Start to Finish Relationship

PDM Relationships – Start to Finish

This article extends my previous article on Project Network Diagram. Project Network Diagrams are used to pictorially represent Project Schedule and Project Dependencies. You can also read my other articles on Project Dependencies – What are Project Dependencies and 4 Types of Project Dependencies.

There are many ways to draw a Project Network Diagram. One of them is Precedence Diagramming Method (PDM). PDM defines 4 Logical Relationships to represent Project Dependencies. This post to describes Start to Finish (SF) Relationship.  Start to Finish is one of the 4 Logical Relationships. The other 3 Logical Relationships are Finish to Start, Start to Start and Finish to Finish.

Definition of Start to Finish Relationship

It is a Logical Relationship in which a Successor Activity cannot finish until a Predecessor Activity has started. In other words, the Finish of a Successor is Dependent on Start of the Predecessor.

The most common and most natural relationship is Finish to Start (FS). Start to Finish Relationship is very rarely used. The Project Managers have some flexibility while defining the relationship between 2 activities. Usually it is possible for them to transform a SF Relationship to a FS Relationship.

You can also look at Max Wideman’s Glossary for complete set of definitions on PDM Logical Relationships.

Project Network Diagram Representation

Let us consider two activities A and B.

• Duration of A – 3 days
• Duration of B – 1 day
• B has a Start to Finish Relationship with A – B cannot Finish until A Starts

The Project Team will need a total of 4 days to complete these activities.

Mathematical Representation

B can Finish (F) only after A Starts (S)

B(S) = A(F)

Examples

Let us consider 2 activities A and B. Let us also consider A to be the Predecessor and B to be the Successor.

• A – Duty of Evening Guard (E), B – Duty of Morning Guard (M). M cannot Finish her/his duty till E Starts. M cannot abandon the post.
• A – Start using New Software System (N), B – Phase out Old Software System (O). It is assumed that N & O cannot be used in parallel.

You can also look at some of my other articles on Precedence Diagramming Method

2 thoughts on “Start to Finish Relationship”

1. Nice post. SF dependency explained nicely with illustration.