Electric radiant heat, installed directly over cement board, plywood, a mortar bed, or a concrete slab, is a plastic mat with interwoven heater cable. The mat is imbedded in thinset before the final flooring material is installed. A wall-mount thermostat or timer controls the heat.
The 120-volt circuit or power source for the radiant heat mats must be GFCI-protected. Mats are available in a variety of lengths. Check the manufacturer's specifications for the wattage your situation requires.
About 8 hours to install mat, wire, and tile for an average bathroom
Digital ohmmeter, drill, 1/2-inch bit, drywall saw, fish tape, chisel, hot-glue gun, 3/8-inch trowel, screwdriver, stripper, long-nose pliers, lineman's pliers, tools for laying the flooring, jeweler's screwdriver
Stripping, splicing, and connecting wires to terminals; installing boxes; running cable into boxes; setting tile
Rough-in the plumbing; install the subfloor.
12/2 cable, mat, box, armored power cable, thermostat and/or timer, thinset, flooring, mortar or grout
Press down on the tape to adhere it to the cement board, then pull off the backing and firmly press the mat onto the tape. Weave the sensor bulb between two heating elements. Adhere the sensor bulb wire with dots of hot glue. Check resistance with an ohmmeter. Record the reading.
With the flat side of a 3/8-inch notched trowel, apply thinset over an area of the mat. Then turn the trowel over and rake the thinset to 1/4-inch uniform depth. Be careful not to snag the mat. Do not clean the trowel by banging it on the mat. Tile the area of the floor covered with thinset.