Insulating a Concrete Basement Floor

Installing Sleepers and Rigid Foam Insulation to Build an Insulated Concrete Basement Floor

By Mark J. Donovan

If you have plans of finishing your basement and desire a warmer feeling floor, and/or plan to install wood or carpet flooring, you may want to install a subfloor. Installing a wood subfloor over your basement’s concrete floor will enable you to insulate the concrete basement floor and prevent the threat of moisture damage to your wood or carpet flooring.

To insulate a concrete basement floor you first need to build a grid of sleepers (2x4s) over the basement floor. This can be accomplished by using either pressure treated 2x4s or 2x3s.

Building the Wood Subfloor

To begin the process of installing a basement subfloor, you should first confirm that you do not have a water problem in your basement.

Assuming there is no basement water problem, you should then apply 6 mil thick polyethylene plastic to the floor of the basement. Make sure you overlap the seams by approximately 6 inches and tape them with duct tape. The plastic should also go up the basement walls 4 to 6 inches. Apply an adhesive to the back of the plastic to have it stick to the walls.

Next, install the pressure treated 2x4s, on their flat side around the perimeter of the basement using a powder actuated nail gun to secure them to the concrete floor.

It is best to begin the installation of sleepers at the highest point in the basement floor, thus, you can install shims where necessary to raise the subfloor to the highest subfloor level.

 Basement Remodeling Bid Sheet

Use a spirit level frequently to make sure the sleepers are installed level to each other and throughout the basement floor area.

Next, install a grid work of 2x4s, again on their flat side, in-between the perimeter of 2x4s. As you install the grid of sleepers, use a spirit level and apply shims where necessary to make sure the floor is level.

With the grid work of 2x4s installed, now install rigid foam insulation in-between the sleepers.

Once the insulation has been installed in-between the sleepers, install ¾” tongue and grove plywood or Oriented Strand Board (OSB) to the sleepers.

Once the plywood or OSB decking has been installed, your basement floor should be much warmer and is ready for wood or carpet flooring.

Insulating concrete basement floors

For more help on Basement Additions, see’s Basement Remodeling Bid sheet. The Basement Remodeling Bid Sheet will help ensure that your hire the right contractor so that your basement remodeling project is done correctly and you get the project finished on time and budget.

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