Rotting wood under bathroom tile

The tile in front of the shower has loosened, and it's obvious that the wood underneath was rotting due to moisture. Some kind of plywood maybe. Question now is how to fix it. Several things in play...
1. Best way to remove the rotting wood. The oak flooring underneath is fine, but the 3/4" ply over that is done. I can just chisel most of it out, but some areas are still pretty hard. Any shortcuts for removing that?
2. Replace with what? I was going to just pour concrete in the whole removed area. I do have a small tube of Sakrete fast-setting cement Patcher (Home Depot, I think). Someone told me to put plywood back in rather than using 3/4" of cement patcher. But I'd prefer not to have a repeat performance. Will the cement patcher work in that thickness?
3. I should probably waterproof the surrounding remaining ply and the oak flooring. I was thinking about "Wood Hardener" if I can work up the nerve to ask for it. ("Gimme some wood hardener...and some caulk!") What else would seal off the inevitable shower leakage...some kind of thinned epoxy? Water-base urethane?
4. The floor tiles are an odd size (nothing is going right, so why that?) It's around 4-5/16" or maybe it's 11cm. Can't find replacements. Someone advised just doing that section as a different look. Kind of a step-stone into/out of the shower. But I'd have to get tile cut then.
5. Any intermediate layers necessary? It looked like the rotted ply originally had some kind of hard layer on top.
Random comments welcome. I'm sure some of you have had to deal with this before.
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On Sunday, June 16, 2013 8:44:43 PM UTC-7, VM wrote:

The tile should never have been installed on top of wood in the first place. Who did the installation? Does the installer have a license?
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*I had a similar problem with a small section of plywood in front of the tub. However mine was a complete bathroom renovation. I did use Minwax wood hardener generously. Then I used a floor patch (Henry's from Home Depot) to level off that section. Then I put down Hardibacker on the entire floor and walls before tiling. It has been several years and the patch job seems to be fine.
You can use a multifunction tool to plunge cut out the section of plywood. Maybe install a piece of cement board instead of putting plywood back.
I think Home Depot stopped selling the Minwax wood hardener and now only sells water based wood hardener. Try a hardware or paint store.
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On Mon, 17 Jun 2013 07:18:44 -0400, "John Grabowski"

Hardibacker is some type of cement board? After hearing 'cement board' a few times, I'm starting to suspect that there must be a flaw in my original plan of just filling the hole with a thicker layer of cement.

I think I have some of the older stuff somewhere. I remember it smelled like a petroleum distillate. Seemed to penetrate pretty well, but I'm not sure it helped keep the wood from disintegrating.
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*Hardibacker is a brand of cement board. There are others such as Wonderboard. Follow the manufacturers instructions.
The Minwax wood hardener is still available, but not at Home Depot. I have used it several times on wood that is exposed to the elements and it has held up fine. The stuff is so thin that it is absorbed into the wood immediately. Be sure to let it dry for several hours before covering.
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VM wrote:

Umm, cut off saw with shoe set to proper depth? ______________________

Cement backer board. Comes (usually) in 3' x 5' sheets, 1/4 or 1/2 thick. Screw/nail it down. Leave 1/8 - 1/4" gap where it meets a wall and caulk fill that gap with silicone caulk. Pure silicone caulk, not "siliconized something or the other".
If you need it 3/4" thick you could put 1/4 on top of 1/2 or use 1/2 and build up the difference with mortar as you lay the tile. ________________________

I have no idea what "wood hardener" is but if it isn't thinned down epoxy I wouldn't be using it. I would be more inclined to a liberal application of wood preservative. In days past, I would have used Cuprinol; now that we are in the Age of Wusses, about the best would be a borate.
Ideally, the oak floor would have had a membrane, then cement board, then tile. _________________________

If you are going to lay tile, you have to cut tile. No big deal, you can get a perfectly fine "score & snap" cutter for less than $30. Add a stone to smooth the edges and you are still in Cheapville.
You can also get little tile wet saws with diamond blades for under $100.
--

dadiOH
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Or rent a tile saw for the day. But for a small job like this with what sounds like just a rectangle, the score/snap is probably all he needs.
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wrote:

I tried using a circular saw (actually a trim saw, I guess). DIdn't work as well as I expected. Problem may be that there are alternate areas of soft and hard wood, and some stretches still have the hard top surface. I'll try again.

