As part of the Wind-RCI family of online tools for the roofing community, this calculator determines the resistance of the tested low-slope membrane roofing specimens in accordance with the CSA Group’s standard CSA A123.21, "Standard test method for the dynamic wind uplift resistance of membrane-roofing systems".
Wind design loads of roof coverings are calculated based on Load Resistance Factor Design (LRFD) as specified by the 2015 National Building Code of Canada (NBC) or the Wind Load calculator tool. To meet the building code requirements, roofing systems will be tested in accordance with the requirements of the CSA A123.21 standard. Reports from a calibrated lab provide sustained pressure, or rating, for a constructed specimen. A specimen’s resistance is obtained by multiplying the sustained pressure with a resistance factor (refer to the NBC, Division B, Table 126.96.36.199).
The CSA A123.21 standard provides two options to determine the resistance factor: (1) using sustained pressure from three tested specimens with identical construction details or (2) use of 0.65 as maximum value when the specimen sustained pressure is less than or equal to 11.5 kPa (240 psf). In the case former, the calculated coefficient of variation should be less than or equal to 15% to account for experimental uncertainties.
The Wind Uplift Resistance Calculator has been developed and is maintained by the National Research Council of Canada.
The licence agreement must be read and accepted before being able to use the Wind Uplift Resistance Calculator.