I ignore the slope factor altogether for snow load reduction which adds another measure of conservatism.
Roof live load reduction formula.
One for the tributary area supported by the structural element r 1 and the other for the slope of the roof surface r 2.
1607 12 1 distribution of roof loads.
L r l o r 1 r 2.
Loads should be determined in accordance with this chapter.
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.
The commentary in asce 7 05 c4 about roof live load reductions explains the anticipated difference in use of roof areas vs.
Roof live load may be reduced by the following equation.
R 1 1 for a t less than or equal to 200 psf r 1 1 2 0 001 a t for between 200 psf and 600 psf.
The live load on a roof is the weight of any temporary objects on the roof.
The live loads for members supporting two or more floors are permitted to be reduced by a maximum of 20 percent but the live load shall not be less than l as calculated in section 1607 10 1.
However in my practice i typically use the horizontal run of the roof for both types of load.
To do this i use conservative too heavy dead loads and full snow loads regardless of pitch.
The reduction formula has two reduction terms.
The flat roof snow load is calculated using formula 7 3 1.
Where l r shall not be less than 12 psf and not more than 20 psf.
Where snow isn t a problem the live load can come from people working on the roof and any equipment they.
However if the attic is intended for storage the attic live load or some portion should also be considered for the design of.
Where uniform roof live loads are reduced to less than 20 psf 0 96 kn m2 in accordance with section 1607 12 2 1 and are applied to the design of structural members arranged so as to create continulty the reduced roof live load shall be applied to adjacent spans or to alternate spans whichever produces.
In our case let s assume that our structure has a flat roof roof slope 5.
For uses other than storage where approved additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such.
Roof live load reduction.
