jimrutherford.com 1990-2016
Home Improvement:
Kitchen Electrical and Lighting The Computer Modeling Basement
The tile substrate starts with a layer of 3/8” plywood underlayment screwed to the top of the 3/4” plywood subfloor.   There are a ridiculous number of screws - running every 8” in the plywood with 6” at the underlayment edges.  As usual, Ruby is helping.

NuHeat Warm Floor

Cabling

Warm Tootsies!

One of the many unplanned detours on the project was the last minute decision to put in electric heating elements in the thinset below the tile floor.  Although I’m a fan of radiant heating where the building surfaces radiate heat rather than heating the air, this was really just to take the edge off winter mornings on bare feet.
After finishing underlayment, each cabinet is marked in permanent marker so that the electric cable can be planned without needlessly heating underneath cabinets or a refrigerator.
Note how the grid goes to where the toekick will wind up in the cabinet, but not under the cabinet itself.  The guides have pegs that are pitched at every inch.  So we used a 3” pitch for most of this floor..
The last bit is finished, but then we found out that the floor was not at all flat.  There was a distinct ridge in the plywood centered around a basement lally column. We hadn’t discovered this until the thinset part was all done.  It looked flat, but a 6 foot straightedge showed that we’d after flatten the floor.
Here, you can see the spool of electric cable that is run back and forth between the guides.  Off the right side of the picture is the black lead that goes up into the wall to the floor heating thermostat.
We had enough cable to continue down the hall and into the hallway half bath.  Since you can’t (or are not supposed to) trim and rejoin the cable, it is handy to have an area where you can run the cable long
The finished cable grid is shown below.  This was a relatively straightforward process.  There is a more popular option to go with pre-wired thin mats that are thinset-ed into place onto the underlayment.  this is both easier and less expensive for a regular layout like a simple combination of rectangles.  However, each rectangle has its own leads and all of them have to be make it back to a (big) splice at the thermostat.  I didn’t like the idea of 5 thick cables coming up through the wall and the pair of 5-wire splices, so instead I ordered the long cable / guides, and ran it in the pattern below.   The cable has a dead-end at the far side, and the cable actually has both electrical wires inside so that so that the circuit is formed.  Obviously, there is no ability to field-trim the cable
The manufacturer (NuHeat, in this case) supplies cable guides that can be easily cut and tacked into place so that the electric grid of cables stays neat until embedded in thinset mortar
After running the cable and before somebody breaks it from walking on it, the cable is covered in either thinset or Self Leveling Compound.  We chose Laticrete 254 latex modified thinset.  Incredibly smooth, sticky, and hard when cured.
Another batch of Laticrete being mixed and troweled over the wires.
II had a couple of helpers on this one - That’s Ruby and Joe above