How to Insulate a Basement Floor

  • 6-20 hours
  • Beginner
  • 500-1,250
What You'll Need
A push broom
A wet/dry vacuum
Concrete sealer
A paint roller
A paint roller pan
Polyethylene plastic sheeting
Duct tape
A utility knife
Pressure treated lumber
Rigid foam insulation
Galvanized wood screws
Masonry screws
Tongue and groove subflooring
A drill

Insulating a basement floor requires a simple framework for the insulation. You will gain a more comfortable home environment, a mold-free basement, and savings on your yearly energy bills.

Step 1 - Clearing the Basement

Remove all furniture and storage items that are located in the basement area.

Step 2 - Checking the Floor

Be sure that the floor of your basement has no water issues. If there are water leaks or plumbing problems, deal with them before you begin to do any insulating work.

Step 3 - Sealing the Cement

Use a strong concrete sealer to seal the cement basement floor. Check with a professional at your local hardware store for the best brand and type of sealant for your home improvement job. Use a push broom or wet/dry vacuum to remove all dust, dirt, and debris from the concrete floor.

When the floor is completely clean, pour the concrete sealer into the paint roller pan. Use a paint roller to roll a layer of the concrete sealer onto the concrete. Allow the sealer 24 hours to dry. Apply a second coat of sealer with the paint roller. Allow the second coat of concrete sealer 24 hours to dry thoroughly.

Step 4 - Laying the Plastic

Place sheets of polyethylene plastic onto the sealed concrete basement floor. The plastic sheets should overlap by 3-inches. Apply a strip of duct tape on the seam between the plastic sheets. Use a utility knife to remove any excess plastic.

Step 5 - Building the Framework

Be sure that the lumber you are using for the framework is pressure treated to prevent it from rotting over time. Place the 2x4-inch boards on the floor around the entire perimeter of the basement with the flat side facing down. Use a drill and 3-inch masonry screws to secure the boards to the concrete floor.

The screws should be secured every 2-feet. Space the boards by 1-inch. When all of the boards have been placed onto the floor, the framework will look like a grid. Secure the boards to the lumber around the perimeter of the basement floor.

Step 6 - Installing the Rigid Foam Insulation Boards

Install 1.5-inch thick rigid foam insulation into the spaces between the boards. Use 15-inch wide rigid foam boards. Cut the boards with a utility knife, to the necessary lengths.

Step 7 - Covering the Insulation

Use tongue-and-groove plywood to cover the pretreated lumber and insulation boards. Use a drill and screws to secure the plywood to the frame. Secure the galvanized 2-inch screws every 8-inches along the plywood.