Is inclement weather a drag on your project schedule? Why not bake bad weather into your project schedule before it becomes a problem?
Inclement weather is a common stressor on outdoor projects. It can cause unpredictable delays on projects that stretch days or even weeks. But how do you plan for poor weather conditions? You never know with certainty which days in your project life will have no work days. This makes bad weather day planning difficult.
This article demonstrates a Primavera P6 Professional schedule including a bad weather day reserve to mitigate the negative impact of inclement weather.
You may consider padding estimates to account for the possibility of bad weather days. But estimate padding is not considered a good idea. It artificially inflates the schedule duration to give the project room to expand or cover unexpected delays. In padding the reason behind the pessimistic estimate is not documented. It is much better to be forthright and visible about the potential effect of inclement weather on the project. This is why a bad weather buffer or reserve is a more appropriate scheduling tool.
This bad weather day reserve should be owned by management. The project manager decides based on historical data how many days to set aside for bad weather. The goal for the project manager is to optimize the schedule to achieve cost and time objectives in a timely and efficient manner. And the bad weather day reserve is like a concentrated safety margin at the end of the project. Further, it is only used when bad weather occurs. If no bad weather occurs, congratulations, your schedule finishes early.
We have in Figure 1 our demonstration Primavera P6 Professional project.
This is a simple construction project consisting of three activities: remove damaged piping, install piping, and inspect installed piping. Notice that the project commences on April 1st. Well, we all know April showers bring May flowers, so we want our schedule to consider rainy weather conditions. We are also confident that rain days are expected, so we can boldly set aside reserve time labeled rainy day reserve. We therefore insert a rainy day reserve activity after inspect installed piping. This rainy day reserve has no assigned resources. And its duration is estimated from prior year weather conditions.
In Figure 2 we have our schedule, including a rainy day reserve or buffer.
This reserve is located at the end of the project. Our rainy day reserve does have a noticeable effect on the schedule. Originally, the schedule was set to conclude on April 12th, the inclusion of the rainy day reserve delayed project completion till April 17th. But that is only if all rain days are incurred.
Yes, it is possible that the weather is agreeable and no rain days occur. This becomes good news; our project completes earlier than planned. But if not we are fully prepared because we have baked in the rain days into the project schedule during the planning stage. So there should be no hysteria when the rain days occur. We have implemented a plan to mitigate the negative impact of rainy weather.
Bad weather happens. It is a reality in project scheduling. Some have sought to adjust for the potential of rainy weather, but inserting no work rain days directly on the calendar. This is not recommended. It embeds and hides weather day delays in the calendar, which is not good.
A better approach is to create a rainy day reserve strategically located at the end of the project. As rainy days occur and delay activity effort the duration of the rain day reserve is reduced, accordingly, until it is all used up. The ideal is for one or two rain reserve days to remain at the conclusion of the project. Again, this means your project concludes a day or two earlier, which is always good to hear.
So, consider the effect of rainy weather in the planning stages of your project. The earlier the rain days are considered the better, and project execution will have a greater opportunity to meet realistic completion dates. And your schedule transparency will be much appreciated by your project stakeholders.