About this Project

Finishing off a basement? Rigid foam insulation planks or soft blankets or batts offer two ways to go. Which you choose depends on where you live and how much space you're willing to give up to the installation.

If your winters are mild, you can get by with a R-value of 7; in colder areas, aim for R-11. To achieve either of these R-values with batts or blankets, you'll need to frame out 2x3 or 2x4 stud walls over the masonry walls, then staple the insulation between the studs of your new built-out walls. You then can cover the wall surface with drywall or paneling.

Rigid foam insulation planks let you keep a new wall's thickness to a minimum because their R-values per inch are higher. Simply line the walls with furring strips, then glue or friction-fit planks between the furring. But because of foam's combustibility, building codes require you to cover it with a minimum of 1/2-inch drywall -- even if you're planning to install wood or hardboard paneling as your final finished surface.

Solve moisture problems before you begin. Seepage or leaks render insulating materials useless. Don't worry about mild condensation; insulation and a vapor barrier usually will eliminate this.

Insulation is less critical below ground level. To save money, you might insulate only that part of the wall the extends above ground level -- although insulating the walls' full height will provide additional value. Either way, pay special attention to spaces above the sill. As with crawlspace walls, these insulating techniques could cause frost-heave problems in extremely cold regions. Check your local building codes for approved insulation procedures.