due to some water damage we had to remove a part of the subfloor in our bathroom which went right to the wall. The probem is that there is no joist under the wall but it is in the next room.
Here is a sketch how it looks like:
My plan is to screw a 2x4 under the wall on which I can screw the edge of the replacement plywood.
I also want to install a 2x4 parallel to the wall on the bottom and a couple of 2x4 struts between this and the one screwed to the wall frame in order to support the wall.
Is this sufficient to keep the wall stable and as a good basis for the tiling (in the end the floor should cosist of 2 5/8 layers of plywood)
can you get to the joists from below?? basement, crawl space??
if so, the I would run 2x4's perpendicular between the joists to support the wall. then if you want, you can put in cross braces for nailing strips parallel to the wall. this will be more than strong enough for what you are doing and the span you are repairing.