By the time hurricane Katrina's floodwaters had been pumped from
New Orleans, up to 250,000 homes had sat in stagnant water for
weeks — some for months. The combination of wet homes and
warm weather created a petri dish environment in which black mold
flourished. Spore counts reached as much as 12 times the acceptable
limits as mold quickly covered the insides of homes. The demand for
mold remediation mushroomed, and it also raised the question of how
much training a contractor really needs to do this type of work.
The answers apply not just to the Gulf Coast but to any contractor
faced with cleaning a flooded, moldy home.
While Louisiana requires contractors to be licensed for mold
remediation, the need for thousands of homes to be gutted to the
studs outstripped the supply of qualified crews. According to
George Harrison, co-owner AirScrubbers, a New Orleans mold
remediation firm, many inexperienced and unlicensed crews have been
performing such work, and he has seen them make a lot of mistakes
that may come back to bite them later. These include trying to kill
mold with ineffective chemicals, leaving materials in place that
should have been torn out, insufficiently drying the house before
starting to rebuild, and not supplying workers with adequate
Improper removal can even make a mold problem worse. And it doesn't
take a Category 5 hurricane. A tropical storm or brisk nor'easter
blowing rain through soffits and windows can soak drywall,
insulation, and carpets, which must be addressed quickly to avoid
mold growth. It doesn't necessarily take a storm: Last July, Dante
DeCapri, a building diagnostician and certified remediator of the
Richmond, Va.-based EnviroGroup, visited a $1 million home in
Williamsburg that had mold growing in part of a walkout basement.
The problem: The insulation contractor had sprayed wet cellulose
insulation between the wall studs, but the builder didn't give it
enough time to dry before having the drywall installed. "We told
him that the drywall had to be removed," DeCapri recalls. "It
wasn't that he didn't want to spend the money. He just didn't
believe it was a problem." Instead, the contractor hired someone to
spray a sealant over the drywall and repaint it. It didn't work.
DeCapri was called back in December to find that the mold had
spread throughout the basement. The only solution was to gut the
walls of drywall and insulation after the space had been finished
and the customer had moved in. "What had been a $7,500 problem was
now a $75,000 problem," DeCapri exclaims.
Mold work requires basic worker protections, including nitrile
gloves, an N95 or N100 mask, safety glasses, shoe covers, and a
Tyvek suit. If a remediation firm isn't providing this level of
protection for its crew, it may not be paying attention to other
industry guidelines for safe mold removal.
That job illustrates an important point: While the health effects
of improper mold remediation are debatable, the financial liability
isn't. In fact, the Williamsburg builder was lucky not to have
found himself on the receiving end of a lawsuit that his liability
insurance wouldn't cover. According to David Governo, a Boston
lawyer who defends builders against construction defect and
mold-related claims, insurance companies are increasingly likely to
deny claims against contractors who try to solve mold-related
problems themselves, rather than calling in a specialist. Mold
remediation may include familiar processes like tearing out
drywall, but insurers see it as equivalent to doing plumbing
without a license. "If you haven't done everything that the current
state of the art [in mold remediation] calls for, you're not
complying with the standard of care in the industry," he
That standard includes the ability to measure moisture in wall
cavities and other inaccessible places, something few contractors
have the equipment or know-how to do. It also includes precautions
to protect workers: nitrile gloves, an N95 or N100 mask, safety
glasses, shoe covers, and a Tyvek suit. If you don't require the
right protection and one of your workers files a workers' comp
claim, you could have big problems. The safest way to stay out of
trouble, says Governo, is to subcontract all mold-related work to
Specialists include companies that test the house, dry the house,
and remove or clean moldy materials. DeCapri advises builders to
hire only mold professionals certified by the Indoor Air Quality
Association (www.iaqa.org) who follow industry guidelines published
by the Institute of Inspection, Cleaning and Restoration
Certification. (The institute's Web site, www.iicrc.org, lets you
search for qualified contractors by city and state.) He also warns
that a number of so-called remediators are doing restoration work
without proper insurance, so be sure to ask for proof of
A qualified testing company can earn its keep by bringing some
rationality to an often-emotional situation. "We talk with a lot of
mothers who are terrified that their kids are going to die because
there's mold in the house," says DeCapri. He blames it on media
hype about "toxic mold."
