Instructions on how to Insulate Concrete Block Basement Walls
By Mark J. Donovan
|If your basement has concrete block walls, and you are looking to either finish the basement or create a warmer basement, you should insulate the concrete block walls. When contemplating how to insulate concrete block walls you basically have two choices, insulate just the interior concrete block walls, or both the interior and exterior of the walls. Insulating the exterior concrete block walls involves digging around the home’s foundation and installing rigid foam insulation up against the walls and then backfilling.
In regards to insulating inside concrete block walls, the best solution is to attach wood framed stud walls, or furring strips, up against the concrete block walls, and then adding insulation in-between the stud bays, or furring strips.
If you create standard 2×4 walls you can install an R-11 (3.5” thick) insulation in-between the stud bays. If you use 2x4s attached to the concrete block walls on their flat side, known as attaching furring strips, you can install rigid foam insulation with R-values between R-4 and R-8.
|Before installing any framing walls or insulation up against the concrete basement walls, however, you should first attach a vapor barrier to the concrete block walls. Make sure to tape all of the seams. This will help to reduce moisture from permeating inwards from the concrete block walls onto the insulation.
If you choose to create framed stud walls, the walls should be constructed using pressure treated 2×4 lumber for the bottom plate, and standard kiln dried 2×4 lumber for the top plate and vertical stud members.
The vertical stud members should be placed on 16 inch centers. The framed stud walls should be nailed and glued (e.g. Liquid Nails) to the concrete basement floor, as well as nailed to the first level floor joists.
If you attach 2×4’s on their flat side up against the concrete block walls, fasten them to the walls with Tapcon anchors or a powder actuated nail, and some liquid nails. The furring strips should be placed on 16 inch centers.
An alternative technique for insulating concrete block walls, is to first install rigid foam insulation up against the concrete block walls (after installing the vapor barrier) and then build the 2×4 walls. You can then add additional rolled or batt insulation in the 2×4 walls to create an even higher R-Value for the concrete block walls.
By following these simple insulation techniques you should be able to create a drier and warmer finished basement.
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