Question: My house was built in 1926 and has cinderblock walls in the basement. I would like to finish the walls with 2-by-4s, insulate with a vapor barrier and cover with wood paneling. I also thought about putting a 6-mil plastic sheet between the studs and block wall, as it sweats during the change of the seasons. I run a humidifier in the basement spring and summer. My question: Is it OK to put the plastic between the studs and the wall?
Answer: I don't think it's a good idea to use a vapor barrier against the concrete-block walls or between the block walls and the new wood walls. The trapped moisture would migrate to the wood plate on top of the block walls where it would condense back to a liquid.
When wood gets wet and stays wet, it will decay. Do not use a vapor barrier between the wood studs and the paneling. Moisture trapped between the block walls and the new wood walls would soak the insulation and cause the new paneling to warp.
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It is a good idea to control the humidity levels in your basement, especially after the walls have been paneled, and the way to do this is to dehumidify the conditioned air. A heating/cooling contractor should be consulted on the size and type of conditioning unit you will need. In most cases, the existing central air-conditioning system will handle the humidity levels in the basement. However, if you have to add ductwork for the basement it may be necessary to upgrade the central air-conditioning system for the added rooms.
To insulate the basement, use a thin layer of Styrofoam insulation glued and secured to the block walls. Construct the interior walls of common 2-by-4 lumber set at 16 inches on center and make sure the bottom (sill) plate is pressure-treated lumber to resist decay and infestation.
Leave a small gap of one-quarter to one-half inch of clearance between the Styrofoam insulation and the 2-by-4 wall. You may find that the basement block wall has some bowing or curving that can be hidden if you have a space between the two walls. The space also serves as a capillary break to prevent water damage to the wood wall should the block walls sweat or leak.
After electrical wiring and cables have been installed, insulate the stud cavities with a Kraft-faced fiberglass insulation, making sure the Kraft paper faces the paneled side of the wall. Secure the insulation with staples to the face of each stud. If you plan to use a thin sheet of finished paneling, I would recommend you first cover the stud walls with half-inch-thick drywall to provide a firm mounting surface. Thin paneling will warp and cup if there is no backing for support.
