Ground Snow Load Vs Roof Snow Load

Horizontal distance from eave to ridge.

Ground snow load vs roof snow load. The bottom line is that the irc requires you to design the roof structure to the greater roof load and in my region that s the ground snow load. Ground snow load or roof snow load snow load. In my region on cape cod we have a ground snow load design of 25 psf which is a greater design load than the live load 12 psf to 20 psf over an entire roof system. In our case let s assume that our structure has a flat roof roof slope 5.

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. 1 0 exposure factor ce. 1 0 importance factor i. 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.

Figure 7 1 pages 84 85 and table 7 1 page 92. 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. If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow.

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. From eave to ridge w. Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. P s c s p f the thermal factor c t from table e 3 determines if a roof is cold or warm slippery surface values shall be used only where the roof s surface is unobstructed and sufficient space is.

Ground snow load pg. 70 60 50 40 35 30 25 x0 7 x0 7 x0 7 x0 7 x0 7 x0 7 x0 7 roof snow load. 49 42 35 28 24 5 21 17 5 assumed value thermal factor ct. The sloped roof snow load p s shall be obtained by multiplying the flat roof snow load p f by the roof slope factor c s.

Length of low roof ll. 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. Length of roof upwind of the snow drift. 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.

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. Weight of permanent materials like trusses sheathing and roofing material. Length of roof downwind of the snow drift. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.

Length of high roof lu.