Ridge Board

[Bobby]

I have a 10 X 15' pavilion with a 4 12 pitch. How big must the ridge board. Is two 2 X 12's 15 ft long sufficient?

[tom]

You can use 1x for the ridge, your rafters should be opposite each other. It would seem you can get away with 2x6 for rafters going 16" O.C. You may want a 2 x 8 for ridge for appearance reasons only, if the rafters/ridge will be exposed. Otherwise I wouldn't go over 2 x 6 for the ridge.

Why 2x12, and why 2 of them?

[Colbyt]

If you need a structural ridge because there are no cross-ties, only a structural engineer can answer that question for you.

In any other case a single 2x stock that fully supports ridge cut of the rafters is fine.

[Nonny]

I'm probably way out of date, but when we were framing houses, a

2X10 made a swell ridge beam and if there were joists parallel to the rafters, there was no call for collars. Think of the downward force on the ridge beam: the force would be supported at each pair of back-to-back rafters perfectly and if they were not back-to-back exactly, the 2X thickness would still probably be fine. The downward force would want to spread or flatten the rafters, but that would be contained by the joists, or collars if there were no joists (like a cathedral ceiling).