Rotting wood under bathroom tile


There's a spot in front of a shower where 3 or 4 of the tiles were unstable. On lifting them, I found wood (probably cheap ply) that had rotted due to leakage from the shower. The problem seems localized, and the floor will eventually be replaced anyway. So for now, I'm just repairing the one spot, about 12" by 6".
One problem is that the underlying wood has an uneven surface. I need to find something that can fill in and level the surface, and of course waterproof the area. And I presume that some coating will be required to afford a solid base for the tile to adhere. (Again, keeping in mind that I'll want to replace it later)
Anyone here have any experience doing this?
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Rob wrote:

If you have access from below, prop up the mushy area with thick ply or 1x strips, supported by cleats screwed to the adjacent joists. If the plywood subfloor is too mushy to stabilize and stiffen with epoxy, piece in a patch of the same thickness. This work-around may fine-tune reality long enough to buy you a few years until budget allows a proper redo of the whole room.
-- aem sends...
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wrote:

Before I lifted the tiles I expected just that--rotted wood right over the joists. But actually there are oak floorboards under the rotted ply. The oak seems to be in decent condition. So basically I just have to fill in the area where the ply has partially decomposed. Unfortunately that's not real uniform, as the ply only rotted in some areas. So I was thinking about pouring a layer of concrete or something. I probably should strengthen the oak and remaining ply fragments first though. Sorry for not explaining that well enough the first time.
So I guess the question is whether concrete is the right thing to use, or whether there is some other type of filler that would do it. There's about 3/4" variation in height (from where the ply has remained to where it's completely gone), so whatever I use will have to fill that in and remain stable.

That's exactly what I'm looking for. It will eventually be done by a pro. Not looking forward to the prospect of removing that layer of plywood though.
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with the carpenter and plumber looking for work, why not estimate the materials and time and hire one at a price you would like to pay? everything is negotiable, even terms on materials. you want to rip out all the wet and damaged stuff so that the spread of the damage and potential for mold or mildew stops too. track down the leak, it just takes a small seepage past the shower door or curtain to cause the damage you describe. realize that you're ready to pay a dollar a day for a nice hot shower to yourself for the next three years, and now your budget is $1095. (!)
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On Thu, 11 Mar 2010 01:44:53 -0800 (PST), buffalobill

Thanks for your reply. I believe that any leaks in the shower itself are sealed now (crappy work by the previous plumber. I had to spend a whole caulking tube of 3M marine sealer on the inside of the shower). I'm going to completely remodel the bathroom in a year or two, and most of the damage is to only about 1 sq ft, so I'll wait for to hire the pros (and hope that they're better than the last 'pros'). The concern for the moment is to keep tiles in that small area from wobbling and breaking.
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I've popped the molding off many doors to shim the casing out (often the finishing nails just pull through the trim). The garage door on my last house almost fell out. The dumb bastards nailed through the brick mold into the casing and frame. There was nothing through the hinges or striker, into the frame, at all.
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*I had a similar problem when I redid a bathroom. I used a product from Home Depot made by Henry. It was their Premixed Patch n' Level. It is easily applied using regular trowels. It took longer to harden than the directions said, but the result was a nice hard solid surface. I used my orbital sander (50 grit) to smooth the finish the next day before it got really hard. I then put Hardibacker board on top of that.
Some of the wood was flimsy so I pretreated it with Minwax Wood Hardener first and let that dry for a few days.
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I've used that stuff as well. In this case I think you could level it with mortar too.
Before doing anything I'd point a fan at it for a couple days to get it dried out real well. And start by soaking what's left in epoxy thinned with a little alcohol.
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On Thu, 11 Mar 2010 06:53:21 -0500, "John Grabowski"

Thanks to all for the replies. I'll follow up on all here.
I printed out the collected advice in this thread and went to a couple hardware stores to find the stuff. Some helpful people in the hardware stores as well, but of course everyone's approach differs.
One said that Patch 'n Level was great as long as you didn't have much depth to fill, and that it would have to be layered 1/8" at a time. Depth here is around 3/4" to make up for spots where the ply rotted out. (P 'n L sounds great for more shallow fills, but I need to get this done quicker.)
Another said the industrial concrete (I forget the exact name at the moment) was the way to go because it was solid and water-resistant.
Another said concrete was good for deeper fills but would chip on the thinner areas, and that Ready Patch would fill the depth (about 3/4") easily and would be less likely to chip. Of course 'concrete guy' had mentioned that Ready Patch would be susceptible to moisture.
Etc. So...roll of the dice I suppose. It sounds like there's no perfect solution with the products at hand, unless any of that info was wrong.
I did end up buying the Minwax wood hardener. Couldn't find an epoxy that looked like it would thin down easily. And picked up a small tube of grout, which I was told could be used for adhering the tile.
Obviously it's the first I've done this, though I don't shy from manual labor. Just haven't had occasion. The info will help later when I redo the entire floor.
Not sure which product I'll end up with for now for the main filler. It seems like a more flexible 'plastic-y' filler would be better than a harder but chip-prone concrete. Not sure where Ready Patch stands in that picture, but I was told it handles deeper fills quickly.
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Rob wrote:

1. Dig out bad wood
2. Hammer in 3-4 nails into good wood so heads will be about midway in the area to be filled
3. Fill with thinset
--

dadiOH
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