I'm not the foremost expert on glass tile, but I've never heard of anyone saying it can't be installed over Kerdi. Sounds to me like they're having a hard time with it and trying to get out of using it by telling you that it can't be done. Just the first picture alone belies that statement. If that were true, that ceiling wouldn't be covered.

Have you called the tile manufacturer and Kerdi? I sure hope you don't have to rip it all out :( It's beautiful tile!
Monica

I'm only a homeowner and don't know about this stuff, but something smells wrong here.

Kerdi is installed with thinset.

When my contractor installed glass tiles like yours in two locations, he said he could not use thinset, but had to use "glue."

You need a more analytical, logical and broken down, description of the problem from your contractor.

What adhesive did he use for the glass tile?
Did he cover the kerdi with thinset?
What exactly is the bond that is not holding.

Why on earth did he Kerdi the ceiling?

Your best bet is to post on the John Bridge forum which is full of professional tile people and specializes in all questions Kerdi.

Good luck.

Frank

He kerdi'd the ceiling because it's a steam shower, and has to have a completely watertight envelope.

As for the contractor who used mastic, I'll guarantee you that's coing back down, whether you take it down, or it comes down on its own.

Builder and tile guy have talked with Kerdi rep and builder "thinks" tile guy used the modified thinset that the Kerdi rep recommended for glass tile.

Builder has a call in to the glass tile manufacturer, so we'll see what she has to say.

Bill - I believe my builder may be giving you a call today for your opinion. I don't think anyone really used mastic in this shower. I confused my terminology in my previous post.

Another problem is that humidity is outrageously high here right now and we think that the humidity could be affecting the drying time and qualities of the modified thinset.

I have checked out John Bridges forum and there is no consensus re installing glass tiles over kerdi:

http://johnbridge.com/vbulletin/showthread.php?t=49944

http://www.johnbridge.com/vbulletin/showthread.php?t=41088&highlight=kerdi+glass+tile

You might want to check the following thread, as well. It starts out about a different subject, but start reading at reply #14, at the bottom of page one.

Here is a link that might be useful: Re: Modifieds over Kerdi

"As for the contractor who used mastic, I'll guarantee you that's coing back down, whether you take it down, or it comes down on its own."

Glass tile was installed in kitchen backsplash and non-wet wall of bath. Do you really thing there will be problems?

The backsplash should be okay, even though mastic's not the thing to use. The wall in the bath, though, if there's a shower head over this bath, then yes, you've got problems.

Soonermagic,

Kerdi is the perfect choice for a steam shower. No if's and's or but's.

Here's the deal as best as I can describe on the forum...what follows is not a perfect description, but generalities:

Unmodified thinset cures via a chemical reaction. Essentially, it does not need air to cure and harden. The chemical reaction consumes water in the cure. Put a dollop of unmodifed thinset in a zip lock bag and it will still cure and harden.

Add a latex modifier to the thinset for lightly modified thinset? You still have the "no air required" chemical cure for the thinset, but the latex modifier needs exposure to free air to dry. No air, it'll remain slightly soft.

Highly modified thinsets need even more exposure to free air so the additional latex modified portion of the thinset can fully dry. Put a dollop of highly modified in a ziplock bag and it may not fully harden, even after several days.

What is Kerdi? A polyethylene sheet membrane. Air can't pass through it.

Air can't pass through glass tile either.

So a modified thinset will take longer to cure and harden when sammiched between Kerdi and glass than would an unmodified thinset.

Small glass mosaic tiles like yours have a lot of grout joints, the modified thinset can "air dry" through those joints. It may take longer than glass over cement board (air can pass through cement board), but will usually eventually dry.

This is why Kerdi recommends using non-modified thinset in a lot of their installation documents. It depends on what you're tiling, the size of the tile, etc, but in general Kerdi recommends non-modified, or "dry set" thinset.

Glass tile, being smooth, needs something that will grab and hold it. That's why most glass manufacturer's will recommend a modified thinset to adhere glass, as the modified has better bonding properties and has a bit more flex to it, meaning it's bond is not as brittle as a dry set bond.

Therein lays the conflict.

I've installed a lot of glass over Kerdi. You just need to know what you're doing before you attempt it.

It takes a bit of reconciliation between the tile installation instructions and the Kerdi instructions, with a bit of common sense thrown in.

Tilers need to better educate themselves before attacking installations like yours. Tile products have evolved over the years, and continuing education is the difference between a true professional and someone who just shows up to work with his lunch pail.

I'm not necessarily knocking your installer, but your GC and tiler should have been on top of this long before the first batch of thinset was mixed.

Best,

Mongo

Any recommendations for a specific thinset product to use if installing 3x6 glass tile over kerdi? (Maybe the 3x6 glass/Kerdi combo is simply too risky.)

Thanks, Bill

I cannot agree with Mongo enough! Tile installers have to follow up with all the latest installation procedures every few months at the least! Tile installation has moved forward so fast since the days of me lugging up wire and mud for a scratch coat!

To answer your question further, A silicone adhesive will dry on its own, stick to the tile and adhere to the Kerdi's fiberglass surface! You will have to make a jig to hold the tile and high enough to leave a 1/8' layer of silicone on the tile when you screed over it! Also you will have to use a grout that will move with the expansion and contraction of the tile! Its a lot of extra work and the price is going to be up there, but it will give you what you want! See paulgrubbtile.com for a look at the jig!

Good luck!

Here is a link that might be useful: paulgrubb tile .com

I tiled my fireplace surround with a glass tile. I used the wrong tile colors.. can I now tile over these tiles with another glass tile? Removing the tile is far to damaging to my surround.. it is on well with mastic.. help.