AEC definitions
A work breakdown structure is a hierarchy that breaks the project into smaller deliverables until each piece can be estimated, scheduled, and assigned. The top is the project. The bottom is work packages. It is organized by what will be delivered, not by the departments doing the work.
Definition
A good WBS is a scope map. Schedule activities hang under work packages. Cost codes map to the same packages so the estimate and the schedule talk about the same concrete. A WBS dictionary defines what is inside each package and what is not. Without the dictionary, the tree is a picture. The structure is not the same on every job. A contractor's WBS for self-performed work will differ from an owner's WBS for a program of buildings. They should be mapped, not forced into one shape.
In depth
'Level 2 structure' is a deliverable. 'Coordinate' is a verb and does not belong as a WBS element. Activities under the package can be verbs. The package itself is a thing you can hand over.
One hundred percent of the scope sits in the tree. If it is in the contract and not in the WBS, it will be forgotten in the estimate or the schedule.
Break down until a package can be estimated and given to a superintendent or a subcontractor. Past that, you have a procedure, not a WBS. Three to five levels is common. The right number is the one the team will maintain.
Number the packages and keep the numbers stable. Renumbering mid-job breaks the cost history.
Each work package should have a budget and at least one schedule activity. A cost with no activity, or an activity with no cost, is a controls gap. The schedule of values can roll packages up for the owner.
Change orders add or revise packages. They should not be dumped into a miscellaneous code forever.
The dictionary states inclusions, exclusions, and the spec sections. That is how two people agree the package contains the slab and not the excavation.
Disputes about 'complete' often start with a WBS that was only a graphic.
Examples
The WBS breaks the building into structure, enclosure, and interiors, then into packages such as level-two slab. The estimate and the schedule both use that package number.
A dictionary entry says the slab package includes rebar and excludes the vapor barrier, which sits in the enclosure package.
A change order adds a package instead of charging the new work to a miscellaneous code.
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