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?