What Is a Work Breakdown Structure in Construction?
A work breakdown structure (WBS) in construction is a hierarchical way of organizing a building project. The WBS is a single document that divides the project deliverables into manageable chunks known as work packages.
Project managers create a visual representation of the construction WBS; the image resembles a family tree or an organization chart. At the very top of the diagram, the finished building (or parent) appears. Each layer beneath the parent breaks the project down into children.
The bottom layer represents the smallest division of work, where supervisors cannot reasonably decompose the elements further. At this level, you can find work packages of specific components, such as the roof or the interior paint. Construction planners call these groups of specific components terminal elements.
A key principle of the WBS for a building project is the 100 percent rule. According to this rule, the work breakdown structure must show the entire project scope, including all deliverables: design, engineering, and project management services.
Work outside the scope does not appear in the WBS. As a corollary of the 100 percent rule, all construction work at the child level must equal the total work represented by the parent.
In addition to showing the graphical representation, a construction manager can display the WBS in text and tables. WBS software can translate this information into various formats and synchronize your changes throughout.
The WBS is a versatile project management tool that you can use in many fields. To learn the basics and history of work breakdown structures, see “Getting Started with Work Breakdown Structures.”
There are two dominant schools of thought on the best way to organize a work breakdown structure: by deliverable or by phase.
A Deliverable-Oriented Work Breakdown Structure
Many construction specialists favor a deliverable-oriented (or product-oriented) WBS, which revolves around tangible deliverables, not processes. The hierarchy for this kind of WBS captures what you will build rather than how you will build it.
In construction, the elements of a deliverable-oriented WBS are physical components of the building or interim deliverables that you need in order to produce pieces of the building. Interim deliverables can include plans and specifications.
The components of a deliverable-oriented WBS are nouns rather than verbs, because this particular structure focuses on the tangible products of a project rather than on processes.
Here is an example of a deliverable construction WBS for a house. Though this example doesn’t decompose the project into terminal elements, its hierarchy displays the finished house at the top of the image. Major parts of the project branch off underneath, and more detailed elements appear at the bottom.
Here are the advantages of a deliverable-oriented WBS:
- It simplifies the process of cost estimating.
- It allows you to see the total work scope.
- It clarifies the relationships among elements.
- You can use it during all project phases.
- It’s easier to modify as your project changes.
- It supports earned value management.
A Phase-Based Work Breakdown Structure
Alternatively, a phase-based WBS divides construction into steps or stages. This kind of WBS focuses on the processes you require to achieve the deliverables. Verbs rather than nouns appear in this type of WBS.
This kind of document is also known as a process-oriented, task-oriented, or activity-oriented work breakdown structure. A construction manager divides the project into its component activities. In the graphical representation of a phase-based WBS, these activities often proceed in chronological order.
Some project managers believe that a phase-based WBS is not a true work breakdown structure as defined by the Project Management Book of Knowledge. They hold this belief because the phase-based WBS focuses on processes rather than on deliverables. Proponents of a phase-based WBS disagree with this interpretation, noting that levels beneath the major stages in the document are often concrete deliverables rather than processes.
The phase-based WBS arose in part to ease the transition from a deliverable WBS to a project schedule. Those who favor the deliverable WBS say that you can solve this transition issue by planning your project properly and creating a full set of construction documents. Planners translate the deliverables into activities and milestones, then create a project schedule network diagram. This diagram, which consists of boxes and corresponding arrows indicating the flow of work, is the basis of the project schedule.
A phase-based WBS can be subject to error because capturing all the construction activities is more difficult than defining the deliverables. Due to this difficulty, child-level actions can sometimes total more or less than the full project scope.
Directly below is an example of a phase-based WBS for a tunnel-building project. The WBS here shows the five major phases of tunnel construction: site work, drawings approval, mobilization, construction, and closeout. The relevant component activities appear under each phase heading.
The Goal of a WBS in a Construction Project
The goal of a work breakdown structure in construction is to make the project more manageable.
The WBS breaks down the building work into pieces that define the project scope and all deliverables in detail. Decomposing the work into individual elements enables project planners to do a better job of estimating costs, assigning tasks, and checking progress against the schedule and budget.
The WBS also lays the groundwork for clear communication among all the stakeholders in the project.
