Snow is a major part of where we live, whether you love that white stuff or despise its existence. Every winter it blankets our homes and streets while ushering in the frigid air of January and February. When the snow's piled high, you’ve probably seen neighbors or friends shoveling it off of their roofs. Maybe you’ve even wondered, how much snow can my roof handle?
Unfortunately there isn’t a straight forward answer to how much snow your roof can hold. It would be nice to say something like, after 12 inches of snow you need to clean off your roof, but it’s not that easy. There are a lot of variables, like the type of snow that’s falling and when your home was built, which make the answer a little more complicated. Luckily this guide can help you clarify how much snow your roof can handle before you need to pull out the old shovel.
Weight's What Matters
Snow's Weight: Because snow comes in all kinds of different forms, like the fluffy powder skiers dream about or the back breaking slush everyone hates to shovel, it’s more important to focus on the weight of the snow than on how much snow there is.
The Federal Emergency Management Agency (FEMA) has provided snow load safety guidelines that describe how much different types of snow weigh and how that weight affects your roof. For example they state that “the weight of 1 foot of snow ranges from 3 pounds per square foot for light, dry snow to 21 pounds per square foot for wet, heavy snow." Structure Tech agrees with the guidelines created by FEMA. They’ve even created a table, shown below, that breaks down the weight of different snow types (depicted in pounds per square foot). Using this table to calculate the weight of the snow of your roof is the first step in determining if you need to shovel it off or not.
Your Roof’s Strength: Now that we’ve got a good idea of how much snow weighs, let’s see how much weight your roof can support. In 1997 a code was created that builders must follow called the International Builders Cod (IBC). The IBC has a Roof Strength Requirement that helps ensure your roof is strong enough to support more than the normal amount of snowfall in your area. So as long as your home is built to code, it should be able to withstand the amounts shown in the table below (depicted in pounds per square foot).
What about homes built before the IBC was adopted in 1997? While older homes may not be able to support the weight requirements of the IBC, they are still built to support a good amount of weight. According to the Insurance Institute for Business and Home Safety, homes built before 1997 can typically support between 15 and 20 pounds per square foot.
Once you’ve determined the strength of your roof and how much the snow up there weighs, you’ll have a better idea of when you need to shovel off your roof. Just remember that other factors, like the pitch of your roof or accumulation from multiple snow storms, can alter these numbers. That’s why it’s always a good idea to err on the side of caution. Taking the time to shovel snow off of your roof could be a lot easier than dealing with a leaking roof or structural issue.
Signs That There's Too Much Snow on Your Roof
The biggest clue that you’ve got too much weight on your roof is when interior doors start to stick or get caught. The weight of the snow will push down on your home, distorting the door frames which cause them to stick. Other signs to watch out for include leaks, visible cracks in the drywall or plaster around door frames and windows, and cracking or creaking sounds. If you notice any of these signs, you should try to quickly remove snow from your roof to prevent permanent damage.