How Much Snow Is Too Much On A Roof

As everyone knows cold fluffy snow is very light while wet snow can be extremely heavy.

How much snow is too much on a roof.

How much snow is too much for a roof to handle. A new house can typically hold around 100 pounds per square foot on the roof. A cubic foot of water weighs about 62 pounds. But as the chart below shows packed snow with ice can easily overload a roof once it reaches about 12 off depth.

Last winter we had snow on the ground that was up to our hips. The weight of snow depends on how much water it contains. How much snow a roof can hold depends on the type of snow roofline and material among other considerations. Unfortunately that means a roof can collapse with as little as 18 inches of snow.

Most roof designs can handle snow loads of 20 40 lbs per square foot. The chart below courtesy of paul schimnowski p e gives some examples of snow loads. According to the national research council of canada a roof should be able to withstand pressure of at least 21 pounds per square foot psf this number can fluctuate based on regional building regulations but any well built roof should be able to sustain this much weight before it gets too stressed. This mainly occurs when the snow is concentrated in one area of the roof.

Remove excess snow and ice. Wet snow weighs considerably more than dry or fluffy snow because as you can probably guess water weighs more than air. Older homes however can only handle about 45 pounds per square foot. Of snow equals about 1 to 1 1 2 psf.

How much snow can my roof hold. You have probably heard of or seen the difference between wet snow and fluffy snow. The drifts on the roof were 5 feet deep. Most residential roofs can support snow loads of up to 20 pounds per square foot.

If that sounds a little involved the national research council of canada estimates that 1 in. Light fluffy snow weighs less than heavy dense flakes do and packed snow weighs more than freshly fallen snow. That means clearing amounts above 20 pounds per square foot. One of the major determining factors for how much snow is too much for your roof is how heavy the snow fall is.

These questions aren t quite so easy to answer because there are several variables. How to safely get the snow off your roof. For the twin cities metro area the roof snow load equals 35 pounds per square foot or 7 x 50. Melting down a cubic foot of snow tells you how much water it holds and consequently how much the snow weighs.