# Finish to Start Relationship

## PDM Relationships – Finish to Start

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 Finish to Start (FS) Relationship.  Finish to Start is one of the 4 Logical Relationships. The other 3 Logical Relationships are Start to Start, Finish to Finish and Start to Finish.

### Definition of Finish to Start Relationship

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

Finish to Start Relationship is the most common among 4 Logical Relationships. Almost any Project Dependency can be defined by using 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 Finish to Start Relationship with A – B cannot Start until A Finishes

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

### Mathematical Representation

B can Start (S) only after A Finishes (F)

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 – Document Requirements, B – Get Approval
• A – Design Machine, B – Develop Prototype
• A – Write User Manual, B – Print User Manual

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