Keep Mold From Taking Hold

Rebuild Smarter

Rashida's house sits on piers 3 feet above grade, but when the levees broke the area was flooded with 6 feet of water. So unfortunately, her main protection against future flooding is faith that the levees will hold. But for many of the city's citizens who live in postwar housing, a first line of defense is to elevate their homes to weather a storm surge, a traditional building practice in the area.

Beyond just keeping out of a flood's path, innovative construction practices can minimize the chance of mold coming back. At Louisiana State University in Baton Rouge, Claudette Reichel oversees La House, a demonstration home that showcases both essential measures and what she calls lagniappe, Louisiana French for "a little something extra."

Essential antimold steps include ­sloping soil away from the house, ­water­proofing the roof by tying it down with extra fasteners and special edging to ­resist wind, and assembling walls with interior air flow so moisture can ­evaporate. In hot, humid ­climates like that of New Orleans, moisture usually moves from the outside to the air-­conditioned inside, so a sealed interior surface creates a habitat for mold in the walls. "No vinyl wall coverings, no impermeable paneling," Reichel says.

Some lagniappe approaches are simple, like leaving a gap (covered by chair rail) between a wall's lower and upper drywall panels so moisture can't wick up, limiting flood damage. At the other end of the scale is what Reichel calls a "drainable, dryable wall." You move the wiring above the flood level and spray a 2-inch-deep layer of closed-cell polyurethane foam between the studs. Leaving the rest of the space empty, you screw on paperless drywall, which contains nothing that mold can feed on, but you create small gaps at the top and bottom that are then covered by crown molding and baseboard. If another flood occurs, you just pry off the molding, flush out the wall cavity from the top, vacuum up the water at the bottom, and set up fans so the wall dries quickly. "If the house were under water for six weeks, the paperless drywall probably wouldn't survive," Reichel says. "But with shorter-term flooding, it would often be restorable."

The preventive measures at Rashida's house will take their cue from these recommendations. The walls will be finished with Georgia Pacific's Dens­Armor, a paperless drywall, and the insulation will be Icynene, an open-cell spray foam that contains nothing cellular for mold to feed on. Icynene is porous, so as long as floodwaters aren't contaminated, the insulation will drain and dry out easily with no lasting ill ­effects. So if there is another disastrous flood, with a little cleanup, Rashida will be able to return to her house quickly, relieved to know that this time she has truly escaped the mold.

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