Normal Network

Laddering

When planning a project, every Project Manager or Project Scheduler endeavours to find the least possible time by which the project can be completed. However, this is one of the most difficult tasks to conduct. We discuss a technique called Laddering, which can help in reducing the planned total duration of a project.

Laddering is a technique where we break down certain tasks into smaller units and try to fit them into the Project Plan. Laddering is possible if an activity can be broken down into two or more sub-activities and a succeeding activity is similarly broken down into the same number of sub-activities as its predecessor.

I will demonstrate below how this can lead to reduced Project Duration.

Consider that we have the following Work Breakdown Structure (WBS).

WBS

From this WBS, we get the following Network.

Initial Network

We can see that the Critical Path is 11 units in duration. So, the project is expected to take 11 units of time.

Our objective is to reduce the Project Duration to below 11 units of time. So, we apply Laddering.

To apply Laddering, we need to select 2 tasks, one of which is the predecessor of the other. Also, we should select the two tasks on the Critical Path. Next, we need to break these 2 tasks into equal number of sub-tasks.

Suppose, the determine that tasks A and B can each be broken into 2 tasks. A can be broken into A1 and A2. And B can be broken into B1 and B2.

A1 and A2 will need 1 unit of duration each. Thus, the overall duration for task A remains 2 units.

Similarly, B1 and B2 will need 2 units of duration each. Thus, the overall duration of task B remains 4 units.

Now, we further define that task B1 can be performed only after task A1 is completed. Also, task B2 can be performed only after tasks A2 and B1 have been completed.

So, now the network diagram looks like as shown below.

Laddered Network

Notice that we have managed to reduce the total project duration by 1 unit.

Notice also that by Laddering, we now have 2 Critical Paths. It is a general rule of thumb that if there are more than one Critical Paths in Project Plan, it increases the risk of the project schedule.

That brings to the questions as to what kinds of tasks can be taken up for Laddering.

One of the most suitable set of candidate tasks in IT Software Projects are Design and Development activities. Generally, Development follows Design. Now, it is generally possible that instead of completing the complete design and then starting development, we can break the Design Phase into 2 or more sub-phases. To the broken up Design Phases, we can associate equal number of Development Phases.

Another suitable set of candidates in IT Software Projects are Development and Testing activities.

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