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Old 09-30-2010, 12:29 PM   #1
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frustrated with thinset


I'm trying to lay ceramic tile over an (electric) heated floor in my bathroom. The electric floor mats have been installed and are buried under a 3/8" layer of thinset (per manufacturer instructions... luckily, thats just a minimum thickness!). I'd be all set to start tiling... IF i could get rid of the high and low spots in the thinset.

I've tried evening out the floor by spreading more thinset and cant seem to get it right. After several tries, there are still high and low spots. Its getting better with every try, but the locations change- so I know its something I'm doing wrong. I know the high spots can be sanded down with the tile stone (no big deal there!), but the low spots are random and range from about 1/8"-1/4" deep.

I'm getting kinda frustrated... Is there a trick to this? Or can I make up the difference with adhesive when I install the tiles?

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Old 09-30-2010, 07:24 PM   #2
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frustrated with thinset


I'm not a floor tile guy but something doesn't sound right there. Did you let the thinset dry? It just seems like that thinset should have been spread to 3/8" minimum as the manufacturer stated then the tile set in before the thinset set up. If you are talking about wet thinset, they sell tile levelers at the home improvement stores that look relatively easy to use.

I would be interested in hearing what the tile pros say.

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Old 09-30-2010, 07:35 PM   #3
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frustrated with thinset


The idea situation is a perfect flat floor. You need to get rid of the really bad spots, high and low. Your notched trowel will help with some of the floor being uneven. You just have to be aware, when installing, if your tile is too high or if it's too low. You may need a little more thinset on a tile that is low in relation to others around it or remove some thinset if a tile is too high. A bad floor makes for a tougher installation. I just installed my daughters bathroom tonight and had a couple where I had to put just a little thinset on a couple of tiles to bring them up so they where even. Good luck.
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Old 09-30-2010, 07:47 PM   #4
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frustrated with thinset


Joneus,

So, you're saying the manufacturer says to cover the warming mats with 3/8" of thin set mortar? I'd like to read that. What brand mats do you have?

BTW, those mats warm the tiles, they will not warm the room. It's not heat as in 'in-floor-radiant heat'. I'm sure you knew that but some may not.

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Old 10-01-2010, 12:00 PM   #5
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Joneus,

So, you're saying the manufacturer says to cover the warming mats with 3/8" of thin set mortar? I'd like to read that. What brand mats do you have?

BTW, those mats warm the tiles, they will not warm the room. It's not heat as in 'in-floor-radiant heat'. I'm sure you knew that but some may not.

Jaz
The mats come from "Warmly Yours" and, yes, in the instructions, they say to cover the mats with thinset to a 3/8" minimum thickness and then tile. Of course, looking at the website, their instructions are different between the website and the written instructions that came with the mats (the website says to cover with 1/8" thinset, let it cure, then add the tiles with a second layer of thinset.

I think I need to call them...
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Old 10-01-2010, 07:49 PM   #6
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Thinset mortar dose not have large stones in it and is easy to scrap down using a razor scrapper. Use a straight edge and check your floor. Circle all of the high spots and scrape them down 1/8 inch tolerance is all that is needed. Depending on the size of the tile you will be using anything from a 1/4 to 1/2 inch notched trowel.
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Old 10-01-2010, 09:05 PM   #7
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I installed a similar installation in my house. Be EXTREMELY careful if you scrape down the thinset that you do not nick the wire with the razor, this will ruin your installation and make your day very bad indeed. When installing thinset over wire, you need to be very careful not to nick the wire with the notch on the trowel, possibly the Warmly Yours instructions suggested using a plastic trowel when applying thinset over wire. We actually used a metal trowel, but were extremely careful about nicking the wire. A little tense I would say.
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Old 10-01-2010, 09:25 PM   #8
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Boy, those instructions, even the short video is real bad, no wonder it's confusing.

In the written instruction they do mention a total of 3/8" of thin set from the top of the element to the bottom of the tiles. But that includes the approx. 1/8" bonds coat.

