I have a curved stair case and I'm looking to drywall it up going into the basement. I'm looking for guidance on how to best frame the area below the stairs to drywall it up.
I would install thin, flexible boards against the wall and mount crossbars (ceiling joists) to them. I would not mount drywall directly to the stairs.
- Establish lines on the wall. This could be done with semi-rigid pipe held against the staircase to create smooth curves.
- Rip 1x4 boards in half to yield 1x2 boards with nice square edges. 1x2 lumber usually has very rounded edges.
- Mount these runners on the line with the narrow edge and square corners against the wall. Use 3" construction screws and pre-drill so as to not crack the boards. If you find the curves too tight, soak the boards in warm water for a few hours.
- Mount 2x4 boards flatwise across the span, screwing them into the runners with 2-1/2" construction screws. Pre-drill here, too.
This strategy, along with the corner tape joints, will leave you with a very strong ceiling. It'll be isolated from the staircase, so that any vibration and movement in the stairs won't result in cracks.
| <-- wall |__________ | | <-- 1x2 runner, screwed to the wall studs |__________|_________________________________________________________ | | 2x4 ceiling joist, screwed into the 1x2 runner | |_____________________________________________________________________ |
One suggestion for fitting the drywall (the most challenging part of all this) is to do it one side at a time. Fit pieces that run about 2/3 the way across the span to the wall. Do this from each side, mounting loosely near the walls and lapping the center area. Then use a rotary cutter to slice up the middle through both layers. Remove the scrap and screw it all tight.
Use 1/2" plywood ripped 3 3/4" wide, pushed into the wall, with the top edge following the slope of the stairs on both sides. You may need to use a thinner plywood to conform to the inner radius but the idea is to conform to the radius and the twist the wall will make the plywood do. do 2 layers of 1/2", and 3 layers if you need to go with a thinner plywood. After that is done, cut 2x4s to go between the plywood strips. No the 2X will not line up perfectly on either side meeting the plywood, because the inside and outside are at 2 different angles, but it will work for drywall. When done the framing will look like the spokes of a wheel radiating out from the center. Use the risers to establish the line to follow for your framing. If you cannot get 6' 8" to the finish for code, rip the plywood 1 3/4" and set the 2x flat.
Use 1/4" drywall for the ceiling, it will conform to the helix, the ceiling is. use 2 layers in your framing you place at 8" centers on the tight radius so it will be perhaps, 12-16" centers at the larger radius. Closer framing centers the better.