PMGT1865 Chap.2 Building a Work Breakdown Structure
Building a Work Breakdown Structure
A work breakdown structure takes everything the project team has to execute and splits it, level by level, into deliverables inside deliverables. It is the tool for defining scope in operational terms: it organises activities top down from the overall goal, unpacking each higher level item into the lower level items inside it.
It is also the artefact everything else in the unit is built on, which is why its rule about completeness is absolute: the structure must capture everything the project plans to do and everything it plans to buy. Work missing here is missing from the schedule, the budget and the resource plan simultaneously, and it is usually found during execution.
Week 2 covers the two formats, the level vocabulary from phase down through control account, work package, activity and task, the five structural rules and the failure each one prevents, and the question of when to stop decomposing. Two things the structure deliberately ignores are worth noting early: chronology, which the schedule handles, and who does what, which the responsibility matrix handles.
What this chapter covers
- 01
Decomposition as a definition exercise, and why working downwards makes completeness structural
- 02
The two formats: an indented list and a tree, carrying identical information
- 03
Grouping a flat list into sub-categories, and the four ways a top level can legitimately be organised
- 04
Why chronology and resources belong to the schedule and the responsibility matrix rather than here
- 05
The level ladder: phase or deliverable, control account, work package, activity, task
- 06
Which level a budget attaches to, and which level becomes a network node
- 07
The five rules: completeness, no duplication, no single child categories, one parent only, sensible grouping
- 08
Choosing a planning level, and taking either the category or everything below it but never a mix
- 09
How far to decompose, and the three reasons to keep going past the usual stopping point
- 10
Four habits: include the project management work, unpack horizontally, start descriptions with a verb, vary the depth
Decomposing one parent activity two levels down
- +1Name the deliverable rather than the department. Exhibitor management is the parent because the project produces a set of confirmed, paid, briefed exhibitors, not because somebody holds that job title.
- +1Split into level two by outcome. 3.1 Exhibitor recruitment, 3.2 Contracting and payment, 3.3 Stand allocation, 3.4 Exhibitor briefing and on the day support. Four children, each of which is either done or not done.
- +1Unpack each into work packages. Recruitment gives build the target list, prepare the prospectus, approach and follow up. Contracting gives issue agreements and invoice and reconcile. Stand allocation gives draw the floor plan and allocate and confirm. Briefing gives write and send the pack and staff the desk on the day.
- +1Check the rules. Every package sits under exactly one parent, nothing is duplicated, no category holds a single child, and the four children together do deliver a briefed, paid, seated exhibitor set.
- +1State where you stopped. Level three, because each package can be given to one committee member and estimated as a whole. Only the floor plan would go deeper, and only if the venue has fixed services that constrain the layout.
Key terms
- Decomposition
- Taking a named deliverable and asking what smaller deliverables it is made of, then repeating that on each of those. Done in that direction the structure is complete by construction, because you stop at every step only when the children add up to the parent.
- Control account
- The level of the structure at which cost is accumulated and reported. It sits above work packages and below the top level grouping, and it is the level a cost baseline attaches to.
- Work package
- The smallest unit that can be assigned to a single owner and estimated as a whole. Most projects stop decomposing here and go deeper only in the branches that need it.
- Activity
- The item that becomes a node in the network diagram and carries a duration. Its description begins with a verb, because a noun is a topic and nobody can say when a topic is finished.
- Completeness rule
- The requirement that the children of any box, taken together, deliver that box completely. It is checked upwards: read the children of a box and ask whether doing all of them delivers the parent.
- One-within-one
- A category containing exactly one activity. It adds a level of numbering and no information, and its presence usually means either the category is really the activity or the decomposition is unfinished.
Building a Work Breakdown Structure FAQ
Should the top level be organised by phase or by deliverable?
Either, and two other options as well. It does not matter how the top level is structured provided the five rules hold, so phase, deliverable, technical domain, cost account and supplier are all legitimate. Choose the one the people doing the work already think in, because a structure that matches how a team talks gets maintained and one that does not gets abandoned.
The only common trap is grouping by time, which duplicates the schedule and cannot carry a budget.
How deep should the structure go?
Stop when an item can be allocated to one person, or once you reach packages that a package manager can own outright, or when further detail would not change any decision you are about to make. Keep going where team members need more direction, where a portion of work is ambiguous or complex, or where a portion is important enough that you want to watch it move.
Depth that varies between branches is a sign somebody thought about it; uniform depth everywhere usually means it was chosen before the work was understood.
Does the project management work itself belong in the structure?
Yes, and leaving it out is one of the more expensive omissions. Planning and closure both contain real project management effort, and during implementation there is an ongoing package covering status reports, team meetings and coordination. A structure that prices all the delivery work and none of the managing produces a budget that is wrong by a predictable and embarrassing amount.
Assessment move
This chapter is graded on whether you can build one rather than describe one, so build one. Take the small project you invented in the previous chapter and decompose it properly: pick a top level grouping and say why, unpack each branch until the packages have single owners, number it decimally, and then run the five rules over it as a checklist.
Search specifically for the two failures that survive a casual read: a category with exactly one child, and the same wording appearing under two different parents. Then do the money test, which is the fastest completeness check there is: read the whole structure and ask whether there is anything the project will spend money on that has no home in it.
Insurance, licences, freight, venue hire, training and the project management effort itself are the usual gaps, because they are bought or absorbed rather than done. Finally, read every lowest level item and confirm it starts with a verb. If it does not, you cannot estimate it, and every chapter after this one assumes you can.
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