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Al Launier
07-17-2018, 4:36 PM
I have 12" sq. tiles in my bathrooms & some of them have separated from the mortar on the plywood sub-floor. I haven't pulled any tiles yet, so I'm not sure of the actual cause, or of the construction, but I believe the mortar has dried over the past 20+ years and lost their adhesion. As I step on specific tiles there is a loud popping noise leading me to think my weight is pinching the tile on their side edges. In any event, I'm considering re-mortaring these tiles, but am concerned that as I try to remove the individual tiles that adjacent ones may loosen as well leading me to have to chase more loosened tiles to lift all the loose ones out. Also, is it reasonable to expect that the old mortar will scrape off cleanly to allow the new mortar to adhere properly?

I'm a long time DIYer, but if this has the ear marks of a problem type of project, perhaps I should hire someone to do this.

I'd appreciate your thoughts.

Jim Becker
07-17-2018, 6:25 PM
With any luck, the adjacent tiles will be fine, but if they do come loose, that's a good thing since they would probably do that on their own at some point anyway. Be really careful about damaging them, however, unless you have extras hanging around. The biggest challenge with re-sticking will be cleaning out the old mastic/mortar so you can properly apply the new stick-um and get a good bond while also getting the tiles even with their neighbors.

Stephen Tashiro
07-17-2018, 6:37 PM
some of them have separated from the mortar on the plywood sub-floor.

Was the mortar applied directly to the plywood? Is it actual mortar or is it an adhesive?

Wayne Lomman
07-17-2018, 6:48 PM
Loose tiles means the adhesive has failed, whatever it is. It will be the same under the adjacent tiles, just not as obvious. The ones you walk on most commonly have just failed first. Expect to remove all the floor tiles and be pleasantly surprised if you don't have to. The cause of failure can be the mortar bed failing, the adhesive failing or excessive movement in the floor structure that is causing one of these to fail. It can also be water leaking in between the tiles and the mortar bed.

You can do a minimal repair or you can strip the whole floor, check it for movement and repair as necessary, redo the membrane and relay your mortar bed and tiles. Its within the skills of a competent DIYer. You will know for sure that it is done properly then. Keep in mind Jim's comment about spares and damage. It will be almost impossible to get new ones to match. Cheers

Peter Rawlings
07-17-2018, 7:54 PM
I have 12" sq. tiles in my bathrooms & some of them have separated from the mortar on the plywood sub-floor. I haven't pulled any tiles yet, so I'm not sure of the actual cause, or of the construction, but I believe the mortar has dried over the past 20+ years and lost their adhesion. As I step on specific tiles there is a loud popping noise leading me to think my weight is pinching the tile on their side edges. In any event, I'm considering re-mortaring these tiles, but am concerned that as I try to remove the individual tiles that adjacent ones may loosen as well leading me to have to chase more loosened tiles to lift all the loose ones out. Also, is it reasonable to expect that the old mortar will scrape off cleanly to allow the new mortar to adhere properly?

I'm a long time DIYer, but if this has the ear marks of a problem type of project, perhaps I should hire someone to do this.

I'd appreciate your thoughts.

Al, in my experience, mortar itself rarely fails, but installation errors, excessive deflection of substrate or wrong products used will describe 95% of failures. Whatever is going on isn't just happening under one or two tiles even though it may seem that way. As much as I like this place, and even if you decide to have someone else do the work, I'd suggest you visit one of the best resources I know of for all things tile: John Bridge Tile Forum. If you have an understanding of what's happening, then you can better evaluate if a proposed solution is viable.

Anything you do to repair a few tiles will most likely need to be, or should have been done, to entire installation.

To get best advice here or John Bridge, knowing a little more about installation methods or better yet photos will get you further down a better road to rectify problem. Full disclosure, I post on John Bridge as well as other places as carbidetooth.

George Bokros
07-17-2018, 8:05 PM
I would plan on putting down the proper under layment i.e cement board screwed per directions to the sub floor and I would screw the sub floor to the floor joists prior to installing the cement board. This will prevent movement of the sub floor and provide a solid substrate for the cement board.

Mike Cutler
07-17-2018, 8:11 PM
Al

20 years ago puts you square in the middle of the 90's. The "big renovation" back then was to do your own flooring.
Every big box store was selling Mapei Mastic to adhere tile to plywood with no other substrate prep. They were also using it to adhere tile to drywall.

Brutal honesty, you're better off getting the tool to lift the tiles from the floor and do it again.

A big +1 for the John Bridges tiling forum. It's a tremendous resource for tiling.

Rich Engelhardt
07-18-2018, 5:29 AM
Yep - John Bridge is the place to go and ask about this.

Alan Rutherford
07-18-2018, 9:58 AM
Plywood? Bathroom? As Wayne suggests, my first concern would not be the mortar. It would be the plywood. You might as well pop one or two up and see what you've got but you might need to dig deeper.

Robert Engel
07-18-2018, 12:13 PM
I agree to do this right, it needs to be demo'd & use wonderboard or hardiboard. There is a right & wrong way to do that, to :-)

Short of that, anything will be a temporary fix.

Steve Rozmiarek
07-21-2018, 12:34 PM
I do this for a living, and I go to the John Bridge site with questions too. Problem is, as woodworkers know, wood moves and tile doesn't as much which breaks down the bond over time. A failure will cause more, as the floors can now flex in a different place with the overall integrity of the tile changed. It'll pop one, then start working on it's neighbor. You need to decouple the tile from the wood. Cement board is the old standard, screwed to the subfloor. It works, but its heavy, dusty, and a PITA to cut. You also still have seams to deal with to keep things from cracking. I'd use Schluter's Ditra instead, after making sure the floor is actually stiff enough for tile.

That being said, if you reset the tile, you may get another 20 years before you have to do it again, but it will fail again.

Mike Cutler
07-21-2018, 9:49 PM
Steve

Ditra is nice stuff.
I've used it three times now and it just makes everything so much easier.