Ed Light, a certified industrial hygienist and president of
Building Dynamics in Ashton, Md., agrees with DeCapri's assessment.
"There is a lot of misinformation and exaggeration concerning
mold," he notes. "Much of mold remediation that is going on is
based on the idea that it is like asbestos or is toxic, but mold is
normally present in all our environments. It's not toxic and does
not cause diseases. It is simply an allergen, and that is how we
deal with it."
On a significant mold job, the testing company will ask a hygienist
like Light to write a testing protocol that takes the people who
live in the house into account and outlines the conditions under
which various types of tests should be done. A good protocol will
minimize costs by specifying only the tests that are necessary.
"There are a lot of specialized and highly priced experts who are
generally not needed," explains Light. "Issues with mold are pretty
straightforward and so are the corrections. For instance, when
something has been underwater for any length of time, it needs to
While black mold has been a rampant problem in post-Katrina New
Orleans, it doesn't take a Category 5 hurricane to cause a problem.
The mold growth in a walkout basement of a $1 million home in
Williamsburg, Va., was caused by wet-spray cellulose that was
covered over too quickly.
That length of time is typically 48 hours, which is how long
something has to stay wet before mold begins to grow. Because of
this, drywall that has been soaked for two days or more will have
to be torn out and discarded, as will other porous materials such
as furnishings and carpet.
A research project led by Gina Solomon, a physician with the
Natural Resources Defense Council (NRDC), showed what happens when
these materials aren't fully removed. Solomon led a team that
sampled mold levels in homes across New Orleans in mid-October and
then went back for follow-ups a month later. Indoor mold levels
remained very high in homes that had been only partially cleaned.
By contrast, homes that had been thoroughly cleaned, and where
carpeting and drywall had been removed, had indoor mold levels
comparable to mold levels outdoors.
The ability to accurately test for mold is an important reason
to hire a specialist. Test procedures vary and must be specific to
the site conditions. Not all tests are required in all situations.
A remediator's final report should outline every step taken,
including details about measurement techniques, calibration
procedures for the measurement tools, and control samples used to
evaluate the severity of the problem.
Tear-out. If you want to minimize liability, don't
approach gutting a mold-infested home as normal demolition. What
you can do depends, in part, on when you come onto the scene.
Because it takes 48 hours for mold to appear, drywall that has been
soaked for less than two days can probably be safely torn out, if
done immediately. If it has been wet longer, consider hiring a
The proper way to do tear-outs and remediation includes using
containment barriers and negative air pressurization techniques to
keep mold from spreading to places where it wasn't present before.
Containment often means sealing the area that's being torn out with
plastic barriers. DeCapri says that most professionals use the
ZipWall product (www.zipwall.com), a dust-barrier system that uses
telescoping twist-locking poles and plastic sheeting. Negative
pressurization is simply a blower that sucks air out of the room.
The blower should have a HEPA filter to catch spores as they pass
through, to keep them from spreading to other areas. Before
tear-out, George Harrison of AirScrubbers sprays drywall with
ShockWave, an EPA-registered ammonium chloride cleaner (available
from Fiberlock Technologies (www.fiberlock.com) that helps prevent spores
from becoming airborne.
Containment also protects occupants from airborne spores, so how
tight the barrier needs to be will depend in part on the occupants'
sensitivities, according to Light. "Most of the time we look at
site-specific circumstances. In cases where no occupants will be
exposed and the area can be protected before their return, we may
not suggest full containment."
Mold removal. Once the drywall has been hauled away,
any mold on the framing will have to be physically removed.
