Q. I occasionally receive framing lumber that has some mold on it. Will this mold continue to grow and cause rot once the wood is in the dry? Do I have to clean it off? I’m also concerned about customer perception.
A. Mac Pearce, an environmental health consultant in St. Paul, Minn., responds: Decay is a process that starts with wood and ends with dirt. Surface mold growth is the beginning of the process. If the wood stays wet enough for long enough, wood rot can set in and destroy the structural integrity of the lumber. By themselves, most molds lack the digestive enzymes needed to penetrate the complex matrix of lignin compounds. Therefore mold growth on framing lumber tends to be confined to the surface, where the colonies feed on wood sugars and cellulose. By aggressively treating the surface, you can render the wood “good as new.”
First scrub the wood with soap and water, then soak it with bleach for 15 minutes before rinsing. The wood can then be sanded and painted with a fungistatic coating. If damp conditions return and persist, mold will grow on the wood, regardless of its past history — but leaving the moldy surface untreated gives the process a head start. Cleaning the wood properly leaves it at no greater risk for further mold problems than wood that has never shown previous mold growth.
Unfortunately, this is a time-consuming and therefore expensive procedure. Better to select lumber that has no visible mold growth. If your lumber is delivered with mold on it, your lumber supplier should be giving you a big discount. If the mold is the result of poor storage on the job site, then you’ll have to bear the cost.
Given the choice, customers will always pick a building that is mold-free. Trying to persuade a buyer that a little mold on the framing lumber is no big deal has to be a tough sell.
