BC Building Code Part 9 vs Part 4: When Is a Structural Engineer Required?

Understanding BC Building Code Part 9 vs Part 4 is important before structural drawings are prepared or a permit is submitted. A project may qualify as a Part 9 building and still contain structural components that require Part 4 engineering.

BC Building Code 2024 official BC Building Code 2024 page applies to most of British Columbia, including Surrey, Burnaby, Victoria, and Kelowna. The City of Vancouver uses the Vancouver Building By-law 2025, which includes additional professional requirements in some situations.

by Merah Putih

Part 9 Buildings in British Columbia

Part 9 of Division B covers housing and small buildings that are no more than three storeys in building height, have a building area not exceeding 600 m², and fall within the permitted Group C, D, E, F2, or F3 major occupancies.

It provides prescriptive requirements for common construction conditions, including conventional framing, spans, foundations, and lateral bracing where the design remains within Code limits.

A structural engineer is therefore not automatically required simply because a project is a house or another Part 9 building. The BC Building Code confirms that registered professionals are sometimes, rather than always, required for Part 9 buildings.

Part 4 Structural Design Requirements

Part 4 addresses structural design where engineering analysis is required rather than relying only on Part 9 prescriptive provisions. It considers gravity, snow, wind, earthquake, and other applicable structural effects.

Depending on the material, BCBC 2024 references standards including CSA O86:19 for wood, CSA S16:19 for steel, CSA A23.3:19 for concrete, and CSA S304-14 for masonry.

Buildings outside the scope of Part 9 generally require professional structural design under Part 4.

Part 9 Buildings With Part 4 Structural Components

A Part 9 building can contain individual components that fall outside Part 9. This is one of the most important distinctions for contractors and designers in BC.

Provincial guidance BC Guide to the Letters of Assurance identifies examples that may require Part 4 structural design:

• Beams carrying point or concentrated loads

• Girder trusses

• Trusses spanning more than 12.2 m

• Proprietary engineered structural components

• Members exceeding applicable Part 9 limits

An open-concept renovation in Surrey or custom home in Kelowna, for example, may introduce concentrated reactions or unusual framing that cannot be selected directly from Part 9 tables.

Structural Engineering Triggers in Part 9 Projects

Engineering becomes necessary when a structural condition is outside the scope of Part 9. Common triggers include:

• Long or heavily loaded beams

• Large structural openings

• Non-standard wall or roof framing

• Complex load paths

• Alterations affecting existing supports

• Foundation conditions outside Part 9 limits

At Parsways Inc., reviewing the architectural scope early helps identify which components remain prescriptive and which require engineered design.

Schedule B for Engineered Part 9 Components

BCBC 2024 Division C requires Letters of Assurance for structural components in Part 9 buildings when those components are outside the scope of Part 9. The registered professional responsible for that structural scope may therefore need to provide a Schedule B.

Where numerous Part 4 components are present, some authorities having jurisdiction require the engineer’s responsibility to extend to the integrated structural design and field review of the building. Permit requirements should be coordinated with the local authority.

Local Permit Requirements Across BC

Municipalities administer building permits, so submission requirements can differ across British Columbia. Projects in Burnaby, Surrey, Victoria, and other communities may require sealed structural drawings and professional assurance where engineered components are involved.

The determining issue is not simply whether the building is classified as Part 9. It is whether the proposed structural work remains within Part 9 provisions.

Conclusion

BC Building Code Part 9 provides prescriptive solutions for many small buildings, but Part 9 classification does not eliminate structural engineering requirements. When a structural component exceeds Part 9 limits, Part 4 design and professional involvement may be required.

At Parsways Inc., we provide structural engineering for Part 9 projects across British Columbia, including engineered beams, structural openings, framing modifications, foundations, and other components requiring Part 4 design, coordinated with BCBC 2024 and applicable permit requirements.