Microsoft Project has the capability to model both workday lag and 24-hour elapsed time lags within one schedule. When you’re working with projects that require a mixture of working time and elapsed time, you’ll need to understand how to describe this in your schedule.
Microsoft Project Example
Let’s look at an example using Microsoft Project 2013. After the inspection of an underground pipe system, you are tasked to repair a PVC-to-Metal flange adapter, and then install a pipe thrust block to prevent future adapter failures.
You model all the tasks using the classic Finish-to-Start relationship. This seems to work well for your sequential oriented project. However, you note two likely delays between tasks.
- A 4-day business time delay from the moment your pipe adapter is ordered to the moment it is received on site.
- A 4-day “round the clock” cure time delay from the time your thrust block concrete is poured to the time it is cured, so that the forms can be removed.
How should your schedule account for these delays?
This article describes how to add lag to the classic Finish-to-Start task relationship to describe both delivery delays and cure time delays.
Modeling Delivery Delays
A leak was discovered in an underground piping system located at the interface between the PVC and metal piping and a company located across the country sells an improved replacement part.
The remaining outstanding issue is that the supply company can only guarantee you a 4-day business day delivery of the replacement part. Here we show how to model this delivery delay using a standard lag in Microsoft Project 2013.
The sequentially ordered Pipe Repair & Improvement project is displayed in Figure 1.
Note that the Installation PVC Piping & Adapter summary task is scheduled to take 3-days. Also, note that the Acquire PVC-Metal Adapter task is only scheduled to take 1-day, but we know that we still have to model a 4-business day time delay. We can model this delay by following a few simple steps.
First, select the successor of the Acquire PVC-Metal Adapter and click the Information icon in the Task tab on the ribbon above, Figure 2.
In the resulting Task Information dialog, Figure 3, notice that the current task is the Install Piping & Adapter task and the Predecessor to this task is the Acquire PVC-Metal Adapter. We can also see the Finish-to-Start (FS) relationship in the Type column. Finally, in the Lag column replace the current 0d lag with a 4d lag to describe the 4-business day delivery delay.
Select OK in the Task Information dialog and your schedule tasks and Gantt chart will update to that displayed in Figure 4.
Note now that your Installation PVC Piping & Adapter summary task has a 7-day duration now, instead of 3-days. We can then manage the project accordingly.
Modeling Cure Time Delays
A subcontractor has recommended the installation of a cement thrust block at the 90-degree fittings to prevent future leaks. So we now schedule the installation of a thrust block into the schedule.
We will now have to model another schedule lag delay to account for the cure time of the concrete. To model this delay select the Remove Strike Forms task, and, as before, click the Information icon in the Task tab, Figure 5.
This again brings up the Task Information dialog, Figure 6.
Note that Remove/Strike Forms is the current task, and Pour Concrete is the Predecessor. The relationship type is the classic Finish-to-Start. In the Lag column change the 0d lag to 4ed lag, which stands for elapsed days. So it is 4 elapsed days, which includes the weekend non-work daytime.
Select OK in the Task Information dialog and your schedule tasks and Gantt chart will update as displayed in Figure 7.
Note first that your original 3-day Install Pipe Thrust Block summary task now has a schedule duration of 5-days. You added a 4-day lag, but it only resulted in the addition of 2-days to your schedule. That is because the lag was elapsed time, i.e. 24-hour anytime, which includes the weekend non-work days. So your 4-day cure time only impacted your schedule by 2 work days.
Microsoft Project has both standard lag and elapsed time lag to model business day delays and anytime delays, respectively. These features are especially useful if delivery time adds precious days to your project or cured concrete is absolutely essential before commencement of the successor activity. Business time and elapsed time task lags are just two of the many features available to the scheduler in Microsoft Project 2013 to describe the relationships between project tasks.