How to Use Rigid Foam Insulation on Basement Walls and Floors

Lead Image for How to Use Rigid Foam Insulation on Basement Walls and Floors
  • 8-24 hours
  • Beginner
  • 800-2,500
What You'll Need
Concrete sealer
Rigid foam insulation
Broom or dust mop
Dust pan
Concrete sealer
Painters roller
Measuring tape
Pressure treated lumber 2x4s several planks
3-inch masonry screws
Utility knife
Finishing nails

If you are redoing your basement and need to add rigid foam insulation, there are a few steps that should be taken before you begin. However, after checking on a few minor things, you will be able to add the insulation with just a few of the right tools.

Before You Begin

If your basement floor is made out of concrete as most are, you will need to make sure it is completely sealed before adding the insulation. You can do this with a concrete sealer. Many hardware stores will rent them if you do not want to purchase one for this project. The way you seal your floor will depend on the sealer model you obtain. Make sure you follow those directions correctly as it is important that your floor is done correctly.

Make sure that you do not have a water problem in your basement. If you ever get leaks or if your basement floods during the year, you should not place insulation on the floors as they will immediately get ruined. If you want to still add the insulation, make sure that all water issues are fixed prior to the installation.

Clean the Floor

Make sure that you completely clean the floor before you being to lay insulation. Make sure that there is no dirt or grime left behind. You can use a broom and dust mop to ensure that everything is picked up.

Apply Concrete Sealer

Once the floor is completely clean, you will need to apply 2 layers of concrete sealer with a painter’s roller. You may need to wait between each coat to allow it to dry. Follow the manufacturer’s instructions that came with your brand of sealer.

If you want to place insulation on your walls as well and the walls are made from concrete, you will need to apply 2 layers of the sealer to each. However, you may want to wait until your floor is completed before doing this step.

Build the “Sleepers”

Once the floor has been cleaned and sealed, you will need to build a raised floor, and to do this, you will need to build “sleepers” throughout your floor. If doing your walls as well, you will want to follow the same process after your floor is done.

To do this, you will need to lay out your 2 x 4s around the room against each wall. Use masonry screws to connect them to the walls and floor. Once they have been laid around the room, you will need to lay down an additional 2 x 4s every 16 to 18 inches from each other from one side of the wall to the other. Once you have created these sleepers parallel to one wall, you will want to place additional sleepers in a cross-way that will allow a grid-like pattern. On this opposite way, you can place new sleepers every 3 to 4 feet.

Install the Insulation

Place your rigid foam insulation between the sleepers in the open areas. You may need to cut the insulation down with a utility knife to make sure it fits properly between each grid.

Cover with Plywood

Once the insulation has been placed, you will want to cover it up with plywood. Marking where the sleepers are on the wood as you go, place the plywood over the sleepers and use finishing nails to hold it in place. It is good to place nails every 6 to 10 inches to keep the plywood stable.

Once you have finished these steps, you can add plaster to the walls and or carpets to your floors for a better home-style look.