When mold takes hold

Discovering that your house has been slimed by mold can be a shocker. Find out why it happens - and how to prevent it.

It can happen in the midst of a home improvement project, an archaeological expedition to the basement or attic, or even during a pre-sale home inspection.

That's when you can unearth the shocking truth: You've got mold.

Discovering a streak of black, green or reddish crud growing behind your drywall, spreading beneath your basement carpet or lurking on a wall behind the bedroom bureau can be disconcerting, to say the least.

But armed with the right information, you can learn how to eradicate mold growth, and even prevent it from coming back.

IT'S A NATURAL

The first thing you should know about mold is that it's everywhere. There are thousands of species of molds. So it's not feasible to try to rid your home of every trace of mold. But you can keep its presence at a minimum.

Neither plant nor animal, mold is classified as part of the fungi world - a world also populated by mushrooms, yeast and mildew.

Out in the forest, mold plays an important role in the ecosystem. Molds chow down on dead leaves and other plant matter, assisting in the decomposition process. A few molds have been domesticated, yoked into service to produce cheese or antibiotics.

But when mold invades our homes, it can cause health problems. The most common molds found indoors, according to the Centers for Disease Control and Prevention, are Cladosporium, Penicillium, Aspergillus and Alternaria.

Mold can grow on cellulose in building materials, on cloth, leather, wood or any other organic material that can serve as food. If you see it in the shower, it's most likely settled into the grout between tiles. There, it can feed on collected dead skin cells left over from your last shower.

Most people know mold when they see it. But if it's growing somewhere hidden, you might recognize it by its smell, which is usually described as musty, earthy or even stinky.

Mold spores - the "seeds" by which molds reproduce - are natural substances that travel through the air like pollen. All they need to take hold are a source of food, the right temperature and - most important - a steady moisture source.

You might assume that our rainy Northwest corner of the country has more than its fair share of mold. But in fact, the humidity level and temperatures are often lower here than in places like Florida or Texas, where mold growth is an even bigger problem. And the preponderance of wood structures, as opposed to stucco or brick, makes a difference as well.

"Wood is very forgiving - if you don't dump mass quantities of water on it," says Ed Keith, senior engineer with the Tacoma-based APA-Engineered Wood Association (formerly the American Plywood Association).

PUT A HOLD ON MOLD

Plugging leaks, ensuring proper drainage outside your home and making sure there's effective air ventilation inside are three of the most important ways you can prevent mold growth.

Keith says there are some common mistakes that can lead to mold problems. Among them:

* Errors in home construction, repair or maintenance. Improperly installed chimney flashing, roof shingles, windows or doors can let water leak in and lead to mold growth. Covering basement walls or floors without installing a proper vapor barrier or vent space can also lead to problems. (In fact, some experts say you should avoid carpeting in the basement altogether.) Keith reminds homeowners that caulking around windows and doors is not permanent. He advises a reapplication every few years.

* Too much moist air inside the house. Condensation on windows is a clue to this problem. Some homeowners vent their clothes dryer so that warm, moist air flows inside instead of outside. Keith says it's a misguided attempt to conserve heat, but will only end up causing too much moisture in the house.

* Venting the bathroom or kitchen fan into the attic instead of outside can promote mold growth in the attic.

* Airtight construction. Designed to save energy by preventing heat loss, newer construction methods can also lead to mold problems, unless windows are vented or there's a forced-air ventilation system in the house. In the absence of a built-in home ventilation system, you need to open doors or crack windows to create a cross flow of air.

* Poor drainage around the foundation, downspouts that release rain too close to the house, even clogged gutters that send water cascading down the foundation: All can lead to damp basements - and mold.

MOLD-RELATED ILLNESS

A few years ago, a particular type of mold known as Stachybotrys got a lot of bad press. News stories reported cases of homeowners driven from their houses by what was described as "toxic mold" or "black mold." Some reports linked the mold, called stachy for short, to a type of pulmonary hemorrhage in infants. But the CDC says that the link has not been proved, and instead urges more study of the disease.

Other reports fingered mold as the culprit in chronic fatigue, memory loss and other conditions. Health officials say that these links have not been proved, either.
What is known is this: Some people are sensitive to mold, and they can experience allergic reactions. These include a stuffy nose, itchy, watery or red eyes, wheezing or skin irritation. Inhaling or touching mold spores can prompt an allergic reaction in some people. Allergic reactions to mold are common, according to the Environmental Protection Agency.
Mold can also provoke asthma attacks.

A certain type of pneumonialike disease is caused by chronic exposure to mold, usually in a work environment.

Finally, molds pose a grave danger to people with compromised immune systems.
The CDC says fretting over what type of mold you have in your house isn't necessary. Rather, the agency says, all molds should be treated the same with respect to potential health risks and removal.