Test Standard CSA 123.21 – Application Policy

November 2023

Wind uplift is a significant factor that can affect the integrity of roofing systems. This following outlines CRCA and its members commitment to addressing wind uplift concerns and the responsibilities of both the roofing contractors and design community to ensure the structural and functional integrity of roofing systems.

WHEREAS, The Canadian Roofing Contractors Association (CRCA) supports the design and installation of roofing systems that will perform and withstand adverse weather conditions.

WHEREAS, the contractor needs to provide a proper bid associated with a project, tender documents provide by designers must contain all necessary components to meet current code requirements.

WHEREAS, designers should be providing the required wind loads and a roof system design that meet or exceed required loads as per building code requirements at the design stage of a project.

WHEREAS, the responsibilities, including proper design drawings and specifications, associated with these calculations rest with the design authority.

WHEREAS, roofing contractors are responsible for understanding the design specifications including the wind uplift design requirements. They must ensure that all roofing systems and installation methods are consistent with the approved design.

WHEREAS, CRCA issued an advisory bulletin in June 2018 titled Roofing Contractors and Designers Responsibility detailing the different responsibilities that arise on a roofing project.

It is the CRCA policy that,

“Roofing contractors should not bear the responsibility of determining wind loads and the proper roof system design to meet or exceed those wind loads.”

What is CSA A123.21 wind uplift standard?

CSA A123.21 Standard test method for the dynamic wind uplift resistance of membrane roofing systems is a standard to ensure that roofing systems are tested for wind resistance. The standard describes a method of the wind uplift testing of roofing systems that must be completed by an accredited laboratory.

The standard was developed through the Special Interest Group on Dynamic Evaluation of Roofing Systems (SIGDERS) research program. SIGDERS is a consortium of members of the North American roofing community that was created as a means of evaluating the effect of dynamic wind loads on roofing systems.

Wind uplift and code requirements

CSA A123.21 was first introduced in the National Model Building Code in 2015 and focused the attention of the design community on wind uplift resistance of roof systems.
Article Determination of Wind Load of NBCC 2020 references CSA A123.21 as follows: Determination of Wind Load
“1) This Article applies to the determination of wind load to be used in the design of materials, components and assemblies, including their connections, that separate dissimilar environments or are exposed to the exterior, where these are
                  a) subject to wind load, and
                  b) required to be designed to resist wind load.
2) Except as provided in Sentence (3), the wind load referred to in Sentence (1) shall be 100% of the specified wind load determined in accordance with Article
3) Where it can be shown by test or analysis that a material, component, assembly or connection referred to in Sentence (1) will be subject to less than 100% of the specified wind load, the wind load referred to in Sentence (1) shall be not less than the load determined by test or analysis.
4) Except as provided in Sentence (5), the wind uplift resistance of membrane roofing assemblies shall be determined in accordance with the requirements of CAN/CSA-A123.21, “Standard test method for the dynamic wind uplift resistance of membrane-roofing systems.” (See Note A-
5) Membrane roofing assemblies with proven past performance for the anticipated wind loads need not comply with Sentence (4). (See Note A-”
Article specifies the procedures that are used to determine the design wind load on a particular building. These procedures should be completed by a designer.

Simply stated, the wind uplift resistance of a roofing system that is determined using CSA A123.21 must meet or exceed the design wind load that is specified in Article