Installing Garage Floor Insulation

Lead Image for Installing Garage Floor Insulation
  • 8 hours
  • Intermediate
  • 250-400
What You'll Need
2 by 4-inch timber
Concrete screws
Polystyrene board insulation
Duct tape

If you’re going to convert your garage, you’ll need to insulate your garage floor. Not only will this make it warmer, but the floor will be a lot safer than bare concrete. It’s not a difficult job, although it will take some time and you’ll need the proper materials in order to properly insulate the garage floor.


Before you start to insulate the garage floor, you need to clear and clean it. Start by moving everything out of the garage and sweep the concrete garage floor clean. You’ll need to clean up any stains on the floor that could potentially seep into the insulation. Once you’ve done this, allow to dry and then use a shop vac to finish cleaning the floor.

Measure the length and width of the garage. You’ll need by 2 by 4-inch lumber to be the surround and the joists on the floor. The joists will run across the garage, spaced 2 feet apart. You’ll also need to buy polystyrene board insulation. This should be 2 inches thick and 2 feet wide.


Start by putting in the surround of timber on the garage floor. Use the timber with the 4-inch side down. Drill through at 12-inch intervals into the concrete and put in concrete screws to hold the frame firm.

Once you’ve done this all around the perimeter of the garage floor, you’re ready to start putting in the joists. Begin at one end of the garage. Measure in 2 feet on either side and lay a piece of 2 by 4-inch timber. Put in place between the frame, so the gap from the frame to the joist is 2 feet. Drill and screw into place on the garage floor. Continue along the floor, making sure there’s a 2 feet gap between the joists.


Once you have all joists secure on the garage floor, it’s time to put in the insulation. The polystyrene board insulation won’t be long enough to stretch across the entire garage. This means you’ll need to connect several boards. Do this with duct tape, which will comply with most building codes. It stops the boards from shifting on the garage floor. Lay the insulation in place, making sure it’s flat on the floor. Move on to the next gap and repeat it.

To make sure you don’t step on the insulation as you move along, use boards over the joists for walking and kneeling. Continue with the insulation until you’ve covered all the gaps.


Now that you’ve laid the insulation, you need to cover it. Use 1/3 inch plywood for this. Start in one corner of the garage and fit the edges snug against the walls. Screw down onto the joists. Continue across the width of the garage, and then along the length of the garage until you’ve covered the entire garage floor.