CPM (Critical Path Method) scheduling is the development and use of a comprehensive work plan that represents the construction logic of a construction project using network diagrams. These network diagrams show how the work will be done and is used as a guide to coordinating and managing the work. For that reason, it is crucial to manage a schedule well - or else it could result in large costly problems.
While there are plenty of benefits to CPM scheduling, there are a few common hurdles in the CPM Scheduling process, which are as follows:
- Logic is not formally thought out, ultimately affecting the legitimacy of the “critical path”, putting the project at risk. If a project is managed without an accurate critical path, it is impossible to determine what is actually driving the project, thus making it difficult to manage delay. Both hard logic and crew logic need to be contemplated and deliberated and organized in great detail to produce a quality schedule, which unfortunately is often not the case in commercial construction.
- Too much or too little detail - Some schedule managers (which includes “schedulers” and “PM’s”) want to put way too many activities, which ultimately requires much more time while risk is embedded within the accuracy of the data (due to it being so time consuming), or put way too little activities, which comes with the risk of coordination issues and inefficiencies - due to lack of detail. Anyway, the sweet spot for me is 500-2000 activities for a project $20M+, with somewhat of a correlation between number of activities and project size.
- Crashing logic - When schedules are updated, sometimes they are delayed. There are three ways to deal with this: A) Accepting the delay and updating the schedule without any changes B) understanding delay issues and making modifications based on well thought out mitigation strategies or C) changing logic as quickly as possible so the delay goes away. Unfortunately C is the most common & widespread.
Tips for CPM Scheduling
- Make scheduling a team effort and utilize an organization breakdown structure.
- Get buy in from trade contractors
- Update the schedule on at least a monthly basis by using the most accurate and current details available.
- Study historical delay issues and resultant mitigation plans (at every update).
- Utilize the schedule to help with daily planning, troubleshooting, claims, cash flow, historical record and resource planning.
- Make sure that higher management is committed to the schedule of the project
These breakdowns should not deter from the primary advantage of the CPM – its ability to identify the relationships and dependencies between all of the activities within the total project network. The CPM also creates a sort of blueprint that will showcase the relationships between both construction and non-construction activities that will affect the performance.
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