How to Insulate Concrete Basement Walls

If you would like to keep your home warmer and drier, insulating the concrete walls of your basement is a good place to start. Insulating concrete walls can be a special challenge though, since basement walls are notoriously damp and cold, making them ripe for the development of mold. Using the right combination of materials on the walls of your basement can help prevent mold from forming and keep the cold air out.

Difficulty: Challenging

Instructions

Things You'll Need:

• Cement sealant
• Paint roller
• Polystyrene insulation boards
• Styrofoam spray adhesive
• Styrofoam tape
• Tape measure
• 2-by-4s
• Saw
• 3-inch concrete screws
• Drill
• Clamp
• Pencil
• 10d Penny nails
• Hammer
• 2-inch-thick composite decking
• 2 1/2-inch wood screws
• Fiberglass and staple gun or spray foam insulation

Line the wall

1. Check the walls for any leaks or cracks. Wait until after a rain and inspect every wall that you will be insulating for signs of moisture. If moisture is getting in, seal the entire wall with cement sealer, which should be applied in thin layers using a paint roller.

2. Attach polystyrene insulation boards directly to the wall with Styrofoam spray adhesive once the cement sealant has dried. Simply spray the wall in a light application and press the board into place, holding it for thirty to sixty seconds while the spray dries.

3. Tape all of the places where the polystyrene insulation boards meet. Make sure that all cracks are covered to prevent moisture and cold from leaking through the boards.

Frame the wall

4. Measure the length of the wall and cut one 2-by-4 the length of the room for a top plate. Screw the top plate into the ceiling flush against the polystyrene insulation boards using a drill and three-inch concrete screws.

5. Cut two more boards the same length to serve as the second top plate and the base plate of the wall. Clamp the two boards together and mark both boards at 1 1/2-inches. This will be the edge of the first 2-by-4. Measure 16 inches over from the first line and mark both boards. Then measure 1 1/2 inches from that line and mark again. Continue this process of marking the boards at intervals of 16 inches and 1 1/2 inches all the way across the board. This will give you the placement of each wall stud.

6. Cut the wall studs to size. Measure the height of the wall between the top plate that is already attached to the ceiling and the floor. The wall studs will be this height, minus 3 inches for the second top plate and base plate and another 2 inches for a layer of composite decking. In the end, your studs will be the same height as the height of the basement from floor to ceiling, minus 6 1/2 inches.
   
   Attach the studs to the second top plate and the base plate by laying the top plate and base plate on the floor facing each other and placing the studs between them so that they line up with the marks you made. Each stud can be attached using two 3-inch, or 10d, penny nails.

7. Screw a piece of composite decking to the floor directly against the polystyrene insulation boards and beneath the top plate with concrete screws. The composite decking will keep moisture from drawing up into the wood, which will prevent mold in the framework and insulation.

8. Raise the frame against the wall so that it is lined up beneath the original top plate, above the composite decking and flush against the polystyrene insulation boards. Screw the second top plate to the top plate that is already attached to the ceiling and screw the base plate into the composite decking.

Insulate the wall

9. Fill in the cavities in the wood frame between the studs with insulation. Choose either standard fiberglass insulation or spray foam insulation.

10. Install fiberglass insulation by placing the insulation in the openings of the framework. Staple the insulation to the wood frame with a staple gun to hold it in place.

11. If using foam insulation, spray the foam insulation into the open places in the framework. The foam will expand and stick by itself, without need for additional adhesive.

References

• Home Construction Improvement
• Wayne of the Woods
• Sizes.com