The ibc becomes the governing code for the truss design and associated load paths if the structure falls outside of these limits see irc r301 1 3.
Irc roof live load.
Except for uni form live loads at roofs all other minimum uniformly distrib uted live loads lo in table 1607 1 are permitted to be reduced in accordance with section 1607 10 1 or 1607 10 2.
Maximum ground snow load of 70 psf 3352 pa with roof snow load computed as 0 7p g.
Live loads roof live loads snow loads rain loads wind loads and earthquake loads are all examples of variable loads.
2018 irc chapter 3 2020 colorado code consulting llc 2 r301 1 application buildings and structures and all parts thereof shall be constructed to safely support all loads including dead loads live loads roof loads flood loads snow loads wind loads and seismic loads as prescribed by this code.
The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.
1607 10 1 basic uniform live load reduction.
Uniform live loads at roofs are permitted to be reduced in accordance with section 1607 12 2.
2020 colorado code consulting llc 5.
Live loads for assembly spaces other than those described in this table shall be determined from the occupant load requirements as established by section 1004 of this code using the formula 1 000 net floor area per occupant but shall not be less than 50 psf nor more than 100 psf.
Further in most areas of the united states design winds are produced by either hurricanes or thunderstorms.
Note the roof is designed for the roof live load not more than 20 psf or the snow load whichever is greater.
The bottom line is that the irc requires you to design the roof structure to the greater roof load and in my region that s the ground snow load.
In my region on cape cod we have a ground snow load design of 25 psf which is a greater design load than the live load 12 psf to 20 psf over an entire roof system.
The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process.
Live loads irc table r301 5 minimum uniformly distributed live loads 2018 irc essentials use live load psf uninhabitable attics without storage 10 uninhabitable attics with limited storage 20 habitable attics and attics served with fixed stairs 30 balconies exterior and decks 40 fire escapes 40 rooms other than sleeping rooms 40 sleeping rooms 30.
