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-   -   tile on tile? (http://www.diychatroom.com/f5/tile-tile-22563/)

kshankle 06-20-2008 06:00 PM

tile on tile?
 
can you place new tile over old tile without demoing the old stuff?

angus242 06-20-2008 06:04 PM

Can you? Under the right and rare circumstances.
Should you? No. :no:

kshankle 06-20-2008 06:12 PM

thanks...

HomeDepot23 06-20-2008 07:27 PM

If you do it do not skimp on a cheap thinset. Get a good thinset with an acrylic admix. If you go with a thinset fortified with acrylic, make sure it is the best quality.

angus242 06-20-2008 07:35 PM

Your tile job is only as good as your substrate. Has to do with a lot more than just a good thinset. Original substrate, condition of current tile/grout, type of tile, is the tile glazed.......:whistling2:

HomeDepot23 06-20-2008 07:39 PM

Not to mention your floor height will have just doubled causing other problems like finishing off the neighboring flooring.

angus242 06-20-2008 07:41 PM

Quote:

Originally Posted by HomeDepot23 (Post 132259)
Not to mention your floor height will have just doubled causing other problems like finishing off the neighboring flooring.

Another good point

HomeDepot23 06-20-2008 07:44 PM

Thanks. I was speaking as a carpet installer on that one. The high tile and hardwood finishes can drive us crazy.

Nestor_Kelebay 06-20-2008 08:11 PM

I fully understand that a difference in flooring height is going to result if you tile over tile.

However, if the existing tile is sound, and not cracking because the floor isn't strong enough, and floor height is not a consideration, then WHY is it not a good idea to tile directly over tile.

And, if the response is gonna be something like "Well, the old ceramic tile might be glazed or have a sealer on it that the thin set might not stick well to." then let's presume the home owner is of good intelligence and understands that he can overcome those hurdles by sanding glazed or porcelain tiles or using a solvent to strip a sealer off, or by just using a thin set that's go so much "polymer modified" in it that it'll stick to a raw egg yolk.
It seems to me that the reason you need a tile backer board to tile over is not because tile backer boards are strong, or water proof, or made out of cement, or that everyone uses them to tile over or any other irrelevant thing. It seems to me that tiling manufacturers recommend that tile be set over tile backer board because, unlike wood, cement board (or concrete, or brick, or plaster or even drywall) is dimensionally stable.

Wood swells and shrinks with changes in it's moisture content caused by seasonal changes in humidity. Cement doesn't do that, and neither does ceramic tile.

So, I ask again. Can someone please explain exactly why ceramic tile wouldn't make AS GOOD a substrate for ceramic tile as cement board?

(And, if I may be so bold, let's please not have any of those "Cuz I been around for 400 years and never seen it done so there must be a good reason and who cares what that reason is!" or "Cuz it's stoopid to do that!" or "Why would you even want to tile over perfectly good tile?" arguments.) If people are saying "NO, don't do it!", let's hear their reasoning if they actually have any.

HomeDepot23 06-20-2008 08:28 PM

My only arguments would be that IF the tile that is currently down should, with age begin to lose its bond with the substrate or subfloor, your new tile will also then fail. So your new floor is only as good as the the previous installation.

Second argument is that tile is not meant to have products glued to it. Many adhesives have been used to adhere to and repair ceramic tiles and have failed.

Yes, a modified adhesive will stick. But not nearly as well as it will to concrete or backerboard.

The PSI ratings put out by the manufacturer will surely drop if put on tile. That is more a question than a definite statement. If this is correct, then will the tile now be easier to break if something were dropped on it? (anoter question) :eek:

Nestor_Kelebay 06-20-2008 08:49 PM

Quote:

Originally Posted by HomeDepot23 (Post 132277)
My only arguments would be that IF the tile that is currently down should, with age begin to lose its bond with the substrate or subfloor, your new tile will also then fail. So your new floor is only as good as the the previous installation.

That applies to any flooring, but I just finished installing new vinyl composition tile over old vinyl compostion tile, and I expect that both will last a very long time.

Quote:

Second argument is that tile is not meant to have products glued to it. Many adhesives have been used to adhere to and repair ceramic tiles and have failed.
I can't think of any flooring that's meant to have another flooring glued down over it, but that happens all the time too.

I don't believe that getting something to stick to a smooth surface will be a problem. Even ordinary mastic is a hassle to get off glazed ceramic tile, so the smooth surface isn't an obstacle. Silicone caulk sticks like crazy to glazed ceramic tile.

Quote:

Yes, a modified adhesive will stick. But not nearly as well as it will to concrete or backerboard.
It doesn't need to stick like chewing gum to the underside of a church pew. It's a floor. It's not going to fall off. Besides, some of these ULTRAFLEX IV (with the racing stripe) thin sets from Mapei are more glue than they are cement. They'll stick to darn near anything, including glazed wall tiles. I have no doubt that you could find a thin set that would stick to glazed tile even without roughening it's surface.

Quote:

The PSI ratings put out by the manufacturer will surely drop if put on tile. That is more a question than a definite statement. If this is correct, then will the tile now be easier to break if something were dropped on it? (anoter question) :eek:
Personally, I really don't see any logical reason why existing ceramic tile wouldn't make as good a tile substrate as any other masonary material, or as good as any tile backer board.

