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How much snow your roof can support?

Miscellaneous

Every winter, Québec homeowners have the same concern: “What is the maximum amount of snow the roof can support?” According to the Insurance Institute for Business & Home Safety, unless the roof structure is damaged or decayed, most residential roofs regardless of the location of the house should be able to support 20 pounds per square foot of snow before they become stressed. For greater clarity, some elements must be considered.

The different styles of roofs in Québec

The Québec landscape features many properties with several different architectural styles. As a result, the shape of the roofs can be very different from one house to another. In particular, we find:

  • The lean-to roof (or mono-pitched roof)
  • The peaked roof (or gable roof)
  • The roof with valleys and cornices 
  • The mansard roof (or 2- or 4- gable roof)
  • The pool roof (with a drain in the center to accommodate water and snow)
  • The flat roof

When a house is built, an engineer must make various calculations to propose the materials and structure that will support the roof, as well as the weight of snow that it will be able to support without problem depending on the region of Québec where the property is located. However, care must be taken if the building structure has been modified over the years, as the initial calculations are probably no longer valid.

It is also important when you live in a semi-detached home where the two parts are not separated by a firewall, to be aware that you share the same roof structure as your neighbour. Therefore, it is recommended to clear the entire roof to avoid creating a snow load on a single section and weaken the structure.

The weight of snow on a roof varies according to its nature

Depending on its state, fresh, packed or ice, the weight of the snow will not be the same on the roof. To help us get around this, the IIBHS provides us with its general guidelines to best assess the maximum snow weight that can be build up on the roof before it is necessary to clear it.

  • Fresh snow
    25 to 30 cm (10 to 12 in.) of fresh snow is equivalent to 2.5 cm (1 in.) of water or about 2.3 kg (5 pounds) per square foot of roof. This means that you can have a maximum snow load of 1.2 m (4 ft.) before the roof becomes stressed.
  • Packed snow
    7.5 to 12.5 cm (3 to 5 in.) of old snow is equivalent to 2.5 cm (1 in.) of water, or about 2.3 kg (5 pounds) per square foot of roof space. A depth of more than 30 cm of snow may be greater than your roof can support.
  • Total accumulated weight
    A depth of 60 cm (24 in.) of built-up snow or 60 cm (24 in.) of fresh snow can weigh as much as 27 kg (60 pounds) per square foot of roof space. This is beyond the maximum recommended snowfall on a roof.
  • Ice
    A thin layer of ice of 2.5 cm (1 in.) is equivalent to 30 cm (12 in.) of fresh snow! It is therefore crucial to monitor ice dams and act quickly.

Since Québec is characterized by fluctuating winter temperatures, it is not uncommon for several layers of snow to be piled up on the roof. Rain, ice and periods of thaw are conducive to the formation of ice and layers of packed snow. These temperatures can cause water infiltration and damage to the home. In addition, as accumulations can vary from one roof section to another due to wind, inspect all parts of your roof carefully.

In general, if the roof slope is low and the roof covering is rough, snow accumulation is greater than when the angle is very steep or the covering is slippery, as is the case for metal roofs.

Click here to calculate the approximate snow weight on your roof.

Some signs that indicate an overload of snow on the roof.

Still wondering if it’s time to clear your roof of snow? If your home’s interior doors are difficult to close or rub, if you notice cracks in the walls or deformation of the ceiling, you will need to act quickly to prevent structural collapse or water infiltration. For other signs that your roof is carrying too much snow, read our article: Top signs that it’s time to remove snow from your roof.

Too much snow on your roof? Here’s what you need to do! 

To ensure that you protect your home, you must clear your roof of snow. This will prevent damage to your gutters, reduce the efficiency of your roof-mounted ventilation equipment and damage to the building structure. In addition, snow accumulation is a danger to people travelling near the building due to the risk of avalanches.

The safest and most economical way to clear snow is to use a roof shovel. PolarMade offers two models, the SnowPeeler and the SnowPeeler Premium. They allow you to clear snow safely by keeping both feet firmly on the ground! The Premium model even offers a range of up to 9 m (30 feet). The SnowPeeler is designed for use on sloped roofs at any angle. It is a risk-free tool for covering your roof and allows you to clear snow with a minimum of effort. This will save you a few visits to the chiropractor. Finally, when clearing snow, it is not necessary to remove all the snow. Leaving a thin layer will prevent roof damage and facilitate water flow as temperatures warm.

 

Easily remove the snow accumulated on the roof with the SnowPeeler!

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