Ceadr Beam Substitute

[mikeo56]

I have to replace a 4" X 8" cedar beam with a 12' span supporting a flat roof asphalt roll covered roof of 2" X 8" joists 16" on center spanning 12' also.
Can I use two 2" X 8" and one 1" X 8" glued together with polyurethane caulk as a substitute?
Thanks, Mike.

 

[SlideRuleEra]

The pair of 2x8s and 1x8 would have similar properties (moment of inertia and section modulus) to a 4x8 and should make a suitable substitute (assuming the 4x8 is adequate for the load). Suggest gluing the the 3 members together with plenty of construction adhesive; the 1x8 in the middle. Also use lots of 3 1/2 inch deck screws(half driven from each side)to hold the "sandwitch" together. Could consider 16d common nails instead of screws but they may tend to split the lumber.