Multiple Work Breakdown Structure (WBS) is a powerful method to document, analyse and report project activities via different lenses. This approach provides an opportunity to understand project delivery from many perspectives and increases chances for success.

Unfortunately, many project practitioners never apply more than one WBS for the same project, don’t understand the concept of Multiple WBS, and even believe that a project may only have one WBS. At the same time, project stakeholders often have different views on the optimal WBS. It results in project conflicts, program restructures, schedule redevelopments and hidden schedules.

Project work could be reviewed as a list of activities or in an aggregated hierarchical way known as Work Breakdown Structure. For effective project analysis and control, it is very useful to understand project work from more than one perspective and apply Multiple WBS.

In simple words: WBS is a hierarchical decomposition of the project deliverables into smaller, more manageable components. WBS provides an aggregated view of project work. There are many ways how work could be aggregated.

The WBS is a generic term that doesn’t explain the way of aggregation.

Three Work Breakdown Structures are applicable to most of the projects: based on project deliverables, project processes and responsibilities.

• Scope Breakdown Structure
  Structure helps define project boundaries and breaks down the scope of a project into smaller, more manageable pieces and verifies that all scope elements are in a project delivery plan, and ‘out of scope’ elements are excluded.

• Process Breakdown Structure
  Focuses on project processes required to complete project activities. The structure includes primary and supportive processes.

•  Responsibility Breakdown Structure (Organisation Breakdown Structure)
  Work grouped by responsibilities and help identify and organise resources required for successful project delivery.

Depending on the nature of the project, some other Work Breakdown Structures could also be helpful to apply:

• Contract Breakdown Structure
  The highest level represents the overall contract, and each subsequent level includes work delivered by subcontractors.

• Release Breakdown Structure
  Each level of the RBS represents a different level of detail in the project release components, with the highest level representing the overall release and each subsequent level representing smaller, more detailed components of the release. RBS is a popular structure for technology projects or business projects with technology components.

• Location Breakdown Structure
  Project work grouped by physical locations of project deliverables.

A base for each WBS is the same: a complete list of activities. It means that:

• Project activities are the same in all structures
• The logic between project activities is the same in all structures
• Critical path is the same in all structures

Usually, it is easy to start with “Top-Down” approach and develop a Scope Breakdown Structure first, starting from the decomposition of the project scope into smaller and more manageable work components. The decomposition can stop when the built structure helps find answers to the project’s key questions (What and How) with a sufficient degree of accuracy. This structure is a Primary WBS.

After the primary WBS is developed, each element in the structure could be extended with project activities and logic between them.

For smaller projects, it could be easier to start with the ‘Bottom-Up’ approach and develop a list of activities. Only then group these activities into a structure.

After an alternative WBS is developed, each activity is mapped to a relevant WBS element in the new structure.

There is a chance that the developed project delivery plan has some activities missing or that further decomposition is required. Multiple WBS can help in identifying these gaps:

• If a WBS element in the new structure doesn’t contain any activities, it could be a sign that project activities are missing in the primary WBS
• If there is no WBS element in the new structure where activities could be moved, it could be a gap in the new WBS.

If the primary and the new WBS vary only at the top levels, the lower-level WBS elements are mapped instead. Activities already belong to the lowest level WBS elements, and there are the same in both structures.

Microsoft Project doesn’t have dedicated WBS features, Primavera supports one WBS and Spider Project supports Multiple WBS.

Microsoft Project and Primavera P6

While Microsoft Project and Primavera don’t support Multiple WBS, there is a workaround to get visibility of project work from different perspectives. Both systems provide an opportunity to group activities. Combined with custom activity codes, it is possible to get multiple hierarchical structures and switch between them.

Grouping in Microsoft Project:

A hierarchical structure in Microsoft Project could be organised via custom fields.

Text custom fields support only one level, so multiple levels are organised via different custom fields. This is time-consuming and leads to data quality issues. Instead, it is recommended use Outline codes as they support multiple levels.

Outline Code in Microsoft Project:

Hierarchical structure in Microsoft Project:

 Primavera also supports hierarchical structures in activity codes. 

For portfolio scheduling, hierarchical structures should be developed in Enterprise codes and applied across all projects in the portfolio.

Microsoft Project and Primavera P6 automatically recalculate duration, cost and dates but don’t store the calculation results. When the view is changed, the result of the calculation is lost.

In theory, it is possible to export schedules for quality, performance or risk analysis in an external tool. Still, practically the imported schedule will have only one structure. I am not aware of any risk and quality analysis tool that supports Multiple WBS.

Spider Project

Spider Project allows having an unlimited number of Work Breakdown Structures and offers features that help users develop new  WBS in a simple and fast way.

