Task Relationships

Task Relationships are the links between the tasks in the Dependency Chart. There are four main relationship types:

  • Finish to Start
  • Start to Start
  • Finish to Finish
  • Start to Finish

We will look at each in turn. Each Relationship Type can also be affected by Lead Time and Lag Time.

Finish to Start

The Finish to Start relationship means that the first task must finish before the second task can start. In the Dependency chart it is shown as follows. The ‘X’ denotes the Lead Time (a negative number) or Lag Time (a positive number).

Finish to Start

Finish to Start

On a Gantt Chart, the dependencies will look like the following diagram. Firstly with no Lead or Lag, secondly with Lag Time, and finally with Lead Time.

Finish to Start Gantt

Finish to Start Gantt

This is the most common type of relationship type.

Start to Start

The Start to Start relationship means that the first task and the second task should start at the same time. In the Dependency chart it is shown as follows. The ‘X’ denotes the Lead Time (a negative number) or Lag Time (a positive number).

Start to Start

Start to Start

On a Gantt Chart, the dependencies will look like the following diagram. Firstly with no Lead or Lag, secondly with Lag Time, and finally with Lead Time.

Start to Start Gantt

Start to Start Gantt

The same could be achieved by using a Finish to Start relationship type, and adding Lead Time to equal the duration of the first task.

Finish to Finish

The Finish to Finish relationship means that the first task must finish at the same time as the second task. In the Dependency chart it is shown as follows. The ‘X’ denotes the Lead Time (a negative number) or Lag Time (a positive number).

Finish to Finish

Finish to Finish

On a Gantt Chart, the dependencies will look like the following diagram. Firstly with no Lead or Lag, secondly with Lag Time, and finally with Lead Time.

Finish to Finish Gantt

Finish to Finish Gantt

This relationship type has arrows pointing from right to left, which can be very confusing.

Start to Finish

The Finish to Start relationship means that the first task cannot start second task has finished. In the Dependency chart it is shown as follows. The ‘X’ denotes the Lead Time (a negative number) or Lag Time (a positive number).

Start to Finish

Start to Finish

On a Gantt Chart, the dependencies will look like the following diagram. Firstly with no Lead or Lag, secondly with Lag Time, and finally with Lead Time.

Start to Finish Gantt

Start to Finish Gantt

Again, this relationship type has arrows pointing from right to left. The same affect could be achieved by doing the tasks in the other order.

Summary

That covers the four different relationship types. Lead Time and Lag Time complicate the relationships.

Keep it simple. Use Finish to Start Relationships by default, and only use the other types where absolutely necessary.


Posted On: 7th April 2021

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