Roof Live Load Reduction Formula

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.

Roof live load reduction formula.

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. Loads should be determined in accordance with this chapter. Where l r shall not be less than 12 psf and not more than 20 psf. However in my practice i typically use the horizontal run of the roof for both types of load.

I ignore the slope factor altogether for snow load reduction which adds another measure of conservatism. Roof live load may be reduced by the following equation. In our case let s assume that our structure has a flat roof roof slope 5. Where snow isn t a problem the live load can come from people working on the roof and any equipment they.

Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10. To do this i use conservative too heavy dead loads and full snow loads regardless of pitch. L r l o r 1 r 2. The live load on a roof is the weight of any temporary objects on the roof.

The commentary in asce 7 05 c4 about roof live load reductions explains the anticipated difference in use of roof areas vs. The snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load. The reduction formula has two reduction terms. 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.

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. One for the tributary area supported by the structural element r 1 and the other for the slope of the roof surface r 2. Roof live load reduction. 1607 12 1 distribution of roof loads.

However if the attic is intended for storage the attic live load or some portion should also be considered for the design of. 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.