Although electric under-floor heat in the bathrooms uses a fair bit of energy (9 watts per heated square foot), it is a little luxury that we can choose to use or not to warm our feet in the cool of our winters.
We bought the Flextherm heating system kit, which includes the appropriate length of green-covered heating cable for the size of the room, as well as round guides for the wire. The thermostat is purchased separately. I chose to donate the guides to the Habitat For Humanity Restore (whence cometh many of our building materials).
The Flexsnap system
Instead, I purchased the Flexsnap 12″ gridded squares to clip the wire into. It is easier, will raise the level of the tile equal to the 3/4″ fir flooring that meets it at the doorway, and at $2 each, for a small room, I thought I could justify the expense. Another advantage is that they stabilize the floor so that a second layer of plywood is not necessary before tiling. Some internet research suggested that one could just hot-glue the wires in place, forget about the guides or gridded squares. I’m very glad I didn’t try cheaping out on that step. It would have been constricting, and I would fret over whether I was damaging the wires.
The orange Flexsnap blocks are quick to install directly onto the plywood sub-floor with screws.
The heating cable clips into the tiles, 3 or 4 inches apart. It starts near the thermostat.
After installing, the wire needs to be checked with an ohmmeter (or multimeter) to make sure it is conducting electricity/verifying the resistance/not broken.
I’ve spent far too many hours cutting the white 1″ square tiles out of the all-white 12″ blocks of tiles and replacing them with brown ones. 88 x 25 = 2200! 
The "renovated" bathroom tiles.
I hot-glued them into place, but found when it came time to install them, many of the brown tiles fell out of the blocks. Just made more work. I learned that only good-quality large glue sticks work, not the little craft sticks.
All the voids in the Flexsnap tiles have to be filled with the flat part of the trowel before the notched trowel is used to raise the mortar to accept the ceramic tiles. The 88 square feet of floor used up four 50-lb bags of polymer-modified mortar.
Raff came to help, mixing the polymer-modified mortar in the wheelbarrow for me, so I could steadily apply the tiles on top of the Flextherm heating wires. This made the job go much more smoothly.
The bathroom floor
{ 3 comments… read them below or add one }
Aah, but the floor looks fantastic! And matches the cabinetry.
Nice work Ma and Raff!
Yay floor. Looks terrific. Looking forward to seeing more cabinets in too! The tub is going to be so beautiful on those tiles.
I want one too! I’m jealous that you got mocha brown. It may be my new favourite colour.