Modeling relationships between tasks in any scheduling tool requires knowledge of both the project work and how it will be performed as well as the tool. Simple Finish-to-Start relationships may not always give you the optimum schedule efficiency or allow you to model the work as it will actually occur.
This article describes how to use a Finish-to-Finish relationship in Microsoft Project 2013 to describe two processes occurring in parallel, but ending in series (one after the other).
There are many ways to use relationships to model the work flow in a schedule and the examples in this article are just one of several options.
Microsoft Project Example
Here is an example. You are improving an underground piping system by installing a cement thrust block at the 90-degree fittings to make certain water pressure on the fittings do not cause the nearby coupling to fail, i.e. leak.
You schedule the project tasks using classic Finish-to-Start relationship. However, upper level management is not happy with the completion date. They want the project to complete sooner.
You review your schedule and realize that the Insulate Pipe task can commence during the concrete cure process, which takes place after the Pour Concrete task. You just have to make certain the removal of the concrete forms completes before the end of the Insulate Pipe task. That way you can ensure your pipe is insulated right up to the cement thrust block. So your concrete cure process and insulate pipe task can take place in parallel.
So how do you describe these parallel processes in your schedule? Well, Microsoft Project 2013 has a Finish-to-Finish task relationship that may be used to describe this parallel process, and the importance of the Strike Forms task completing before the Insulate Pipe task.
Figure 1 displays your original schedule where all activities are in series with the classic Finish-to-Start relationship.
Notice in your Install Thrust Block summary task that the Pour Concrete task has a 6-day elapsed time (24/7) lag following it to allow the concrete time to cure before removing the Forms, task D – Strike Forms. Task E – Insulate Pipe follows task D – Strike Forms in series. You want to use a Finish-to-Finish relationship between Task D – Strike Forms and Task E – Insulate Pipe. You can do this using a few simple steps.
First highlight Task E – Insulate Pipe, then select Information in the upper Task tab, Figure 2.
In the resulting Task Information dialog, Figure 3, note the current task E – Insulate Pipe and the Predecessor task D – Strike Forms. In the Type column select Finish-to-Finish (FF) in the drop down menu, Figure 3. Select OK.
Also, create a Finish-to-Start relationship between task C – Pour Concrete and task E – Insulate Pipe. The Insulate Pipe task now will be fully defined, Figure 4.
Note that the concrete cure process (described as lag between Task C – Pour Concrete and task D – Strike Forms) and task D – Strike Forms are performed in parallel with task E – Insulate Pipe. Ideally, your Insulate Pipe task will momentarily suspend during the Strike Forms task, but that is a minor delay. Well, to plan for this minor pipe insulation delay let us add one more day to task E- Insulate Pipe, Figure 5.
The pipe insulation task has been increased from 3-days to 4-days, so the pipe insulators will commence work on Monday instead of Tuesday. Note that your overall project duration remains the same at 13-days. Adding the extra day to task E – Insulate Pipe had no effect on the project duration.
The important points to note are that your Insulate Pipe task commences during the cure process and ends after the Strike Forms task. You can see your original Improve Piping project duration of 16-days shown in Figure 1, and then your updated Improve Piping project duration of 13-days shown in Figure 5.
You improved your project completion date by 3-days simply by changing the relationship between task D – Strike Forms and task E – Insulate Pipe from Finish-to-Start to Finish-to-Finish. Finally, note that your task D –Strike Forms and task E – Insulate Pipe are both on your critical path, Figure 6.
Microsoft Project 2013 has the ability to describe tasks performed in series and tasks performed in parallel. The Finish-to-Finish relationship is used to model tasks performed in parallel, but ending in series. This is particularly useful when the start relationship between parallel tasks has leeway, but where the end relationship between these same parallel tasks requires that one task complete before the other.