How do dependency types work?
FS, SS, FF and SF explained.
How Do I...?Project Manager Last updated 13 Aug 2026
Dependency types
- FS (Finish-to-Start) — successor starts after the predecessor finishes. Most common.
- SS (Start-to-Start) — successor starts when the predecessor starts.
- FF (Finish-to-Finish) — successor finishes when the predecessor finishes.
- SF (Start-to-Finish) — successor finishes when the predecessor starts.
Lag
Lag adds a delay (in working days) after the predecessor before the successor can begin.
Example: FS with 2 days lag = "start 2 working days after the predecessor finishes."