Roof Snowload Vs Ground Snow Load

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Roof snowload vs ground snow load.

Enter the information requested like the rise and the roof ground snow load for your city exposure roof type etc. 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. The flat roof snow load is calculated using formula 7 3 1. Figure 1608 2 for any location in the state of michigan.

The calculator will tell you the pounds per square foot of snow. It was released in 1986 by the department of civil engineering at the university of idaho. The determination of the drift load that is required for unbalanced snow load cases requires the use of the ground snow load pg not the roof snow load. 70 60 50 40 35 30 25 x0 7 x0 7 x0 7 x0 7 x0 7 x0 7 x0 7 roof snow load.

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. 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. 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. 49 42 35 28 24 5 21 17 5 assumed value thermal factor ct.

You can click on the map below to find the design ground snow load for that location. 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. Snow loads can be presented in two different ways. 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.

In our case let s assume that our structure has a flat roof roof slope 5. 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. Use our michigan ground snow loads map to easily determine the ground snow load 2009 michigan building code. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.

Ground snow load or roof snow load snow load. Then follow the instructions. Weight of permanent. 1 0 importance factor i.

Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. 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. Ground and roof snow loads for idaho 1986 this report was compiled by ron sack and a. It s quite easy to find one online.