HomeDepot23 06-20-2008 08:58 PM

Like I said earlier, if you do it. Do it with modified or fortified thinsets like Ultraset ot flex-bond. Many people say scarify the tile, others add a primer. Custom building products in California will answer any questions if you use their products. Call any Home Depot for the number or get it off the bags.

Good luck with it.

nap 06-20-2008 09:03 PM

I have seen pros do it and I have even seen them use scrap tile to buildup a section of floor when needed.

with that, I would see no problem IF you follow homedepot's direction using the correct and quality materials and only if the tile now is in great condition (bonding wise)

angus242 06-20-2008 09:17 PM

Nestor,

This is a DIY site. So when advice is given, it's assumed that regular circumstances should apply. There are MANY circumstances in home improvement where an alternative procedure MAY work.
As I said, it can be done under the proper circumstances. I don't feel it is sound advice to try to tempt a home owner down a path of unknowns. In this situation, without being able to determine all of the "what ifs" myself, I feel the best advice it to not perform the alternative procedure.
FYI, it is not recommended to use thinset over any substrate that has been chemically altered; so you should not attempt to apply thinset over a glazed tile that has treated with solvent to attempt better adhesion.
And finally, I would say it's not a very fair argument to assume you are 100% sure how the original tiles had been adhered. What may look fine, may be a failure about to happen. Then again, maybe not. Are you willing to take that chance?

So again, for a DIY site, I stick with my original advice to remove the original tile.

Nestor_Kelebay 06-20-2008 10:39 PM

Angus242:

With utmost respect...

The people in this forum are looking for good advice. However, ideally they'd like to have the knowledge to answer the question for themselves. That way they don't have to ask for advice the next time they have a question.

And, despite the polical uncorrectness of it all, it's really disputes over issues like this one that help the most. Like it or not, listening in on experts "argue" a technical matter like this one is the best way for newbies to learn enough about all aspects of a technical issue that they can walk away with enough insight to form their own opinion.

I heard a lot of hemming and hawing about how we shouldn't suggest anything that might not be "strictly by the book" to a newbie, and how every situation is full of unknowns (which are equally unknown to the expert). I think "lots of words, but no substance."

The bottom line is that there has to be a fundamental reason why some materials make good tiling substrates and some don't, and that reason (if known) would also give us insight as to whether ceramic tile itself would make a good tiling substrate. Notably, masonary materials like concrete and brick and plaster and cement board make good tiling substrates and plywood (or any wood for that matter) doesn't. In fact, in dry areas, it's common to put ceramic tile over drywall and the tiling on that drywall will last for many many years without the grout joints cracking or the tiles popping off. What is it about wood that is different than all these other materials?

Wood swells and shrinks. If it gets wet, it swells, and as it dries up, it shrinks again. They add adhesives to thin sets and grouts to give them more flexibility and elasticity, but wood swells and shrinks A LOT, more than "Mr. Polymer Modified" can accomodate.

In fact, if you take green softwood (like fir or pine or poplar) and dry it in an oven, it'll shrink a full 8 percent across it's grain as it dries from a saturated to oven dried condition. That's a full inch across a 2X12 ! ! ! Normally, you never see that kind of change in moisture content or dimensional change in wood, but in a bathroom, where wood can go from "kiln dried" to saturated, you can get large dimensional changes that the elasticity of modified grouts and thin sets simply can't accomodate.

And, of course, it's easy to see the problem getting worse. If you tile over wood, any swelling of the wood if it gets wet is going to cause the grout lines to crack. In a wet area, that could very likely causing more wetting of the wood substrate, causing more swelling, which in turn causes more cracking of the grout, causing more swelling, causing more cracking. A snowball rolling down hill, if you'll allow the analogy.

By setting a cement tile backer board in thin set over that wood, or merely screwing a cement tile backer down over the wood, you physically isolate the swelling and shrinking from the tiling. If you spill water on your tiling and it seeps through the tiling and through the cement backer board and into the underlying wood and causes the latter to swell, then the stress between the wood wanting to swell and the tile backer refusing to are borne by the tile backer. It's the tile backer that feels the wood under it wanting to stretch, but the tile backer board is strong enough to resist that force.

The situation is similar to standing on a fault line the day before the earthquake. There may be tremendous stresses in the rock below your feet, but you're completely unaware of it. Grout lines on the tile backer are in exactly the same position; there could be stress between the wood and the tile backer board, but the grout lines don't feel any of that stress at all. Thus, the grout lines simply don't have an excuse to crack. And, they won't crack unless and until the situation gets so bad that the cement tile backer board starts to stretch, thereby putting stress on the tiles and grout joints.

So, if we ask the question: "Can I tile over tile?" I think the correct answer is that tile, being dimensionally stable, would make as good a tiling substrate as any other dimensionally stable material, such as Wonderboard or plaster or concrete.

There may be issues with adhesion and the remaining lifespan of the old thin set holding the existing tiling in place and unknowns that exist in every situation, but these are all peripheral to the central issue, which is whether ceramic tile itself would make a suitable tiling substrate.

In my humble opinion, it would. For the reasons outlined above.

Would you not agree?


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