Community News

Should You Be Shovelling Your Roof

Feb 08. 18

Public Service Announcement - Snowloads

#2018-02
February 7, 2018
 

SMITHERS – The recent volume of snowfall has prompted residents to be concerned with accumulated snow loads on home roofs.

Homes built prior to 1985 or homes that are developing icicles or ice damming at the eaves may need some clearing.  Attic ventilation—ridge vents, whirly vents, flat vents—that are blocked, may be restricting air flow that cools and removes moisture from the attic.  Heat escaping from the house and trapped in attic spaces can melt snow at the shingles and cause a flow of water to the cold overhang at the soffits.  So clearing vents is a place to start!

The BC Building Code establishes the Ground Snow Load which is used to calculate the Roof Snow Load that engineers and builders factor in construction.  The Ground Snow Load has changed over the past three decades:  1985—2.2 Kpa, 1998—2.7 Kpa, 2003—2.9 Kpa, 2006 to present—3.2 Kpa.

The Town of Smithers’ current ground snow load is 3.2 kPa plus 0.2 kPa rain component, for a total 3.4 kPa, or 69 lbs/ft2. For building design, this value is generally reduced by 40% for residential buildings and by 20% for commercial buildings, known as the specified roof snow loads. This equates to 41psf for residential and 55psf for commercial.

Pure water density is around 1000 kg (or one tonne) per cubic metre or 62.4 lbs  per cubic foot. Newly fallen snow more typically weighs 70 to 150 kg per cubic metre (4.4 to 9.4 lbs/cubic foot). Typically winter snowpacks have a density of 200-300 kg per cubic metre (12.5-18.7 lbs per cubic foot).

If we use 300kg/m3 (18.7pcf), then the current design depth of snow on roofs is 2.2ft on residential and 2.9ft on commercial. Owners should consider removing the snow if the packed accumulated snow exceeds these depths.  If heavy rains fall on these snow depths, the roof loading and risks of structure failure increase significantly.

Owners of older homes and buildings that were designed to a lighter snow load should consider removing snow at lower depths than those listed  above.

1. Do not shovel alone – have a spotter
2. Use fall-restraint or a rope safety line
3. Do not over-exert yourself
4. Remove snow evenly from the roof to avoid unbalanced loading
5. Do not shovel all the way to the roof surface – leave 50mm (2 inches)
6. COMMERCIAL BUILDING ROOFS—Do not clear onto public sidewalks or roadways unless barricades are set up, and follow up to clear the right of way for public safety.

View more Community News


In Our Community

  • Happy Family Day

    Happy Family Day from Staff and Management of Bulkley Valley Credit Union. To allow our staff to spend the day with their families all branches will be closed from Saturday, February 16th and re-open on Tuesday, February 19th with regular business hours.

    Read More

  • Turbo Tax offer!

    TurboTax makes it easy to do your taxes right and get your maximum tax refund guaranteed.1 What’s best, as a valued member of Bulkley Valley Credit Union, you can get a special 20% discount on TurboTax Online products.

    Read More

  • Last Chance for Bursary Applications!

    Bulkley Valley Credit Union is proud to help Bulkley Valley and Lakes District students reach their post-secondary education goals through the Credit Unions of BC Bursary Program. Submit your bursary application today and get help towards funding your future! Deadline is to apply for a bursary up to $2000 is February 15. Continue reading for more information!

    Read More