jgregg66
10-02-2004, 04:11 AM
I am trying to figure out the whole collar-tie thing. Oddly enough, there's not a whole lot of technical information regarding them that is being returned by google. And what I have found, is often conflicting info.
Some say they help in reducing outward thrust on the walls carying them, whereas others say that the floor/ceiling joists (if parallel to the rafters) take care of the thrust, and that collar ties are for keeping the ridge tight in areas prone to high wind, and are only required by code in southern states (where hurricanes are common).
However, nothing I have found has any elaboration on the relationship between roof pitch and placement of collar-ties. Very frustrating.
My curiosity relates to this: My house is a typical early-70's Bungalow, with the standard 12/12 roof. I am currently in the middle of gutting the upstairs in order to insulate it correctly, unlike the moron who built the house (but that's a whole other story!). Once I had all the sheetrock and insulation torn out, I decided I wanted to raise the ceiling (a.k.a. collar-ties) up about a foot, simply to make the bedrooms a little less claustrophobic. The current ceiling is a single 2x4 at about 7ft high, tying every rafter pair, spaced at apprx 24in. OC. I explained this all to a friend who became worried about the integrity of the structure, thrust, etc. So I started looking around, and now I am typing this. What also confuses me is that my garage roof, which is not quite as steep, only has collar-ties on the four middle rafter-pairs, all the way up butting against the rigde.
Can anyone shed some light on this for me? Or, is this privileged info to engineers only? ;)
Thanks in advance!
-John
Here's a rough drawing of what I want to do. I think the application referenced below is slightly different in that it sounds more like he wants to vault up through where ceiling joists would be. Whereas, my application is on the second floor upon which the rafters rest. My apologies for not stating that in my original post...
http://homepage.mac.com/jgregg/.Pictures/collar-tie.JPG
Some say they help in reducing outward thrust on the walls carying them, whereas others say that the floor/ceiling joists (if parallel to the rafters) take care of the thrust, and that collar ties are for keeping the ridge tight in areas prone to high wind, and are only required by code in southern states (where hurricanes are common).
However, nothing I have found has any elaboration on the relationship between roof pitch and placement of collar-ties. Very frustrating.
My curiosity relates to this: My house is a typical early-70's Bungalow, with the standard 12/12 roof. I am currently in the middle of gutting the upstairs in order to insulate it correctly, unlike the moron who built the house (but that's a whole other story!). Once I had all the sheetrock and insulation torn out, I decided I wanted to raise the ceiling (a.k.a. collar-ties) up about a foot, simply to make the bedrooms a little less claustrophobic. The current ceiling is a single 2x4 at about 7ft high, tying every rafter pair, spaced at apprx 24in. OC. I explained this all to a friend who became worried about the integrity of the structure, thrust, etc. So I started looking around, and now I am typing this. What also confuses me is that my garage roof, which is not quite as steep, only has collar-ties on the four middle rafter-pairs, all the way up butting against the rigde.
Can anyone shed some light on this for me? Or, is this privileged info to engineers only? ;)
Thanks in advance!
-John
Here's a rough drawing of what I want to do. I think the application referenced below is slightly different in that it sounds more like he wants to vault up through where ceiling joists would be. Whereas, my application is on the second floor upon which the rafters rest. My apologies for not stating that in my original post...
http://homepage.mac.com/jgregg/.Pictures/collar-tie.JPG