I am looking for advice .I have to add collar ties to an old house that the rafters do not oppose each other .How can I make a connection across the building .On one side I can nail on the side of the rafter but one the other side? The rafters are all roughsawn and of variable thickness 2-2 and1/4 as the building is 110 years old.This limits the use of a lot of Simpson hardware.These will not become ceiling joists.Thanks for looking
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steel rods/cables with turnbuckles
You could run a beam down the middle, and tie off half-ties to that. ####wood I-beam or LVL, layed horizontally, would probably do the trick, or you could use dimension lumber. Sizing would depend mostly on the spacing between rafters. Would take a bit of invention to figure out how to fasten the half-ties to the beam, though, and you'd probably need to also add hangers from the ridge, to keep the beam from sagging.
Alternatively, you could fasten a nailer horizontally along one side, to receive the collar ties from the other side. You'd generally want it laying flat, similar to the beam down the middle, though.
happy?
The number of connections and the direction thay stress would make that one an engineers worst nightmare.I vote for steel cable and turnbuckle ties.
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Actually, the cables and turnbuckles are an engineering nightmare, in the general case. With out-of-plane forces you need to make sure you won't cause a rafter to displace sideways. Using a beam of some sort puts all the forces back in-plane.Of course, a lot depends on the specific geometry. If joists are spaced at 2 feet or closer then any approach will likely work. If they're spaced at 4 feet then it gets much more complicated.Similarly, we need to know the purpose of the "collar tie". If this is a required retrofit near the ridge, to hold the roof together in high wind, then the steel cable, strung at low tension, will probably do the job.If the ties are being placed mid-span on the rafters, and their intent is to support sagging rafters, obviously cables won't hack it.If the ties are being placed mid-span or lower to resist outward spread of the walls, the steady-state forces can be considerable and out-of-plane force must be considered as a problem.
If ignorance is bliss why aren't more people
happy?
The ties are going to be just above the ceiling rafters( but at 90*to them) to stop spreading the walls.I like the idea of a 2by 8 nailed across the rafters and a connection to that
PeteVa had my answer, until, that is, I started thinking about it.
To "do" rod or cable, you'd need some engineering to either make the attachment plates, or to locate a hole for a pin through the rafter.
Either meant getting an engineer involved, which may be the best answer in any event.
After all--who said to collar tie the 110 y/o building in the first place? Might be it just needs 7 or 8 of 13 layers of roof stripped off. (That, and only an engineer is likely to make the force diagram of non-oppsed rafters connected by a collar tie work out--it's bending my head, and I have enough headaches today <G-ouch->)