Snow Load Profile On Roof

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.

Snow load profile on roof.

Snow loads are influenced by elevation general weather and moisture patterns slope direction exposure roof or trail bridge configuration and wind direction and severity. It also informs you whether you should immediately remove some of the snow or you can wait a little bit longer. 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. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.

Or the 25 psf snow load could be entered as a roof snow load with the unbalanced snow loading option turned off. As snow melts and refreezes a layer of ice may sit under a foot of fresh snow to make the snow load weigh around 10 pounds per square foot. Make sure to not wait for too long though. Loads increase on roofs as fresh snow becomes packed and new snow falls.

Light fluffy snow may only weigh about seven pounds per cubic foot. The weight of snow varies greatly. 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. You can shovel out a cubic foot of snow from the roof place it in a container and quickly weight it on a scale.

If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. Your roof may be supporting 60 pounds per square foot of roof when snow and ice accumulate on the surface. 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. The flat roof snow load is calculated using formula 7 3 1.

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. Then measure the depth of snow on the roof and multiply it by the weight of a cubic foot of that snow. 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.