Introduction
The Finish-to-Start (FS) relationship is the most commonly used dependency in project scheduling, both in Primavera P6 and other project management tools. This relationship type ensures that the successor activity cannot start until the predecessor activity has finished.
The Finish-to-Start relationship establishes a sequential order where one task must be fully completed before the next one begins. This is the most straightforward way to manage dependencies between activities in a project timeline.
Key Characteristics of Finish-to-Start (FS) Relationship
- Sequential Order:
- One task (predecessor) finishes, and only then can the next task (successor) start.
- Most Common Relationship:
- This type of relationship is used in most projects where tasks are dependent on each other in a straightforward manner.
- Simple and Logical:
- This relationship is easy to understand and apply, making it ideal for projects with linear workflows.
- No Overlap:
- There is no overlap between activities unless a lead is introduced.
Real-Life Examples of FS Relationship
Example 1: Construction Project
- Predecessor Activity: Complete excavation for a building’s foundation.
- Successor Activity: Start pouring concrete for the foundation.
In this scenario, the concrete pouring cannot begin until the excavation is completed. The FS relationship ensures that there is a clear dependency between the two activities, as the second task relies on the completion of the first one.
Example 2: Software Development Project
- Predecessor Activity: Finish the design phase of the software.
- Successor Activity: Start coding the software.
The design phase must be fully completed before the coding phase can begin, as the developers need the final design to start their work. This is a typical Finish-to-Start relationship in software development projects.
Example 3: Manufacturing Process
- Predecessor Activity: Finish assembling the engine.
- Successor Activity: Begin testing the engine.
In a manufacturing process, the engine testing cannot commence until the assembly is finished, as there needs to be a completed engine to test.
Using FS Relationship in Primavera P6
In Primavera P6, when defining a Finish-to-Start (FS) relationship, you link two activities in the following steps:
- Create or Select Activities: Ensure you have defined both the predecessor and successor activities.
- Assign FS Relationship: In the Activity Details section under the Relationships tab, select the FS dependency for the successor activity, linking it to the predecessor.
- Set Lag or Lead (Optional): If necessary, you can introduce a lag (delay) or lead (negative lag, overlap) to adjust the time between the end of the predecessor and the start of the successor.
Lag and Lead in FS Relationship
- Lag: A lag introduces a delay between the finish of the predecessor and the start of the successor. For example, after completing the foundation (predecessor), there might be a 3-day waiting period (lag) before concrete pouring (successor) can start.
- Lead: A lead (or negative lag) allows the successor activity to start slightly before the predecessor finishes. For example, you might allow landscaping to start when 90% of the exterior painting is complete.
Advantages of FS Relationship
- Simple and Logical: This relationship is easy to apply and understand, making it suitable for straightforward projects.
- Reduces Complexity: By defining clear, sequential steps, it simplifies project scheduling.
- Commonly Used: It fits into many project scenarios, making it versatile for different industries.
Limitations of FS Relationship
- No Overlap: Activities in a pure FS relationship don’t overlap, which might increase project duration if not managed properly.
- Limited Flexibility: FS doesn’t allow parallel activities, which can lead to delays when tasks could be performed simultaneously with SS or FF relationships.
Conclusion
The Finish-to-Start (FS) relationship is the most fundamental and frequently used type of activity relationship in Primavera P6. It provides a simple, logical way to manage dependencies by ensuring one activity finishes before the next begins. While it is ideal for linear processes, project managers should also be aware of other relationship types and the option to introduce lag or lead to optimize project scheduling.
