CSA A123.21-04

This section serves exclusively to issue publications of test results by various manufacturers who perform laboratory tests on wind design of mechanically attached flexible membrane roofs. The results stated in this publication may be used for design as well as a knowledge base by architects, designers and all other professionals in the field. These publications are valid until the date they are removed from the website. It is therefore the designer’s responsibility to verify that these publications are always active on the website prior to designing a system.

Equipment

The test apparatus shall consist of a pressure chamber and shall be as shown below. Its interior dimensions shall be 6100 ± 50mm (240 ± 2 in) x 2200 ± 50mm (87 ± 2 in). The structural stiffness of the test apparatus shall withstand a minimum of 20 kPa (400 psf) suction pressure. The test apparatus shall consist of a movable top chamber 800 ± 50 mm (31 ± 2 in) high mounted on a height-adjustable bottom frame that is fixed to the floor and on which the test specimen shall be installed. The height of the bottom frame shall be adjustable to accommodate roof assemblies with different thicknesses. The roof deck shall be installed on structural purlins with spacing based on the structural span requirements. The roofing specimen shall be installed between the top chamber and the bottom frame. The maximum applicable pressure for test purposes shall be 7.4 kPa (155 psf).

What Is the CSA A123.21 Standard?

CSA A123.21 is a standard test method for the dynamic wind uplift resistance of mechanically attached membrane roofing systems. This standard is the result of ten years of research conducted by the NRC/IRC, from an industry consortium which consists of building owners, government agencies, roofing trade associations and roofing product manufacturers. The consortium is known as SIGDERS (Special Interest Group on Dynamic Evaluation of Roofing Systems) and it is still active in the wind uplift research of roofing systems. Its activities will most likely result in revisions to the CSA A123.21 standard to broaden its scope, to include all types of roofing systems. In May of 2004 the CSA's Technical Committee on Bituminous Roofing Materials prepared this standard under the jurisdiction of the Strategic Steering Committee on Building Products and Systems and was formally approved by the Technical Committee. The scope of this standard as well as a copy is available on CSA's online store at www.ShopCSA.ca.

Design Guide

SIGDERS Also published in 2005 a guide for wind design of mechanically attached roof assemblies which is available at the online from the NRC. Laboratoires Shermont has introduced several recommendations form the Design Guide into the systems test report to facilitate the design and specification process. Designers are encouraged to consult the guide to fully comprehend the good design and application practice of roof constructions in relation to wind uplift resistance.

How to Specify Wind Uplift Resistance

1. Calculate the wind uplift resistance required for the roof being designed. This can be accomplished in one of two ways: by following the instructions in the National Building Code of Canada (or provincial codes) or by using the online WindRCI calculator. Before accessing the WindRCI online calculator designers will need the information to enter data into items 1, 2 and 3 and for items 4, 5 and 6 choices are given, which are explained with an excerpt of the NBC. The process for the online calculator is as follows:

1. Select building location
2. Enter the building dimensions (height, width and length)
3. Select a roof type (i.e. low slope, gable, saw tooth)
4. Select the building exposure (designers are given choices, which are explained with an excerpt of the NBC)
5. Select the building openings (designers are given choices, which are explained with an excerpt of the NBC)
6. Select the importance category (designers are given choices, which are explained with an excerpt from the NBC).

2. The resulting report gives a summary of the input and the design load at the corner, edge and field of the roof. As prescribed in the design guide, the design load must be multiplied by a safety factor of 1.5. Once the calculation is completed a roofing systems can be selected from the manufacturers list, which demonstrates a wind uplift resistance greater than the design load (with the safety factor).

3. Insert the CSA A123.21 standard in the specification. Les Laboratoires Shermont suggest the following clause be included in the "Standards Section" of the specification:

REFERENCE STANDARD(S)
Submit a report or reports, issued by a certified materials testing laboratory, attesting that the roofing system offered, was tested in accordance with CSA A123.21-04 ''Standard Test Method for the Dynamic Wind Uplift Resistance of Mechanically Attached Membrane Roofing Systems''. Test results shall demonstrate that the roofing system sustained wind uplift pressures of [  ]KPa for the field of  he roof, [  ]KPa for the edge of the roof and [  ]KPa for the corners of the roof.

Why a Dynamic Wind Uplift Resistance Test?

The National Building Code of Canada and the Provincial Building Codes (where applicable), requires that the wind load resistance be calculated with a dynamic factor. The CSA A123.21 standard was developed to a test method that mimics as close as possible the dynamic wind action that a roof assembly will have to endure during its useful service life.

Les Laboratoires Shermont Inc. obtained exclusive rights from the NRC for test equipment as per CSA A123.21 standards.

For more information, please contact Mr. Dominic Mercier, Eng. at

819 477-3775 dominic.mercier@labo-shermont.com  

or Mr. Paul Hébert, Eng. at 514 521-4290

paul.hebert@labo-shermont.com