The system also allows users to exclude activities from a structure.

Excluded activities are hidden, not deleted. If required, excluded activities could be added back. It unlocks some interesting and powerful opportunities for the users.

For example, Partial WBS could be used to control a level of access to different stakeholders or combined with layouts used for data collection and reporting.

‘Enclose into a new phase’ is a new feature added in January 2023 release (23.06.13).

WBS in Spider Project:    

Activities in both structures are the same but grouped based on different WBS. Activities 8 & 9 are hidden in WBS2. 

 WBS 1

WBS 2

Work Breakdown Structure is not the only type of hieratical structure in a project. Other project portfolio parameters could also be organised hieratically for better analysis and control.

• Cost Breakdown Structure
  The main structure for project cost control. The CBS typically includes different types of costs: labour costs, material costs, equipment costs, overhead costs, and contingency costs. CBS in scheduling and financial systems has to be aligned.

• Portfolio Contract Breakdown Structure
  A vendor could be involved in multiple projects. Portfolio Contract Breakdown Structures are used to get reports on the contract performance and contract cash flows.

• Material Breakdown Structure
  This structure helps to plan and control materials and components that are required to deliver the project. Materials are usually grouped by materials cost centres.

• Product Breakdown Structure
  This structure helps document, analyse and communicate the outcomes of a project, and the components leading to these outcomes.

• Risk Breakdown Structure
  Project work is organised by risks category. Structure helps to predict risks, assess their likelihood and impact, and add mitigation actions to the project delivery plan.

• Enterprise Breakdown Structure
  Project activities may have relationships with other projects in an organisation. This structure helps to understand, control and analysis impacts of these relationships.

• Value Breakdown Structure
  A concept introduced by Stephen Devaux as part of the total project control (TPC) approach. VBS separates project’s work packages into mandatory and optional categories and estimates the value-added for each optional activity and/or component of the project.

• Work Breakdown Structure is a hierarchical decomposition of the project deliverables
• WBS is a generic term. There are many ways how project activities could be grouped.
• The key benefit of Multiple WBS is that each WBS element could be used for analysis and communication
• Grouping views and Multiple WBS are not the same
• Multiple WBS is a powerful method that allows documenting, analysing and reporting projects via applying it via different lenses. This approach provides an opportunity to understand project delivery from many perspectives and increases chances for success.

Multiple Work Breakdown Structure (WBS) is a powerful method to document, analyse and report project activities via different lenses. This approach provides an opportunity to understand project delivery from many perspectives and increases chances for success.

Unfortunately, many project practitioners never apply more than one WBS for the same project, don’t understand the concept of Multiple WBS, and even believe that a project may only have one WBS. At the same time, project stakeholders often have different views on the optimal WBS. It results in project conflicts, program restructures, schedule redevelopments and hidden schedules.

Project work could be reviewed as a list of activities or in an aggregated hierarchical way known as Work Breakdown Structure. For effective project analysis and control, it is very useful to understand project work from more than one perspective and apply Multiple WBS.

In simple words: WBS is a hierarchical decomposition of the project deliverables into smaller, more manageable components. WBS provides an aggregated view of project work. There are many ways how work could be aggregated.

The WBS is a generic term that doesn’t explain the way of aggregation.

Three Work Breakdown Structures are applicable to most of the projects: based on project deliverables, project processes and responsibilities.

• Scope Breakdown Structure
  Structure helps define project boundaries and breaks down the scope of a project into smaller, more manageable pieces and verifies that all scope elements are in a project delivery plan, and ‘out of scope’ elements are excluded.

• Process Breakdown Structure
  Focuses on project processes required to complete project activities. The structure includes primary and supportive processes.

•  Responsibility Breakdown Structure (Organisation Breakdown Structure)
  Work grouped by responsibilities and help identify and organise resources required for successful project delivery.

Depending on the nature of the project, some other Work Breakdown Structures could also be helpful to apply:

• Contract Breakdown Structure
  The highest level represents the overall contract, and each subsequent level includes work delivered by subcontractors.

• Release Breakdown Structure
  Each level of the RBS represents a different level of detail in the project release components, with the highest level representing the overall release and each subsequent level representing smaller, more detailed components of the release. RBS is a popular structure for technology projects or business projects with technology components.

• Location Breakdown Structure
  Project work grouped by physical locations of project deliverables.

A base for each WBS is the same: a complete list of activities. It means that:

• Project activities are the same in all structures
• The logic between project activities is the same in all structures
• Critical path is the same in all structures

Usually, it is easy to start with “Top-Down” approach and develop a Scope Breakdown Structure first, starting from the decomposition of the project scope into smaller and more manageable work components. The decomposition can stop when the built structure helps find answers to the project’s key questions (What and How) with a sufficient degree of accuracy. This structure is a Primary WBS.