Here are the main objectives of WBS in construction:
- Detailing tasks and deliverables for crews and subcontractors
- Laying out milestones and progress checkpoints
- Defining quality control and acceptance criteria
- Giving information on construction methods for each deliverable
Construction WBS Examples
Use these work breakdown structure examples for construction to capture the essence of a building project.
The examples below break down the end deliverable into successively smaller pieces of work. The image for each example displays, in descending order from top to bottom, those successively smaller pieces of work.
- A Typical Construction Project WBS with Phases: This sample makes clear how a phase-based construction project WBS typically moves from planning to construction, control, and closeout. Note that many of the work packages are processes and activities.
- A Typical Commercial Construction Project WBS: This construction work breakdown structure example for a standard commercial building shows major milestones and deliverables, from site preparation to final walkthrough. The hierarchy decomposes into objects, such as plumbing, and into processes, such as inspecting. By including objects (nouns) and processes (verbs), this example utilizes a combination of the deliverable-oriented and phase-based structures.
- An Engineering Project Plan WBS: This is an example of a work breakdown structure for the engineering of a factory expansion. It illustrates the important deliverables for engineers on a project, including conducting a feasibility study, engineering different aspects of manufacturing (from piping to controls), and responding to construction RFIs.
- A WBS for the Construction of a Wastewater Treatment Plant: This sample work breakdown structure lays out the deliverables for a plant that treats wastewater in order to remove contaminants. The WBS first breaks down into the major plant sections, then further into component structures.
- A Construction Work Breakdown Structure for a Retail Store: This WBS example shows four levels of detail for the build-out of a retail store. The primary overarching structure (e.g., a mall or other existing building) is already in place. But the project still requires the design of both the interior and the exterior, as well as the construction of necessary spaces, including a delivery zone and fitting rooms. The project manager must also install point-of-sale and inventory management systems.
- A Construction WBS for a Healthcare Facility: Building a hospital is a major undertaking. This example of a WBS for the construction of a regional medical center breaks down into the major wings of the complex, from trauma units to food service.
Free Construction WBS Template
Create a WBS for a construction project with this free downloadable template, which you can customize for any building type. The hierarchy shows the finished project first breaking into its major sections and then, underneath, decomposing into more detailed components.
This template works with either a phase or a deliverable approach.
Download Construction Project WBS Template - Excel
You can find more WBS templates (including those specifically for engineering) and a WBS dictionary in “Free Work Breakdown Structure Templates.”
How to Use a WBS in Construction
A work breakdown structure for construction usually has at least three levels. Put the final product on the first level, major deliverables on the second, and work packages on the third.
A so-called WBS dictionary usually accompanies the work breakdown structure diagram. The dictionary defines each element of the building work, including deliverables, milestones, resources, and construction methods. In construction, building information modeling (BIM) data often appears in WBS dictionaries, because the standardized system makes it easy for everyone on the project to speak the same language.
Uniformat, a standard for classifying BIM in North America, designates specific building systems, while Masterformat, a numbering standard, applies to materials. The Uniformat codes start with one of eight letters, each corresponding to the major building systems, and then add digits as the work becomes more specific. For example, the Uniformat code for substructure is A, and standard foundations are A1010. The Masterformat code for concrete formwork is 03-11-00.
Who Do You Need to Include in a Construction Project WBS?
The construction project work breakdown structure is a team effort. Major project participants, including architects, engineers, general contractors, financial managers, and owners, contribute to the WBS. The project manager typically owns the WBS and controls any changes.
Whom you exclude from your construction project WBS is as important as whom you include. You might find that managing the building of the work breakdown structure becomes untenable when too many people participate.
Site superintendents, subcontractors, and work crews do not usually have a hand in creating the WBS, though project managers should get feedback from them on the draft.
How Do You Create a Construction WBS?
To create a construction work breakdown structure, take the end goal of a project — a finished building — and sequentially break it down into smaller units until you reach the smallest element of work.
(You can also perform reverse engineering by starting with the beginning of a project — i.e., the smallest elements of work — and progressing toward the largest element, such as a completed building.)
These are the major steps to create a WBS for a building project:
- Gather all available information on the construction project. This information will vary, depending on the project’s level of refinement, and might include drawings, engineering studies, pre-design work, or proposals.
- Define the ultimate goal — i.e., what you are building. On the WBS diagram, this goal appears at the top in the form of a simple label, such as Smith Residence or 147 Spruce St. Office Tower. The dictionary, project list, and project plan describe other aspects in more detail.
