Start To Finish is a logical relationship (or dependency) in which a successor activity cannot finish until its predecessor activity has started.
Start to Finish (SF) is one of the four activity relationships of project management. These are used while preparing project schedule. The other three relationships are:
Let us understand SF relationship in greater depth by using examples, Gantt Chart, Network Diagram, and Mathematical formulas.
Start to Finish Relationship (Dependency) in Project Management
As per the PMBOK Guide “Start To Finish is a Logical Relationship in which a Successor Activity cannot finish until a Predecessor Activity has started”.
However a better definition is, “Start to Finish is a Logical Relationship in which finishing event of a Successor Activity is dependent on the starting event of a Predecessor Activity”.
To understand the above definition, let us look at the events of an activity and not the whole activity. The two distinct events of any activity are:
- Start Event (S)
- Finish Event (F)
In SF relationship, the Finish event of the Second Activity is dependent on the Start event of First Activity. The Second Activity is called the Successor and the First Activity is called the Predecessor.
You can also look at Max Wideman’s Glossary for a complete set of PDM definitions.
Note: An activity or task relationship is loosely termed as project dependency. However, these two terms are different. A relationship between two activities can be established only if one activity is dependent on the other. Just like relationships, there are four type of project dependencies.
Start To Finish Examples
Let us consider two activities X and Y. X and Y are predecessor and successor activities respectively. The following examples show SF relationship between X and Y:
- X – Duty of Evening Guard (E), Y – Duty of Morning Guard (M). M cannot Finish her/his duty till E Starts. Simple speaking M cannot abandon the post even if E gets delayed.
- X – Start using New Software System (N), Y – Phase out Old Software System (O). It is assumed that N & O cannot be used in parallel. O cannot be phased out until N is started.
Representation of Start To Finish
An SF relationship can be visually depicted using using Time Scaled Bar Charts, which are popularly known as Gantt Charts.
Let us consider two activities A and B.
- Duration of A is 3 days.
- Duration of B is 1 day.
- B has a SF relationship with A
The Gantt Chart below shows SF relationship between A and B.
As per the above diagram B’s Finish is dependent on A’s Start, which means that B can Finish(F) as soon as A Starts(S).
In the above example, A and B together are scheduled to be completed in 4 days.
Project Network Diagram
An SF relationship can also be drawn by using Precedence Diagramming Method (PDM), which can be visually depicted by Project Network Diagrams.
Let us again consider the above two activities A and B. The Network Diagram below shows SF relationship between A and B.
Again considering the above two activities A and B and using 0 method, we can mathematically represent the relationship between A and B as:
B(F) = A(S)
Or, if we use 1 method, we can say that:
B(F) = A(S) – 1
Start to Finish with Lead and Lag
SF relationships can be further modified by introducing Lead and Lag modifiers.
The following Lead and Lag examples use 0 method representation.
Two activities J and K having SF relationship with 1 day of Lead:
K(F) = J(S) – 1 day
Two activities L and M having SF relationship with 2 days of Lag:
M(F) = L(S) + 2 days
Finish to Start is Different from Start to Finish
FS is the most common and natural relationship but it cannot represent every sequence of activities. Although SF can be mathematically transformed to FS to achieve seemingly similar results, the mathematical transformation modifies and tampers the natural logic.
Let’s revisit the Guard example from the previous section to understand why SF is more natural than FS. In the above example, there were two Guards who are doing a shift duty – Evening Guard (E) and Morning Guard (M).
In a natural scenario, M can “Finish” her/his duty only “only after” E “Starts” his/her duty. The critical point here is that “M cannot Finish her/his duty even one minute before E Starts”, otherwise it will be tantamount to abandoning the post. Since M cannot abandon the post, she/he has to guard the post even if E gets delayed in starting her/his duty.
The Finish of M is logically dependent on Start of E.
SF is not a very difficult concept to understand but sometimes it is confused with Finish to Start (FS) relationship. Some authors (incorrectly) claim that FS and SF are essentially same but it is not true.
Over to You
PDM Relationships can be represented by using mathematical equations. However, not all mathematical relationships represent the natural logic. While making a project schedule, you should ensure that all dependencies follow the natural logic and are true in the real world.
Do you think SF relationship is useful in real projects? Have you ever used it in you project(s)? Or have you seen it being used?
I would love to hear from you.
PMP Exam Formulas
I have also compiled a PMP Formulas Cheat Sheet. It contains 45 formulas and 57 abbrviations. It will help you in your exam prep. It is the best and most comprehensive cheat sheet based on the PMBOK Guide 6th edition. You can download it free of cost for your studies.
If you are looking beyond a cheat sheet, then I would suggest you to buy detailed PMP Exam Formula Study Guide by Cornelius Fichtner. It contains detailed explanations of all the formulas along with examples and 105 practice questions.
Disclosure: This article contains affiliate links - it means that, if you buy from any of these links, then I will receive a small commission that would help me in maintaining this blog for free. However, for you, there is no extra cost. I recommend only those products that I believe will definitely help the certification aspirants.