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Discussion Starter #1
Hello! We just put down slate tile in our entryway. Carefully made the sure the temp in the room was above the minimum for the adhesive. Did the job right - over hardibacker, used the right tools, all tiles with an even layer of adhesive under them, the floor was nice and smooth, etc. We left it to cure for 72 hours ... and found that tiles are now loose. At first it was 5, but we have since found more. The only operator-error we can think of is that perhaps the temp in the room dipped too low at night during those 72 hours of curing. So. Do we proceed to remove and reset just the loose tiles, then grout etc .... Or do we have to assume that ALL of the adhesive is compromise and redo the whole job?? I know what I want the answer to be, but also don't want to be finding more loose times as time goes on and have a never-ending project. Thank you!!
 

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I can only surmise, by your description of what you did, that you applied your thinset too dry, OR used premixed crud. Did you mix it yourself? It is doubtful temperature would have had an adverse effect on it unless it dipped to below freezing in the room. Slate tile, may should have been installed with LFT thinset (Large Format Tile). Fill us in more.
 

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Discussion Starter #3
So, we did use a premixed bucket of adhesive (Mapei Type 1 is what I recall - the empty bucket has since gone to the dump). The stuff we got to re-do the tiles is also Mapei premix - "Premium mortar for tile & stone up to 20" for wet & dry areas." Sounds like it may be a mistake to use a premix again?? I doubt the room would have dropped below freezing. Temps outside might have gone to 31 or 32 degrees at lowest, but the room is insulated and attached to a heated house. For now we are carefully scraping the tiles & hardibacker clean.
 

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I've always have used the powdered thinset and never had a problem. It dries like concrete! Did you put the adhesive on both sides?
 

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None of the experienced tilesetters will suggest to use pre-mixed adhesive, but you should not have seen the issue that you describe even using that. My guess is that you very carefully troweled the applied adhesive, taking your time to ensure that everything was done right, but let the troweled adhesive sit for too long before laying the tile. That allowed it to “skin over”, so that a good bond with the tile didn’t happen. See this recent thread with a similar problem for how you should be testing the coverage after setting the first tile.
https://www.diychatroom.com/f84/removing-dried-thinset-other-tiles-falling-off-683447/

You most definitely need to take all the tile up and start over.

The instructions for Mapei “Type 1” says to not use for setting natural stone.
http://www.mapei.com/public/CA/products/Type_1_TDS_EA.pdf

Chris
 

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Discussion Starter #6
Thank you both for your input! We did pull up all the tile, scrape everything very clean & start again with a new (appropriate) adhesive. Here's hoping everything stays in place this time. Hands down the stupidest home project mistake we have ever made! Very grateful for you folks to get advice from - thanks!
 

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Thank you both for your input! We did pull up all the tile, scrape everything very clean & start again with a new (appropriate) adhesive. Here's hoping everything stays in place this time. Hands down the stupidest home project mistake we have ever made! Very grateful for you folks to get advice from - thanks!
Hey, don't kick yourself too much. My wife's first tile job was a disaster. She did not know to use concrete board and this was a crawl space foundation with wood subflooring. It was a big ole kitchen and it looked great when she laid it down.

Then came back the next day and everywhere we stepped it cracked and moved and pieces came up and she just collapsed in anguish. It was sad. But she did what you two did, pulled it all up, did it right and today she's a tile master. Not kidding - she's the tile expert. I do most of the cutting, and the whining, and she does all the rest.

Live and learn. Stay positive you'll do great.
 
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Are you using an appropriately sized trowel? Did you identify what the problem was the first time?
 

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Discussion Starter #9
It looks like the first time we had the wrong adhesive - one that was not made for natural stone (Type 1 Mapei). Oy. Second try is curing for another 24 hours & then we will see .... here's hoping we checked all the boxes this time! Thanks for the support, everyone!
 

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Too late now.....but with hardibacker sucks up moisture real fast.. with some adhesives you need to wet the section of Hardy that you are working on with a sponge before applying adhesive. Also as noted need right size openings on trowel, need to push adhesive hard into surface with flat side first, and need to keep trowel at correct angle while combing it out else it will be too thin. Hope it came out alright! Ron
 
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