Get Organized with a Work Breakdown Structure


Table of Contents

A project can be big or small; anything from changing a light bulb to building a fighter jet. As the complexity of a project increases and the duration extends to weeks and months, it’s helpful to decompose the overall program into smaller steps. A work breakdown structure is a project management tool for exactly that purpose.

Thinking of a project as one single entity is a recipe for disaster; you have to break things up into smaller chunks. But, human brains have limited working memory and can only keep track of a finite number of things at once. 

You need to be smart about how you split up the pieces of your project so you stay efficient. Work breakdown structures (commonly abbreviated as WBS) apply a systematic approach to this. They make complex things more manageable.

In this article, we’ll clarify what a WBS is, why it’s important, and how you can use it on your shipping container building project to have the best outcome possible.

Work Breakdown Structure Overview

A WBS is a project management fundamental. While not particularly exciting, they often form the backbone upon which the schedule, budget, and other documents are built. 

What is a Work Breakdown Structure

The basic formula for a WBS is to take the complete scope of the project, break it up into pieces, then organize them into a logical hierarchy. All the items at a lower level are needed to complete the item at the next highest level. Using multiple smaller pieces allows each one to be defined, managed, and monitored.

It’s very likely that you’ve been making WBS’s mentally all along and just didn’t have a name for it. Clearly then, what we’re sharing here isn’t earth-shattering knowledge. Rather, it’s a way to systematically do what you were likely already doing in order to make your existing process better.

A WBS is typically based on outcomes or deliverables. In other words, each smaller piece, as well as the overall project, actually creates or does something. For instance, simply thinking about something, though important, would not be a good WBS task. Rather, the decision or document that’s a result of that thinking is what you should record in a WBS.

The hierarchical nature of a WBS means it is really just a certain type of taxonomy or classification. Think about the way we put every biological species into progressively larger groups like genus, family, order, etc. Or the way military units are divided the same way into platoons, companies, and battalions.

Almost every type of work uses classifications, and project management is no different. A WBS is that tool that helps you breakdown and classify smaller pieces of a project. Before we go much further, an example WBS will probably be helpful.

WBS of a bicycle

As you can see, the bicycle is divided into assemblies and parts until everything is accounted for and just from looking at the words, you have a good idea of how everything goes together.

Benefits of a Work Breakdown Structure

In many ways, a WBS is an intermediate piece of a larger process. By itself, a WBS is interesting but not necessarily all that useful. Instead, view it as a stepping stone.

Think about making a project schedule. How helpful would it be to have only a single line item inside it without any breakout for specific phases of work? Even something as simple as food recipe has multiple steps after all.

How about a cost estimate or budget? Wouldn’t it be much easier to break up a project into smaller pieces, estimate the costs of those, and then add them together instead of trying to come up with the cost of the entire project in one effort?

Or if you were getting ready to hire a subcontractor and wanted to know what exactly they would be doing so you didn’t accidentally hire someone else to do part of the same work by mistake?

Having a WBS can help tremendously with these types of problems and issues and provide benefits like:

  • Accountability: It’s incredibly important to clearly delegate who has responsibility for what, but that can only be done if everyone is clear on the ‘what’. Even if you’re working by yourself, you can hold yourself accountable if you have to visually look at what you’re trying to do in writing.
  • Risk Management: Ambiguity is the enemy of successful projects. Anytime there is a question of who is doing what, what has to get done first, or where on the project a particular material goes, there can be construction errors, time delays, or cost overruns. Having a WBS helps you managed and reduce project risk.
  • Clarity: The simple act of making the WBS will force you to better understand the project and all its intricacies, which will only benefit you. If you can see it (written down), you can measure it. And as they say, what gets measured gets done. This applies across time, money, and even quality.
  • Efficiency: Having a WBS in hand allows you to more holistically view your project. With that perspective, you can more easily see opportunities like buying similar materials in bulk, accomplishing similar types of work at the same time, etc. 

Importance of a Work Breakdown Structure

Most lessons are born out of mistakes. Ideally, you can learn from the mistakes of others instead of making your own. The project planning process exists specifically to minimize and ideally avoid mistakes, and creating a WBS is an integral part of that process.

The quote may be a little extreme, but the sentiment is true: The act of making a plan is arguably more important than the plan itself

There are plenty of maxims related to project planning. One popular version of the Seven P’s of Planning states: Proper Prior Planning Prevents Painfully Poor Performance (there are some other, less polite versions as well). Or a similar, shorter saying: If you fail to plan, you plan to fail.

No matter how you say it, the overall idea is the same. Making a concerted effort on the front-end of your project to think through resources, activities, and relationships will go far toward ensuring you finish the project as well as you start it. A WBS isn’t the only part of planning, or even the most important, but it is certainly a significant piece.

