OK, I know I’m probably overdoing this, but I’m about to install collar ties in the roof of my addition, and I want to through-bolt them to the rafters, in addition to nailing.
I expect to use carriage bolts, with lock washers & nuts, though the idea of lags has been raised.
Two questions: Is this dramatic overkill, and what diameter bolt would I use? 5/16″?
thanks,
-TJ
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Replies
I do it on heavier rafters (like on some types of timber framing) and I have done it on 2 X framing when the rafter span is fairly long. I usually use 3/8" or 1/2" through bolts (carriage bolts are fine, although if you really want to get anal, you can use split rings, shear plates and malleable washers).
Drill your holes same diameter as the bolt for a snug fit.
Don't use lags.
lag bolts or lag screws?
TDo not try this at home!
I am a trained professional!
Technicallly, most engineered solutions that I've seen where collar ties are not nailed to top plates CALL FOR BOLTS. They are specified as to size, number, and drill placement pattern. I've never seen less than 1/2" speced but that might just be the preference of my engineer. Too big and you are making the wood poor like swiss cheese. Too small and you have no shear stregnth or displacement value. Too many and, again, you have brutalized the wood. An engineer figures the load and stresses that are being conteracted by the collar tie and designs a connection to resist those forces. Bolts are definitely not overkill. 5/16" souinds lightweight but mavbe it's just a shed or you are planning five of them for each connection....
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"......where collar ties are not nailed to top plates......."
If the collar ties are on the top plates, they're ceiling joists, aren't they? Or did I miss something (Again). Friends help you move. Real friends help you move bodies.
I was beginning to think I was the only one. For any cut roof with ceiling joists within 2' vertical distance of the top plates , collar ties in the upper third nailed with a minimum of 4 16d c.c. at each connection has been the norm. I dont see the need to bolt them.
Edited 11/3/2002 4:35:12 PM ET by benny
As I was using the definition (I'm not alone because in a couple hours of research yesterday, I found that most sites and builders discussing it had the same misunderstanding as myself. Even a couple engineered solutiuons with the piece of lumber in the lower third distance were called collar ties and bolted in) a ceiling joist or a collar tie - properly called a rafter tie - do the same thing. They keep the walls from spreading. So it the primary purpose is to frame the ceiling, you can call them ceiling joists while they function as rafter ties.
In a truss, the name is different - bottom chord - but they are performing the same dual function. .
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