Advice on repairing bathroom floor tile


Old 01-31-18, 08:44 AM
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Advice on repairing bathroom floor tile

Hello all,
We discovered water dripping from the basement ceiling. Turns out its from the first floor bathroom - water has over time been escaping through the shower door, onto the bathroom floor and through a cracked tile.
I pulled the cracked tile up (it was already loose and wobbly) and everything under it is soaked. Looks like a layer of plywood which has turned to pulp and I was able to scrape it away. There appears to be some kind of subfloor (possibly covered with old vinyl) under the plywood which seems solid, but I can't be sure.

Question: How do I go about fixing this?
I don't want to replace the whole floor, but I expect the water damage has spread further than just the one tile I pulled up, possibly to adjacent tiles and under the shower floor. Should I continue pulling up tiles where it is wet underneath?

Should I simply replace the wet plywood with a new piece of plywood, cut to a shape to fill the area that I'll eventually scrape/cut out > screw it down > thinset > tile > grout?

I don't know exactly how tile flooring works. I've read that you need backer board under the tile - is that what the plywood is?

Also, is tile flooring in general expected to be waterproof? I will of course try to remedy the water that's escaping through the shower door (replace vinyl door seals etc.) but if some water from showering (inevitably) gets onto the floor, assuming the repairs are done well, will this be a problem in the future (water damaging the floor and leaking through to basement)?

Couple of pictures of the hole are attached (you can kinda see the various layers under the tile from bottom to top in the picture - mortar, plywood, vinyl). Any and all advice for a layperson is appreciated. Thanks
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Old 01-31-18, 08:54 AM
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I am afraid you are in for a major repair. This is likely not a simple job of just replacing that small bit of plywood and sticking that one tile back down. The water damage and rot likely extends underneath the shower and at least somewhat under more of the floor. The full extent can not be determined until you start doing demo. Basically you remove tile and wood until you get back to solid, undamaged wood.

I do not see where your tile was installed over a proper backing material so that's a whole other issue. Also, a tile floor is NOT water proof. Neither is the tile in your shower. The waterproofing comes from the waterproof layer that should be underneath the tile. Tile floors are generally not water proofed but are good enough to withstand the minor wetness from cleaning but they can not withstand water pooling or puddling as the water can seep through the grout joints.
Old 01-31-18, 09:30 AM
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Thanks Pilot Dane
Unfortunately we're only now discovering subpar construction all over the house (my wife owned it before we met but we have been living elsewhere for years) so I'm not surprised there is no backing board under the tile. I suppose that explains why it cracked - water got through, softened the wood, made problem worse etc.
We're currently fixing the big issues before we try and sell this money pit - that's why I wasn't keen to rip out too much.
Appreciate your advice about removing tile till I get to dry wood. I think I will take this approach and replace the damaged wood, but I doubt I will redo the whole floor (i.e., properly with backing board etc.).
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