If you live in an area that gets significant snow during the winter months, you might have cause to wonder about the snow load on roof. The weight of snow that a roof can handle is called the snow load. Several factors affect a roof’s ability to handle snow including the pitch, the amount of bracing in the roof and the distribution of the load.
The steeper the pitch, the less likely the roof is to collapse under the weight because the snow slides off quickly. Areas that get a lot of snow have steeply pitched roofs, although porch roofs and additions are sometimes flatter. This can be a problem when snow gives way higher up and falls onto a shallower roof, especially if the rafters are not braced.
Properly constructed roof trusses have collar ties that go across the face of one rafter to another. Unfortunately, homeowners or inexperienced contractors sometimes remove the collar ties to get more headroom into an attic space. This weakens the roof structure and lessens the snow load on the roof.
With all of those problems, why don’t more roofs collapse during a heavy snowfall? Three factors work together to protect a roof. The first is that rafters have a certain amount of give to them, which allows them to bend under a load. Bending doesn’t sound good, but when combined with the roof sheathing, the load is distributed over a larger area. Finally, the snow doesn’t stay there for very long. The wind blows it off the roof, it melts or it is removed before the roof is in danger.
A tool called a roof rake is very helpful for clearing piled up snow from a roof. It looks like a shovel with a bent handle and sections can be added to allow you to remove the snow without going onto the roof.
Don’t take chances with your roof. Make sure it is well-constructed and safe.