In the video they show SLC while at the same time talking about thin set and SLC. If you didn't know you'd think that stuff in the video was thin set, it's SLC.

I would use SLC and if the floor is level I'd try to keep it at 1/8" or a hair more. If the floor is not level you will end up with areas that are thicker of course. Be sure to plug or dam all holes and gaps with foam. BTW, Self Leveling Cement, is not entirely self leveling, needs a little help.

The spec for flatness is within 1/4" in 10 ft. AND 1/16" in 12" of the required plane. For large tiles, shiny and or rectified, I 'd want within 1/8" in 10 ft. instead.

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Old 10-02-2010, 10:54 PM   #9
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I would use SLC and if the floor is level I'd try to keep it at 1/8" or a hair more. If the floor is not level you will end up with areas that are thicker of course. Be sure to plug or dam all holes and gaps with foam. BTW, Self Leveling Cement, is not entirely self leveling, needs a little help.

The spec for flatness is within 1/4" in 10 ft. AND 1/16" in 12" of the required plane. For large tiles, shiny and or rectified, I 'd want within 1/8" in 10 ft. instead.

Jaz
Can I put SLC over the thinset? If so, do I let it cure before starting to tile? Or can I use it as an adhesive?

Thanks for the specs! My tiles are 11 3/4 x 11 3/4 x 1/4" ceramic with a matte finish. I laid out the "dry run" today and was really pleased that only a few of them rocked when laid into the grid. It looks like the biggest dip is 1/4" deep, along the short wall where the toilet will go.

Quote:
I installed a similar installation in my house. Be EXTREMELY careful if you scrape down the thinset that you do not nick the wire with the razor, this will ruin your installation and make your day very bad indeed. When installing thinset over wire, you need to be very careful not to nick the wire with the notch on the trowel, possibly the Warmly Yours instructions suggested using a plastic trowel when applying thinset over wire. We actually used a metal trowel, but were extremely careful about nicking the wire. A little tense I would say.
The instructions didnt mention anything about a plastic trowel (tho, that would have been a good idea!)- they just gave reminders to be careful to not nick the wires on pretty much every page!

The wires are already completely covered. I suspect thats where my problem started with trying to keep everything level without nicking the wires. Luckily- they passed the circuit test after the thinset covering!
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Old 10-03-2010, 07:57 AM   #10
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frustrated with thinset


If you dry laid the floor with only a couple that rocked, fix those spots and fill that 1/4 deep spot. Your 1/4" x 1/4" notched trowel will help with some of the uneven spots. Based on what you have said I wouldn't put down the self leveler. Just make sure you add thinset to a spot that is low or it will be hollow and eventually crack. You can remove a little thinset if a tile is too high but it would be better to get rid of the hump before starting. Good luck
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Old 10-03-2010, 08:25 PM   #11
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All of those heat suppliers suggest the thinset method of cover up as an alternative to the Self Levellers. That method is just plain stupid. There is just no way that can be done without major issues. Self Levelling Compound is the only way to cover the heat systems.

SLC's cost considerably more than thinset but as you can see is the only way to go.

YES, you can go over the entire mess now using SLC. Be sure to use the correct primer first.

There is no way a novice could successfully do what they suggest using thinset - HELL, even a pro wouldn't attempt to do that.
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Old 10-03-2010, 08:52 PM   #12
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There is no way a novice could successfully do what they suggest using thinset - HELL, even a pro wouldn't attempt to do that.
THAT, right there, makes me feel a WHOLE lot better... because I sure as s&!% have no idea what I'm doing. I'm taking it really slow, researching as much as I can, and giving it my best shot (as the ultimate plan for this badly built lake cottage will be to bulldoze it, put in a real foundation, and drop a modular on it... but thats YEARS down the road!)

Thanks, all, for your help!
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Old 10-03-2010, 09:08 PM   #13
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Don't waste any more of your time with the current plan. Use SLC and get back on the right road to completion.

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