Sometimes it has to be scraped off the surface, and doing this
incorrectly can also send spores airborne, so the containment
barrier and fans need to be in place during this part of the job as
Semiporous materials like wood studs are usually cleaned and
sanitized with antimicrobials. Most people assume that bleach is an
effective mold remover, but while it may work on countertops and
other hard surfaces, it's ineffective on porous materials such as
wood or drywall. "We've already had one call from a lady whose
contractors sprayed studs with bleach, and mold is now growing
behind the drywall," reports Michael Gurtler, president of Gurtler
Bros. Consultants, a New Orleans remediation company. Instead,
remediators use special cleaners, like Fiberlock Technologies'
AfterShock, to kill spores. Gurtler also coats wood framing with an
antimicrobial sealant that dries to a plastic-like film,
permanently trapping the spores in the wood (available from Foster
Products, www.fosterproducts.com). He cautions that some
contractors are using the right chemicals but not following the
instructions from the manufacturer. "These products are very
expensive, and some people try to spread them thin to save money,"
he says. "But each manufacturer requires specific amounts of
coverage, and if the sealant isn't applied thickly enough, it will
shrink as it dries, leaving gaps that allow microscopic mold spores
to creep in."
Drying. A house must be dried out before the walls
are reinsulated and drywalled. If you want the job done quickly,
you can't beat "vortex drying." This technique uses a series of
blowers set up around the room's perimeter, 10 to 14 feet apart, to
move air in a counterclockwise direction. The moving air creates a
low-pressure area, or vortex, in the center of the room, which
sucks moisture from the circulating air — a miniature
hurricane, in effect. The drying company sets up
industrial-strength dehumidifiers in this low-pressure area to dry
The standard of care for mold removal operations includes
containing the work area using plastic barriers and depressurizing
the area with large blowers — both techniques that will keep
the mold from spreading to areas of the home where it was not
previously a problem.
The principles of vortex drying are used in numerous systems but
may be called by other names. Insurance companies may use the term
"applied structural drying." Other terms such as "top-down drying"
and "in-place drying" are also used in the industry to refer to the
vortex-drying principles. Rainbow International, a drying company
based in Waco, Texas, prefers the term "rapid structural drying" to
describe the system used by its franchises worldwide.
In tandem with blowers used to create low-pressure areas within a
room or building cavity, Rainbow International applies concentrated
air pressure (either positive or negative) using equipment that
targets slow-drying areas — floors and subfloors, cabinet
kickspaces, and other confined spaces — to minimize
demolition. To train its crews to use this equipment, the company
built a completely furnished 1,200-square-foot home that it
repeatedly soaks with water. "We hose down sofas, walls, and
floors. We actually wait until hardwood flooring edges start to
curve up a little," explains Rainbow International vice president
Bruce Vogt. After this soaking, Vogt says the company can dry the
house in a few days. Carpet is the first thing to dry; sill plates
the last. "When we're done, you can walk across the hardwood floor
and not feel a ripple."
One of the biggest mistakes made by contractors attempting to
cure a mold problem is using a simple bleach to kill mold spores.
Bleach is only effective on nonporous material like countertops and
finished floors. Semiporous material, such as wood studs, are
usually cleaned and sanitized with specialized
To minimize demolition, Rainbow International employs equipment
that applies concentrated air pressure to dry floors (above),
cabinet kickspaces (left), and other confined spaces. This
equipment is used in tandem with blowers arranged in the larger
spaces that create a vortex, drawing moisture to low-pressure
areas, where industrial-strength dehumidifiers rapidly dry the
Post-remediation assessment. At the end
of a job, the home must be tested to confirm successful
remediation. A good remediation firm will not only perform these
tests but will provide a final report outlining the results as
well. This report should include documentation of all the steps
taken throughout the remediation process, explaining details such
as the measurement techniques the company used in sampling spore
counts, calibration procedures for the measurement tools, and
control sampling (measurements taken outside the home that provide
a point of comparison for indoor samples). "I can't stress how
important this last step is," notes Dante DeCapri. "It's the
assurance you have that the homeowner can safely move back home."
And if a problem does arise in the future, thorough documentation
may be enough to send an attorney elsewhere to look for causes
instead of pointing at your work. ~
Charles Wardell writes on construction topics from Vineyard Haven,