News release

National Building Code Advisory

Service Nova Scotia and Municipal Relations (Oct. 2000 - March 2014)

Owners of buildings with arched or curved roofs should be aware of a revision to the 1995 National Building Code of Canada. The Canadian Commission on Building and Fire Codes issued the change to correct a design shortcoming in these roofs, which are often found on long-span commercial, industrial and recreational buildings, such as rinks.

The code change was initiated because of concern that these types of roofs may not be able to support unbalanced snow loads, typically snow drifts created by high winds. Owners of curved- or arched-roof buildings designed prior to this change should consider having the structures evaluated by a qualified structural engineer. The evaluation will determine if the structures have the capacity to support the snow loads now specified by the National Building Code, with adequate margins of safety.

Of particular concern would be arched roofs with height-to-span ratios lower than 1/10 and higher than 1/20. The commission has advised that this code change applies to all types of curved or arched structures -- wood and steel trusses, glulam arches and those made of corrugated metal, for example. The loading issue arises from the geometry of the roof surface rather than from the type of underlying structure.

The unbalanced loading condition can build up quickly when strong winds and heavy snowfall occur at the same time. Until such buildings have been checked or the snow removed, the commission suggests it might be prudent to avoid using these buildings when such conditions prevail.

An information package that includes a description of the types of buildings and detailed technical information is available on the Nova Scotia Building Code Web site at www.gov.ns.ca/snsmr/muns/code , or by calling 1-800-670-4357, or 902-424-5200 in the Halifax area.

Detailed information regarding the revised snow-load design criteria can be obtained by contacting the Canadian Codes Centre at 613-993-9960 or by e-mail to codes@nrc.ca .