Mold is a major-league nuisance. It blackens the grout
lines in your shower, discolors drywall, shows up as black spots on siding,
darkens decks, and grows on and rots damp wood everywhere. Even worse, it can
be bad for your health. It releases microscopic spores that cause allergic
reactions, runny noses and sneezing, as well as irritating, even injurious,
odors.
Almost every home gets mold infestations. The trick is to
stop them before they get big and harm both you and your home. In this article,
we’ll show you how to identify mold and eliminate the small infestations
as well as the big ones that have gotten out of hand.
You can easily remove minor mold with ordinary household
cleaning products. But disturbing big infestations can be bad for
your health, particularly if you are an allergy sufferer or have a weakened
immune system. When you discover an extensive mold problem, we recommend that
you use the rigorous protective measures we show in
Photos 1 – 6, or consider calling in a
professional to handle the problem. (Look under “Industrial Hygiene
Consultants” or “Environmental and Ecological Consultants” in
your Yellow Pages. Or call your local public health department.) And even if
you hire pros, read through this article and make sure they follow similar
precautions to keep the mold from spreading throughout your
house.
How to Identify Mold
Mold is everywhere. It’s a type of fungus that grows
from tiny spores that float in the air. It can grow almost anywhere that spores
land and find moisture and a comfortable temperature, between 40 and 100
degrees F. Typically that includes about every damp place in your
home.
You can easily spot the most visible type of mold, called
mildew, which begins as tiny, usually black spots but often grows into larger
colonies. It’s the black stuff you see in the grout lines in your shower,
on damp walls, and outdoors on the surfaces of deck boards and painted siding,
especially in damp and shady areas. A mildewed surface is often difficult to
distinguish from a dirty one. To test for mildew, simply dab a few drops of
household bleach on the blackened area. If it lightens after one to two
minutes, you have mildew. If the area remains dark, you probably have
dirt.
Tips for Mold Prevention
The key to stopping most mold is to
control dampness. The worst infestations usually occur in damp crawlspaces, in
attics and walls where water has leaked in from the outside, and in basements
with poor foundation drainage. Stopping leaks, ensuring good ventilation in
attics, keeping crawlspaces dry and routing water away from the foundation are
the best defenses.
Mildewcide in paint is usually effective
for controlling surface mold in damp rooms like bathrooms and outside in shady
areas. Many paints already have mildewcide in them. Check with your paint
dealer to be sure. You can add mildewcide, although you might void the paint
warranty.
Mildew is a surface type of mold that won’t damage
your home’s structure. But other types of mold cause rot. Probe the
suspect area with a screwdriver or other sharp tool (Photo 3). If the wood is soft or crumbles, the
fungi have taken hold and rot has begun.
If you have a high concentration of mold, you may smell
it. If you detect the typical musty odor, check for mold on damp carpets, damp
walls, damp crawlspaces and wet wood under your floors, wet roof sheathing and
other damp areas. Clean up these infestations right away before they get worse.
CAUTION: A FEW TYPES OF MOLD ARE HIGHLY
TOXIC. IF YOU HAVE AN ALLERGIC REACTION TO MOLD OR A HEAVY INFESTATION INSIDE
YOUR HOME, CALL IN A PRO TO ANALYZE THE TYPES. OR CALL YOUR LOCAL PUBLIC HEALTH
DEPARTMENT AND ASK FOR MOLD-TESTING ADVICE.
Removing Large Infestations Requires
Precautions—and Work!
You can scrub away the surface mold common to bathrooms,
decks and siding in a matter of minutes with a 1-to-8 bleach/water solution. But often mold grows and spreads in places you
don’t notice, until you spot surface staining, feel mushy drywall or
detect that musty smell. If you have to remove mold concentrations covering
more than a few square feet, where the musty odor is strong or where you find
extensive water damage, we recommend that you take special precautions. You
want to not only avoid contaminating the rest of the house but also protect
yourself from breathing high concentrations of spores and
VOCs.
-
Wear old clothes and shoes that you can launder or throw
away after the cleanup work.
-
Wear special N-95 or P-100 respirators, in addition to
goggles and gloves. See the Buyer’s Guide, below, for a
source.
-
Set an old box fan or a cheap new one in a window to
ventilate the room while working. Throw it out when you’re done cleaning,
because the spores are almost impossible to clean off. Tape plywood or
cardboard around the window openings so the spores can’t blow back in
(Photo 1).
-
Wrap and tape moldy carpeting in 6-mil plastic, and
double-bag mold-infested debris in garbage bags for disposal (Photos 1 and 4).
-
To control airborne spores, moisten moldy areas with a
garden sprayer while you work (Photo 1).
-
Turn off your furnace and air conditioner and cover ducts
and doors to contain spores.
-
Keep your wet/dry vacuum outside when you vacuum
(Photo 5).
Moisture damage and large mold infestations go hand in
hand.
Photos 1 – 7 demonstrate cleaning under an
old leaky window where wind-driven rain frequently got into the wall and gave
mold a foothold.
