Setting up two predecessors to the same task in MS Project

Question

Let's suppose there are two tasks (A and B) among others. I'd like to restrict B in such a way that:

• It starts 5 natural days after A starts
• It finishes 5 laborable days after A has finished

Assuming A has already its own predecessor, is there a way to set up B so that it respects both restrictions at the same time?

I could set up each restriction separately using A as predecessor of B, but not both at the same time. Is there a way? Thank you!

EDIT: More info about the problem

• My goal is to be able to change the duration of A, and have the duration of B change automatically to honor the restrictions I described above.
• The actual task is: I'm installing a pipe in a trench which is already dug. A is the task of pouring the concrete. Then we have to wait 5 calendar days to start installing the pipe (task B), but even then, more concrete will still be being poured ahead on the trench. Then we have to wait other 5 workable days to be able to finish the pipe installation.

Answer 1

The short answer is no. You are asking about two concepts neither of which works in MS Project. I want to be sure I address each.

First is the idea of having two predecessor/successor links or relationships between the same two tasks. You are looking to have both start to start plus 5 day and a finish to finish plus 5 day links from Task A to Task B. MS Project will only support one link between two tasks. It does not treat the finish to finish link as something different.

Second is the idea of "natural" -vs- "workable" days. I would call those calendar days and working days. These kinds of restrictions are set up by creating different calendars or just putting different periods of working days or non-working days in whatever calendar you are using.

Edit: OP commented that we can use edays as the unit so we get elapsed days. Non working times will be ignored. I have not used this, but it is correct. Thank you for this! End edit

Then ... you can assign one calendar to a task. MS Project does not support calendar assignments to predecessor / successor links. That would be pretty complex and would require additional settings for which calendar to honor if the tasks and the links had calendars assigned. I digress.

Edit:

Based on the use case my solution would be to put a tasks in for pouring, allowing the concrete to set, and installing the pipe for each section. (I assume set time is the reason for the 5 day wait)

Like this:

Or like this:

The advantage of the 2nd way is you can copy/paste at the summary task level to more easily replicate many pipe sections.

I prefer more detail. I've worked jobs where there is a laboratory analysis that comes back at 7 days after the pour. If the concrete is not up to strength the next tasks have to wait another seven days. So if that happened you just extend that one task and everything gets pushed out.

Hope that helps!

End Edit

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