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Tiling over Electric Radiant Heat Mat

SGRepp's picture

I'm putting electric radiant heating under my bathroom floor tile in a small bathroom.  I'm using a brand "DomoTeck", which was recommended by my tile supply house.

The heating element is a wire that zig-zags back and forth, and is held by a fabric mesh.  The directions recommend embedding the heating element in thinset, applied with a 1/4" notched trowel, then "flattening out" the thinset on top with the flat side of a trowel.  Easy enough.

My question: The heating element is only supposed to go under non-obstructed tile -- nothing under the toilet or vanity. In my case, the floor area is about 20 sq ft total, and I'm using 10 sq ft of heating mat. So, what do I do on those parts of the floor where the heating mat isn't installed? Do I need to build those parts up, using either floor leveler or even 1/4" HardieBacker board?  Or will the difference betweeen those parts of the floor that have the mat and those that don't small enough that I can just run my tile (12" square tiles) over the entire floor and not have a noticeable slope between the two slightly-different surface levels?

I did read this article, written by Tom Meehan:

in which he describes installing a similare radiant heating mat. After he thinsets down the mat, he writes "and the remainder of the job is a regular tile job".  It sort of IMPLIES that he justs runs the finish tile over both the areas with and without the heating mat, but doesn't specifically say so.

But I'm a little worried that the parts of the floor with the heating element are going to be thick enough (maybe 1/8" to 3/16's" ??) that I'll be able to notice the slight difference in heights.

Anyone have any recommendations on how to handle this?



You level out the floor, (post #209594, reply #1 of 7)

You level out the floor, roughly duplicating how you embedded the mat, but with no mat.

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Again... (post #209594, reply #2 of 7)

Tom's article doesn't mention anything about leveling out the rest of the floor, and rather implies that he just tiles over both areas.

Steve (post #209594, reply #3 of 7)

I think fairly new from schluter-the benefit of uncoupling w/heat cable added.  Cover the floor and put the cable where you want it.

Then, thinset the tile-no filling in where there's no heat.

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There are so many options (post #209594, reply #7 of 7)

There are so many options available when it comes to your flooring needs and generally many prefer to go for the natural stone tiles to beautify their floors as they not only offer a luxurious look and feel to the floors but are also sturdy and durable in the long run at all.

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Too late! (post #209594, reply #4 of 7)

Yes, I saw that Schluter had announced this product - unfortunately, after I'd already started the install of the other brand!

I'll definitely use that on my next bathroom job...

SLC (post #209594, reply #5 of 7)

Not sure how adept you are at tiling, but troweling thinset flat over a bathroom floor can be a bit of a pain. Even if you trowel it dead flat, if the "thin"set went on "thick", as the thinset cures it can shrink here and there and give you a wonky out-of-flat floor. I highly recommend instaling the RFH mat, tacking it down, then covering it with SLC. 

If you've never use SLC, it's all in the preparation. SLC will give you a stellar dead-flat base to tile upon for both your heated and non-heated sections of floor, and it works fabulously well with RFH mats.

What is the heating mat installed on top of?

Also, the thing that goes bad in an electric RFH installation is usually the floor temp sensor. I usually install two sensors and run the wires of both to the j-box. I'll wire up one sensor and leave the second set of wires capped, labeled, and waiting in reserve. Just in case.

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Thanks! (post #209594, reply #6 of 7)

I'm pretty good at tiling -- not a professional, but have done 5 or 6 different projects with pretty good results, and had a long apprenticeship working for my GC neighbor while putting myself through college .

I ended up doing roughly what you suggested there, with the exception that I installed a layer of 1/4" HardieBacker in the areas where the mat wasn't being run.  The mat embedded in thinset was a bit lower than that (maybe 3/16ths"), so I used self leveling compound to bring the areas over the mat up to the same level as the HB, then thinset & tiled over the entire area. Looks pretty good, if I do say so myself! The mat is installed over a layer of 3/4" plywood, which is screwed on a roughly 6" schedule over the 3/4" subfloor.

Yeah, I had read that recommendation to install two sensors from someone else, but in my eagerness to get it done, neglected to run the other one as a backup, so hope I don't run into issues.  Haven't wired up the heating mat yet, but everything ohms out ok, so hopefully I'll be good.

Thanks for taking the time to respond! (Still wondering how Tom Meehan installed his tile in that article though!)