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jmille72 11-19-2007 03:14 PM

20" Porcelain Tile with heated wires - Please help!
I am ready to begin putting down my porcelain tile, but having read more, I am wondering if I should go with a smaller tile. I have 3/4" plywood floor on 16" joists. I put 1/4 hardibacker down on top of this. I am running heated electrical cables on top of the hardibacker prior to tiling.

My first question is whether or not I should install self-leveling mortar over the wires and let that set prior to laying the tiles. The wire manufacturer says you can do it either way. I'm concerned with the cost of the self-levelilng mortar as I'm doing about 300 square feet. However, I'm concerned with trowelling over the wire and damaging it if I don't use the mortar. Any advice on this from the experts is greatly appreciated!

My second question is concern about using "large" tile such as 20" x 20". We are debating using smaller tiles (13 x 13), but we prefer the 20 x 20. Are the larger tiles more likely to crack? What is the minimum trowel side I need to use? Do I need to backbutter the tiles?

I really want to do this right especially since I am spending a lot of extra money on heating the floor!


NateHanson 11-19-2007 08:15 PM

I'm no pro with tiling, but I've done enough to know that large tiles need flat floors. If you have slight inconsistancies in the floor, the tiles will not lay flat, and you'll have some corners higher than others where they meet.

I've also heard that electric radiant heating mats are easily damaged. And if you damage it during installation, you'll have to tear up the floor to get it working.

So I'd take every possible precaution to protect the radiant wires, and also to provide a flat floor for the mammoth tiles. I'd use the Self-leveling mortar.

Steven62 11-27-2007 03:17 PM

Heated floors, leveling etc.
If you want the best results possible, and you are not a tile installer, I suggest using self leveling mortar. It is actually easier to avoid "lippage" with the big tiles than smaller ones, and it can be done as you go. With self leveling mortar, I have heard that it is not as strong as thinset, and some underlayments do not work well with it, and are not TCA approved for that use, so make sure your floor meets the deflection requirements.
Snagging the wire is generally not an issue if it is well attached and you are aware that they are there, and trowel accordingly.
Most, if not all electric floor heating cables are repairable even after they are under the tile, but it will obviously require demolishing at least one tile to get to it, and there are tools for locating the faults as well. At least Suntouch is that way. If using thinset, use a minimum 3/8" notch trowel for tile that big, maybe bigger. Best ask an expert in tiling on that one.
I hope this helps!

Brik 11-29-2007 08:38 AM

I recently did one of these. Electric radiant heat wires and large tiles (12"X20" iirc). I did not do the self leveling stuff first. I used a 1/4" notched trowel on floor and back buttered the tiles (to fill in between the ridges on the back)

The Mfg of my particular radiant had a little buzzer/tester you could buy and install that would tell you if you broke a wire during install. Teh idea is to leave it hooked up while you are working, if anything went wrong the alarm would sound. I didn't buy the thing and had no problems but I was careful and had done many tile projects in the past. The one I'm talking about was my first with elec heat.

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