You have to open up the wall to get at the mold growing
inside (Photo 4). Since you have to repair the wall
anyway, don’t hesitate to cut the drywall back beyond the obvious damage
to find all the mold and let the wall dry out. To avoid cutting electrical
wires, poke a hole through the damaged section and locate the wires first. Turn
off the power to the outlets before you cut.
If the moisture damage has been neglected or gone
unnoticed for long, you’re likely to find rot. Where possible, remove and
replace soft, spongy studs and wall sheathing. Where removal is difficult,
treat the affected areas with a wood preservative (available at home centers),
after cleaning the wood and allowing it to dry. Then double up rotted members
with pressure-treated wood.
Complete the initial cleanup by vacuuming up the debris
(Photo 5). Thoroughly clean the wet/ dry vac
afterward by disposing of the filter and washing out the tank, hose and
attachments with the bleach-and-water solution.
After scrubbing the surfaces (Photo 6), simply allow the bleach solution to
continue to penetrate the surfaces and dry. Wash concrete floors with TSP,
automatic dishwasher detergent or a chlorinated cleaner such as
Comet.
Set out dehumidifiers and
new fans to dry the now-cleaned areas for at
least three days, then check them (by sight and smell) for mold. If you
discover more mold, clean again with bleach.
When you’re sure the mold has been eliminated, seal
the wood surfaces with pigmented shellac like BIN or an oil-based primer like
KILZ (Photo 7).
Techniques for Cleaning Surface Mold
Surface molds grow in just about any damp location, such as
the grout lines of a ceramic tiled shower (see photo). They’re easy to
scrub away with a mixture of 1/2 cup bleach, 1 qt. water and a little
detergent. The bleach in the cleaning mixture kills the mold, and the detergent
helps lift it off the surface so you can rinse it away so it won’t return
as fast. You can also buy a mildew cleaner at hardware stores, paint stores and
most home centers.
Even for simple cleaning, protect
yourself from contact with mold and the bleach solution by wearing a
long-sleeve shirt and long pants as well as plastic or rubber gloves and
goggles.
Tip: Special gloves made of nitrile are
as tough as latex but thinner and more protective. See the Buyer’s Guide
for a source.
If the mold doesn’t disappear
after light scrubbing, reapply the cleaning mix and let it sit for a minute or
two. Then lightly scrub again.
Seal the clean surfaces when
they’re thoroughly dry to slow future moisture penetration. Apply a grout
sealer ($5 to $25 per quart from tile shops and home centers) to tile
joints.
CAUTION: Don’t mix ammonia or any detergent containing
ammonia with bleach. The combination forms a poisonous gas.
Repaint cleaned wall surfaces with a regular latex paint that
contains a mildewcide to help stop future mold growth. And keep in mind that if
the moisture returns, mold will return.
Buyer’s Guide
For
local sources of safety gear, see “Safety Equipment and Clothing”
in your Yellow Pages.
DIRECT SAFETY INC.: (800)
528-7405. www.directsafety.com. Source for N-95 particulate respirator masks
(item No. 03-017, about $24 for box of 10), unlined 13-in. nitrile gloves (item
No. 07-121, about $2 a pair) and anti-fog goggles (item No. 02-709, about
$4).
Click image to enlarge.
1. Cut stained or musty carpet and pads into 6 x
8-ft. sections with a utility knife. Using a pump sprayer, mist the surfaces
with water to control the spread of spores, and roll up the sections.
Double-wrap them in 6-mil plastic and tape them with duct tape for disposal.
Wear protective clothing (see text) and run an exhaust fan in the
window.
Click image to enlarge.
2. Seal the room from the rest of the house. Cover
the doorway with a barrier made of overlapping plastic sheeting and tape it to
the wall and floor. Cover all air ducts in the room with plastic and
tape.
3. Pry off baseboards and trim from contaminated
areas with a pry bar and block of wood. Probe heavily stained or
moisture-swollen walls using a screwdriver to discover and open up moisture
damage and hidden mold in the insulation and wall framing.
Click image to enlarge.
4. Turn off the electrical power to the room and
cut open the damaged wall with a reciprocating saw, drywall saw or utility
knife. Mist the moldy drywall and insulation with the pump sprayer to avoid
spreading mold spores. Double-bag moldy material in heavy-duty plastic bags and
tie them shut.
Click image to enlarge.
5. Vacuum up moldy debris with a standard wet/dry
vacuum. Buy an extra length of hose and run it out the window so you can keep
the vacuum outside to avoid further spore spread.
6. Scrub the surface mold stains from walls and
wood trim with a mixture of 1 qt. water and 1/2 cup bleach to kill the mold.
Use a soft brush and work until signs of the mold disappear. Wipe off, but do
not rinse these surfaces. Set trim in direct sunlight to dry. Scrub concrete
with TSP or automatic dishwasher detergent.
Click image to enlarge.
7. Allow to dry, then seal all previously infested
areas with a pigmented shellac- or oil-based primer. Then install new
insulation and drywall and nail the trim back on.
