Replies

1. 
   carloa007 | Jul 17, 2009 03:30pm | #1

   I did a similar job recently.

   Plywood subfloor -> Hardi backer -> Heat mat -> SLC -> Thinset -> Tile

   I taped the heating mat down to hardi with the supplied adhesive strips, and then poured SLC over the mat and the unheated areas of the floor. Gave me a nice level cementitous base to tile over.

   One suggestion if you go this route is to make sure you tape down the corners of the mat. The particular mat I used was a plastic mesh, and the corners peeled up before the SLC hardered and I had to go around cutting this out and cleaning up so they would interfere with the tile.

1. 
   Piffin | Jul 17, 2009 08:55pm | #3

   SLC = self leveling compound? 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

1. 
   carloa007 | Jul 17, 2009 09:28pm | #4

   Yubba.

   It doesn't "Self Level" perfectly, so after pouring a 5 gallon bucket, I float it into place.

   Screed would give you 100% level. I didnt bother, made up for any slight variations while setting the tile with thinset.

1. 
   Piffin | Jul 17, 2009 10:21pm | #5

   I generally used it witha afloat when needed.My concern was partly that there could be some added movement where the change from heated to unheated happens.Demos I've seen had the het mat bedded into thinset too, instead of adhesive. 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

2. 
   paulbny | Jul 17, 2009 03:33pm | #2

   We just did one, we put hardi down first, then the mat, then self leveler.  Just make sure you block any floor vents well, you can guess why I give that advice.

3. 
   mike_maines | Jul 17, 2009 11:50pm | #6

   Piffin, we've done it on a few jobs--we used Ditra on the subfloor, then layed the heating elements on the Ditra.  We taped down the edges that want to curl up.  If you have a nice rectangular area it shouldn't be a problem, but we were using if for oddly shaped areas so we cut the mat and flipped it around to fill the space which made the elements want to lift up.

   Over that, float a watery coat of thinset, and let it set up.  Then tile like normal.  You might have to backbutter each tile though if your thinset wasn't thick enough to cover the wires.

   One tip--keep a continuity tester attached to the mat while tiling.  Our electrician set us up with ones that beep if you lose continuity.  If only our tiler hadn't disconnected it on that one job....

4. 
   aimless | Jul 18, 2009 12:25am | #7

   Our contractors did a lot weird stuff, but our floor so far seems really nice: subfloor - heat mat - mudbase(?) - tile. They might have used SLC for the mudbase but it wasn't watery, looked stiffer.

   That is definitely the most comfortable room in our house, and the floor is the only source of heat.

5. 
   Sbds | Jul 18, 2009 03:04am | #8

   I have had great luck using a process I read about in JLC written by Michael Byrne.

   1) Primer for SLC on plywood floor.
   2) Lath nailed down with roofing nails.
   3) Heating mat (I used Warmly Yours) stapled or taped down
   4) SLC
   5) Thinset
   6) Tile.

6. 
   Billy | Jul 18, 2009 04:10am | #9

   Check the installation recommendation of the heat mat manufacturer.  They will tell you straightaway.  Surprisingly, NuHeat and other recommend you put the heat mat under the Ditra.  They claim doesn't appreciably slow the heating of the tile and it sure does come in handy if you ever have to chip out a broken tile without damaging the heat mat.

   Here's the order:

   - thinset
   - bed the heat mat in the thinset and flatten with a wood float (don't use your steel one to nick it)
   - let it dry
   - skim coat thinset over the heat mat at a steep angle to give a protective layer for the next step
   - let it dry
   - install Ditra and tile as usual

   A few photos attached.

   Billy