Roof Live Load Less Than 20

On a roof with a slope greater than 4 to 12 the live load limit is typically adjusted downward from 20 psf to 15 psf to allow for the relatively greater dead load on the steeper roof.

Roof live load less than 20.

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. 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. Where uniform roof live loads are reduced to less than 20 psf 0 96 kn m 2 in accordance with section 1607 13 2 1 and are applied to the design of structural members arranged so as to create continuity the reduced roof live load shall be applied to adjacent spans or to alternate spans whichever produces the most unfavorable load effect see section 1607 13 2 for reductions in minimum roof.

Where uniform roof live loads are reduced to less than 20 psf 0 96 kn m 2 in accordance with section 1607 12 2 1 and are applied to the design of structural members arranged so as to create continuity the reduced roof live load shall be applied to adjacent spans or to alternate spans whichever produces the most unfavorable load effect. 1607 12 1 distribution of roof loads. The loads are based on adjusted roof snow loads from the governing building code. L r l o r 1 r 2.

For roof live loads less than 20 pounds per square foot psf rafter spans and required e values tabulated for 20 psf shall be permitted to be adjusted in accordance with the fol lowing table. In other words on a steep roof less material would be stacked in a concentrated area at one time to avoid having it slide off. For roof live loads of 12 psf or 16 psf. 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.

Many factors influence how a system responds to loading. Af pa s appendix a lists a variety of live and dead load combinations for floors ceilings and rafters. Roof live load of 20 psf or less see ibc 1607 and chapter 3 of this publication r rain load see ibc 1611 and chapter 3 of this publication s snow load see ibc 1608 chapter 7 of asce sei 7 and chapter 4 of this publication t cumulative effects of self straining forces and effects see asce sei 2 3 4 and 2 4 4 w load due to wind pressure see ibc. For example appendix a indicates that one type of clay tile roof system has a live load value of 20 psf and a dead load value of 15 psf.