Project start date calculation in a Finish to Finish dependency scenario

In a Project task Finish to Finish relationship scenario, assume there are only 2 tasks in a project. Task B should not be Finished until Task A is finished. Task A takes 2 days and assume it is starting on 5-Jan (also project start date) (for simplicity all 7 days are working days). Task B takes 4 days complete. When i add the dependency of F-F, should the date for Project Start date to be changed to 3-Jan to make Task A and B to end on Same date i.e 6-Jan or should the Project start date to still remain as 5-Jan push the end date of Task B as 8-Jan ?

The finish-to-finish relationship says that you cannot finish B unless A is done. As an example, you cannot deliver a cake which is still not ready.

That being said, B will overlap A (Starting after A and finishing later than A).

Example:

Suppose you start your project on January 1st and every single day is a normal working day.

A finishes on January 3rd and B (consequently your project) finishes on January 5th.

Edited

Source 2: PMP Exam Prep, Eighth Edition - Rita Mulcahy (Pag. 202)

• Baked cake and delivery of that cake is a FS relationship. You cannot start the delivery, i.e., put unfinished cake that is still in the oven into the delivery truck, until the cake is out of the oven. Jul 28, 2015 at 19:57
• ...unless, of course, your truck is also an oven!!! Jul 28, 2015 at 19:58
– user16743
Jul 28, 2015 at 20:23
• Horrible example by whoever wrote that blog. Think about your resources for delivery: truck, truck driver, fuel. What are these three doing while the cake is being decorated? Jul 28, 2015 at 20:28
• Not really David. You can start several activities related to the cake delivery but you can only complete it when the cake is ready.
– user16743
Jul 28, 2015 at 20:29

Both are possible - it depends on the nature of Task B

should the date for Project Start date to be changed to 3-Jan to make Task A and B to end on Same date i.e 6-Jan

In some cases you can start Task B earlier. For example, let us say Task A is 'Add wiring' and Task B is 'Inspect electrical'. You can start Task B earlier by studying the wiring diagram and preparing an inspection checklist. In this case, if you coordinate very tightly, you may be able to finish Task B very close to the time Task A finishes.

or should the Project start date to still remain as 5-Jan push the end date of Task B as 8-Jan ?

In some cases Task B can only be started after Task A starts. For example, let us say Task A is 'Hang drywall' and Task B is 'Paint drywall'. In this case you cannot start Task B before Task A starts. Here you won't have any choice but to push the end date out.

• Since Kris used project start in her question, it can only be the latter. If these tasks were somewhere in the middle of the project, an early start might be possible. Jul 28, 2015 at 19:59
• Her? How do you know "Kris" is a woman? :-) You and your assumptions...
– user16743
Jul 28, 2015 at 20:51

The latter. The project start date is considered a constraint, right? It is a chosen date to have resources on site to begin work and spending money. You cannot arbitrarily start earlier. Therefore, if you have a FF relationship, you need to let schedule push the finish date such that the relationship can be honored.

A good example of this is if you have a management LOE task that has a FF relationship with a discrete task. Management can go no where until the discrete task is finished. Therefore, the discrete task will cause the finish the management LOE task to continue until it finishes.

• You clearly don't understand the FF concept. By the way, also a lot of fantasy in your answer with so many interesting assumptions. I suggest you to take a look at Rita Mulcahy's PMP preparation book 8th edition at page 202.
– user16743
Jul 28, 2015 at 20:48