Commentary in asce 7 05 c4 about roof live load reductions explains the anticipated difference in use of roof areas vs.
Roof live load reductino.
1603 1 2 roof live load the roof live load used in the design shall be indicated for roof areas section 1607 13.
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.
Use of live load reduction in accordance with section 1607 11 shall be indicated for each type of live load used in the design.
L r l o r 1 r 2.
Where l r shall not be less than 12 psf and not more than 20 psf.
Roof live load may be reduced by the following equation.
Likewise roof live loads in the hong kong building regulation can be reduced as a function of the slope.
1603 1 3 roof snow load data.
Hence the magnitude of the roof live loads should be specified as for a flat roof and the program allowed to make the reduction based on the slope of the framing.
The nature of roof live load is different from that of floor live load so the approach to reducing roof live load is different from that used for floor the requirement is presented in asce 7 05 4 9.