Insulate Basement Walls

Using Blanket Insulation
Measure the height of the wall and use a utility knife to cut insulation batts to fit snugly between the top and bottom plates - the horizontal members to which studs are attached. Make sure it fits well between the studs, too. If you are using high-density (R-15) unfaced batts or special unfaced insulation for masonry walls, press the insulation into place. If you are using a faced batt, press it into place and staple the flanges to the edges or sides of the studs every 8 to 12". Work from the top down, pulling the flange down as you staple to remove any puckering.

Helpful Tip

To cut fiberglass insulation, you'll need a sharp utility knife and two scrap pieces of plywood. Place the insulation kraft (paper) side down on a scrap of plywood. Lay a board across the roll and press down to compress the insulation while you cut through the insulation with a sharp utility knife in one or two passes.

Safety Alert!

Airborne Fiberglass is irritating to your skin, eyes and lungs. Always wear a dust mask or respirator and gloves when working with insulation. Be sure to wear safety glasses and clothing that covers your skin. Wash work clothes separately and run an extra rinse cycle.

Using Rigid Foam Board
Using a utility knife, cut the foam board insulation to fit in between the studs on your wall frame. It helps to bend the board a bit where you're going to cut and then slicing through with the knife. Using construction adhesive, attach the boards to the basement wall. Don't use nails, as the holes will make the insulation less effective.

In walls perpendicular to the first-floor joists, cut short lengths of unfaced batt insulation and press them between the joists and against the band joist. On walls parallel to joists, press faced insulation with the kraft side facing toward the floor above, holding it in place with wire insulation hangers pressed between the joists. Faced insulation may be used only if it will be covered with drywall.

Helpful Tip

In very cold climates, insulating the band joists with batt insulation can result in condensation on the band joist. As an alternative, carefully cut blocks of extruded polystyrene foam against the band joist and seal with caulk around the perimeter. This will prevent moist interior air from getting behind the insulation. Cover the insulation with drywall for fire protection.

If you use unfaced insulation, you'll have to apply 4-mil polyethylene sheeting over the entire wall. Staple it to the top plate and studs, and seal any accidental tears with duct tape or red construction tape sold for Tyvek and other air-infiltration barrier films.

Once the insulation is installed, it's time to hang drywall. Building codes require that you cover insulated walls with gypsum drywall, wood paneling or some other wall finish.

Because it's the most commonly used, the following steps outline how to hang drywall. A single layer wall of 1/2" or 5/8" drywall is the easiest, fastest and most economical way to cover your newly insulated wall frame.

Mark the location of studs on the floor using chalk. Measure the dimensions of your stud wall to determine how much drywall sheeting you'll need and how to cut the pieces so all the will sheets fit. You can easily cut wallboard with a scoring or trimming knife and a 4" straightedge. Using a T-square will help you get an even and straight cut.

Measure accurately and make marks with a pencil before cutting the wallboard. Using your straightedge, score along your marks. Hold the knife at a right angle to the board and score completely through the face paper, making sure to cut through the paper and into the inner core. The board will break easily at the point where it is scored. After the drywall snaps, trim the paper on the uncut side with a pair of shears or a sharp knife.

Use drywall nails or a drywall gun and drywall screws to fasten each sheet to the wall studs. Attach the sheet in a couple of places first to hold it in place. Pushing the drywall sheet firmly against the wall frame, start in the corner and fasten the drywall to the studs, placing screws or nails every 6" to 8". Continue around your basement, butting sheets against each other and making sure the ends are centered on studs. Use drywall joint tape to cover and seal the seams. Once all drywall has been installed, you're ready to prime and paint your new walls.

Congratulations! You've insulated your basement walls and made your home more energy-efficient while adding value to your home by getting a start on a finished basement.