As a guide, most roofs in the USA are designed to hold 20 pounds per sq ft of snow. Although the type of snow on your roof will vary, freshly fallen snow weighs between 3 to 5 pounds per sq ft, which means your roof should be able to structurally hold around 4-5 feet of freshly fallen dry snow.
But if you have ever looked up and thought, wow, just how much snow can my roof hold? Don’t worry, here I give you a guide on how to calculate just that.
Yes, roofs are built to last, but, too much snow on your roof can cause it to collapse. Although I can’t give you exact numbers on how much square foot of snow is too much. I can help you make a strong estimate of how much snow your roof can support and the best ways to get snow off your roof.
How Do You Calculate Snow Load on a Roof?
Too much snow on your roof can be the cause of roof leaks or even total roof collapse. The last thing you want to happen in the middle of the snow season. So I’ve made this snow on the roof to weight chart for you to help guide your calculations before you dig your snow roof rake out of storage.
Snow weight is calculated by translating the depth of snow into water weight. However, the type of snow i.e. dry and airy vs wet and compacted makes a big difference in this calculation.
Although I have done my best to give average snow loads, please, only use the chart as an estimate.
There are many factors that influence how much your roof can handle. This includes the fact that there may even be layers of different types of snow. It is always safer to assume that the snow is heavier than you might think.
How Much Does A Foot Of Snow Weigh?
Once again, I repeat that the weight of snow per square foot is very different depending on whether it is dry or wet snow. 8 inches of new dry snowfall does not weigh the same as 8 inches of wet packed snow.
For ease, I prefer to calculate in 5 pounds per square foot. Different types of snow make the difference to how many inches of snow is equal to 5 lbs.
Here are the numbers that I work with to find out what 5 pounds per square foot is equal to with the different types, as always this is an approximation.
- 10 inches dry fresh snow
- 3 inches wet compacted snow
- 1-inch ice
How Much Snow Can My Roof Hold?
Here in the USA, most roofs are built to withstand up to 20 pounds per square foot. Because of this limit, it is important to either know how to remove snow safely. Either by using a roof rake or, bringing in a specialist roof snow removal company to clear it for you. Especially true if you live in an area with high snowfall.
To answer, how much weight can a roof hold, you need to know about a few different important factors.
You will need to think about the roofing material, roof structure, and slope (angle) of the roof. Snow is more likely to naturally fall off smooth and steep roofs which means that roof collapses are a greater risk for a flat roof or roofing with a textured shape.
Also, sturdier slate or asphalt shingles are at less risk of damage.
Look Out For Warning Signs Of An Overloaded Roof
Besides your excellent math skills, there are other telltale signs of too much snow. Walk around your home looking for doors sticking in the door frames, check for slight bends in the rafters, cracks in the walls, and leaks, especially in the attic.
Before winter is upon you, check the overall roof condition on the outside of the house. Specifically, look out for ice dams (melted snow that has refrozen along with leaves). Not only are these a serious hazard to anyone walking by, but they can also cause water damage due to the water in the gutterings not being able to flow.
Best Roof Pitch For Snow
Did you know that in states with a lot of snow there is a minimum roof pitch for a snow load? For a home up north, the recommended minimum pitch is a 10-degree angle.
I often hear people say that a flat roof cannot take as big a load as a slanted roof. There is some truth to this but technically speaking, a well-constructed roof should be able to carry the same weight.
The difference is that snow won’t naturally glide off the flatter roof. Which then results in the snow becoming compacted and heavy. This is the real reason why flat roofs require snow removal sooner than pitched roofs.
Wrapping Things Up
There you have it guys, how to keep your home safe throughout the winter months. I will give a strong word of warning as my conclusion to this blog though.
NEVER get onto a roof to clear snow unless you have the appropriate training and experience. Happy snowballing!
Other Commonly Asked Questions
Besides a roof collapse, too much snow on the roof comes with many hazards. So, let me leave you with a few homeowners tips to stay safe in snow country.
When should you remove snow from your roof?
The general rule of thumb is that you should remove snow from your roof at about 6 inches deep. This is the safest way unless you can calculate exactly how many inches of snow equals 20 pounds per square foot.
Can ice dams cause roof damage?
Ice dams are one of the biggest causes of roof damage in homes. As meltwater gets stuck in the gutters it can start to seep through the roof or leak through openings such as vents and skylights. It’s important to know how to remove ice dams fast if you see them forming.
Can you put salt on your roof to melt ice?
You should never put salt on your roof to melt ice and for very good reason. Salt and similar products are corrosive and may cause damage to roofing materials. In addition to that when the ice does melt you will have a runoff that is toxic to the plants below.