Contractors must deliver projects on schedule and within budget — or risk taking a loss. That’s why many of today’s project managers apply an approach that has been widely used by larger construction companies: the critical path method (CPM).
Staying on course
CPM is a scheduling technique used to calculate a project’s duration and illustrate how schedules are affected when certain variables change. It identifies the “critical path,” which is the longest sequence of scheduled activities that determines when a project can be completed. Any delay in the critical path slows down the job.
In many cases, some tasks won’t affect other activities and can be pushed back without pushing out the planned completion date. Other tasks can be performed in parallel with the primary steps. But each job task that lies on the critical path must be completed before any later tasks can begin.
Optimizing the route
CPM analysis shows what needs to be done and when. It breaks a construction project into several manageable activities, displays them in a flow chart showing the “activity sequence” (the order in which tasks must be performed), and calculates the project timeline based on the estimated duration of each task.
For smaller jobs, this can be done with pencil and paper. The project manager draws a diagram with circles that represent activities/time durations and — where one activity cannot begin until another is completed — connecting those circles with arrows to show the necessary order of primary job tasks. The completed diagram will reveal arrow paths indicating activity sequences and how long it will take to complete them.
For larger, more complex projects that may have multiple critical paths and overlapping, interconnected activities, creating diagrams by hand can be time consuming and difficult. CPM software makes the process faster, easier and less prone to human error. When things are constantly changing — particularly at the beginning or end of a project — these applications allow far easier updating of the analysis and production of new diagrams.
Many of today’s CPM software products are moderately priced and worth considering. They can quickly identify the critical path, instantly process updates and even calculate float times for noncritical activities.
Some solutions can model the effects of schedule-compression techniques, such as fast-tracking (tackling multiple tasks simultaneously) and crashing (adding extra resources). With the software installed on mobile devices and data stored on the Internet, it’s easy to share CPM charts and access them from the field.
Exploring the approach
CPM isn’t a silver bullet for every scheduling problem, but it’s helped many contractors. If your project managers aren’t using it, consider exploring the concept and technology with them.
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