Roof Rafter Deflection Limit

Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.

Roof rafter deflection limit.

The l is the length in inches of the clear span of the joists or rafters that make up the ceiling. Dead load weight of structure and fixed loads 15 lbs ft2. 3 stud construction standard utility. If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6.

The maximum allowable deflection of a ceiling is expressed as a fraction in the format l x. So these are the limits set by the code. Live load is weight of furniture wind snow and more. L 240 for unplastered floor construction.

For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360. Spacing in 12 16 19 2 24. For continuous aluminum structural members supporting edge of glass the total load deflection shall not exceed l 175 for each glass lite or l 60 for the entire length of the member whichever is more stringent. The code section on working load deflection states.

Clear span in inches l over a given number. And l 180 for unplastered roof construction. 2 are indicated below. Default deflection criteria for the following members.

This is the easiest way to determine allowable dead loads live loads and deflection limits. This publication has a much more extensive. Ridge beam double span. See the table below.

L 720 l 600 l 480 l 360 l 240 l 180. A floor joist appropriately selected to span 10 feet with an l 360 limit will deflect no more than 120 360 1 3 inches under maximum design loads. Maximum deflection limits are set by building codes. Floor joists ceiling joists rafters snow load rafters roof live load deflection limit.

You can also use af pa s span tables for joists and rafters. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. Ridge beam single span. 1 psf lbf ft2 47 88 n m2.

The deflection of floor and roof assemblies shall not be greater than l 360 for plastered construction. Roof beam single span. 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. Supporting roof and floor.

Roof beam double span.