National Building Code of Canada (NBC)

The National Building Code of Canada (NBC) is Canada's model building code. It is developed by the Canadian Commission on Building and Fire Codes and published by the National Research Council of Canada (NRC) as part of the "Codes Canada" family, which also includes national fire, plumbing and energy codes. The current edition is NBC 2020, published in two volumes and available as a free PDF from the NRC as well as in print.

History and legal status

The federal government published the first National Building Code in 1941. It was revised roughly every five years from 1960 to 1995, followed by editions in 2005, 2010, 2015 and 2020. The 2005 edition introduced an objective-based format, linking each requirement to the objective it serves.

The NBC is a model code: it has no legal force until a province, territory or municipality adopts it. Some provinces adopt it largely as written; others, such as British Columbia, Alberta, Ontario and Quebec, publish their own codes based on it with provincial changes. Users must check which edition applies in their jurisdiction.

Structure and roofing

The NBC is divided into Parts. Two matter most for roofing:

• Part 9 – Housing and Small Buildings. Covers buildings of three storeys or less and up to 600 m² (about 6,460 ft²) in building area. It is highly prescriptive, designed so that builders can apply it directly. Part 9 contains rules for roofing materials, slopes, underlays, eave protection in snow climates, flashing and attic ventilation.
• Part 5 – Environmental Separation, and Part 4 – Structural Design. For larger buildings, roofs must be designed to resist wind, snow and rain loads using Part 4, and to control heat, air and moisture under Part 5.

Referenced standards

The NBC references many CSA standards for roofing products, including the CSA A123 series for asphalt shingles, roll roofing and membranes, and CSA A123.21 for the dynamic wind uplift testing of membrane roofs. Fire performance of roof coverings is tested under CAN/ULC-S107.

Product evaluation

Innovative products not covered by referenced standards can be evaluated by the Canadian Construction Materials Centre (CCMC), whose assessments help building officials accept them under the code.