/Estimator of the project be involved in constructing the Schedule.

If that is not the case with your company, work closely with the estimator in developing your Schedule. He or she understands the project in a very detailed way. 

To determine the durations, I develop this from the construction estimate. For example, in the rough framing stage of the project I have identified the takeoff quantities for this work.

 From there as you see in Figure 4, you can determine the duration of that particular scope of work. That is the durations that I start with.

 I also, at this early rough draft of this schedule, include the Trade Contractors and include their anticipated durations. 

                                                                Figure 3

From the Activities of the construction Takeoff and estimate, I then input them into my computer scheduling system. I use the Suretrak software system. It is a subsystem of Primavira. (Figure 4)

The activities are set in order as you would build a project. The sequence is determined from similar past projects.

In this house project, the activities would follow the normal progression of the project in the following order.

Demolition of the existing structures. Site Clearing and excavation, foundation construction, framing of the structure, installing the roof, and then completing the interiors.

All of these activities thus need to be linked to one another in a sequence that minimizes the overall duration of the project. 

                                                          Figure 4

These activities thus need to be linked to one another in a sequence that minimizes the project's overall duration. 

Next, you want to establish milestone dates at this rough draft stage.

Milestone dates are target dates that identify major tasks that must be completed. These dates should be broadcast to all the members of the project so that they understand their roles as the project commences. 

As the project progresses you want to update the schedule every week.

You input the actual dates of completion and durations. The blue bars represent the As-built status of the project.

At this time, you have to look at the future items in the schedule that are to be completed. You may have to adjust the durations or the sequence of some items. You may also have to add some activities to show a more detailed look at a particular phase of the project.

Develop a Variance Report on every updated schedule and include it as you send out the updated schedule to all your interested parties.

Review your upcoming weather if you are building outside and before your building is weather-tight. Adjust upcoming activities if need be.

Stay a top of your projects with your CPM schedules. Save the preliminary schedule of the project and compare it to your completed schedule. Keep your as-built schedule for future projects. 

Shettig Construction Management provides Professional Design-Build Construction Management Services from the inception of your project through completion. www.shettig.com , mshettig@gmail.com