- 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
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.