Live Load Wood Lattice Roof

Ground snow load might seem somewhat confusing until you read the basic premise that is identified in irc section r301 6 which states.

Live load wood lattice roof.

Since it is possible to use the attic for storage the live load of the attic floor is set at 20 psf according to code. If you had a 40 ft tall open lattice structure i e. 0 9d 1 0w a load factor of 1 6 when adding to load 7. For any particular load the allowable span of patio cover joists and beams depends on wood species and board size.

The roof shall be designed for the live load indicated in table r301 6 or the snow load indicated. For any species the allowable span generally increases as the joist or beam increases in size. Minimum design loads for buildings and other structures location uniform load psf. Unlike the trussed roof live load and dead load of the rafters and ceiling joists must be accounted for as separate systems.

Minimum uniformly distributed live loads adapted from sei asce 7 10. 1 2d 1 0e l 0 2s when h loads are present they shall have 6. 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. As a result the live load dead load and distribution of forces are different.

This issue of live load vs. What happens if you put 20 psf or 300 on the joists only not the purlins. When you refer to a beam s allowable span what you re really describing is the allowable spacing between posts. In the end i think this all boils down to good rationale ca notes and your local building code.