Snow Load Profile On Roof

If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow.

Snow load profile on roof.

Your roof may be supporting 60 pounds per square foot of roof when snow and ice accumulate on the surface. Loads increase on roofs as fresh snow becomes packed and new snow falls. A great deal of confusion currently exists among engineers architects recreation specialists and maintenance personnel concerning the proper snow loading to use for the design and maintenance of trail bridges building roofs and other structures in mountainous high snow load areas. If unbalanced snow loading isn t required or specified the truss designer may enter the 25 psf snow load as a top chord live load tcll set the load duration factor to 1 15 for snow and turn snow loading off completely.

The flat roof snow load is calculated using formula 7 3 1. The weight of snow varies greatly. Basing on the roof parameters you specified in the first section our snow load calculator displays the maximum allowable snow cover thickness and snow weight. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.

Snow loads are influenced by elevation general weather and moisture patterns slope direction exposure roof or trail bridge configuration and wind direction and severity. Or the 25 psf snow load could be entered as a roof snow load with the unbalanced snow loading option turned off. Light fluffy snow may only weigh about seven pounds per cubic foot. Once the ground snow load at the building site is determined it must then be converted to roof snow loads according to asce 7 with appropriate treatment of exposure to wind thermal properties of the roof roof slope unbalanced snow loads drifting and risk exposure.

In our case let s assume that our structure has a flat roof roof slope 5. Table r301 2 1 climatic and geographic design criteria ground snow load. Roof snow and wind loads are based on the historical records for a given location however the local building authority should always be consulted to determine the correct roof snow and wind load to use for a given site and application. Thus snow weighing 10 pounds per cubic foot and at a depth of 18 inches on a roof is exerting 15 pounds of pressure per square foot.

Then measure the depth of snow on the roof and multiply it by the weight of a cubic foot of that snow. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load. 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. Make sure to not wait for too long though.

You can shovel out a cubic foot of snow from the roof place it in a container and quickly weight it on a scale.