What Is a Work Breakdown Structure (WBS)?
A WBS is a hierarchical decomposition of the project scope into work packages that can be estimated, assigned and measured — the shared basis of both cost and schedule.
Definition
The structure starts with the whole project at the top and branches down: buildings → systems → elements → work packages. The golden rule is that the children sum exactly to the parent (the 100% rule) so that no scope is lost and none is counted twice.
What it is used for
It gives a single coding scheme that cost (cost codes), schedule (activities), responsibility (a RACI matrix) and risk all hang from — so reports can be rolled up at any level: package, system, building, project.
The WBS and the BOQ
In contracting, the BOQ sections can be treated as one level of the WBS and its items as the quantitative leaves. Linking the two lets you answer a question such as “what have the electrical works on the third floor cost to date?” in a single click.
Worked example
A tower project: 1 Tower → 1.3 Structure → 1.3.2 Typical floors → 1.3.2.7 Seventh-floor slab (a work package with its own duration, cost and owner).
FAQ
How big should a work package be?
A practical rule: whatever can be estimated, assigned to one owner and measured for progress within a single reporting cycle (the 8/80 rule: between 8 and 80 work hours on general projects, and reasonably larger in construction).
Is the WBS the same as the schedule?
No. The WBS answers “what will be delivered” and the schedule answers “when and in what sequence” — activities are derived from the work packages and then scheduled.
Put this to work with Work Breakdown Structure (WBS)
Break your project down with a solid WBS linking scope to cost and schedule
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