What fire-resistance rating is required between the dwelling unit and an attached garage?
Fire Separation Requirements Between a Dwelling Unit and an Attached Garage in Canada
The required fire-resistance rating between a dwelling unit and an attached garage depends on the size of the garage, whether it serves only that dwelling unit, and whether the building is sprinklered, with the base requirement being 1 hour for garages of five vehicles or fewer.
General Rule for Storage Garages
Under both the NBC 2020 and NBC 2025, storage garages containing five or fewer vehicles shall be separated from other occupancies by a fire separation of not less than 1 h [Source: National Building Code of Canada - 2020, Page 879, Section 9.10.9.18.(2)]. Larger storage garages require a fire separation of not less than 1.5 h [Source: National Building Code of Canada - 2020, Page 879, Section 9.10.9.18.(1)].
Exception: Garage Serving Only Its Attached Dwelling Unit (Part 9 Buildings)
Where a storage garage serves only the dwelling unit to which it is attached or in which it is built, it shall be considered as part of that dwelling unit and the 1 h fire separation need not be provided between the garage and the dwelling unit [Source: National Building Code of Canada - 2020, Page 879, Section 9.10.9.18.(3)]. The NBC 2025 carries the same provision [Source: National Building Code of Canada 2025, Page 918, Section 9.10.9.18.(3)].
However, even when no rated fire separation is required, the code still mandates:
An air barrier system between the garage and the remainder of the building, to provide an effective barrier to gas and exhaust fumes [Source: National Building Code of Canada - 2020, Page 879, Section 9.10.9.18.(4)(a)].
Every door between the garage and the remainder of the building shall conform to Article 9.10.13.15 [Source: National Building Code of Canada - 2020, Page 879, Section 9.10.9.18.(4)(b)].
Part 3 Buildings: Dwelling Units in Larger Residential Buildings
For larger residential buildings governed by Part 3, the fire separation required by Sentence 3.3.5.6.(1) may be waived between a dwelling unit and an attached storage garage of five vehicles or fewer, provided that both spaces are sprinklered and separated from the remainder of the building, no air duct systems connect the garage to the dwelling unit, an effective gas and fume barrier is in place, and every connecting door is tight fitting, weather-stripped, fitted with a self-closing device, and not located in a sleeping room [Source: National Building Code of Canada - 2020, Page 279, Section 3.3.4.2.(4)].
Where the garage serves only its own dwelling unit, the fire separation required by Sentence 3.3.5.6.(1) is not required at all, provided the same conditions regarding fume barriers and door requirements are met [Source: National Building Code of Canada - 2020, Page 279, Section 3.3.4.2.(5)].
NBC 2025 Alignment
The NBC 2025 carries forward the same framework, with no substantive change to the garage separation rules [Source: National Building Code of Canada 2025, Page 277, Section 3.3.4.3.(4)][Source: National Building Code of Canada 2025, Page 277, Section 3.3.4.3.(5)].
Quebec
The Quebec Construction Code (2020 edition) adopts the same provisions as the NBC 2020 without amendment to these garage separation requirements [Source: Quebec Construction Code - 2020, Page 295, Section 3.3.4.2.(4)].
Summary
In short, an attached garage serving only its own dwelling unit does not require a rated fire separation from that unit, but robust gas and fume barriers, and compliant doors, remain mandatory in all cases. A garage shared with or serving other suites or occupancies requires at minimum a 1 h rated fire separation.
This answer is AI-generated from the cited sources. While CodesWise grounds every response in the official code documents, you remain responsible for verifying the requirements that apply to your specific project. Always confirm against the authoritative code for your jurisdiction.