No, I don't care what you say; I'm changing it from three to two!
Today, I looked at two houses with the same inherent construction problem, both attributable to contractor ignorance or amateur construction.
It's called failure to provide a structural ridge "beam" to support a cathedral ceiling (rafter-framed) roof.
In conventional rafter-framed (stick-framed) construction, the rafters span from birds-mouth cuts bearing on the exterior stud walls up to some board called a "ridge board"---just a board---not a beam!
If we remove the critical ceiling joist ties and expect the remaining rafters and non-structural ridge board not to move---we are idiots for not understanding why this doesn't work. In rafter construction, the peak ridge board is simply a convenient faceplate to mate opposing rafters at the ridge/peak from opposite walls during roof construction. The ridge board is not structural...just a convenient component of rafter-framed roof construction.
When we use this common, simple method of roof-frame construction, we must have complimentary ceiling joists connected to the opposing rafters at their base, at their birds-mouth cut bearing on the exterior stud walls, and these ceiling joists continue across the home to the opposite exterior wall and connect to the opposing rafters. The ceiling joists create a critical "structural tie" across the home and prevent the rafters from pushing down and out---spreading the supporting exterior walls.
If we remove the critical ceiling joist ties and expect the remaining rafters and non-structural ridge board not to move---we are idiots for not understanding why this doesn't work
So today, when I saw the consequence of this ignorance at two separate houses --with sagging ridge boards and outward-leaning exterior walls (the gable roofs looked like saddles!) I felt compelled to write this article and bring this important information to everyone's attention.
Moral to the story:
"Ask your contractor to explain the difference between a ridge board and ridge beam. If he says he doesn't understand your question or says there's no difference, tell them you just got an important text from God and must leave now!"
Or, take the four-foot level you used to read outward lean in your great room walls, and bop them across their heads!