Originally Posted by
Tom M King
Cut the slot for the wall through the drywall, leaving 1/4" on each side, for a total width of 4". Cut lengths of 2x6 that you can get in there, that will hit the joist on one side, and cross the slot as much as it can on top of the sheetrock on the other side.
Buy some tubes of Powergrab, and some 8x construction adhesive. Cut enough of those lengths of 2x6, so you can put one every foot, or such. Put the 8x on the end that's going to be jambed against a joist, and the Powergrab on the flat face that will bed down on the sheetrock. Alternate each piece to jamb against the opposite joist. Slide them back, and forth a little bit, pushing on them to get the construction adhesive to give as much surface area as possible.
Let that set up for a day, or two, and screw the top plate to those blocks. Cut each stud a little long, and hold it in place on top of one side of the sole plate, and beside the top plate. Use a sharp pencil to mark the length perfectly, for a slide fit. You want the fit of each stud to be a slide fit, that touches both ends, but doesn't push the top plate up any.
If you can also glue a few brackets of plywood against the blocks, and the joists, it would make it some stronger, but that should be okay for a partition wall.
Gather all your worn out socks, washcloths, and any such to use as wet rags to wipe away any Powergrab that gets squeezed out where the top plate needs to go, while it's still wet.
Mark the length of each stud where it goes, before you start cutting them. Start with the longest. If one ends up a hair short, it can be used at one of the shorter locations.