Suddenly, the Christmas decorations are out and we are on our way to some brutally cold weather. What could be better than a heated seat in your car as the icy temperatures approach? Heated tile floor. It is easy to install, cheap to operate, and it won’t take up any extra space! Plus, your feet will love you for it. The concept of in-heat flooring is pretty simple. While installing new tile, a mat with a continuous heating element woven in, will be placed in the mortar underneath the tile, taking that icy chill right out.
Step 1: Finding a power source
- For larger areas, it’s a good idea to install a dedicated circuit with its own wiring and circuit breaker. Having your new heated floor struggle with your hair dryer wouldn’t be an ideal scenario.
- For smaller areas, you can choose to draw power from an adjacent GFCI (ground fault circuit interrupter) protected outlet. If the thermostat you purchase is already GFCI protected, you can use any outlet. In any case, the mat must be GFCI protected.
Step 2: Ordering your custom-sized mat
- You should be able to find standard sizes at home improvement or tile stores, but you can also place a custom order for the exact size and shape you need.
- Make sure to send in a detailed drawing of the floor plan and location of fixtures. The mats are available in 12, 24 and 30-inch widths.
- When in doubt, get a smaller mat than you think you need, as the cable in the mat cannot be cut.
Step 3: Testing, testing
- Before installing the mat, make sure to obtain a resistance reading using a volt-ohm meter to make sure it wasn’t damaged during manufacturing or shipping.
- Prep your floor as you would for any tiling job. Install 1/2-in. cement backer board, securing it to the existing subfloor with mortar and cement board screws.
- Make sure that no screw- or nail heads protrude above the cement board. Sharp edges can damage the cable.
- Tape and mortar the seams to create a solid, continuous surface. Snap tile layout lines on the floor once the mortar has dried.
Step 4: Check the fit
Before proceeding with the actual installation, do a test layout. Here are some guidelines:
- Install the mat up to the area where the vanity cabinet or pedestal sink will sit, but not under it; that can cause excessive heat buildup.
- Keep the mat 4 inches away from walls, showers and tubs.
- Keep the mat at least 4 inches away from the toilet wax ring, as the heat can melt the wax.
- Keep the blue heating cable at least 2 inches away from itself. Never overlap the cable.
- Don’t leave large gaps between the mats. Your feet will be able to tell!
- If your mat is undersized, give priority to the areas where you’ll be standing barefoot more often
Following your preliminary layout, mark the path of the thick “power lead” between the mat and wall cavity and chisel a shallow trench into the floor. Notch the bottom plate to accommodate the two conduits that will contain the power lead and the wires for the thermostat-sensing bulb.
Step 5: Gluing down the mat
- Install the mat, securing it lightly to the cement board with double-face tape. To make turns, cut the mat between two loops in the cable, then flip the mat and run it the opposite direction.
- Never, ever cut, nick or stress the cable itself. Where the full-width mat won’t fit, or where you encounter angles or jogs, carefully cut the mat from around the cable, and hot-melt glue the cable to the floor. Continue using the full mat again when you can.
- Install the entire mat complete with cuts, flips and turns to make sure it fits the space right, make any final adjustments, then press the mat firmly into the tape.
- Use hot-melt glue to additionally secure the mat. Don’t leave any bumps or loose edges; you’ll snag them with your notched trowel when you’re applying the thin-set mortar. If you’re not going to tile right away, lay thick corrugated cardboard over the mat to protect the cable.
Step 6: Thermostat wires
- Fish the power lead and thermostat wires through two 58-in. lengths of conduit and connect the tops of the conduit to a 4 x 4-inch electrical box.
- Position the lower end of the conduits in the notches and secure the electrical box to the studs.
- Weave the thermostat wire through the mesh so the sensing bulb is an equal distance between wires and 12 inches into the warming area.
- Use hot-melt glue to secure the thermostat wires to the floor and the power lead in the groove. Cover the notches in the bottom plate with protective metal plates. Do another resistance test.
- Install conduit connectors to both ends of two pieces of 58-in. long 1/2-inches electrical metal tubing (EMT). Fish the power lead cable through one length of conduit.
Step 7: It’s time for the tile
- Select tile that’s at least 6 inches square so each tile will span two or more sections of cable. Smaller tiles are more likely to conform to the minor hills and valleys of the cable when you tamp them in place, creating a wavy surface.
- Spread the mortar over a 5- to 10-sq.-ft. area of floor. Use the flat side of the trowel to press the mortar firmly through the mat and into contact with the cement board.
- You can establish a flat, uniform layer by lightly floating the trowel across the tops of the cable. Then, use the notched side to comb the mortar to create ridges; a 3/8 x 1/4-in. trowel works well for most tiles. Again, lightly skim your trowel over the cable. The sheathing on the cable is tough, but you still need to avoid any “sawing” type action or jabs with the trowel. It takes a little trial and error to get a flat layer.
- The No. 1 goof that people make is slamming the edge of their trowel on the floor to knock excess thin-set loose—cutting or nicking the cable.
- Place the tile, and then tap it firmly into place with a rubber mallet.
- Do two resistance tests while installing the tile to ensure you haven’t damaged the cable. (If the resistance test fails, see the manufacturer’s instructions to find the problem.)
- Once the mortar has dried, grout the joints.
Step 8: Final steps
- Wire the thermostat according to the manufacturer’s instructions. Some thermostats have individual pigtails for securing the wires from the power lead and the cable running from the main panel.
- Have your electrician make the final connections in the main circuit panel.
- Power up the system for 10 or 15 minutes to ensure that the floor heat functions, then turn it off and keep it off for two to four weeks while the mastic and grout cure and harden.
[Always make sure to follow the manufacturer’s instructions, as products will vary.]