Step 1: Prepare the Subfloor

Electric radiant floor warming systems have electrical resistance coils embedded in a mesh sheet designed for installation under a tile or poured concrete floor. Kits usually include all necessary materials and include suggested layouts you can adapt to your floor plan. The system is wired to a thermostat installed separately.

The plywood subfloor needs to be absolutely clean before the mesh is installed. Sweep and vacuum the floor and be sure there are no protruding elements in the floor that could break the coils.

Cover the floor with standard #15 (15-pound) roofing felt. Overlap the edges and tack it down with a hammer stapler or staple gun. Flatten the staples with a hammer until they are all flush with the surface.

Step 2: Test the System's Electrical Resistance

Use an ohmmeter to test the electrical resistance of the heat coils at several steps during installation to ensure that the coils remain undamaged. Coils should be tested at least four times -- before you begin, after the mesh is laid out, after the mesh is secured and just before the concrete is poured over it.

A tag attached to the mesh sheet will indicate the resistance levels recorded at the factory. Your test numbers should be within 10 percent of these numbers. Record your test results at each step.

Also test the system's ground wires to be sure there is no short in either of the two wires.

Step 3: Install the Mesh Sheet

Lay out the mesh according to the floor plan. Begin in a corner and lay one strip along the wall to the end wall. At the end of the run, use scissors to cut through just enough of the mesh so that you can turn it 180 degrees and double-back alongside the first strip. Do NOT to cut or nick the coil wires.

Staple down the mesh, again being careful to avoid the coil wires.

Step 4: Complete the Wiring

When the mat and coils are in place, secure the lead wires to the floor and run them to the wall thermostat location.

Weave the unit’s temperature sensor through the mesh (Image 1).

Install and connect the thermostat (Image 2).

At this point, an electrical inspector needs to check and approve all connections to the floor warming system before it is permanently covered with concrete or tile.

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    Image 1

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    Image 2