Cut, Level, Shim, Repeat

Today I started tackling the problem of the out of level floor in the bathroom. After some extensive work with the 4' level the other day, I got a better idea of just how bad the problem is. In the worst spot, we need to make up almost 1-1/2" over a span of about 40". Just what does that mean? Continue on and the pictures will tell the story. After much cogitating, I decided the best plan of action was to rebuild the area around the step, making it level, and then use it as a guide for the thinset I'll have to use to level up the rest of the floor. Here's what I started with.After removing all the warped, splintered, unsupported, and out of place boards, here's what I was left with. My plan of attack was to cut a big piece of 3/4" OSB to support the toilet and also act as the step. I would attach it flush with the floor on the left side of this picture and level it across the floor joists. It took a good couple hours, but this is what I wound up with. You can't tell from the picture, but the 2x4 under the front of the step is more than 1" taller on the right than the left. Crazy, huh? Here's the back side. Right now, the OSB is only supported on the front edge and the corners. My job now is to do some very tedious shim work to support it on the floor joists. When it comes time to level the rest of the floor, this will serve as my thickness guide for the thinset mortar I'll use to level things up. I also found that the floor below the step is out of level too. It's not as bad or as widespread as above, but I will still need to level about 4' wide all the way over to where the closet starts.