Level Plywood Subfloor

[bcinvest]

I have a joist that bows upward, causing my plywood subfloor to be uneven (3/4" over 4ft). How do I level the plywood subfloor in order to install nail-down 3/4" wood flooring? I thought about using a leveling compound such as LevelQuik RS, but I was told that the compound will crack if I try to nail the flooring through it and into the subfloor. I tried using some roofing shingles that I had in my garage as someone suggested. When I test fitted the flooring, the 3/4" drop was cured, but I ended up with a new problem: The flooring was uneven in the other direction, creating gaps and a buckling effect.

Any other suggestions?

Thanks.

P.S. I don't want to go to the extreme of cutting and sistering the joist if I can get around it.

[Mulan]

[Jonny]

Just pop a chalkline end to end, cut the upwards bow portion out. Be patient while cutting this. If joist can be replaced, replace instead.

[Shannon Pate]

Don't try to level the floor.

Try to minimize the out of level condition. 3/4" in 4ft is noticable, but

3/4" or 1/2" over 10-12 feet probably isn't noticable to most people.

Instead of using roofing shingles, use #30 and/or #15 building paper. You can then layer the building paper so that the bow gradually transitions into the rest of the floor. You'll probably need to use a string line to create your taper, and then build up with paper to the string.

Shannon Pate

[JerryD(upstateNY)]

Any other suggestions?

Cut the offending joist completely in half at it's highest point and slide in another STRAIGHT joist next to it. Nail the two together, flush at the top. You might need to pull the crowned joist down to make it flush with the staright one. It's a ten minute job. Don't make it an all day affair.

[SteveF]

Having just done this to the whole second floor of my house, if it's only one joist you will spend more time screwing around with shingles and leveling compound that just pulling up the plywood and fixing the joist.

Pull out the plywood nails with a nail puller. Correctly done it should be a gouge the size of a dime.

Buy or make a very straight board. Clamp the board to the side of the problem joist down far enough to use it as a guide for your circular saw. Run the circular saw down the length of the crowned joist and cut the 3/4" rise off.

Replace plywood.

Steve.