How to Install Radiant Heat Under a Solid Wood Floor

In this video This Old House general contractor Tom Silva demonstrates how to install radiant heating under solid wood floors.

Steps for Installing Radiant Heat Under Solid Wood Flooring

1. Fasten the heat transfer plates to the underside of the old floor with ½-inch screws. Install two parallel rows of plates between each pair of floor joists.
2. Snap the flexible PEX tubing into the grooves of the heat transfer plates. When necessary, bore ⅝-inch holes through the joists to continue the run of tubing.
3. Cover the tubing and transfer plates with aluminum foil.
4. Spray open-cell foam insulation between the floor joists, covering the foil and insulating the tubing.
5. Use a ⅛-inch notched trowel to spread flooring mastic onto the old hardwood floor. Work in small sections to prevent the mastic from drying out.
6. Set the new hardwood flooring down into the mastic, then fasten it with an 18-gauge pneumatic nailer filled with 1-inch nails.
7. Use a hammer and chisel to pry the floorboards tight together prior to shooting in the nails.
8. Fill the nail holes, if desired, with wood putty, then sand the floor smooth.
9. Apply at least three coats of polyurethane to the new floor.

Materials

• Wood putty

Tools