I’ve decided to add rafter ties to my home. Im thinking of using cable.
1952 house. This house was built with NO rafter ties and very few collar ties. The joists run from gable to gable. Ridge is not sagging, walls are not bowing. However, I have added hurricane straps and gable supports. Soon, i will be replacing the roof and while at it, screwing the roof planking to the rafters. Im making my home as hurricane resistant as possible.
Therefor I have also decided to add cable rafter ties and 2×6 collar ties.
I need advice.
pa
Replies
No rafter ties? Are you sure? Could there be inside walls that run eve to eve with top plates serving as ties? If not, how much span are we talking about?
Anyway, if you do need them because nothing exists, why not simply use wood? Although I've no experience using cable, a problem with that approach is deciding on the tension as you install it. Too much could pull the walls together and too little does nothing.
Why?
You've said it yourself: 1952 house with no sagging ridge and no bowed walls.
Why fix something that aint broke (for over a half century)? Does your local meteroligist know something we don't?.
cable is easier and stronger and you can tension it, so there will be NO sagging. Wood rafter ties would need the roof to settle a little before there is tension.
It sounds like you've made a decision.
"stronger" is
"stronger" is relative.
Your forgetting that cable cannot act (at all) in compression. Wood members can. If you're making your house "as hurrican proof" as possible, then you're forgetting that hurricane force winds can produce tremendous uplift load on leeward side of roofs and (in some extreme cases) put collar ties into compression.
Rafter ties?
I guess I am confused....Are the rafter ties we are talking about taking place in an attic or a room with a catherdral type celing?
If it's in an attic, why would you consider using anything but lumber? As stated already, it works wonderfully in compression and tension, it's easy to make connections, it's much cheaper than cable. I could also see the scenario where you tighten one cable and it loosens the ones each side of it. Cable also stretches - It would requrie some monitoring over time to make sure it's not sagging. How do you verify the load capacity of the able connections? How do you distribute the load from the cables to the rafters? Etc, etc...