Every winter many roofs collapse due to heavy snow or ice loads. Add rain or heavy, wet snowfalls on top and you’ve got a dangerous combination. Often roofs collapse suddenly, giving occupants little, if any, warning to evacuate the building.
A well-documented example was the collapse of the Metrodome in Minnesota after a heavy snowfall. As you can see in the video below, once the weight of snow becomes unbearable any roof can collapse in a matter of seconds.
This is why it’s important to know how much snow is too much for your roof to support and then make sure that this threshold is not exceeded.
How Much Snow Can Your Roof Support?
Roof collapse can happen to new and old buildings alike and can cause extensive damage to the building and contents. Low pitched and flat roofs are most susceptible to collapses. Most roof designs can handle snow loads of 20-40 lbs per square foot. But, as the chart below shows, packed snow with ice can easily overload a roof once it reaches about 12″ off depth.
|Snow Type||Approximate Density
(lbs per square foot for every 12” of depth)
|Light and Fluffy||5-20|
|Packed with Ice||40-58|
How To Protect Your Roof
Watch for ice build up on the edge and valleys of your roof. When heat escapes through your attic, it melts the snow. When this water freezes at the edge of your roof, it forms an ice dam and allows water to back up and enter the building under the shingles and wood decking. Besides adding extra weight to your roof, ice dams can cause extensive water damage inside.
Excessive accumulations of snow and ice will require removal. For safe removal that won’t endanger you or damage your roof, consult a roofing contractor. Be certain the contractor is covered by WSIB (Workers Compensation) and provides you with a current liability insurance certificate.
Clearing Snow From Your Roof
If you are removing the snow on your own, be very careful as the roof can be very slippery. Here are a couple of tips to follow if you choose to tackle this job yourself:
1. Wear Safe Attire
Choose a pair of boots with excellent traction.
2. Choose a Proper Shovel
A plastic bucket (scoop) shovel with a large handle is best so you can scoop and slid the snow off the roof’s edge.
3. Save Your Shingles
Don’t pick or chip at ice near the roof surface or dig deep as you may damage the shingles and shorten the roof’s life expectancy.
4. Minimize The Stress
Do not pile all the snow in one area before removing it. This may overstress that section of the roof causing it to collapse.
5. Be Safe, Not Sorry
Removing snow from your roof is not a job to rush.
Protect your home and your family this winter by keeping your roof clear from snow build-up. Use the chart above to estimate when the snow needs to be cleared and then be careful to get the job done safely and properly.