Roof Live Load Reduction Formula

L r l o r 1 r 2.

Roof live load reduction formula.

I am looking at irc2009 don t have irc2006. The live load on a roof is the weight of any temporary objects on the roof. R2 is a reduction factor for roof slope above 4 12. Snow load thickness density.

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. 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. You can also find the load per square meter or square foot of roofing by opening the advanced mode. Once you know these values our snow load calculator automatically finds the total weight of snow on your roof.

Live load reduction is a reduction in live load that contributes to the actions on a member. If you want to calculate these values by hand use the following formulas. 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 equation in the ibc is lr lor1r2.

R1 is for tributary area above 200 sq. Roof live load may be reduced by the following equation. I live in a municipality that does not allow any roof live load reduction. The reduction formula has two reduction terms.

Also table r301 7 is for allowable deflection of structural members. Roof live load reduction. Snow load is different than roof live load. However in my practice i typically use the horizontal run of the roof for both types of load.

The op s question was with regards to live load and you are referring to roof live load. No where it talks about any reduction is live load unless i am missing something. If the roof design load is 20psf and you are considering the compression in a web member that is located near the mid span than i would not use live load reduction for the compression in that member. To do this i use conservative too heavy dead loads and full snow loads regardless of pitch.

The building codes allow for a roof live load reduction for tributary area and roof slope. The commentary in asce 7 05 c4 about roof live load reductions explains the anticipated difference in use of roof areas vs. Where l r shall not be less than 12 psf and not more than 20 psf. Where d is floor dead load.

T 1x 300 300 sq ft 400 no live load reduction permitted. I ignore the slope factor altogether for snow load reduction which adds another measure of conservatism.