Snow Depth On A Roof

Intuitively this is the number of inches of snow on your roof in the place where the cover is the thickest.

Snow depth on a roof.

Estimates for the actual weight of snow range from 1 to 1 5 psf per inch of depth. Snow loads are influenced by elevation general weather and moisture patterns slope direction exposure roof or trail bridge configuration and wind direction and severity. Fresh fallen snow is often very lose compacted to snow even an hour old. Snow design loads are based on figures published by the asce.

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. Note that the density of snow increases as depth increases. 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.

As a practical side low snow weights than 40 psf are on wet compacted snow. They hold the snow in place and keep it from accumulating and then sliding off in large slabs that can be dangerous. If the snow weighs 10 pounds per cubic foot and there are 1 5 feet on the roof each square foot of the roof is getting 15 pounds of pressure. Significantly more than heavy wet snow per inch depth.

If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. Snow in the western part of the united states is typically lighter and less. 2 2 3 regional and local considerations. The density of snow depends on whether it s fresh wet wind packed or mixed with ice.

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. 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. 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.

These questions aren t quite so easy to answer because there are several variables. In part this is why it is important to prevent ice buildup on a roof structure. How much snow a roof can hold depends on the type of snow roofline and material among other considerations. Dense than snow on the east coast which tends to be wetter and denser.