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Handyman on Call

Does she have to run a dehumidifier in the basement?

Q. I have just purchased a home that has a partially finished basement. During the home inspection, it was pointed out that the carpeting was put directly on the slab. There are two dehumidifiers running 24/7. No moisture was noted. What should be placed on the slab before any type of flooring and what flooring would be best?

Hampton, N.H.

A. Moisture got into a basement from water vapor coming up through the concrete slab in a closed-up basement. There is nothing you can put on a basement floor that will stop water vapor, except a 6 ml polyethylene vapor barrier under the slab. Since that is not practical, you can continue with the carpet, if that is acceptable, and the dehumidifiers that must run in still air (no ventilation).

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Since no moisture is detected, I suggest you shut down one of the dehumidifiers. If no more moisture is detected, shut down the second, and use one when needed. Also, you could also use ventilation to keep the basement dry and save using the dehumidifiers, which are very expensive to run. Avoid venting in hot, humid weather. The best flooring on a concrete slab is large-sized ceramic tiles. Then area rugs can be used.

Q. I am planning on refinishing a bedroom floor. I was hoping to just use three coats of Vermont Natural Coating PolyWhey floor finish on the freshly sanded floor. Do you know of any downside to using this product? What about durability? After it cures, does it still give off odor as does a regular water-based polyurethane?

LIZ NASH, by e-mail

A. I don’t know anything about PolyWhey floor finish, and I know even less when I Googled it. It’s amazing how manufacturers give long “descriptions” of a product without saying what it is and what it’s made of. According to the website for Vermont Natural Coatings, PolyWhey uses “recycled whey protein” to make a sealer and topcoat in one. But since you ask me, I think three coats of a water-based polyurethane varnish will do very well and last many years. All finishes smell when they cure, but the water-based ones have the least smell.

Q. We have something that appears to be growing behind our refrigerator and can’t figure out what it is. The crust crumbles when touched. The back of the refrigerator is dry and there is no water source above this wall. When it creeps out to the other side of the wood partition we wipe it up, but it keeps coming back. Any ideas what it is or where it’s coming from?

MATT COLLINS, Boxford

A. It seems as if moisture and mold, which comes in many colors including the ubiquitous black, are deteriorating the plasterboard. The moisture is caused by water vapor condensing on the plasterboard in a very tight enclosure, restricting air flow, and apparently it comes and goes. To fix it, replace that section of plasterboard and paint it, then pull the refrigerator out to provide more air circulation. Make sure there is good space under the fridge and above it as well as to the sides. You might have to enlarge the alcove for more air flow.

Globe Handyman on Call Peter Hotton also appears in the Sunday Real Estate section. He is available 1-6 p.m. Tuesdays to answer questions on house repair. Call 617-929-2930. Hotton (photton@globe.com) also chats online about house matters 2-3 p.m. Thursdays. Go to www.boston.com

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