After the primary WBS is developed, each element in the structure could be extended with project activities and logic between them.

For smaller projects, it could be easier to start with the ‘Bottom-Up’ approach and develop a list of activities. Only then group these activities into a structure.

After an alternative WBS is developed, each activity is mapped to a relevant WBS element in the new structure.

There is a chance that the developed project delivery plan has some activities missing or that further decomposition is required. Multiple WBS can help in identifying these gaps:

• If a WBS element in the new structure doesn’t contain any activities, it could be a sign that project activities are missing in the primary WBS
• If there is no WBS element in the new structure where activities could be moved, it could be a gap in the new WBS.

If the primary and the new WBS vary only at the top levels, the lower-level WBS elements are mapped instead. Activities already belong to the lowest level WBS elements, and there are the same in both structures.

Microsoft Project doesn’t have dedicated WBS features, Primavera supports one WBS and Spider Project supports Multiple WBS.

Microsoft Project and Primavera P6

While Microsoft Project and Primavera don’t support Multiple WBS, there is a workaround to get visibility of project work from different perspectives. Both systems provide an opportunity to group activities. Combined with custom activity codes, it is possible to get multiple hierarchical structures and switch between them.

Grouping example (in Microsoft Project):

A hierarchical structure in Microsoft Project could be organised via custom fields.

Text custom fields support only one level, so multiple levels are organised via different custom fields. This is time-consuming and leads to data quality issues. Instead, it is recommended use Outline codes as they support multiple levels.

Primavera supports hierarchical structures in activity codes:

For portfolio scheduling, hierarchical structures should be developed in Enterprise codes and applied across all projects in the portfolio.

Microsoft Project and Primavera P6 automatically recalculate duration, cost and dates but don’t store the calculation results. When the view is changed, the result of the calculation is lost.

In theory, it is possible to export schedules for quality, performance or risk analysis in an external tool. Still, practically the imported schedule will have only one structure. I am not aware of any risk and quality analysis tool that supports Multiple WBS.

Spider Project

Spider Project allows having an unlimited number of Work Breakdown Structures and offers features that help users develop multiple WBS in a simple and fast way.

The system also allows users to exclude activities from a structure.

Excluded activities are hidden, not deleted. If required, excluded activities could be added back. It unlocks some interesting and powerful opportunities for the users.

‘Enclose into a new phase’ is a new feature added in January 2023 release (23.06.13).

Partial WBS could be used to control a level of access to different stakeholders or combined with layouts used for data collection and reporting.

WBS in Spider Project:    

 WBS 1

WBS 2

WBS is not the only type of hieratical structure in a project. Other project parameters could also be organised hieratically for better analysis and control.

• Cost Breakdown Structure
  The main structure for project cost control. The CBS typically includes different types of costs: labour costs, material costs, equipment costs, overhead costs, and contingency costs. CBS in scheduling and financial system has to be aligned.

• Portfolio Contract Breakdown Structure
  A vendor could be involved in multiple projects. Contract Breakdown Structures are used to get reports on the contract performance and contract cash flows.

• Material Breakdown Structure
  This structure helps to plan and control materials and components that are required to deliver the project. Materials are usually grouped by materials cost centres.

• Product Breakdown Structure
  This structure helps document, analyse and communicate the outcomes of a project, and the components leading to these outcomes.

• Risk Breakdown Structure
  Project work is organised by risks category. Structure helps to predict risks, assess their likelihood and impact, and add mitigation actions to the project delivery plan.

• Enterprise Breakdown Structure
  Project activities may have relationships with other projects in an organisation. This structure helps to understand, control and analysis impacts of these relationships.

• Value Breakdown Structure
  A concept introduced by Stephen Devaux as part of the total project control (TPC) approach. VBS separates project’s work packages into mandatory and optional categories and estimates the value-added for each optional activity and/or component of the project.

• Work Breakdown Structure is a generic term. There are many ways how project activities could be grouped.
• The key benefit of Multiple WBS is that each WBS element could be used for analysis and communication
• Grouping views and multiple WBS are not the same
• Multiple WBS is a powerful method that allows documenting, analysing and reporting projects via applying it via different lenses. This approach provides an opportunity to understand project delivery from many perspectives and increases chances for success.
• Due to technical limitations in popular scheduling tools, many of project practitioners never apply more than one WBS for the same project, don’t understand the concept of Multiple WBS, and even believe that a project may only have one WBS. At the same time, project stakeholders often have different views on the optimal WBS. It results in project conflicts, program restructures, schedule redevelopments and hidden schedules.