To do this i use conservative too heavy dead loads and full snow loads regardless of pitch.
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.
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.
Snow load is different than roof live load.
The op s question was with regards to live load and you are referring to roof live load.
The reduction formula has two reduction terms.
L r l o r 1 r 2.
They are not one and the same.
Snow load thickness density.
Where l r shall not be less than 12 psf and not more than 20 psf.
The building codes allow for a roof live load reduction for tributary area and roof slope.
Once you know these values our snow load calculator automatically finds the total weight of snow on your roof.
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.
R1 is for tributary area above 200 sq.
If you want to calculate these values by hand use the following formulas.
I live in a municipality that does not allow any roof live load reduction.
R2 is a reduction factor for roof slope above 4 12.
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.
However in my practice i typically use the horizontal run of the roof for both types of load.
I am looking at irc2009 don t have irc2006.
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.
You can also find the load per square meter or square foot of roofing by opening the advanced mode.
Where snow isn t a problem the live load can come from people working on the roof and any equipment they.
Where d is floor dead 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.
No where it talks about any reduction is live load unless i am missing something.
The equation in the ibc is lr lor1r2.
Live load reduction is a reduction in live load that contributes to the actions on a member.
Also table r301 7 is for allowable deflection of structural members.
