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Ask the Remodeler: That dank smell may indicate a danger

Ask the Expert Home Improvement
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Q. Three summers ago, while we were on vacation, the faucet head in our town home’s two-car garage burst, causing substantial flooding in the wall between the garage and the mudroom/kitchen and in the garage itself. A landscaper saw the water cascading down our driveway.

We had the wall repaired and painted around the faucet head, yet three years later, the garage still seems damp; condensation forms on the windows of the doors but not on the two large windows on the other side of the garage. The real issue is the increasingly horrible dank, dirt-like odor that has permeated the small mudroom/kitchen. We smell it all year long, but the odor becomes significantly stronger as the weather warms. Any ideas on how to fix this? I have washed down the mudroom and kitchen walls with bleach and OdoBan, but this helps for only a few days. Should we repaint the entire garage, including the floor, as well as the mudroom with a mildew-killing primer? We are desperate.

C.R., North Grafton

A. I am sorry to be the bearer of bad news, but this is a problem that is going to involve more than surface cleaning. The affected walls are going to have to be opened down to the studs and frame. Based on what you are describing, you are going to find mold on the wood framing. A mold-abatement company should handle this. You probably don’t have wood rot; it sounds as if the leak was caught in time. The wood will need to be treated and allowed to dry out completely. You will need to reinsulate and apply new wallboard and plaster. This should all be done as soon as you can. Allowing mold to fester can pose significant health hazards.

Q. Your predecessor answered this question, but I wanted to see whether it is still the prevailing wisdom. What do you think of insulating the roof? By that, I mean spray-foaming between the rafters and eliminating all the venting, making the attic airtight. Should it be open or closed-cell foam?

R.C., Northborough

A. Good question. Insulating the underside of your roof is still an excellent way to tighten up your home and change its thermal envelope. You definitely want to use closed-cell spray foam, which will allow you to seal off all venting holes. There is no need for vents with a properly insulated attic roof. One thing we try to do when insulating an attic with closed-cell is to encase the rafters as well, thus breaking the thermal bridging to the outside.

Mark Philben is the project development manager at Charlie Allen Renovations in Cambridge. Send your questions to [email protected]. Questions are subject to editing. Subscribe to our free real estate newsletter at pages.email.bostonglobe.com/AddressSignUp. Follow us on Facebook, LinkedIn, Instagram, and Twitter @globehomes.