Hardwood Subfloor repair [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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06-28-2016, 06:08 AM
Hello everyone, I have been reading this forum for a few weeks now , and it is finally my turn to ask some questions. I recently purchased my first home and I just began remodeling the main bath. I plan to tile the floor in a pinwheel mosaic and subway tiles on the wall/shower area. The house was built in 1939 and has hardwoods over the joists with no subfloor. I found yesterday after pulling the linoleum, that there was a toilet leak at some point and the wood floor is damaged and needs to be replaced. Luckily the floor is dry.
My question is, should I rip all of the floor out and replace with OSB/plywood, OR should I just remove and replace the damaged section? The biggest concern is that the cast iron tub rests on the original floor and I won't be able to remove that section of floor. I would need to somehow butt the two floors together and I'm not sure I feel that is the best way.
What is the best approach to this situation?
Thank you in advance!

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06-28-2016, 08:12 AM
The best thing to do is tear out and replace with plywood if you plan on tiling.

06-28-2016, 08:25 AM
How should I handle the transition to the original floor that goes under the tub? I want to avoid a lump or ridge where that exists.

06-28-2016, 10:33 AM
How thick is the subfloor? Can you replace the damaged area without getting under the tub? A wider shot of the damaged area might be helpful.

06-28-2016, 10:56 AM
There is no subfloor. The hardwood is nailed directly to the joists. The thickness of that wood is 3/4" I believe. I will need to double check to be sure. I will need to get a bigger picture of the room.

06-28-2016, 01:42 PM
It looks like the existing floor is running perpendicular to the tub. In which case the joists run parallel to the tub. Find the joist closest to the tub; is all the floor damage farther away from the tub than that? If so, you can cut the existing floor at the midline of the joist and install new plywood. (*)

You should be able to match the thickness of the existing floor, either by getting the same sized plywood, or by shimming the top of the joists appropriately. I'm assuming your floor is at least 3/4" thick. (Very old 1x4s may be 7/8" thick, but 7/8" thick sturd-i-floor plywood is made).

Cheers, Wayne

(*) Since the existing floor is likely nailed at the midline of the joist, you may find it easier to cut the existing floor on the side the joist away from the tub, and then add a 2x4 sister to the joist to catch the edge of your new plywood.

06-28-2016, 06:12 PM
I was wondering if that is a legal move or not. The rot doesn't quite make it to the nearest joist, so I should be able cut the floor there. Thanks for the heads up!
I think I will start a build thread of the bathroom to address any further concerns.

Houston Remodeler
06-28-2016, 06:51 PM
We just tiled a floor like that today. Monday we demo'd the old subflooring and repaired the joists. The handy dandy deflectolator told me we needed to double the joists making them 12 inches OC to meet the requirements for tile. The missing subfloor was replaced with 3/4" BC plywood, then the whole floor including the plank subfloor was covered with 1/2" BC plywood.

I don't know how the homeowners didn't fall through the floor at the terlit.

06-29-2016, 06:06 AM
I am very thankful that mine is not that bad! haha

06-29-2016, 10:09 AM
In your case, with 3/4" subfloor and a good bit of it rotted, I think I'd take it all out. Add joists and blocking where needed to for support at the tub and the perimeter of the room, then install 3/4" plywood, glued and screwed to the joists.