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Every day I get home improvement questions by email from people across Canada, and I do my best to answer as many as I can. Below you’ll find a Q&A exchange I had with JM, a homeowner looking to finish an old basement. The questions and answers here apply to many basement situations.

JM We bought a 1927 duplex and discovered a huge and smelly mouse infestation in the basement. My husband took out all the ceiling, drywall and old carpet, but the smell remains. What can we do?

SM I love old houses, but most hold a surprise or two. Mouse infestations are common, and an ozone generator is the best way I know of to get rid of bad smells in all situations.

JM A foundation guy has quoted $10,000 to fill foundation cracks. Does this seem reasonable?

SM It’s absolutely unreasonable! That’s an absurd price based on what I’ve seen in your photos. For $500 to $1,000 in materials you can fill and reinforce those cracks perfectly yourself with the best materials available. I wouldn’t trust anyone who quoted me $10,000 for this job. Crack injection in addition to carbon fiber reinforcement of the crack zone offers the best repair.

Which type of exterior wall insulation?

JM There are 2×6 studs forming exterior basement walls right now. A basement professional said that the fiberglass insulation that used to be there was fine, but we took that out based on your videos. What should be do?

SM Basement finishing professionals are often the last people to give reliable advice about the long-term performance of certain basement strategies. How often would a basement finishing professional cut into walls they built in, say, 1999 to see how they’re doing today? That simply doesn’t happen. Any kind of exterior wall system will work fine in a basement at first, but the issue changes with time. How will it resist internal mold growth 10 or 20 years down the road?

I’d definitely steer clear of any kind of fiber-based insulation between those studs. Spray foam applied between the studs would do a better job, but another option is to take down those existing studs on exterior walls, then reuse them for partition walls. This leaves you free to use rigid sheets of foam on the exterior walls, or insulated basement wall panels.

JM If we use spray foam between the studs won’t it be too close to the wall and not allow for a vapour barrier?

SM If you want to go with spray foam, apply a closed-cell type between the studs and against the masonry wall, but only after coating the masonry with a waterproof paint such as Drylok or Xypex, just to be sure.

JM The concrete floor has heaved a bit in one spot, so we’ll need to level that area. After that we planned to use 24” x 24” subfloor panels followed by underlay and carpet. We’ve been advised not to use the foam subfloor panels but you’ve recommended them before. Is one better than the other?

SM Foam subfloor panels work well and do deliver somewhat more warmth underfoot than panels with plastic legs on the bottom. A new product called InsulArmor is a dense, all-foam subfloor panel that delivers the most warmth of any subfloor option and is fastest and easiest to install in my experience. It’ll be available here in Canada later in 2021.

How long have you been in the house? How dry has the basement been during this time? I always advise at least a year of observation to verify that the basement is truly dry all the time.

Steve Maxwell teaches people how to finish their basements properly online. Visit him online at BaileyLineRoad.com for made-in-Canada home improvement and woodworking resources.

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