Removing Water-Damaged Subfloor

[grains2]

Does anyone have tips/tricks/hints for removing bathroom subfloor (MDF, of course) from under sill plate in order to install new?

Thank you very much.

[Greg]

Start with a circular saw first. Set the blade depth to just go through, about 3/4" and remove the large sections. Once you get down to the tough spots the going gets slow. Some use 4" hand grinders, some use wood chisels whatever works for you. You may want to sister up a 2x on the joist to give you something to fasten to and give the edge more support.

Greg

[Psaltee]

Just finished tearing out master bath, main bath and kitchen. Everything down to the floor and in some cases took our parts of the floor. Follow Gregs lead and start with a circular saw. Remember -- measure twice cut once! Use a good plywood grade. It doesn't have to be expensive. Better that than particle board. The floors look good since we Bellawood the kitchen floor and used floating linoleum on the bathroom floors. All thats left to do is touch-up. It can be done -- just takes time. psaltee

[grains2]

Thanks to both of you, Greg and Psaltee, for the tips and encouragement. How far back under the sill plate would you suggest we remove the subfloor? This is indeed the tricky, slow part of the job.

[Greg]

Get what you can get without driving yourself nuts, You can sister up a 2x on the joist for support.

Greg

[JD]

If the wood is rotted due to water damage, it will pick out pretty easy with a screwdriver or similar tool. The hard part is getting the plywood shoved back into this area. To get the plywood back in, I remove all the nails with a 4 1/2' grinder, strong wire cutters or a metal sawzall blade will get it too, but not as good as a grinder. Then I will use crow bars or a 4x4 fulcrum to open up the slot and shove/pound the plywood in.

If the floor under the wall is dry or dry enough to still work as a spacer to hold the wall up, you can do as Greg was saying and block between the floor joists right at the edge of the wall. This will give you something to nail the new plywood to. Doing it this way, the plywood is cut to 1/8" from the wall and just dropped into place. MUCH easier.

When cutting out the floor, I do the same as the others mentioned. I make my first cut with a
Skilsaw and remove the bulk of the wood near the walls. This allows me to check for plumbing and wiring before sticking blades and chisels down there. I will feel every inch of my cut area before cutting. Then I use a sawzall to cut the floor flush to wall, where I will put in my blocking.

[grains2]

All of this makes sense. Thank you to all. JD--we like the idea of dropping in the plywood, rather than trying to shove the new subfloor under. Surprisingly, the room seems pretty square, but there will still be small gaps between the subfloor and the wall. What is the best way to handle the gaps?

[JD]

If these gaps are large enough to be concerned about, I guess you could drive in a piece of 5/8" wood. You could add a slight bevel to one edge of a piece of 5/8" plywood, pine or fir. If you have 2x4 framing, in particular the bottom mud plate, it could handle a small gap. Many homes have 1x4 or 1x3 bottom plate, where it might be a good idea to shim up the gaps.

It is important that your blocking between the trusses is tight and solid. This framing is making up for the connection on the particle board subfloor to the wall framing. For many years, I cut the blocking with a regular skilsaw. I am very good with a saw, but I found that compounding human error (not exactly straight cuts) resulted in re-cutting often. I have been using a miter saw for floor blocking years now and it is truly the way to go. Measure twice and cut once, love it! I hate it when I cut a piece 3 times and it is still too short.