Heating Floors With Electric Radiant System

Learn how to warm up those cold tiles with a radiant heat floor system.

A radiant heat floor system is easier to install than you might think.

* Note: The installation process for this project takes place in the bathroom.

Materials and Tools:

electric radiant heat floor system w/ thermostat
pry bar
cement backer board
utility knife
thinset adhesive
galvanized screws
notched trowel
fiberglass mesh tape
hot glue gun
drywall saw
paddle bit
bathroom tile
grout and grout float
damp sponge


1. First, remove the door threshold, then move on to the baseboards and molding. Use a pry bar and hammer to loosen the baseboards carefully. Remove the bathroom door from its hinges. Take the time to remove the commode, as well, to make this job far easier.

2. Use a T-square to mark cement backer board for floor installation. Use a circular saw to cut the board, or score and snap the board to the desired measurements.

3. Spread adhesive on the back of each backer board and place the pieces over the existing vinyl floor. Walk on the boards to set, then secure them with galvanized screws every 8 inches.

4. Be aware that adding backer board and tile to the existing floor raises the height of the floor. Door jambs (and even the bottom of the door) will have to be adjusted. Do so by using tile to determine the future height of the floor and cut the door jamb with a saw.

5. Fill each seam between backer boards with adhesive and a notched trowel. Press fiberglass mesh tape into the adhesive, then spread a second layer of adhesive over the tape. Take care of all seams and allow to dry.

6. Before installing the radiant heat mats, check the resistance with an ohm meter to make sure they meet factory qualifications. Sweep the floor of all debris and you are ready for the layout.

7. First, measure off 6 inches from the toilet, tub and wall edges and make a mark (except around the vanity, where the mat will reach to the edge). Lay out the mats and secure them with double-sided tape. You can also use a stapler on the orange weave section to secure.

8. Take another resistance reading to make sure the mats weren't damaged during installation. Do NOT overlap the mats. Also make sure that the mats are laid so that the "cold" lead can easily make it back to the thermostat.

9. Address the wiring by first scoring the backer board with a utility knife and, with a chisel, cut a groove into the board that the wiring will lie in. Attach the sensor conduit with the provided screw. Then, place the cold lead and factory connection wires into the groove and spread hot glue over the wires to hold them in place. Allow the glue to dry.

10. Locate the thermostat box 60 inches from the floor. It's a good idea to place it near a light switch. If you feel uncomfortable running the wiring at this stage, consult an electrician. Cut the area away where the thermostat will be located with a drywall saw.

11. Cut a hole at the bottom of the wall and use a drill and paddle bit to bore two holes at the bottom plate – one hole for the leads and another for the sensor to route the wiring to the thermostat. Drop a string down through the hole and attach the wires – then pull the string back up to the thermostat hole.

12. Pull the conduit up the same way. Remove the cap off the conduit and feed the sensor wire to the tip of the conduit. With the cold leads, run them through the thermostat box and attach the box to the wall. Wire the cold leads over the control contacts on the thermostat. After wiring the thermostat, mount it with the supplied screws.

13. You are finally ready to lay tiles. Vacuum to remove any debris from earlier work. Dry fit the tiles to find a good pattern and to estimate how your work will proceed.

14. Begin in the right corner of the room by spreading adhesive onto the backer board and over the heating mats. Spread at a 45-degree angle. Set the first tile in place with a twisting motion. Use spacers for consistency. Wipe any adhesive that works its way up through the tile. Cover the entire floor.

15. Grout the tile next by using a grout float to spread it evenly across the surface. Scrape off excess and give the tiles a good cleaning with a damp sponge after 20 minutes. Once the surface is dry, buff the tiles with a dry cloth.

16. This project takes three days to complete and costs around $1,000.

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