Builders tend to tackle the job of insulating basement walls the same way they insulate a home’s walls that exist in the upper walls of the house – by framing interior walls with fiberglass batts. If dampness exists and this material becomes wet, the basement walls’ ability to dry out becomes much more difficult – if not impossible – than if the walls had remained bare cement.
Of course, wisely insulating basement walls really begins during home construction. Builders thinking ahead this far make sure the grade of the property slopes away from the foundation of the house, and that guttering and downspouts divert rain away from it.
But when faced with an “after-the-fact” situation in which adding basement wall insulation becomes necessary, some things do exist to help remedy the situation. For instances in which walls stay predominantly dry, installing extruded or expanded polystyrene as a first step makes an economical and effective beginning to insulating basements walls. Seal all joints with mastic and then cover with mesh tape. This prevents the humid air of the basement to come into contact with that of the cooler basement wall and cause condensation.
Use gypsum board to cover the polystyrene, leaving enough space to install electrical hook-ups. After this if your budget allows, pouring a three-inch concrete slab over the existing slab would help ensure an even higher degree of comfort and would also help guard against dampness, but at close to five dollars per square foot, this option may not be viable for many homeowners.
Insulating basement walls that are constantly wet entails a much greater endeavor involving adding perforated drain tile to removed sections of the basement’s foundation. Grooved, extruded polystyrene is then added to the interior walls with the addition of drain mats to divert water to a pre-constructed drainage system at the walls’ perimeters.
Additional concrete is then poured to replace that removed for the drain tile and then gypsum board is installed against the walls with a half-inch allowance (or more) allowed at floor level to prevent dampness if the floor gets wet.
For either dry or wet situations, insulating basement walls does not present an easy task. Be prepared for a good week’s worth of work and plan ahead by doing the job during dry weather. Good luck and remember – there are worse things than the job of insulating basements walls!