There are currently no explicit requirements related to asphalt core boards in Part 9 of Division B of the National Building Code of Canada (NBC), although the material is commonly used in practice as a substrate in flat or low-slope roofing. This lack of requirements leads to inconsistency in the design, construction and performance of asphalt core boards across Canada, which can lead to roof membrane issues and potential water ingress, which could put Canadians at an unacceptable risk of illness due to poor indoor air quality (e.g., exposure to mould resulting from water ingress) and inadequate thermal comfort resulting from the degradation of thermal insulation material following contact with moisture.

Given the current inconsistency in the design, construction and performance of asphalt core boards used as roofing materials in Canada, there is a need to introduce a reference to a standard into the NBC. 

CSA A123.25:18, “Asphalt core boards used in roofing,” is suitable for referencing in the NBC and reflects the minimum performance requirements for substrates of asphalt-based and low-slope roofing membranes (e.g., built-up roofing or modified bitumen). In such systems, the roofing membrane can be adhered to the asphalt core board with hot asphalt or cold-applied adhesive, heat-welded to the asphalt core board, or mechanically attached to the structural deck through the asphalt core board. 

Adding the standard to Table 9.26.2.1.-B would introduce minimum requirements for the performance of asphalt core boards across Canada and thus limit the probability of roof membrane issues and water ingress, which would help minimize health risks associated with poor indoor air quality, inadequate thermal comfort and exposure to moisture.

Manufacturers would need to test their materials according to the standard. The cost of the test ranges from $7,000 to $9,000. This requirement can be a benefit to manufacturers, as it gives them an opportunity to acquire market share through an initial investment in testing, but it may also be a barrier to entry for smaller companies. Since it is an initial investment decision by the manufacturer to acquire market share, no significant additional cost is expected to be incurred by Code users or end users of the building.

Building officials would need to verify that the materials have been tested according to the standard. This verification can be accomplished through communication with the certifying agency or by confirming with the manufacturer’s published literature (e.g., technical data sheets).

Adding the standard to the NBC would decrease workloads for contractors, manufacturers, designers, specification writers and building officials in determining Code compliance by providing minimum performance requirements.

The standard can be enforced without additional resources.

Designers, specifiers, manufacturers, contractors, building owners and building officials.