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Types of linking relationships in MS Project

It is important to understand how project tasks linking relationships work in MS Project software. These relationships lay the foundation for project scheduling, dictating the sequence of activities and ultimately influencing the project’s timeline. Our MS Project lecturer Susan clearly explains each of these relationships for linking project tasks in this YT video:

Types of Linking Relationships

Definitions of linking relationships

1. Finish to Start (FS): This relationship denotes that Task B cannot commence until Task A is completed. It’s the most common and straightforward relationship used in project scheduling.

2. Start to Start (SS): Here, Task B is linked to the start of Task A. Task B cannot begin until Task A has commenced, ensuring a coordinated start for related activities.

3. Finish to Finish (FF): Task B is tied to the completion of Task A. This relationship ensures that Task B cannot finish until Task A reaches completion, synchronizing the finishing points of interconnected tasks.

4. Start to Finish (SF): This relationship specifies that Task B cannot finish until Task A starts. It’s relatively less common but can be useful in certain scenarios where the completion of one task is dependent on the initiation of another.

What is lag in tasks linking relationships?

Lag refers to the delay between tasks within a relationship. It can be positive, indicating a delayed start or finish, or negative, signifying an overlap between tasks. Lag allows for the introduction of buffers or dependencies between activities, thereby refining the project schedule

Finish to Start (FS) linking relationships

The Finish to Start (FS) relationship serves as a cornerstone for establishing task dependencies and sequencing. In this case task B cannot commence until Task A is completed.

Basic example:

The sequence of tasks such as pouring concrete and erecting structural steel. The steel erection task cannot begin until the concrete pouring task is completed. This straightforward FS relationship ensures that the foundation is fully set before the steel structure is erected, maintaining structural integrity and adherence to the project timeline.

Finish to Start relationship

Positive Lag Example:

A construction project where roofing must be completed before installing interior ceilings. To ensure no leaks occur, a positive lag of 3 days is introduced after the roofing task. This delay allows for adequate inspection and preparation before commencing the ceiling installation.

Negative Lag Example:

In exceptional cases, such as fast-tracking certain activities to meet project deadlines, negative lag can be applied in FS relationships. For instance, landscaping might commence 2 days before exterior painting is fully completed, effectively overlapping the tasks and expediting the project timeline.

Start to Start (SS) linking relationships

Start to Start relationship

In Start to Start (SS) relationships in Microsoft Project, Task B (the dependent) can only start once Task A (the predecessor) has commenced. It allows for concurrent execution of activities while maintaining dependencies.

Basic Example:

In a road construction project, the excavation of the roadbed and the installation of drainage systems may have a Start to Start relationship. The excavation work (Task A) must begin before drainage installation (Task B) can start. This ensures that as soon as the excavation starts, the drainage system installation can commence simultaneously, optimizing project timelines and resource utilization.

Positive Lag Example:

When pouring a house foundation, the framing process may begin 2 days after the foundation work commences. This positive lag allows for the initial setting of the foundation before commencing the framing, ensuring structural integrity and alignment with project requirements.

Negative Lag Example:

Consider a scenario where electrical wiring and drywall installation are interconnected tasks. In certain areas where electrical wiring is not required, the drywall installation may start 2 days before the electrical work begins. This negative lag allows for overlapping activities, optimizing resource utilization and expediting project timelines.

Finish to Finish (FF) linking relationships

Finish to Finish relationship

In Finish to Finish (FF) tasks relationships on Microsoft Project, Task B (the dependent task) can only finish once Task A (the predecessor) has been completed. It ensures that two tasks finish simultaneously.

Basic Example:

In the assembly line of a vehicle manufacturing plant, the task of installing the engine (Task A) and the task of installing the transmission (Task B) are linked by a FF relationship. Task B, installing the transmission, cannot finish until Task A, installing the engine, is completed. This ensures that both the engine and transmission are ready simultaneously, facilitating the smooth progression of the assembly process and maintaining the production schedule.

Positive Lag Example:

Consider a scenario where interior painting is dependent on the installation of windows. To facilitate proper ventilation for drying, a positive lag of 4 days is introduced after the completion of window installation. This delay ensures optimal conditions for the painting task, enhancing its quality and effectiveness.

Negative Lag Example:

In certain cases, project schedules may necessitate overlapping activities to expedite project delivery. For instance, to accelerate the handover of a property, cleaning tasks may commence 1 day before the final snag list is completed. This negative lag ensures timely completion of critical activities, aligning with project objectives and deadlines.

Start to Finish (SF) linking relationships

Start to Finish relationship

A Start to Finish (SF) relationship denotes that Task B cannot finish until Task A starts. This type of relationship may seem counterintuitive at first glance but can be useful in specific project scenarios.

Basic Example:

In a construction project, the quantity surveyor’s task of final cost estimation (Task B) depends on the commencement of material procurement (Task A). The procurement process must begin before the quantity surveyor can finalize the cost estimation. This SF relationship ensures that accurate cost projections are based on the availability and pricing of materials, optimizing budget planning and project financial management.

Positive Lag Example:

In a manufacturing project where quality assurance (QA) inspections are crucial, a positive lag may be implemented in the SF relationship between the assembly and QA testing phases. After the assembly begins, there might be a lag of 2 days before QA testing commences. This buffer allows for sufficient time to complete preliminary assembly tasks before initiating the rigorous testing procedures, ensuring thoroughness and accuracy in quality assessments.

Negative Lag Example:

In a software development project, where rapid iterations are essential for meeting tight deadlines, a negative lag could be applied in the SF relationship between coding and debugging tasks. Typically, debugging would start after coding begins. However, to expedite the development process, debugging might commence 1 day before coding starts. This overlap enables developers to identify and address potential issues proactively, streamlining the development lifecycle and accelerating project delivery.

Microsoft Project linking relationships

These concepts are indispensable for effective project scheduling in MS Project and one of the first lessons in our MS project course Project Management with Microsoft Project:

Next up we will delve into the practical application of this knowledge by going through the methods of linking tasks within the Microsoft project software.

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