The live load on a roof is the weight of any temporary objects on the roof.
Roof live load reduction formula.
The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.
However in my practice i typically use the horizontal run of the roof for both types of load.
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 reduction formula has two reduction terms.
1607 12 1 distribution of roof loads.
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.
One for the tributary area supported by the structural element r 1 and the other for the slope of the roof surface r 2.
The commentary in asce 7 05 c4 about roof live load reductions explains the anticipated difference in use of roof areas vs.
Where snow isn t a problem the live load can come from people working on the roof and any equipment they.
Roof live load may be reduced by the following equation.
However if the attic is intended for storage the attic live load or some portion should also be considered for the design of.
Where d is floor dead load.
Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.
L r l o r 1 r 2.
Loads should be determined in accordance with this chapter.
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.
2attic loads may be included in the floor live load but a 10 psf attic load is typically used only to size ceiling joists adequately for access purposes.
To do this i use conservative too heavy dead loads and full snow loads regardless of pitch.
Where l r shall not be less than 12 psf and not more than 20 psf.
I ignore the slope factor altogether for snow load reduction which adds another measure of conservatism.
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.
