Snow Depth On A Roof

Significantly more than heavy wet snow per inch depth.

Snow depth on a roof.

People have been killed by snow avalanches sliding off roofs during big snow winters. Whether a roof can sustain a load without damage or collapse depends mainly on the depth and density of the snow as well as the depth and spacing of the rafters and trusses. Snow in the western part of the united states is typically lighter and less. How much snow a roof can hold depends on the type of snow roofline and material among other considerations.

In a 6 inch snowfall an inch of snow has a design density of 1 25 psf per inch and a real world density closer to 1 psf per inch. To figure out the load on your roof take the depth of snow in feet and multiply it by the weight of a cubic foot of snow. 2 2 3 regional and local considerations. In 48 inch deep snow the design density is more than 2 4 psf per inch while the actual density is probably 1 5 psf per inch or more.

On roof slopes between 4 12 and 6 12 rough textured roofing materials work best. In the high snow areas an additional problem occurs in that after several snow falls with periods of partial melting and or heat loss through the roof the layer against the roof may. If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. They hold the snow in place and keep it from accumulating and then sliding off in large slabs that can be dangerous.

In part this is why it is important to prevent ice buildup on a roof structure. Dense than snow on the east coast which tends to be wetter and denser. Overestimation of snow loads can unnecessarily increase the cost of construction. The minimum roof pitch for shedding snow is around 30 or a 6 12 or 7 12 slope although this is not a definite as the material of your roof the direction of the snow and wind are some factors that can affect whether or not snow will slide as roofs of as little as 10 have been reported to shed snow.

Intuitively this is the number of inches of snow on your roof in the place where the cover is the thickest. Note that the density of snow increases as depth increases. If you re not sure which type to choose always settle for the wetter types as they are denser. These questions aren t quite so easy to answer because there are several variables.

The density of snow depends on whether it s fresh wet wind packed or mixed with ice. Snow design loads are based on figures published by the asce. Fresh fallen snow is often very lose compacted to snow even an hour old. Estimates for the actual weight of snow range from 1 to 1 5 psf per inch of depth.