Pull on your sterile gloves, adjust your respirator, and take cover behind your legal counsel. It's time to do battle with the building industry's equivalent of the black plague... By Matthew Power

Rumors of threats to human health tend to come and go. Remember when Legionnaires' disease stole the headlines? Then, doomsayers predicted that the ebola virus would depopulate the world (at a time when AIDS was doing just that). The anthrax scare seems to have come and gone.

But the latest challenger in the scourge-of-mankind category, stachybotrys chartarum, aka black mold, comes with its own life support system: homeowners and their attorneys. Their growing awareness of mold has brought the building industry to its toes, by threatening to bring it to its knees. Now, according to hundreds of legal firms, "bad" mold found in a home may be linked back to a home builder or a landlord. And where human health is threatened, damages increase exponentially.

If you're one of the lucky (or smart) builders who hasn't left an opening for mold in your previous projects, now is the time to take this bull by the horns and adjust your construction practices, contracts, and subcontractor attitudes. One defect case involving mold can ruin you. It's that bad. Period.

You're not in this alone. Along with builders, manufacturers have seen the mold tsunami and have responded rapidly with new details, products, treatments, and information intended to prevent mold incursions. For example, a company called Nisus Corp., is exploding with sales of its borate-based lumber pretreatment. Originally designed to control termites, the environmentally benign stuff has a nice side effect: It resists mold growth.

And APA-The Engineered Wood Association has launched a major first strike against mold, for obvious reasons. They don't want their wood products implicated if moisture gets into the house structure. Their "Build a Better Home" (www.buildabetterhome.org) program focuses largely on construction details intended to prevent mold problems.

"One problem has been that no manufacturer wants to prescribe a complete [flashing and wall system] setup because of liability," notes Kevin Hayes, spokesperson for APA. "We're really focusing on flashing details and getting people to work together."

Steve Easley, a building science consultant and former professor at Purdue University, lectures widely on mold and its causes. He bears a lot of bad news for builders. For example, he notes that most insurers no longer include mold under their new-home warranties.

"Many attorneys believe mold is gold," he explained, in a room of about 60 builders and developers at the NAHB's International Builders' Show in February. "Now, judgments are being quadrupled because of the medical aspects. And Home Depot now sells a mold kit that tests for stachybotrys."

Best defenses

Jeff Lloyd, vice president of development for Nisus, holds a Ph.D. in biochemistry. He says that for new-home builders, mold problems often occur in the first year of owner occupation.

"In new homes, you typically have 5 tons of water in materials, when you consider concrete, lumber, drywall compound, etc. That 5 tons takes six months to a year to dry out properly. The owner has to maintain adequate ventilation. That means treating the whole house like you would a kitchen or bath. I suggest that you aim for three changes of indoor air volume per hour for the first year after a home is built. After that, one change per hour should be fine."

One of biggest builder panic areas--mold on framing lumber--may have more bark than bite, Lloyd adds, because it's probably not mold at all. Instead, its what's called ceratocystus, a staining fungus. In most cases, it will die naturally as the wood dries out. Nonetheless, he urges builders to pretreat lumber, both to prevent mold and as defense against insects and dry rot. Chemicals like borates also serve as a stopgap if moisture gets into wall cavities, allowing for necessary repairs to be made before mold forms.

Lloyd notes that adopting better building techniques will address most mold risks. "It always comes down to bad design, poor construction techniques, and homeowner ignorance," he says. "One of the big builders just came out and said, 'We're going to spend $2,000 on every home to prevent mold.' What they're really doing is improving their building quality."

Easley also offers a wealth of sound construction advice on how to deal with mold by preventing it from gaining a foothold. Like most mold experts, he focuses on keeping water out of walls and cavities.

A big believer in housewrap, Easley opposes the use of polyethylene barriers on interior walls. Walls built this way trap warm, moist air and don't allow exterior sheathing to dry if it does get wet. "Tight homes, however, are not necessarily causing mold," he adds. "Mold can grow on wall surfaces with moisture content as low as 15 percent. More important is to always keep the relative humidity indoors under 70 percent." He adds that builders should "avoid any trim detail that relies on caulking for waterproofing. Homeowners do not maintain their homes. Where caulk is required, use ASTMC-920. That's the type that will expand 20 percent."

Easley singles out four keys to moisture management: deflecting water from the exterior, providing drainage around the building and behind siding, creating wall systems that can dry out quickly, and using durable components.

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