Ground Snow Load Vs Roof Snow Load

When discussing snow load with anyone it is crucial to have a clear understanding as to if the load is a ground or flat roof snow load.

Ground snow load vs roof snow load.

Asce 7 drift height calculation. Length of roof upwind of the snow drift. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. 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.

Length of high roof lu. 1 0 exposure factor ce. Ground snow load pg. 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.

A predictable load situation that is derived from snowfall records over the years in a particular region photo 2. 1 0 importance factor i. Figure 7 1 pages 84 85 and table 7 1 page 92. Weight of permanent.

If you live in the us our snow load calculator compares the total weight on your roof with the permissible load calculated according to the standards issued by the american society of civil engineers regarding the minimum design loads for buildings and other structures asce7 16. The ground snow load is pretty much what it sounds like. 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.

Snow loads can be presented in two different ways. Roof snow load and the applicable snow. 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. These figures are established by the local jurisdiction in my case the state of massachusetts which lists ground snow loads for each town in the state.

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. Ground snow load or roof snow load snow load. 49 42 35 28 24 5 21 17 5 assumed value thermal factor ct. The flat roof snow load is calculated using formula 7 3 1.

In our case let s assume that our structure has a flat roof roof slope 5. From eave to ridge w. Horizontal distance from eave to ridge. If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow.

Length of roof downwind of the snow drift. 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. Length of low roof ll. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.

Even when the specification is clear regarding ground snow vs.