# Thinset for over Radiant Heat



## Pheasant89 (Apr 1, 2011)

I am putting electric radiant floor heat under a tile floor which is over a concrete slab floor. This is the first time I am doing this so my question is after the grid is in for the radiant heat I have to put a 1/4 in to 3/8 in. Skim over the wire with thinset as followed by directions can I use the cheaper 6.50 a bag thinset from Home Depot to skim this and the use Flexbond to lay the tile with which I always use. There is the 14.00 Versa bond which would be my next option but I was wandering if I needed that being it was grabbing to concrete which is now covered by rug. Floor leveler is a option which I just heard but at 30.00 per bag it puts it way out of budget for this job. 

Thanks


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## donerightwyo (Oct 10, 2011)

IMO self leveler is the only way to go. Trying to put thinset over it is a pita.


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## Pheasant89 (Apr 1, 2011)

now that I see it i wish I would allowed for it but were looking at close to 400.00 worth of Self Leveler at 3/8 of an in at 240 sq. ft. Any ideas on how to put the thinset down , thinking of using 2 pices of moulding 3/8 thick as a screed guide.


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## bowtie (Feb 4, 2012)

Thin-set will not be fun to level with, if you're not able to use "self leveling", use some type of float, not mortar. Custom makes a bedding float that would work much better than mortar..


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## angus242 (Oct 20, 2007)

Pheasant89 said:


> now that I see it i wish I would allowed for it but were looking at close to 400.00 worth of Self Leveler at 3/8 of an in at 240 sq. ft. Any ideas on how to put the thinset down , thinking of using 2 pices of moulding 3/8 thick as a screed guide.


I think there is some confusion here. My calculations are different than yours. I come up with _way_ less than $300 worth of SLC; closer to $250. And why would you need 3/8" thickness? What kind of heat mat is this? Most mats I've dealt with can be covered with 3/16".


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## Pheasant89 (Apr 1, 2011)

Its not a mat it is the Warm Tile radiant heat in 220 it has nail down strips which you you go in and around with coil. The nail down strips seem to me to be at least 1/4 in alone. and in a 50 lb,
. bag of self leveler you get 50 sq ft per 1/8 of an in. so 3/8thick 3bags per 50 sq ft 240 square ft = 15 bags 15x30=450 its getting worse


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## angus242 (Oct 20, 2007)

I dunno. Even in the Warm Tile instructions for cables over plywood, they say, _"Floors with heating cables installed are typically 3/16" higher than those without heating cables"_

And why are you paying $30/bag for SLC? Even the better grade SLC I get is only $17/bag.

But this is your job and you are the one with the strips in hand. If you say they are 1/4", then that's what they are. Personally, I would not want a layer of thinset at 3/8" thick as a substrate for a tile installation. Most thinset is not designed to be that thick and will most likely shrink and crack. Thinset is designed to be troweled at that thickness and then flattened with tile. 1/16"-3/16" is about the true thickness of most thinset applications once installed. 

If it costs you $450 for SLC, I'd considered just eating it and having the install done properly. Maybe you could be a good salesmen and explain the dilemma to the HO. See if they'll split the cost with you. We all make specification mistakes. I'm sure they'd rather have an install designed to last than save $225 on the overall cost.


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## Pheasant89 (Apr 1, 2011)

Angus , I am holding a strip now in my hands and after the crimp is folded it is a 1/4 in to the top of crimp so I would sure want to be a hair higher than the crimp. Also a 50.lb bag of Level Quick brand SFL at Home depot is 29.50 here in Philia.So maybe at the tile supply house I might pay maybe 2.00 cheaper if that or possibly more . What brand floor leveler do you get for 17.00 for 50.lb I will look into it for sure.


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## angus242 (Oct 20, 2007)

I use Mapei products. I don't have pricing in front of me for the "cheaper" version, NovoPlan Easy but the better grade NovoPlan 2 costs me $17/bag + tax. 

You're highly limiting yourself by shopping at HD; both with options and pricing. Furthermore, you really need to be careful with shelf-life with the products you purchase there. I imagine SLC at HD is not a hot seller and you might end up with bags that have been on the shelf too long.

I know none of this is what you wanted to hear but it's the reality of your situation. At least you'll never under spec this type of installation again. :thumbsup:


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## Mud Master (Feb 26, 2007)

I'd eat it and consider it a learning experience rather than risk doing a sub par installation.

Even if you don't have a better supplier and rely on home cheapo for your material, I'd rather spend $400 on one job than to risk my reputation when the floor fails.

Good luck.


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## rjconstructs (Apr 26, 2009)

Don't forget to include a bonding agent in your costs. Make sure all the wires are covered completely with self-leveling. Test your system constantly before tiling.


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## HandyHails (Feb 28, 2009)

$30 per bag for me too. Bostik Duralevel. 3/8" sounds about right for warm tile. I used the cable type all the time. I always use slc at 1/2".

Generally it's in master bathrooms. I lay half inch cbu under any areas that don't get heat and a perimeter of about four inches around the room. Primer on plywood and then I lay the wire. Metal lathe gets installed over that. I then just pour my slc over the floor heating element using my cbu as a sort of form.

I know this doesn't really address your question, but it may help next time.


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