Roofing in Canada

Canadian roofing is defined by cold. Most of the country has long winters, deep snow and repeated freeze-thaw, and the coasts add wind-driven rain and salt. The country's roof history includes highly specialised cold-climate shelters, from the Inuit snow house to the cedar plank houses of the Pacific coast, and the earliest known European buildings in the Americas.

Climate and hazards

• Snow load: the National Building Code of Canada gives ground snow and rain loads for communities across the country.
• Ice dams: heat escaping from a house melts roof snow that refreezes at the cold eaves; insulation, a ventilated cold roof space and an eave membrane are the standard defences.
• Wind-driven rain on the British Columbia coast and in Atlantic Canada, where hurricanes and post-tropical storms occasionally arrive.
• Permafrost and extreme cold in the North, affecting foundations and roof assemblies.

Roofing history

Inuit and Thule shelters. In the Central Arctic and the Qaanaaq area of Greenland, the snow house (iglu, more precisely igluvijaq) was built of wind-packed snow blocks laid in a catenary dome that needs no support during construction. Most other Inuit used snow mainly to insulate dwellings of whalebone and hide. In the transitional seasons, Thule people and their Inuit descendants built the qarmaq, with low walls of snow, stone or sod, a whalebone frame and a roof of skins or, later, canvas, packed with moss; it remained in use into the 1950s (see qarmaq).

Eastern Woodlands. Huron-Wendat, Haudenosaunee, Petun and Neutral communities in Southern Ontario lived in longhouses into about the 18th century. Bent poles lashed to wall posts made a rounded roof sheathed in bark, cedar for the Wendat and elm for the Haudenosaunee, with roof vents over hearths spaced 6-13 m (20-43 ft) apart. A house at the Moyer site in Southern Ontario measured 93 m (305 ft) long (see longhouse-roof).

Pacific coast. From coastal British Columbia to Alaska, Coast Salish, Kwakwaka'wakw and other nations built rectangular houses of split red cedar planks under gabled or shed roofs; the Paul Mason site at Kitselas Canyon, British Columbia, is about 3,000 years old. Simon Fraser recorded a house in 1808 with plank walls 11 ft (3.4 m) high (see plank-house).

Norse turf. At L'Anse aux Meadows, Newfoundland, an 11th-century Norse site of eight buildings had timber frames covered with turf cut from the nearby peat bog (see scandinavian-sod-roofs for the Norse tradition).

New France and after. Settlers in New France used wooden shingles (bardeaux) and later sheet metal. Quebec builders developed a characteristic flat-lock tinplate roof, tôle à la canadienne, in which small sheets are folded together and nailed at an angle; early sheets were flattened from containers and later imported from England. The batten-seam tôle à baguettes, probably introduced around 1800, became common in the 19th century, with tinplate on the oldest roofs, galvanised sheet after about 1850 and copper on prestigious buildings. Slate is scarce in Quebec but was used on some 19th-century churches. Prairie settlers in the 19th and early 20th centuries built sod houses, including the Mennonite semlin.

Traditional and vernacular roofs

• Iglu and qarmaq (Inuktitut).
• Bark longhouse of the Haudenosaunee and Wendat.
• Cedar plank house of the Pacific Northwest.
• Norse turf house at L'Anse aux Meadows.
• Québécois sheet-metal roofs, tôle à la canadienne and tôle à baguettes, on houses, churches and spires.
• Cedar shingles and shakes in British Columbia and the Maritimes.

Roofing today

As in the United States, asphalt shingles are the most common covering on houses. Organic-felt shingles left the Canadian market when the last producer, Building Products of Canada, stopped making them in 2011; current products are glass-mat based. Metal roofing in standing seam panels and stamped profiles is widely used in Quebec, Atlantic Canada and rural and northern areas, partly because it sheds snow. Flat and low-slope roofs on commercial and multi-unit buildings use modified bitumen, built-up roofing and single-ply membranes, often in protected or inverted assemblies with insulation above the membrane.

Codes, standards and regulation

The National Building Code of Canada is a model code published by the National Research Council of Canada for the Canadian Commission on Building and Fire Codes, normally on a five-year cycle. It has no force until adopted: some provinces adopt it directly, while Alberta, British Columbia and Ontario publish their own codes based on it, and Vancouver has its own building by-law. Houses and small buildings of up to three storeys and 600 m² (about 6,460 ft²) fall under Part 9, a prescriptive section written for builders. Toronto adopted a by-law in 2009 requiring green roofs on new residential buildings of six storeys or more and, later, on industrial buildings.

Industry

Canada has domestic producers of asphalt shingles, metal roofing and wood shakes and shingles, and provincial roofing contractor associations. Western red cedar shakes and shingles are a traditional British Columbia export.

Notable roofs

• L'Anse aux Meadows, Newfoundland: reconstructed Norse turf-roofed buildings at a UNESCO World Heritage Site.
• Mother House of the Grey Nuns, Montreal: copper spires and bell tower, restored over 17 months from 1997.
• St. George's Anglican Church, Montreal (1869-1870): green and red slate laid in geometric patterns.
• Sainte-Marie among the Hurons, Midland, Ontario: a reconstruction of a c. 1640 mission with bark-covered longhouses.

Local roofing terms

• Iglu / igluvijaq (Inuktitut): house / snow house.
• Qarmaq (pl. qarmat, Inuktitut): sod, stone or snow-walled house with a skin roof.
• Bardeau (French): wooden shingle.
• Tôle à la canadienne (French): Quebec flat-lock sheet-metal roof.
• Tôle à baguettes (French): batten-seam sheet-metal roof.

Sources and gaps

No Canadian census data on roof material were found in published sources.