May 30, 2012
EMPLOYING LAG RELATIONSHIPS
Lag Relationships are put in place to help more properly setup forward steps within projects. This concept is introduced early on into any project as deliverables are being handed out for completion. This concept creates an environment more appropriate for creating the project timeline so project objectives are started and finished in the correct sequence. 1. Finish to Start
a. The most common type of logical sequencing between tasks is referred to as the Finish to Start Relationship. An example of a delay would be if three activities are linked in a serial path, activity number 3 cannot begin until the scheduled task from activity number 2 is completed in full. 2. Finish to Finish
b. Finish to Finish relationships require that two linked activities share a similar completion point. An example would be in a 10 step/activity project, some of the steps may have the same completion point, i.e. steps 4 and 5. This means you do not need to wait until step 4 is completed prior to starting step 5, you can work them at the same time and complete them on the same completion date. 3. Start to Start
c. Often two or more activities can start simultaneously or a lag takes place between the start of one activity after an earlier activity has commenced. An example would be in a project when one activity can be labeled a ‘burst point’ to multiple successor activities. 4. Start to Finish
d. Perhaps the least common type of lag relationship occurs when a successor’s finish is dependent upon a predecessor’s start. An example of this is when you are building a house, you cannot pour the concrete into the foundation ditch until the entire area is cleared out of groundwater and all drainage is completed.