How to Use a WBS

Purpose of the WBS

To reduce the total project into small elements that are so clearly defined that they, individually, can be accurately defined, budgeted, scheduled and controlled.

The small elements are called activities or work packages.

The WBS ensures that all activities, even minor ones, are accounted for.

Characteristics of Activities

Stand-alone– clearly distinguished from other activities

Time aspect – has a start date, finish date and/or duration

Deliverable – it delivers an end-product

Human resources – responsible person/department assigned to it

Measurable – must be able to measure activity progress

Activity Definition: The element or task that must be performed in order to reach the project end-result. It requires time and resources.

Once the key activities have been identified in the WBS, they should be organised in a logical sequence to maximize concurrency. The duration of and people responsible for each activity should be disregarded at this stage, because it may result in errors in the project logic. An easy way to organise the activities in a logical sequence is to create a project logic diagram, whereby each key activity is written on a separate small card or self-adhesive note sheet. These cards can then be used to build a picture of the entire project, from start to finish. By making it visual (arranging cards on a table, or arranging the notelets on a wall), the project team can question and debate the validity of the logic as it grows. The notelets/cards can be connected with arrows to show the logical flow of the project. Provision should be made for both series activities and concurrent activities, focusing on the dependencies between activities.

Assign Responsibility:

The project manager needs to ensure that the work is done on time and according to quality specifications. Responsibility for the execution of each key activity should be assigned in a fair and even way to the various team members. Young suggests that each member of the team should be persuaded to accept the role of key activity owner (KAO) for one or more key activities. The KAO must then accept the obligation for his key activity to confirm:

• The work to be done is identified at the detailed task level.
• The dependencies are clearly identified.
• The time estimates are accurate and subject to constant scrutiny.
• The work gets done on time in accordance with the quality specifications.
• Regular monitoring is maintained.
• Regular accurate status reports are issued.
• Problems and issues are alerted promptly to the project manager.

Determine the Duration Of Activities

The next step is to estimate and forecast the duration of each key activity. An estimate is a decision about how much time is required to complete an activity at an acceptable standard of performance. The “size” of the activity and the amount of “effort” required in completing the work need to be determined. Duration is the conversion of effort taking into account the number of people involved, their capacities and an allowance for non-productive time. Duration is never the same as the schedule, since it is measured in real working days that take non-available days, weekends, public and staff holidays into account.

In forecasting duration, it is also essential to make provision for contingencies. Murphy’s Law requires that a buffer be built into the estimated duration of each activity. This can be done by developing four time estimates for each activity: the most likely time (estimated time required if normal problems and interruptions occur), the optimistic time (estimated time required if virtually no problems occur), the pessimistic time (estimated time required if problems and interruptions of an unusual nature occur) and the expected time (some form of weighted average of the most likely, optimistic and pessimistic time estimates).

Duration of activities could best be determined in consultation with project specialists and appropriate role-players.

Also refer to methods of determining duration later in this module.

Rules in Developing a WBS

The rules for developing a WBS are as follows:

• Heading with accompanying activities.
• Activities must be verb and noun statements.
• Written in the present tense.
• Each activity must have a unique number.
• The sequence of activities is not important.
• No activity must be overlooked.
• During the WBS process the following questions are asked:
  • What is needed?
  • What is next?
  • Is the WBS functionally oriented?

The table below indicates the steps to develop a WBS:

A WBS ties the entire project together; it portrays scope graphically, allows resources to be assigned, permits estimates of time and cost to be developed, and thus provides the basis for the schedule and the budget.

An estimate is a guess, and an exact estimate is a contradiction in terms.

Be careful that ballpark estimates don’t become targets.

Consensual estimating is a good way to deal with activities for which no history exists.

No learning takes place without feedback; estimate; then track the actual time to improve estimating ability.

Click here to view and download a handout with an example of a work breakdown structure.

Click here to view a video that explains the work breakdown structure.