Task 1 and Task 2 must finish at the same time – they have a Finish-to-Finish dependency.
When the finish date of Task 1 determines the finish date of Task 2, they have a Finish-to-Finish (FF) dependency.
For example, "Inspect electrical" (Task 2) can't finish until "Add wiring" (Task 1) finishes.
Like SS dependencies, FF dependencies reduce the overall amount of time it takes to complete work on two tasks, if the work can overlap or be done in parallel.
- If Task 1 will take 10 days to complete, and Task 2 will take 5 days to complete, and you set an FS dependency, the overall duration of the two tasks is 15 days.
- If you set an FF dependency, the overall duration of the two tasks is only 10 days (the time required by Task 1).
When two tasks have an FS dependency, but the work can overlap or be done in parallel, consider changing their dependency to FF to reduce the overall duration of your project.