Construction Work Breakdown Structure Frameworks

Up to this point, we’ve considered WBS’s as a part of all types of project management. But now, it’s time to dig a little deeper into how these tools apply to construction.

Construction management is a specific part of project management that is really its own area of study. There are organizing bodies, personal certifications, and specific procedures and terminology that just pertain to managing construction projects.

Given the sheer number of construction projects taking place each year and the billions of dollars spent, it’s no wonder that such specialization exists. Even the ISO has gotten involved, creating ISO 12006-2:2015 specifically to outline a framework of classification for construction projects. Yes, that’s the same ISO that sets the standards for the dimensions and requirements of containers.

Still, with all this attention, there are numerous ways to break construction projects up into smaller pieces. You could start by categorizing based on the created product, like walls, roof, or floor. Or you could categorize based on material, like wood, metal, or cement.

Color, size, weight…they are all possible categorizations too. None of them are ‘wrong’, but some are certainly more useful than others.

While you can certainly make up your own way of classifying your project tasks, there are thousands of professionals who do this for a living and have already thought about it. So rather than have you recreate the wheel, it’s better to study what’s already been done.

Construction Specifications as a WBS Framework

Construction specifications are large, written documents that go along with drawings in a large construction project. The drawings tell you where things go and how many to use, while the specifications tell you what kinds of things to use and how to install them. Both are produced by architects and designers as a joint set of documents.

This is an example of part of a specification pertaining to wood

For a smaller project like a container home, specifications may be overkill. However, there is still value in specifications for us. Why? Because of the way construction specifications are organized.

Most specifications are created around a framework that also works perfectly for a WBS. This isn’t just a coincidence. Documents like the WBS, the cost estimate, and the construction specifications are all interrelated, and it makes sense to have them all share a common structure for efficiency. You’ll also find that most specifications use a numbering system that lets you quickly tell where it sits in the hierarchy.

One thing to note is that there are a lot of things categories in construction specifications that aren’t going to apply to the typical container home. These specifications were created to have the flexibility to be used on all kinds of projects, including massive industrial facilities. Most specifications are subtractive, meaning you can just remove what doesn’t apply to you.

In summary, the construction specification standards below don’t exist solely for the creation of Work Breakdown Structures, but they can work well for that purpose. So, let’s take a look at a few construction specification systems that can be used to create WBS’s.


Uniclass is part of the UK-based National Building Specification (NBS) organization. It uses a hierarchical set of 12 tables:

  1. Activities
  2. Complexes
  3. Elements/Functions
  4. Entities
  5. Products
  6. Spaces/Locations
  7. Systems
  8. Roles
  9. CAD
  10. Project Management
  11. Tools and Equipment
  12. Form of Information

Clearly, some of these are more relevant for our purposes than others. Specifically, you’ll be most interested in the first seven tables. Here’s how they relate to another according to NBS:

Spaces/Locations exist in Entities which form part of a wider Complex and Activities may take place in any of these. Entities are composed of Elements/Functions, Systems and then Products.

To give an example, here’s how the Uniclass hierarchy might be used to classify roof framing:

  • Systems
    • 30 Roof, floor and paving systems
      • 30_10 Pitched, arched and domed roof structure systems
        • 30_10_30 Framed roof structure systems
          • 30_10_30_25 Heavy steel roof framing systems


UniFormat arranges data about the physical parts of a construction project by function, meaning what role an element plays in the overall facility or how it is used.

Originally created for the US government (and later codified as the ASTM E1557 standard), UniFormat is now used by public and private entities and managed by the Construction Specifications Institute (CSI). It’s often used at the early stage of projects as it is so intuitive and easy to use, especially when the project is still being defined. It is closely related to, though subtly different from, UNIFORMAT and UNIFORMAT II which are more focused on government projects.

Uniformat has fewer first level groupings than some of the other construction specification standards, so we’ll share both first and second level groupings below to give you an idea of how things are arranged (though we’re leaving off the Level 3 -5 items):

