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Public Service Announcement

The recent snowfalls, forecasted snowfalls and warming trend has prompted residents to be concerned with accumulated snow loads on home roofs. The Town of Smithers' current ground snow load is 3.1 kiloPascals (kPa) plus 0.2 kPa rain component, for a total 3.3 kPa, or 69 pounds per square foot (psf). For building design, the ground snow load is reduced by 45% for residential buildings and by 20% for commercial buildings. Therefore, the specified roof snow loads (including rain) are approximately 40 psf for residential and 56 psf for commercial.

Pure water density is around 1,000 kg per cubic metre (kg/m3) or 62.4 pcf. The density of newly fallen snow is typically 70 to 150 kg/m3 (4.4 to 9.4 pcf). Typically winter snowpacks have a density of 200 to 300 kg/m3 (12.5 to 18.7 pcf).

Using the higher snowpack density of 300 kg/m3 (18.7 pcf), then the current design depth of snow on roofs is 2.1ft on residential and 3.0ft on commercial. Owners should consider removing the snow if the packed accumulated snow exceeds these depths, if heavy rains fall on these snow depths, if the roofs are flat, low-sloped or have valleys, and if more snow-fall and accumulation is forecasted.

Older homes and buildings were designed to a lighter snow load and owners should consider removing snow at lower depths than those listed above.

The Town of Smithers recommends that you keep the following in mind when attempting to remove the accumulated snow from your roof:

1. Do not shovel alone - have a spotter.
2. Do not over-exert yourself.
3. Remove snow evenly from the roof to avoid unbalanced loading.
4. Do not shovel all the way to the roof surface - leave 50 mm (2 inches).

Contact:        
Roye Lovgren, Building Inspector                      
(250) 847-1600