Roof Snow Load From Ground Snow Load

Snow load thickness density the result snow load or the pressure exerted by the snow has the units of kn m or lbs ft.

Roof snow load from ground snow load. The snow load tab defines design related information regarding the building s or shape s roof snow loads. 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. This equation includes factors that take into account exposure and building heat loss. The flat roof snow load is calculated using formula 7 3 1.

The value used for the ground snow load should represent the snow load that has a 50 year mean recurrence interval or in other words a 2 probability of being exceeded in any given year. The equation for converting ground snow load pg to roof snow load pf is asce 7 05 equation 7 1. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. Snow load is not the same as live load and requires a separate input to design the structure correctly.

Or the 25 psf snow load could be entered as a roof snow load with the unbalanced snow loading option turned off. If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. 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. Snow weight length width cos pitch snow load the weight of snowis measured in kgor lbs.

In our case let s assume that our structure has a flat roof roof slope 5. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load. 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.