  • Introduction
    • 10 – Project Description
    • 20 – Owner Development
    • 30 – Procurement Requirements
    • 40 – Contracting Requirements
  • A – Substructure
    • A10 – Foundations
    • A20 – Subgrade Enclosures
    • A40 – Slabs-on-Grade
    • A60 – Water and Gas Mitigation
    • A90 – Substructure Related Activities
  • B – Shell
    • B10 – Superstructure
    • B20 – Exterior Vertical Enclosures
    • B30 – Exterior Horizontal Enclosures
  • C – Interiors
    • C10 – Interior Construction
    • C20 – Interior Finishes
  • D – Services
    • D10 – Conveying
    • D20 – Plumbing
    • D30 -Heating, Ventilation, and Air Conditions (HVAC)
    • D40 – Fire Protection
    • D50 – Electrical
    • D60 – Communications
    • D70 – Electronic Safety and Security
    • D80 – Integrated Automation
  • E – Equipment & Furnishings
    • E10 – Equipment
    • E20 – Furnishings
  • F – Special Construction and Demolition
    • F10 – Special Construction
    • F20 – Facility Remediation
    • F30 -Demolition
  • G – Sitework
    • G10 – Sitework
    • G20 – Site Improvements
    • G30 – Liquid and Gas Site Utilities
    • G40 – Electrical Site Improvements
    • G50 – Site Communications
    • G90 – Miscellaneous Site Construction
  • Z – General
    • Z10 – General Requirements
    • Z70 – Taxes, Permits, Insurance, and Bonds
    • Z90 -Fees and Contingencies

To give an example, here’s how the UniFormat hierarchy might be used to classify roof framing:

  • B – Shell
    • B10 – Superstructure
      • B1020 – Roof Construction
        • B1020.10 – Roof Structural Frame


MasterFormat is the most popular construction specification system in North America. It too is a product of CSI. Unlike UniFormat, it approaches classification from the perspective of materials an 

Prior to 2004, MasterFormat had 16 Divisions but was more recently reorganized into 50 Divisions. The Divisions are broken into a few groups, and quite a few of the 50 total divisions have been skipped below because they are simply placeholders for future expansion:

    • Division 00 — Procurement and Contracting Requirements
    • General Requirements Subgroup
      • Division 01 — General Requirements
    • Facility Construction Subgroup
      • Division 02 — Existing Conditions
      • Division 03 — Concrete
      • Division 04 — Masonry
      • Division 05 — Metals
      • Division 06 — Wood, Plastics, and Composites
      • Division 07 — Thermal and Moisture Protection
      • Division 08 — Openings
      • Division 09 — Finishes
      • Division 10 — Specialties
      • Division 11 — Equipment
      • Division 12 — Furnishings
      • Division 13 — Special Construction
      • Division 14 — Conveying Equipment
    • Facility Services Subgroup:
      • Division 21 — Fire Suppression
      • Division 22 — Plumbing
      • Division 23 — Heating, Ventilating, and Air Conditioning (HVAC)
      • Division 25 — Integrated Automation
      • Division 26 — Electrical
      • Division 27 — Communications
      • Division 28 — Electronic Safety and Security
    • Site and Infrastructure Subgroup:
      • Division 31 — Earthwork
      • Division 32 — Exterior Improvements
      • Division 33 — Utilities
      • Division 34 — Transportation
      • Division 35 — Waterway and Marine Construction
    • Process Equipment Subgroup:
      • Division 40 — Process Interconnections
      • Division 41 — Material Processing and Handling Equipment
      • Division 42 — Process Heating, Cooling, and Drying Equipment
      • Division 43 — Process Gas and Liquid Handling, Purification and Storage Equipment
      • Division 44 — Pollution and Waste Control Equipment
      • Division 45 — Industry-Specific Manufacturing Equipment
      • Division 46 — Water and Wastewater Equipment
      • Division 48 — Electrical Power Generation

To give an example, here’s how the MasterFormat hierarchy might be used to classify roof framing:

  • 05 00 00 – Metals
    • 05 21 00 – Steel Joist Framing
      • 05 21 23 – Steel Joist Girder Framing


OmniClass is a system of 15 tables for organizing all construction information. It is supported by CSI as well. As you can see below, Omniclass incorporates both UniFormat and MasterFormat standards, among other things. 

  • Table 11: Construction Entities by Function
  • Table 12: Construction Entities by Form
  • Table 13: Spaces by Function
  • Table 14: Spaces by Form
  • Table 21: Elements (Copy of UniFormat)
  • Table 22: Work Results (Copy of MasterFormat)
  • Table 23: Products
  • Table 31: Phases
  • Table 32: Services
  • Table 33: Disciplines
  • Table 34: Organizational Roles
  • Table 35: Tools
  • Table 36: Information
  • Table 41: Materials
  • Table 49: Properties

Given the duplication of OmniClass with both Uniformat and MasterFormat, it’s not worth discussing in further detail.

How to Get Started with a WBS for your Container Home

So far, we’ve given you a ton of information on how building professionals use construction specification standards for a variety of purposes, including the creation of work breakdown structures. You may be thinking, “This all seems a little complex…how does this apply to me?”

First, let’s start with two big takeaways:

  1. If you’re paying a builder, and they are professionals, they should be using some type of WBS as part of their overall project management system. But, that’s not really a detail you, as a consumer, need to worry about. Instead, you’ll want to see a cost estimate/budget and a schedule, both of which are informed by their WBS.
  2. If you’re building a DIY container project, remember that the best system is the one you’ll actually use. So read through our recommendations then adapt and tailor as you see fit for your specific circumstances.

