Radiant floor mats are the main component of a floor warming system, which many home owners enjoy because it eliminates stepping onto a cold floor after taking a shower or bath. These floor mats do not consume large amounts of energy, and they are installed beneath floor tile as a heating unit separate from the central heating system. Radiant floor mats are wired to a 120 volt electrical circuit and controlled by a thermostat fixture; many of them also have timers that automatically turn them off.

The most commonly-used radiant floor mats are made from panels of plastic and mesh; each mat is constructed with its own lead wire that can be connected directly to the home’s thermostat. One of the main things to remember when installing is to use a multimeter to check the heat resistance of each wire to ensure they are working correctly before sealing the floor mats underneath the tile. Floor warming systems are available in sizes customized to different bathroom floor plans, so it is a good idea to send a copy of the plans to the manufacturer to ensure accurate floor mat dimensions.

Tools and Materials Needed:

· Radiant floor mats

· Electrical conduit

· Wire connectors

· Thinset mortar

· Thermostat that includes a sensor

· Floor tile

· Junction box

· Staple gun

· Notched trowel

· Glue gun

· Rubber trowel

· Permanent marker

· Router

· Vacuum cleaner

· Tape measure

· Multimeter

· Scissors

Before installing radiant floor mats, note that each mat needs to have a direct connection to the lead from the thermostat; each connection needs to be made at a junction box within the wall cavity. Radiant floor mats cannot be installed in electrical series. Also be sure to install them away from the underside of shower areas, and do not allow any mats to touch or overlap.

To determine the recommended distance between adjoining mats, measure the distance between the internal wire loops in each mat; this should equal the distance between connecting wires in floor mats placed side by side. Smaller floor warming systems can be tied into existing electrical circuits, although larger ones will need their own separate circuits. Be sure to consult all local electrical codes and to enlist the help of an electrical contractor if you have never set up this type of direct circuit.

Step 1 – Install the Electrical Boxes

You will need boxes to house the timer and thermostat; these are usually about 4 feet above the floor level. Some radiant floor mat kits come with a single box for both, while others have separate ones for each. In either case, be sure to fasten them to the wall according to the manufacturer’s recommendations. You also have the option in this step to install a wire fault indicator that will monitor each floor mat for breaks in electrical continuity. This is an alternative to manually checking each mat’s wiring by using a multimeter.

Step 2 – Create Wiring Access Holes

Locate the sole plate leading to your thermostat, and drill holes for the power lead wires that come already attached to each of the radiant floor mats. Each lead will be attached to a supply wire from the thermostat within the wall, and each access hole should be made beneath the knockout plate for each corresponding cable from the thermostat box. The finished holes should join in an L shape made by drilling through the sill plate horizontally and vertically.

Step 3 –Run Electrical Wires

Lengths of conduit wire need to be run from the sill plate to the electrical boxes. When installing several floor mats, the conduit should feed into a junction box located about 6 inches above the sill plate. Each sensor wire needs only about ½ inch of conduit wire from the thermostat box. The finished floor mat installation will be powered by a dedicated 20 ampere circuit run from the main service panel.

Step 4 – Clean Floor and Finalize Mat Layout

Use your vacuum cleaner to remove any dust and debris from your floor prior to laying down any radiant floor mats. This will prevent any possible damage to wire from dust and dirt. Review the layout plan for your specific size floor mats provided by the manufacturer. If a printed layout plan did not come with your floor mat kit, most manufacturers offer online assistance in creating your own plans.

Unpack and unroll each radiant floor mat, and allow each to settle for about 20 to 30 minutes. If needed, you can cut through the plastic and mesh to fit the mats with the floor dimensions, just be sure not the cut through any heating wires within the mats. If you are using a multimeter to test the mat resistance, do so in this step; it is a good idea to check for continuity in a few different mat areas.

Step 5 – Run Sensor Wires

The thermostat sensor wires need to be run from the electrical box down a conduit raceway within the wall structure, and they end with being pulled through the access holes in the sill plate. Mark the location of the thermostat sensor on the floor, and then mark the locations of each connecting wire.

Step 6 – Attach Floor Mats and Add Mortar

Most radiant floor mats come with adhesive backing to secure them to the floor. If you are working with mats that have no adhesive, they can easily be bonded with double-sided tape. Secure the power supply leads and the thermostat sensor with small amounts of hot glue. Once all these are done, spread a coat of thinset mortar approximately ¼ inch thick over all the floor mats and allow this to dry for 24 hours.

Step 7 – Connect the Supply Leads and Sensor Wires

Temporarily cut the electrical power at the fuse box before this step. Attach the power leads from each of the floor mats to the cables coming from the thermostat inside the junction box. About 8 inches of wire should be fed into the junction box. Use cable clamps to protect each of the wires. Run the power supply lead wire and each of the sensor wires to the thermostat and timer boxes; connect these according to the manufacturer’s specifications. Turn the power back on and check that the entire floor heating system works correctly. Once you have determined it works consistently, continue with the rest of the tile installation phase of this project.