How to calculate the weight of snow on your roof

If you’ve made it this far, you probably already know the importance of removing snow from your roof when it’s covered with a certain amount. This prevents damage to eavestroughs, vents and the roof structure.

However, you may be wondering how much snow your roof is currently supporting. This is crucial information that could help you decide whether to shovel your roof or call a roof snow removal service today!

In this case, you’ve come to the right place. Our team explains how to calculate the weight of snow on your roof.

Formula used to calculate the weight of snow on a roof

You can calculate the weight of snow on a roof using the following formula:

Weight of snow = length of roof x width of roof / degree of slope x snow load

You will therefore need certain precise information on hand before performing your calculation. You will then be able to replace the variables with precise data concerning your roof.

Unless the roof structure is weakened, most residential roofs should resist approximately 20 lb/ft² (100 kg/m²) before undergoing structural stress. 

Variables that influence the calculation of the weight of snow on a pitched roof

To help you understand and use the formula presented in the previous paragraph, here is some information about the variables in the formula.

Roof length and width

The roof’s dimensions are important when calculating the weight of the snow it supports. The larger these variables are, the greater the snow load will be.

In the formula used to determine the weight of snow on a roof, the length and width of the roof (expressed in feet or metres) are multiplied together to obtain the surface (or area) that is covered with snow.

Roof pitch

The roof pitch also has an important role to play in calculating the weight of snow on a roof. As a general rule, the steeper the pitch, the lower the snow load will be. 

In the formula, a slope expressed in degrees of inclination should be used. 

Snow load

Snow load is generally measured in lb/ft² or kg/m². It is the last variable you need to apply the formula. It can be obtained by multiplying the snow depth by the snow density. 

However, since it can be difficult to know the exact density of each layer of precipitation on a snow-covered roof, here are some examples of snow loads based on the quality of the snowpack.

Fresh snow

25 to 30 cm (3 to 5 in) of fresh snow corresponds to a load of approximately 2.3 kg (5 lbs) per square foot of the roof.

Compacted snow

7.5 to 12.5 cm (3 to 5 in) of compacted snow is equivalent to a load of approximately 2.3 kg (5 lbs) per square foot of the roof.

Ice

2.5 cm (1 in) of ice is also equivalent to a load of 2.3 kg (5 lbs) per square foot of the roof.

Our roof snow load calculator

Rather than using the formula above, you can enter the requested information in our snow load calculator tool. In a few seconds, you will know how much snow is on your roof and if you need to have snow removal done.

Snow load calculator

**Make sure to adjust the units of measurement according to your data**

Does the snow load calculator indicate that your roof needs to be cleared of snow?

Remember, if you get a result greater than 20 lb/ft² (100 kg/m²) with the calculator or formula, the snow has to be removed from your roof as soon as possible, because the structure of your roof is currently under great stress.If you do not have the time or the equipment and expertise to do it safely, have our team do the job for you. At Couvreurs Duro-Toit, we are specialists in all types of roof snow removal. Contact us to benefit from professional service, even in an emergency!