Rafter/collar ties as cathedral ceiling & rafter thrust
Does anybody know what the new MA Residential code says about this? The rafter span charts all have a multiplier table below them for when this condition is being built. My local inspector says that you now have a truss, which a builder can not engineer.
I have seen cathedral/raised ceilings done with rafter teis many, many times.
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I don't know about the Massachusetts code, so I hope a Massachusetts builder or engineer will be able to answer your question.
In the meantime, I thought I'd point out that there's been a change to the 2006 IRC requirements concerning the location of rafter ties.
The comments under your first link are helpful in explaining the picture. I believe there is a typo, because I can't imagine not allowing collar ties in the upper two thirds of the span.
The picture describes the long-standing prescriptive code that says it's alright to place a rafter tie at the bottom third of the rafter span. I don't know what the current MA code says; I used to have a builder's license there but it's long expired now. I do know that it's easy to overstress a rafter when you have large loads or spans and a raised rafter tie. It usually shows up as kneewalls out of plumb, when the problem is a rafter with a big kink in it at the rafter tie.