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
Finish to Start is a Logical Relationship in which a Successor Activity cannot start until a Predecessor Activity has finished.
In simple words we can say that, the Start of a Successor Activity is Dependent on Finish of the Predecessor Activity.
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
In the above example, the Project Team will need a total of 4 days to complete these activities.
Bar Chart Representation
Mathematical Representation And Formulas
If you are using 0 method
B(S) = A(F)
Or, if you are using 1 method
B(S) = A(F) + 1
Finish to Start 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
Over To You
This is the most common relationship. How often do you use it? Are all your relationships FS?
Please leave a comment.
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