Proposed Code Changes to Secondary Suite Provisions

British Columbia Building Code 2018

Proposed Code Changes to Secondary Suite Provisions

PROPOSED CHANGE: Secondary Suites


CODE REFERENCE: British Columbia Building Code 2018 – Part 9 of Division A and Part 9 of Division B


Harmonize with national building code requirements related to secondary suites, increase options for the design and construction of new secondary suites, and increase the building types where secondary suites may be constructed.


The Province of British Columbia (BC) is working to remove barriers to secondary housing forms including secondary suites. Mid-cycle revisions to the British Columbia Building Code 2018 (BCBC) are proposed to increase options for the design and construction of new secondary suites in buildings.

The BCBC introduced requirements for secondary suites in November 1995, prior to the NBC’s development of secondary suite requirements.  Since 1995, the BCBC’s secondary suite requirements have not been substantially updated. There are some differences between the BCBC and the NBC requirements, including the level of performance for specific systems and functions.  In addition, some existing requirements that present a barrier to the construction of new secondary suites are proposed to be removed and replaced with alternate compensatory measures.

The proposed changes aim to increase harmonization between the BCBC and the NBC while maintaining an appropriate level of health and safety and offering more acceptable solutions to increase the construction of new secondary suites in more building types.


Part 9 of the NBC contains comparable requirements to Section 9.37. of the BCBC to accommodate the construction of secondary suites at a reasonable cost without compromising the health and safety of the occupants.  The proposed changes were developed based on the five principles that guided NBC development:

  1. Reduction in Performance Acceptable where existing requirements are onerous to implement in existing buildings and are not attributed to fire safety;
  2. Requirements for Single Dwelling Units Apply to Houses with a Secondary Suite where risk is not increased due to the possibility of a higher occupant load in a house with a secondary suite;
  3. Trade-Offs Allowed where existing requirements are costly to implement, and equivalent performance levels can be reached by other means;
  4. No Change Required where existing requirements would not normally apply to houses or are necessary to achieve minimum acceptable performance levels for life safety; and
  5. Increase in Performance Required where existing requirements are attributed to safety and are not considered to provide a minimum acceptable level of performance for the additional risk resulting from the possibility of a higher occupant load or increased hazard presented by adding a secondary suite.



References to the BCBC are to the 2018 edition including Revision 1.  References to the NBC are to the 2015 edition. Only the content required for context of the proposed changes is reproduced in this document.

This proposed change arranges provisions differently than previous editions of the BCBC, based on whether they are justifiable for buildings of new construction and additions to existing buildings, or if they are justified only for alterations to existing buildings.  Additional consideration is extended to existing buildings where bringing the existing building into compliance with current requirements could be extremely cost-prohibitive and therefore could be greater hardship to the market in prohibiting the secondary suite than there would be in permitting a separate level of performance.  The proposed changes harmonize with the organization and approach of the NBC which includes provisions for secondary suites throughout Part 9; BC’s unique Section 9.37. is not proposed to be continued.

Alternate compliance methods for alterations to existing buildings are contained in a separate table and are not  available to buildings of new construction or additions to existing buildings where there is no hardship in complying with the current requirements for design and construction. The proposed changes to the BCBC are not intended as evaluation metrics or retroactive construction requirements for existing and occupied secondary suites. The BCBC regulates the activity of design and construction which includes alterations and additions to existing buildings and is not intended to be applied retroactively to existing buildings

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