Ceramic tile did not stick

[EightFingers]

I’m installing ceramic tile on concrete backer on the wall. Decided to use mortar from a bag that was labeled for porcelain tile (since I had it) - it said it could also be used for ceramic tile. 

Didn’t work. 

I mixed it correctly, let it slake and mixed again. Tiles were backbuttered.
Put up about twenty of them and they didn’t seem “right”. All came off.
So starting over tomorrow with some different mortar. 

I had to have dome something wrong, but I don’t know what it was.
BTW, I’m not new to tile work, I’ve laid at least 5000 sqft of tile before this, both ceramic and porcelain and never had this happen.

[Cabinet Monkey]

I’m installing ceramic tile on concrete backer on the wall. Decided to use mortar from a bag that was labeled for porcelain tile (since I had it) - it said it could also be used for ceramic tile. 

Didn’t work. 

I mixed it correctly, let it slake and mixed again. Tiles were backbuttered.
Put up about twenty of them and they didn’t seem “right”. All came off.
So starting over tomorrow with some different mortar. 

I had to have dome something wrong, but I don’t know what it was.
BTW, I’m not new to tile work, I’ve laid at least 5000 sqft of tile before this, both ceramic and porcelain and never had this happen.

Would be helpful to know what mortar you used and what backer board it was placed on. 

When you say they all came off - in what time period ?  Did they just fall off under their own weight or did you help them off to verify your feeling they weren’t “right” ?

Too many details missing to formulate a helpful answer at this stage.

[Snipe Hunter]

When you applied the thinset, did you just swipe it on or did you really press it onto the tile and backer before you made your final swipe?

Also, if the stuff has been sitting a long time and been exposed to even low levels of humidity, it may have hydrated. Meaning it already activated in the bag and won't have much holding power. When this happens, you'll notice that it doesn't seem quite right when mixing and it takes longer to set. It may have had clumps in it, clumps are a clear sign that it already cured. Shelf life for cement is about 6 months in good conditions.

[cams2705]

You didn't mention it, but did you use the correct size notched trough to apply the mortar?  The notch size ensures you have the correct amount of mortar for the size tile and suction effect helps hold the tile in place until it cures.

[EightFingers]

Mapei thin set. Applied to Durock brand 1/2” backer. Tiles are 16”x8”.
Mortar applied with straight edge of trowel, pressed and smoothed. Another pass with 1/4” notch edge at 45* angle. I had the idea it might be possible reuse the backer so I tried to scrape off the mortar. It was pretty well adhered.
Tiles were all “backbuttered” and pressed into place.
This is the desert, humidity is the lowest in the country. Right now it’s about 16%.

I thought it might be too risky to reuse anything, so I removed the backer and started with new.

What I’m thinking is it had to be the mortar since I’ve already tiled three bathrooms using the same procedure above. Only difference was the mortar.
Today I used Versabond mortar labeled for ceramic and porcelain.
So far no problems.

I’m thinking the Mapei product which was labeled for use on both porcelain AND ceramic is not usable for ceramic. It worked great on the porcelain I laid on the floor.

[Snipe Hunter]

Versabond and Mapei both make very good products. Never had an issue with either brand. I usually use Versabond thinset and Mapei grout. I have used "Universal" thinset and didn't like working with it at all.

[Snipe Hunter]

This is the desert, humidity is the lowest in the country. Right now it’s about 16%.

But this stuff is like desiccant. It absorbs water. 16% is still 16%... every day for how long? Mold will grow in 19% humidity with no other moisture added. I think your mortar has gone bad. Unless you are using a small format mortar on a large, heavy format tile.

[EightFingers]

Good point. I bought the mortar a week before the project. I just happened to buy too much of the “porcelain” type and I thought I’d use it up since the bag said it could be used for both porcelain and ceramic.

It could have aged quite a bit on the shelves at Lowe’s.

[Cabinet Monkey]

Mortar has a date code on it.  It's a good idea to check it whether you get it from the big box or the best tile supply in town.

Still hard to say what went wrong.   You say it stuck very well to the durock , what does the back of the tile look like in terms of residue ?   When you said you pressed and smoothed (keyed) the first coat into the backer then made another pass at 45deg........ did you add more thinset so that you had nice, consistent, full coverage  1/4" x 1/4" ridges before pressing in the back buttered tiles ?

The only other thing I can mention is that perhaps whatever mortar you used was highly modified and remained "wet" for longer than you were used to.   You still haven't said whether the tiles fell off on their own or you just thought they weren't stuck enough at the point in time which you checked.   Versabond is lightly modified, emphasis on light.   Meaning it will dry/set faster than a highly modified one.

[2link2]

To the OP if your still interested call the manufacture you'd be amazed at what they know. They will probably get the bottom of it in about 2-3 minutes after asking you exactly what you did.