DIY Network

How to Install an In-Floor Heating System

Host Paul Ryan demonstrates how to install an in-floor heating system and connect the system's heat strips using a crimping tool.

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Step 1: Determine the Layout

Mark where the cabinets will be placed. You won't have to lay tile in these areas. Snap chalk lines to mark how tiles will be placed. Make a layout of the kitchen, and make a cardboard template to determine where the island will be -- you want at least 40" of clearance for pass-through.

make a cardboard template of layout

Step 2: Install the Heating System

Install the heating system (more information on the thermoplastic polymer flooring -- Radiant Floor Heating System -- under Resources, below). Be sure to install per the instructions that come with the floor-heating kit. Use the layout made in step 1 to determine how many strips of thermoplastic polymer to cut. Cut strips with scissors. Staple them to the subfloor.

install radiant floor heating system

Step 3: Add Terminal Wires

Connect terminal wires to the end of each strip. Connect a black "positive" and white "negative" wire to the terminal board (Image 1), which in turn will go to the transformer. Start by cutting a small corner of the plastic element to expose the braided wire that runs the length of each strip. Slip the mental connector over the braided wire at the heating strip (Image 2). Insert the flattened terminal wire into the connector so the two wires are touching.

Step 4: Finish the Connections

Next, use the special crimping tool (Image 1) to crimp the connector so it's good and tight. To finish the connection, cut a short piece of self-adhesive sealant tape, fold it in half, peel away the backing and wrap it around the connection. Press out air and it will form a permanent seal (Image 2). Route all the wires into terminal boards and the transformer (Image 3) and call an electrician to install an off and on switch.

Step 5: Position the Cement Backer Board

Now that the heating elements are in place, you want to create a smooth surface over the heating strips before the tile is laid. You can do this by placing cement backer board over the heating elements. Mark where the wires are on top of the cement backer board.

Step 6: Mix the Thinset

Mix a portland-based thinset with water using a drill with a mixing paddle. After it thickens, give it one last quick spin before applying to get the right consistency. Tip: Before applying the thinset, be sure to eliminate the possibility of nailing through any of the terminal wires by marking the board to show where the wires go.

Step 7: Apply the Thinset

Apply the thinset mortar on top of the heating elements, using a trowel because the ridges in the trowel create a suction effect. This will help hold the boards in place. Note: Most thinset stays workable for several hours, but check the label for exact drying time. Lay boards on top of the mortar. Leave a small gap between the boards for expansion and compression. Use a power nailer with galvanized 1-1/4" roofing nails to secure the boards. Don't walk on the floor for 24 hours.

secure boards with power nailer




  • Radiant floor heating system (STEP Warmfloor) from Electro Plastics Inc.
  • Porcelain tile (Song/model: VS105/color: Nero) from Crossville Poreclain Stone