Roof Live Load Reduction Formula

To do this i use conservative too heavy dead loads and full snow loads regardless of pitch.

Roof live load reduction formula.

Live load reduction is a reduction in live load that contributes to the actions on a member. Snow load thickness density. However in my practice i typically use the horizontal run of the roof for both types of load. The live load on a roof is the weight of any temporary objects on the roof.

If you want to calculate these values by hand use the following formulas. 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. Also table r301 7 is for allowable deflection of structural members. The reduction formula has two reduction terms.

L r l o r 1 r 2. I ignore the slope factor altogether for snow load reduction which adds another measure of conservatism. R1 is for tributary area above 200 sq. 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.

Where l r shall not be less than 12 psf and not more than 20 psf. T 1x 300 300 sq ft 400 no live load reduction permitted. I am looking at irc2009 don t have irc2006. The op s question was with regards to live load and you are referring to roof live load.

They are not one and the same. One for the tributary area supported by the structural element r 1 and the other for the slope of the roof surface r 2. R2 is a reduction factor for roof slope above 4 12. I live in a municipality that does not allow any roof live load reduction.

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. Where d is floor dead load. The commentary in asce 7 05 c4 about roof live load reductions explains the anticipated difference in use of roof areas vs. The equation in the ibc is lr lor1r2.

You can also find the load per square meter or square foot of roofing by opening the advanced mode. Roof live load may be reduced by the following equation. Where snow isn t a problem the live load can come from people working on the roof and any equipment they. No where it talks about any reduction is live load unless i am missing something.

Roof live load reduction. Snow load is different than roof live load.