First Aid for the Ailing House by Henri de Marne

Vinegar and Peroxide Fight Mold Growth on Porous Surfaces

Q: I have mold in the hollow cement block wall in the basement which has a 24-hour running dehumidifier.

Recently, I came across an article that suggested using white vinegar to kill the mold. The article also suggested using one cup of 3 percent hydrogen peroxide per gallon of water to treat the mold. It was said that these two solutions were better than bleach, as bleach causes fumes. Another benefit cited was that vinegar and hydrogen peroxide kill mold on porous surfaces.

Please advise if the white vinegar or hydrogen peroxide is effective in treating mold. Thank you and best regards. -- via email

A: Both distilled white vinegar and hydrogen peroxide will do an effective job of killing mold spores in porous materials. Bleach can only kill mold on non-porous surfaces, as it does not penetrate porous surfaces; so mold roots are left to grow again.

To kill mold spores and their roots, pour straight 3 percent peroxide (H2O2), undiluted, into a spray bottle and saturate the blocks with it.

Let the H2O2 do its work for 10 to 15 minutes, and scrub the walls to remove all dead mold.

You can add vinegar to the H2O2 in the spray bottle to make the solution stronger.

Q: We could really use your expertise to figure out what is causing water marks on a bedroom ceiling. We read your weekly column in the Daily Herald and hope you can help us solve this mystery.

The house is two stories built in 2008. There are three water mark strips along the ceiling of an upstairs bedroom. (I've attached a few photos.) The water strips are approximately four feet apart and five feet long. We originally thought there was a problem with our roof. However, after looking in the attic, there does not appear to be any water damage on the backside of the drywall where the stains are showing in the bedroom. Also, the joists in the attic run perpendicular to the water markings. There are no water lines in the ceiling. We cannot figure out what is causing this problem.

Do you have any idea what might be causing these markings? What type of repair service (roofer, general contractor, etc.) should we call? Any information you can provide would be greatly appreciated. -- Hoffman Estates, Illinois, via email

A: I only received two photos, and the water mark is only clear in one of them. One photo shows a ceiling fan, and the other shows what looks like the base of the same ceiling fan on the other side of the fan.

Assuming the above, it looks like I only see one continuous water stain. If the stains are parallel and four feet apart, it looks like they are at the joints between two drywall sheets.

I really need some clearer photos and a more detailed description to be of help. As it is, I can only make some assumptions, which could be incorrect.

For instance, since the ceiling joists are perpendicular to the water marks, are they attached to a flush center beam or do they run straight through from one exterior wall to the one opposite?

Please send me as many photos as needed to show the entire affected area, and all other data you can find.

INTERESTING COMMENT FROM AN ILLINOIS READER: "I read your column weekly in the Daily Herald. I am a landlord with seven units, so I have found many useful tips in your column over the years.

"This week you had a question about hair spray on bathroom walls (or doors). I have two ideas to share on that topic:

"1. If the buildup is thick, the fastest/best thing I have found is denatured alcohol applied with a white paper towel or cloth. Turn the cloth often as the buildup transfers to it. Remember to turn on the bathroom exhaust fan and to first check a small, out-of-the-way spot to make sure the surface isn't compromised by the denatured alcohol. (I've never had a problem, but I know that if you leave denatured alcohol on latex paint it can soften the paint.) I got this idea by looking at the ingredients label on the hair spray. Denatured alcohol was one of the first ingredients.

"2. For regular maintenance after the buildup is removed, use shampoo. I dissolve a quarter-sized dollop in about a cup of hot water and use a sponge to apply. Let it set for a minute or two, and then wipe down. Rinse with clean water and dry with a towel. When you think about it, this makes lots of sense, because it gently removes hair spray buildup from hair.

"Thank you for your service to the community!" -- Schaumburg, Illinois, via email

Thank you for a very good solution to this problem, which I have been asked about several times over the years.