4 Types Of Precedence Relationships For Projects (+Examples)

In my previous article, I looked at some of the facts that you need to know about activity dependencies for projects. In this article, I want to look at Precedence Relationships for Projects. 

In this article, I want to look at some of the facts that you need to know about precedence relationships for projects. Follow me as we will look at that together in this article.

A precedence relationship is a logical relationship between two activities that describes the sequence in which the activities should be carried out. Each activity has two open points: Start and Finish. 

Precedence relationships consider appropriate logic while connecting these points. Precedence indicates which of the two activities should come first, the predecessor activity and which should come later the successor activity.

Precedence relationships are always assigned to activities based on the Dependencies of each activity.

Dependency determination …

Dependency determination is the determination of the dependencies of one activity over the other. It involves s establishing the Precedence Relationships among activities and creating logical sequences for projects.

Different types…

#1 Finish to Start

The precedence relationship between two activities where the predecessor activity must finish before the successor activity can start. It can be expressed as ” Activity A must finish before Activity B can begin”.

For example, the foundation for a house must be finished before the framing can start. The total time for these two activities is the sum of A and B.

#2 Finish to Finish

The precedence relationship between two activities where the predecessor activity must finish before the successor activity can finish. It can be expressed as ” Activity A must finish before Activity B can finish”.

For example, the construction must be finished before the building inspection can be finished. The total time to complete both activities is based on when B begins.

#3 Start to Start

The Precedence relationship between two activities where the predecessor activity must start before the successor activity can start. It can be expressed as ” Activity A must start before Activity B can start.

For example, the building design must start before the electrical layout design can start. As with the Finish to Finish example, the total time for activities A and B will vary depending on when. activity B starts But in SS, there is a longer window during which Activity B can begin.

#4 Start To Finish

The precedence relationship between two activities where the predecessor activity must start before the successor activity can finish. It can be expressed as “Activity A must start before Activity B can finish “.

A typical example is an electoral inspection must start before you can finish the drywalling. The total time for Activities A and B can vary widely, depending on the relative duration of each activity. This type is rarely used.

Understand Lead And Lag In Project Execution

In my previous article, I talked about some of the factors that must be considered when it comes to the working breakdown structure for the project.

Here, I want to look at some of the facts that you need to know about the use of leads and lag in project execution. Follow me as we will look at that together in this article.

Leads…

A lead is a change in a logical relationship that allows the successor activity to start before the predecessor activity ends in a Finish to start a relationship.

A lead is implemented when you need to accelerate a successor activity in order to shorten the overall project schedule.

Leads will vary in length, depending on the acceleration required by the amended schedule.

Sometimes, a lead introduces a risk of rework because the successor activity starts before the completion of the predecessor activity, and the complete, comprehensive inputs may not be available.

Possible lead

The programmer for a website may decide to start programming the home page four days before the interface design is approved.

Starting the programming may shorten the overall project schedule by four days. However, if the design is not approved, there may be significant rework for the programmer, resulting in the loss of some or all of the four-day gain.

Lag

A lag is a delay At the start of a successor activity. Some relationships require a lag before the subsequent activity can begin.

Lags are determined by an external or mandatory dependency and may affect activities with any of the four precedence relationships.

Example…

When a lag is introduced in an FS relationship, the overall elapsed time required for the chain of activities increases. The start and finish dates of the successor activity are delayed when there is a lag.

Positive lags

There are several reasons why lag occurs. Examples of two possible lags are:

• The permit application takes six weeks to process.
• The adhesive must dry until tricky before the laminate can be installed.

In the first example, the activity that follows the submission of the permit application is delayed by six weeks due to an external dependency of the application processing time.

In the second example, the installation of the laminate activity is delayed by the amount of time the adhesive takes to dry. This is a lag due to a mandatory dependency because the delay is inherent to the work itself.

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