- Decide whether a deliverable-oriented or phase-based WBS is best for your purposes. If you are still in the early stages of planning, a process-based approach makes the most sense because, at this point, you have not yet answered many design and construction method questions.
- List the major deliverables according to either their construction phase or their structural system. These deliverables include milestones and processes. Use a coding system to show which section of work applies to each item’s level of detail.
- Divide each of these deliverables into components until you reach individual chunks of work. These jobs represent the work packages and terminal elements of the WBS diagram. You must be able to define, manage, estimate, and measure these work packages. While each package must be discrete and identifiable, they must also integrate with the other elements. And you must be able to adapt the work packages to project changes. The WBS dictionary and project plan capture the details of these deliverables.
Translating a Construction WBS into a Construction Project Schedule
A building’s WBS is a stepping stone toward a project schedule. To arrive at the schedule, use time estimates for the work packages in the WBS and the critical path of the overall project. The critical path is the sequence of scheduled work that determines a project’s duration.
In order to determine a construction project schedule, begin by listing the following information concerning each terminal element:
- The length of time the work is likely to take in terms of hours, days, or weeks
- Any tasks that you must finish before starting the work package
- The resources you require — i.e., materials, labor, and equipment
- Any time limitations regarding the availability of resources
When you identify the preceding and succeeding activities for a work package, you are finding its dependencies, which are a key part of the critical path method. Limits on the availability of resources are another form of dependency. (For example, you cannot install a prefabricated building component before the manufacturer delivers it.)
Use the information you gather regarding dependencies to create a network diagram and Gantt chart. The network diagram lays out the sequence of work visually and makes clear which tasks must occur on time for the project to meet its deadline.
To create the project schedule, look at the duration of the longest path on the network diagram. Be sure to include in your calculation any of the path’s lead or lag time, such as time for paint to dry before floor work can begin. Then add reasonable buffers for typical construction delays, such as those due to bad weather or to unexpected site conditions. Based on all these factors, assign start dates and target dates for each work element.
A Checklist for a Construction WBS, Featuring Best Practices
After completing your construction work breakdown structure, confirm that there are no critical errors and the WBS adheres to best practices. Doing this will help prevent any unhappy surprises that might arise from omissions or miscalculations.
Check your WBS against this list of common mistakes to see if you are meeting best practices for a WBS in construction:
- Does the WBS cover 100 percent of the building project? Do all the children (work packages) add up to the parent (top-line deliverable)? Capture everything.
- Can a project participant grasp the whole scope of the building project from looking at the WBS? The value of the WBS lies in its ability to make the work immediately comprehensible. If it is confusing or incomplete, it does not serve its purpose.
- Are there any redundancies or overlaps? Does the same element appear twice? All major elements must appear and should appear only once.
- Does the WBS have at least two levels, but avoid going into unwieldy detail? Most construction pros recommend a maximum of three to five levels.
- Do the levels follow a hierarchy? Think of the WBS as a drill-down, rendering each level as a subset of the level above.
- Does each item carry a unique numerical code that relates to its place in the hierarchy and the standard building systems data? Project stakeholders use these numbers to communicate clearly and quickly about aspects of the work. An absence of coding can lead to miscommunication.
- Does the work breakdown structure divide into manageable work packages? If not, add a level.
- Does the WBS use nouns instead of verbs whenever possible? As a best practice, organize the WBS according to tangible deliverables rather than according to processes.
- Does each work package define its acceptance criteria? This criteria lets you know when you have completed a task.
- Can you define, manage, estimate, and measure work packages as you have articulated them in the WBS? If not, the work packages need more refinement.
- If you are working with a deliverable-oriented WBS, have you listed related processes, such as inspections, with their deliverables? You must consider these processes as part of the deliverables, not as stand-alone items.
- When using a phase-based construction WBS, do you make sure that the first level covers all the major stages? It can be easy to overlook steps, such as setting interim contract milestones, processing submittals, procuring, and closing out the project.
- Does the WBS serve as an adequate basis for the project scheduling and budgeting? If not, make the necessary changes. The WBS should also serve as the basis for creating a construction schedule network diagram and defining resource needs.
- Is pre-construction work separate? Design, drawings, financing, and other pre-construction work should appear in its own section, because these activities are not related to any single deliverable.
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