My understanding thus far is a Board is simply a nailer for the rafters, and the Beam post's down through the wall system and is designed to help carry the wieght of the roof.
Right so far?
so when is a ridge beam needed vs just a board?
Wouldn't most roofs benifit from having the beam to help prevent the exterior walls from spreading under the load?
Other than a roof that rests on wall that is bustrested from thrusting outward in some manner I'm trying to undersand why ridge beams aren't used ?