I learned my lesson when I tried to use one of the 'siliconized' things to seal a shower. It was moldy within a couple weeks. Finally ended up using something from a boat shop: 3M 5200. They apparently use it under water.
I'll look around for the cement backer board. Is that different from just pouring a whole layer of cement? (I presume that the surface of a 3/4" layer of cement would probably get uneven as it cured)

I'll check those. I don't think wood hardener is epoxy, as it's not 2-part. But it is designed to soak into wood. Someone in this thread mentioned that the new stuff is water-based, and probably not as good.

If I can think of anything that will stick... _________________________

I may be able to get the tile pre-cut. I was rather surprised that the existing tile size is not commonly made. It's about the size of wall tile, but the surface is different.
That was a very complete reply, DadiOH. Thanks for that!
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VM wrote:

Cement by itself isn't much use; its value is as a binder for other things...sand, rock and - in the case of cement board - fiberglass, Curing has no effect on the eveness of the surface.
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Is the "Oak flooring" a subfloor, or did some idiot just put more layers of flooring over a finished oak floor???
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On Mon, 17 Jun 2013 07:42:25 -0700 (PDT), " snipped-for-privacy@sbcglobal.net"

This is an old factory building, probably 100 years old. Oak floorboards throughout. The bathroom would have been installed probably 35+ years ago over the original oak flooring.
I've heard of people using some kind of plywood under tile, but it never seemed like a good idea to me. The result in front of the shower confirms that. I'll check into 'cement board'.
Thanks to all for the recommendations.
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I'm making a downstairs bath. I'll be using Kerdi drain and Kerdi membrane. Goes over wood, drywall, etc.
Greg
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This couldn't be the Kroehler factory in Naperville, IL by any chance???
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On Mon, 17 Jun 2013 19:37:01 -0700 (PDT), " snipped-for-privacy@sbcglobal.net"

Ha! No, it's a typical NYC "Loft building." There are quite a few downtown. Start off as old textile factories, then renovated by artists as work spaces, and then inevitably as rents climb, they're taken over by wall-streeters who want high ceilings. (I'm closer to the artist category, but I didn't do the original work.)
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It sounds like it was a poor installation to start with, and you'll never match the existing tile. Most bathrooms are a relatively small space. If you're going to the trouble to repair the tile, you would be better off redoing the entire bathroom floor. You'll need to pull the toilet, but that's not a big job. Preferably remove the vanity cabinet too.
Rip up the tile and plywood with flat prybars, bust the tile with hammers, etc. Make sure you have safety glasses so you don't end up with a tile chip in your eye. Demo is messy no matter what you do. Sweep everything up nice, then vaccuum up any remaining dust.
Repair any damage you find to the oak subfloor (if any).
Install a layer of 1/4" or 1/2" hardibacker board so the thickness of the backer and tile is close to the thickness of the adjoining floor in the doorway. You'll need a layer of thinset under the hardibacker, then use the appropriate screws (NOT drywall screws) every six inches. Stagger the seams, if any.
Use fiberglass mesh tape and thinset mortar to join the seams.
If you want an extra layer of protection, install a layer of Kerdi waterproofing membrane.
Then layout and install your tile using the appropriate notched trowel. You can rent the tile cutter, or just buy one of those little wet saw's from Home Depot or Lowes. I only paid $80 for mine and we've used it for numerous jobs. For occasional home use it's more than adequate.
Give it a day to cure, then carefully clean up any thinset that squeezed between the tiles. Then you can grout the tile.
Reinstall the toilet with a new wax ring.
Caulk the gaps between the tile and shower. You should also caulk around the base of the toilet. I've always used regular latex caulk as it's easy to apply and cleanup with water. A damp sponge makes it easy to get a professional looking bead every time.
It will be a bit more work than a patch job, but the results will be much nicer. Besides, you might patch a section now only to have another section fail a year later.
You should check out the John Bridge tile forum for advice. You can see photos of my tiling projects at:
http://www.johnbridge.com/vbulletin/showthread.php?t 876
Good luck!
Anthony Watson www.mountain-software.com/anthony.htm
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On Tue, 18 Jun 2013 14:42:33 +0000 (UTC), HerHusband

