![]() You -could- call or talk to your local building department and find out what the structural requirements are in your locale. Smallest live loading of 20 psf and dead load of 10 psf for the 'bounciest' roof rafters at L/180 deflection limit calls for pretty much 'good' 2x8's on 24" OC (or better).Īnd 3/8 roof sheathing no 24" OC rafters is going to be bouncy-bouncy-bouncy. Smallest live loading of 10 psf and 5 psf dead load (drywall ceiling, no storage!) and 'bouncy' at a deflection limit of L/240 for the ceiling joists calls out for minimum 2x10 with E=1.6 x 10^6 or better (Douglas Fir - Larch #2 or better meets this, but NOT Southern Doug-Fir!, Hem-Fir 2x10 would have to be graded "Select Structural" to meet the E value, Hem-Fir Northern 2x10 #1/#2 meets the E value, visually-graded #2 or better Southern Pine 2x10 meets the E value, etc, etc). ![]() 2圆's are really too small for that wide of a span. TABLE RAFTER SPANS FOR COMMON LUMBER SPECIES (Ground snow load 30 psf, ceiling not attached to rafters, LIA DEAD LOAD 10 pst SPECIES AND GRADE inches) 6 10 5- 3 7 5 5 5- 7 5 -2 7 10 1 6- 7 inches) 11 10 10- 2 12 5. Splitting the OC spacing from 24" OC down to 12" OC will not do enough. Sistering more 2圆 onto the existing 2圆's will not do enough. ![]() ![]() RAFTER SPANS FOR COMMON LUMBER SPECIES (Roof Live Load 20 pounds per square foot, Ceiling Not Attached to Rafters L/ 240) DEAD LOAD 10 pounds per square foot 2x4 2圆 2x8 2x10 2x12. Douglas fir maximum horizontal roof rafter span for Lumber Grade Selected Structural and No. DESIGN VALUES FOR JOISTS AND RAFTERS (a supplement to Span Tables for Joists and Rafters). 2圆 ceiling joists or roof rafters for a 26 ft wide structure are undersized pretty much no matter what you do, unless you have that center load-bearing wall down the middle of the garage. End bearing length shall be increased to 2 inches. ![]()
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