Roof Snow Load From Ground Snow Load

The flat roof snow load is calculated using formula 7 3 1.

Roof snow load from ground snow load.

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. Or the 25 psf snow load could be entered as a roof snow load with the unbalanced snow loading option turned off. 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. 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 snow load tab defines design related information regarding the building s or shape s roof snow loads. Snow load thickness density the result snow load or the pressure exerted by the snow has the units of kn m or lbs ft. The equation for converting ground snow load pg to roof snow load pf is asce 7 05 equation 7 1. 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.

Snow load is not the same as live load and requires a separate input to design the structure correctly. If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow. Snow weight length width cos pitch snow load the weight of snowis measured in kgor lbs. It also includes the importance factor seen in other load types which converts the data.

The basis for the snow load computation in asce 7 05 is the ground snow load. This is the load induced by the weight of snow on the structure and may be expressed as ground snow and or specified min. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.