I built a towel rack once. ;-)
That sounded so simple when you put it like that, but I imagine that would be a year's work for me. You're correct that it wasn't done well to begin with, but I've got to juggle priorities. This started off smaller...one tile came up, etc. So I'm now up to digging out plywood. I'm trying to draw the line here. But I'm saving your post (and others) for the day that I can get the work done right.
Thanks again to all! This is a helpful group.
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Yeah, I understand... :) I'm betting it wouldn't take you more than a few weekends at most. Projects like this sound like a lot of work, but it's really just a bunch of little things put together. The only real complication would be if it is your only bathroom, in which case you might need to rent a port-a-potty or something.
Saturday 1: Measure the floor so you know how much hardibacker, tile, and thinset you'll need. Then go shopping. I would recommend buying a little more than you need. You can always return what you don't use, but it sucks to run short when you're almost finished. When you get home, turn off the toilet supply, and hold down the toilet lever to empty the tank. Scoop any water left in the bowl out with a small cup/bucket/sponge or whatever. Yeah, it's gross, but it's not difficult. Disconnect the water supply hose, then remove the two bolts that hold the toilet down. Lift the toilet straight up, being careful not to hurt your back. Store the toilet some place where it won't get damaged (unless you want to replace the toilet while you have it out). Stuff a rag in the floor drain to keep out sewer gases.
Sunday 1: DEMO DAY! Rip out the tile and plywood with hammers and prybars. Remember your safety glasses! Try not to damage the walls or you'll have more work to do. Then sweep and vaccuum nicely. Stand back and admire your work, as you wonder what the heck you've gotten yourself into. :)
Saturday 2: Dry fit the hardibacker in the room. If you need to make a cut, measure and score a line with a sraight edge, then snap the board on the line. A jigsaw works well for making curved cuts like the hole for the toilet drain. You'll go through lots of blades though. Once you have all the pieces cut so everything fits nicely, lift them out and set them aside (number them if you wish so you know which piece goes where). Mix up some thinset in a bucket of water. The instructions are on the bag. Spread the thinset on the floor with a trowel, then use the notched side to ensure it's the thickness you need. Start in a back corner and work your way out so you don't get trapped in a corner somewhere. :) Then lay down the sheet of hardibacker and secure it with screws. Let things set up for a couple hours, then put fiberglass mesh tape on the seams. Mix up a small batch of thinset and cover the mesh tape, feathering it smoothly so you don't end up with a hump.
Sunday 2: Layout and dryfit the tile in the room. Measure and cut the tile as needed. Once you are happy with the layout, take up the tile and set it aside. Then mix up another batch of thinset. Spread it in a small area, screed it with the notched side of the trowel, and carefully set your tiles into the thinset. Press and wiggle slightly to ensure a good bond. Plastic tile spacers will help keep everything aligned if needed. Remember to start in a back corner and work your way out to the door. You don't want to get trapped in the corner. Cleanup, then stand back and admire your work. Ideally, come back Monday evening to remove the spacers and carefully scrape away any excess thinset that squeezed up between the tiles.
Saturday 3: Wipe down the tiles with a damp sponge, then mix up your grout. Starting in the back corner again, work the grout into the gaps between the tiles with a float. Going diagonally helps prevent digging out the grout you already applied. With a small bathroom floor, you should be able to grout the entire floor before cleaning. Get a bucket of clean water and a sponge, then wipe off the grout from the surface of the tiles. Change the water frequently when it starts to get dirty. When it hazes over again, go back over everything a second time with clean sponge and water again.
Sunday 3: You'll probably have a light haze on the surface of the tile. Wipe it off with clean water and sponge again. If needed, you can use "haze remover" from the home center. Put a new wax ring on the toilet, then bolt it back in place. (Remember to remove the rag from the drain first!) Snug it down, but don't go so tight that you crack the toilet. I usually tighten the bolts lightly, then sit on the toilet and rock around a bit to seat it into the wax ring. Then tighten the bolts more if needed. Gentle, it's not the time to be Mr Muscles. Hook up the toilet supply, turn on the water, and check for leaks.
Saturday 4: Final touches. Apply baseboard trim, caulk between the tile and shower, caulk around the toilet, repaint the walls where you dinged them up, etc. :)
Obviously, I've left out a few small details, but you can find out the tools and steps you need from any tiling book. The johnbridge tile forum can be a big help too if you have questions.
Have everything you need before you mix up the thinset or grout. Dry fitting isn't necessary, but it gives you time to figure out how things fit and correct mistakes before you get started.
If you can work evenings, or take a few days off work, it won't take as long either.

Whatever you decide to do, good luck with your project!
Take care,
Anthony Watson Mountain Software www.mountainsoftware.com/anthony.htm
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