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 follow ing table.
Live load for roof pitch tables.
However if the attic is intended for storage the attic live load or some portion should also be considered for the design of.
For roof live loads of 12 psf or 16 psf.
This information is found in the code book.
Ground snow load might seem somewhat confusing until you read the basic premise that is identified in irc section r301 6 which states.
1607 12 1 distribution of roof loads.
Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run.
2attic loads may be included in the floor live load but a 10 psf attic load is typically used only to size ceiling joists adequately for access purposes.
The roof must be able to support the sum of its dead load and any anticipated live load so the roof has to be designed with a load limit that takes into account both of these loads.
Loads should be determined in accordance with this chapter.
This issue of live load vs.
Span configuration and load conditions.
The roof shall be designed for the live load indicated in table r301 6 or the snow load indicated.
Compression perpendicular to the grain.
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.
The fact that snow loads only act part of the year has been used to create the rafter tables.
If your code book says your snow load is 40 psf then you use the 40 psf live load rafter table.
The snow load is treated as a live load when you use af pa s tables.
The shapes and spans shown here represent only a fraction of the millions of designs produced by alpine engineers.
Victor staley a building official in the town of brewster mass responds.
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.
Roof live loads largest roof loads typically caused by repair and maintenance pitch rise span lr 20 r1r2 12 lr 20 lr horizontal projection roof live load 16 r 1 r 2 live load reduction factors r 1 accounts for size of tributary area of roof column a t r 2 effect of the roof rise.
Roof loads rafter spans are tabulated for the most common roof loads.
The loads are based on adjusted roof snow loads from the governing building code.
