How do I make these tasks so flexible that changes mid construction are easy to make?

Question

I have 4 tasks A-D, each one is a predecessor to the next. My schedule baseline is A->B->C->D. However, tasks A-C order is flexible and doesn't matter which one comes first, they just can't be worked at the same time. Task D has to start once A-C is complete, but as long as all 3 are complete, it doesn't matter if it starts after A or B or C. Once our crew starts the project, the tasks end up being done in a different order (for example B->C->A->D), I have such a hard time updating the schedule because all the links are out of order. I end up having to redo the baseline.

1. What's the best way to set up the baseline schedule for these tasks, knowing that I'm going to have to input large changes in dependencies? I'm at a loss.

Answer 1

Given that they can be done in any order as long as they are all done before you start task D, it sounds like you are trying to create dependencies where none exist between tasks A, B, and C. You only need to create a dependency between each of A and D, B and D, and C and D. If you use resource levelling to ensure that your resources are not over-committed, I think that should handle the timescale issue. You could also manually enter start and finish dates for each of A, B, and C, which can easily be changed without impacting on each other, while still maintaining the relationship of these three tasks with task D.