Joist spacing for purlins & drywall
My garage is about 20x20x8 feet with a hip roof. There are five 2x10" rafters spanning the garage. I just finished ripping out all of the sagging, falling-down drywall ceiling and also the walls so I can insulate and re-do it properly before the hot, muggy Houston summer is in full swing.
I don't know what properly is though.. I'm concerned about 3' and 4' spans between joists in the ceiling. know I should use purlins to mount the drywall to, but I don't know if the 3' spans will droop with 1x3" purlins.
I've considered running extra 2x10 beams to fill the gaps, but I would need to use two pieces and join them in the center somehow. There's no way to mount a one-piece joist without cutting into the hip roof to insert it. I could get 2x10x12 boards, cut to fit and join them with nail plates (not too trustworthy) or get 2x10x16 boards and make a lap joint in the center using a whole lot of nails and screws for support.
I'm not really sure what else to do - I've also considered running 2x4 supports above the purlins but I don't want to weigh down the 5 joists too much because I want to use the small area above for storage and blow-in insulation as well.
What would you do? Could the 1x3" purlins with 1/2" drywall across a 3' span be just fine?
Posted Mar 27, 2018, 1:33 PM UTC · edited
[deleted]
I don't think they're insufficient for their original design intention, which was just to hold tension across the building for the hip roof. When you mentioned the blind header I went to snap a picture of it, and you're absolutely right about 5 joists supporting that much weight - it's badly deformed from the sheetrock that was hanging from it previously. https://imgur.com/a/v4iBY
So I guess there's a definitive answer - I cannot hang sheetrock off the existing joists, period, without reinforcement from additional joists and fixing the deformed blind header.
edit: just wanted to clarify, this is a 40 year old building that originally had open studs and ceiling as pictured, with less of the idiot electrical wiring. In the 80's-90's someone nailed up pegboard and plywood to the walls, then sometime in the last 10 years an idiot installed 3/8" drywall over everything, including across the 3 and 4 foot spans between joists as a ceiling.