Multiple predecessors overriding eachother



I'm having an issue where it seems that when I add a 2nd predecessor, it overrides the first.

I am wanting item #10 to start 1 day after item #4 finishes, and to finish 1 day after item #9 finishes (and therefore the duration will just auto calculate).

Based on this I have added the conditions 4FS + 1d, and 9FF + 1d, however it only seems to consider the "9FF + 1d" portion of this, and ignores the "4FS + 1d".

On the Gantt chart itself it recognises the 4FS + 1d, with an arrow linking the start of 9 with the finish of 4, however the start date just auto-populates as the same as the finish date (i.e.

I have tried to do this in various different steps and methods, and all end up the same. On it's own the 4FS + 1d predecessor works, but as soon as I add the 9FF + 1d it seems to ignore it.

Not sure if this is a known bug/limitation, or if I'm just doing something wrong. Any help would be greatly appreciated.


  • tegill
    tegill ✭✭

    Typically with Gantt charts when you put multiple predecessors in which ever one provides the latest date will be the controlling one. That way it is meeting both criteria. Typically you would use mulitiple predecessors to make sure that those tasks are completed by the time you get to the one you put the predecessors on. You can manually adjust (increase) the duration to meet the line 4 criteria or you may be able to us a formula to calculate the number of days based on the difference between the two dates. I haven't tried that but in theory it should work.

  • Fabio C.

    Dear @PES ,

    I have the same problem with a task that has to last for the whole project (it's a "monitoring task")

    In my case this "monitoring task" should start at the same time as task 1 (wo when the project starts) and finish at the same time as Task 2 (with the delivery of the project deliverbales).

    But when I use SS for Task 1 and FF for Task 2 putting them as predecessors the "monitoring Task" considers Task 2 as a predecessor ignoring Task 1, with the result that the start date and end date of the "monitoring task" are based on Task 2 only.

    It's a strange behaviour, I'll follow the thread.