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Ceiling Joist Direction
Question:
The addition I’ve built onto my house has a shed roof that butts into the side of the house. I’m framing some interior partition walls, and I’ve decided that I would like the ceiling joists to run "parallel to" the shed roof (they would normally run front to back, like a truss). I didn’t explain that right, but I think you get the point. The reason I’d like to run them in the "opposite" direction is that it provides advantages with vent plumbing and ceiling tile installation. Is there any reason, structural or otherwise, that I cannot run them in that direction? Thanks. Brian
Response:
- Hide quoted text — Show quoted text -> If the addition is already framed and weathered in, it’s probably a moot > point at this stage. Joists usually run parallel with rafters because in > addition to being the ceiling, they are also part of the roof structure, > helping to form a tied-together triangle shape that stiffens the roof, and > helps keep it from pancaking and bowing out the outside walls. > Did anyone with actual knowledge about framing bless your addition plans > before you built it? How are the rafters tied into the existing house and > roof? How big is the addition? If it is small, probably no big deal, but if > the span is over 8-10 feet, I’d try to add some sort of tying structure from > old house wall to outside wall, every few feet down the length of the > addition. Doesn’t need to be much- a 2×6 lagged into every other rafter on > outside end, right above the joists, and tying into old house structure in > some solid way. I’d also strap the rafters to the top plate, if you still > have access. Don’t really understand why doing it the ‘normal’ way would > make a difference with plumbing or hanging ceiling. > Standard disclaimer- I’m not an engineer or framing expert, but I did grow > up in the business. > aem sends….
The addition is built and weathered in. It’s small (9 x 12), built in a corner of the existing house. The roof is lagged into the outside wall much as you described above. I simply haven’t put the ceiling joists in yet, and just prior to putting them in, had a thought about changing direction. I understand that "building a triangle" will help to stiffen the whole thing, but I just wasn’t sure how important that was. It’s no big deal… I’ll run them the right way and run furring across them for the ceiling tiles. Thanks for the advice…
Response:
It depends in whether the rafters that support the roof-decking are the same members as the joists that support the ceiling inside. If they’re *NOT*, then the only thing I can think of is that the joists might act as ties, to help resist the small outward thrust of the rafters on the top of the outer wall. If they ARE the same members, then figuring out how to make them stand up vertically, and still have a sloped upper and lower edge to nail decking and sheetrock to, will be a PITA, not to mention how you’re going to ventilate the attic-space. – Hide quoted text — Show quoted text – > The addition I’ve built onto my house has a shed roof that butts into the > side of the house. I’m framing some interior partition walls, and I’ve > decided that I would like the ceiling joists to run "parallel to" the shed > roof (they would normally run front to back, like a truss). I didn’t > explain that right, but I think you get the point. The reason I’d like to > run them in the "opposite" direction is that it provides advantages with > vent plumbing and ceiling tile installation. Is there any reason, > structural or otherwise, that I cannot run them in that direction? Thanks. > Brian
Response:
> The addition I’ve built onto my house has a shed roof that butts into the > side of the house. I’m framing some interior partition walls, and I’ve > decided that I would like the ceiling joists to run "parallel to" the shed > roof (they would normally run front to back, like a truss). I didn’t > explain that right, but I think you get the point. The reason I’d like to > run them in the "opposite" direction is that it provides advantages with > vent plumbing and ceiling tile installation. Is there any reason, > structural or otherwise, that I cannot run them in that direction? Thanks.
If the addition is already framed and weathered in, it’s probably a moot point at this stage. Joists usually run parallel with rafters because in addition to being the ceiling, they are also part of the roof structure, helping to form a tied-together triangle shape that stiffens the roof, and helps keep it from pancaking and bowing out the outside walls. Did anyone with actual knowledge about framing bless your addition plans before you built it? How are the rafters tied into the existing house and roof? How big is the addition? If it is small, probably no big deal, but if the span is over 8-10 feet, I’d try to add some sort of tying structure from old house wall to outside wall, every few feet down the length of the addition. Doesn’t need to be much- a 2×6 lagged into every other rafter on outside end, right above the joists, and tying into old house structure in some solid way. I’d also strap the rafters to the top plate, if you still have access. Don’t really understand why doing it the ‘normal’ way would make a difference with plumbing or hanging ceiling. Standard disclaimer- I’m not an engineer or framing expert, but I did grow up in the business. aem sends….