The flat roof snow load is calculated using formula 7 3 1.
Ground vs roof snow oad.
The roof shall be designed for the live load indicated in table r301 6 or the snow load indicated.
Length of roof downwind of the snow drift.
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.
Victor staley a building official in the town of brewster mass responds.
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.
The purpose of this web site is to provide ground snow load analysis information and data gathered from all 50 states.
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.
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 your roof is 1 000 square feet the total snow load is 15 000 pounds of snow.
The basis for the snow load computation in asce 7 05 is the ground snow load.
Pf is flat roof snow load if as a consumer your concern is snowfall and you want to upgrade the ability of your building to carry it this is the value to increase.
Roof snow load and the applicable snow.
Even when the specification is clear regarding ground snow vs.
Ground snow load pg.
Figure 7 1 pages 84 85 and table 7 1 page 92.
From eave to ridge w.
This issue of live load vs.
Horizontal distance from eave to ridge.
If the ground snow load isn t specified then a ground snow load needs to be assumed and the truss designer and the building designer may not be on the same page as it relates to this design assumption.
Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.
Length of low roof ll.
Length of high roof lu.
Purpose of this web site.
In our case let s assume that our structure has a flat roof roof slope 5.
Each state has a listing of building code and applicable guidelines for snow loads as well as details about where the snow load information may be found or purchased.
Length of roof upwind of the snow drift.
Asce 7 drift height calculation.
