Battling Moldy Wallpaper

Scott Gibson, Contributing Editor

I have an unusual situation involving plaster repair, mold and the conservation of antique wallpaper in my 1907 Atlanta home. Mold is growing from the inside out, penetrating the wallpaper from behind. It's only occurring on exterior walls. There was some repair work on some exterior walls a few years ago but the extent of the work isn't known. What can I do to arrest the growth of the mold without destroying or damaging the wallpaper? Is there something I can inject into the walls, leaving only a small hole in the plaster?

If only getting rid of mold was as simple as going to your doctor and getting a flu shot. Unfortunately, it isn't. Under the right conditions, mold colonies prosper. They need moisture and food, just like us, and the first step in mold remediation is to eliminate the source of water that is allowing it to grow.

Water can come from inside or outside

The list of potential sources of water from the exterior of your house is a long one. It could be getting into the walls because of damaged siding, cracks around door and window trim, a leaky roof, missing flashing or rain gutters in disrepair.

If the repairs you mention were incomplete, or poorly done, any one of those problems could be the culprit. You could start by taking a careful look at the outside of the house, starting at the roof and working down.

Think like a drop of water. Even small gaps present an opening for moisture.

Moisture that starts inside the house can be equally as damaging. Cooking, showering, even breathing all produce water vapor that can be forced into exterior walls where it condenses on cooler surfaces. A damp earthen floor in the basement can hold water and allow moisture to migrate upward and into the house.

Even air conditioning can contribute to moisture problems. In summer, the back side of your plaster walls may be cool enough to condense moisture carried in by hot and humid weather.

Bath and kitchen ventilation can help, as will covering a dirt floor in the basement with heavy polyethylene plastic.

However you accomplish it, ridding the walls of mold won't be possible until you address the cause of the problem, not its symptoms.

Yes, but how can I eliminate the mold that's already there?

Not all mold is toxic to people, but it certainly can cause health problems. It's not a trivial problem. The mold should be removed, and that's not always easy when it has become firmly rooted in wood, paper and other porous materials.

One common approach is to dry out the affected areas and scrub them with a diluted solution of bleach. This assumes, of course, that you can expose the area where mold is growing. That's tough to do when it's inside a wall you're trying to preserve. Sometimes the best solution is to remove affected building materials completely.

What you want to avoid is spreading mold throughout your house, or exposing you or your family to airborne spores. That's why mold remediation is a specialty.

Saving your historic wallpaper may not be possible. But start by calling a mold remediation company in your area that has experience in historic homes like yours. Ask for references.

Arrange for a site visit and keep your fingers crossed. If you can't save the wallpaper at least you can learn how to keep the problem from coming back to haunt you.

About the Author
An accomplished woodworker and carpenter, Scott Gibson is the former editor of Fine Woodworking magazine, and a former editor at Today's Homeowner and Fine Homebuilding magazines. He also is former managing editor of the Kennebec Journal, a daily newspaper in Maine.

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