When it comes to building a WBS, there are a few guidelines we want to share:

  • MECE: This is an acronym for Mutually Exclusive, Collectively Exhaustive
    • Mutually Exclusive: The WBS cannot have any overlap in scope between different elements, meaning the same items can’t be covered in multiple places.
    • Collectively Exhaustive: Also known as the 100% Rule — The WBS must include all of the work of the project, and each ‘child’ level must include all of the work necessary to complete the ‘parent’ element one level up.
  • Nouns, not Verbs: The WBS should be made up of end products, decisions, or deliverables. In short, you want to be classifying outcomes, not the actions that cause them.
  • 8/80 Rule: The WBS can utilize this rough rule of thumb which states that any lowest level element should take somewhere between 8 and 80 hours to complete. Shorter than that and it should be combined with other elements and possible moved up a level to keep the WBS from getting large and unruly. Longer than that and the element should be further split into sub-elements to keep the WBS from being too high level.

Our Recommended WBS for Container Homes

We recommend that you start with the UniFormat standard, then delete and modify sections as necessary. It’s the most intuitive system for people new to construction and thinking at the early stages of a project.

The US Navy has an online version of UniFormat with helpful descriptions and expanding topics that is a great place to get a better understanding of all the elements. When you’re ready to actually create a WBS, you can also download a Microsoft Excel version of UniFormat from the OmniClass Table 21 of Elements (They also have Table 22, the MasterFormat, as well). This makes it easy to delete everything you don’t need.

Taking it One Step Further

If you want to have more detail in your WBS, or even create a set of specifications, you can place relevant, lower-level sections of the MasterFormat system into the Uniformat system. Table 21 of OmniClass makes this super simple by listing out the relevant MasterFormat references that pertain to each UniFormat element.

For instance, let’s say you’re working on the section of your WBS for the interior doors, specifically sliding doors. In UniFormat, you’d have them here:

  • C Interiors
    • C10 Interior Construction
      • C1030 Interior Doors
        • C1030.25 Interior Sliding Doors

In OmniClass Table 21, you’d have them in the same place, just with slightly different numbering (‘C’ is replaced by ’03’):

  • 21-03 Interiors
    • 21-03 10 Interior Construction
      • 21-03 10 30 Interior Doors  
        • 21-03 10 30 25 Interior Sliding Doors

Table 21 OmniClass - Interior Sliding Doors

You’ll notice that the last column is called Table 22 Reference, which shows us the specific MasterFormat work result that is related to interior sliding doors! We see that generic Interior Doors have a Table 22 Reference of 22-08 10 00, while Sliding Doors are at 22-08 11 73. Let’s stay with the example and focus on sliding doors.

Table 22 OmniClass - Interior Sliding Doors

You can see above how sliding doors are classified in Table 22 as Sliding Metal Firedoors. We also scrolled down a bit to find Sliding Wood Doors at number 22-08 14 73 too, just for grins. It’s likely that you’ll find similar products like this closeby in the hierarchy. Also, remember that you can download a Microsoft Excel version of Omniclass Table 22 from the same place you downloaded Table 21, which we mentioned above.

What good does linking Table 21 (UniFormat) and Table 22 (MasterFormat) accomplish? Quite a bit actually.

Because MasterFormat is the industry standard (at least in North America) for specifying materials, many manufacturers and dealers are setup to handle these numbers as well. You can use a site like Arcat to see manufacturers of sliding metal doors, just by going off of the MasterFormat number. You can also get CAD drawings, specifications, and other information for particular products.

Or, if you want to see how the US Government specifies its Sliding Metal Doors, you can look up its free version of the specs for this MasterFormat number by viewing the Unified Facility Guide Specifications from the Whole Building Design Guide. This gives you an idea of the kinds of things professionals value in these products (methods of installation, product certifications, etc.) and that you might want to use as inspiration. Otherwise, you’d need to purchase specs from CSI (although if you hire an architect, they probably already have this).

None of what we’ve covered in this last sub-section is crucial to a small project like a shipping container building, but it just shows you how professionals in the building sciences do their job. And it may help you become better organized, find interesting products, etc.


If you had not ever heard of Work Breakdown Structures before reading this article, you definitely learned a lot! We hope we’ve made it clear that a WBS is a simple yet powerful tool.

As we mentioned, you’ve probably been making mental WBS’s all along. Our purpose here is to help you professionalize that process and learn how to get it in writing. It’s a little work on the front end that will help you throughout the duration of your project as you work to control quality, costs, and timeline.

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