Water is always the cause of mold and mildew, but finding the source of the problem can seem like an unsolvable mystery. Follow our tips for using some handy gadgets and basic detective work to find and eliminate your mold and mildew problems for good,.
If you see mold near water pipes,
waste lines, icemaker lines or plumbing
fixtures, chances are the mold is
feeding off a nearby leak. Let the
water run while you check the pipes
and surrounding area for damp spots.
Remember that water can travel in
any direction—down, sideways or
even up when it wicks into absorbent
material like drywall—so the actual
leak may be some distance from the
Mold can be an early warning sign of a
moisture problem inside walls or ceilings
that could cause an expensive problem
like wood rot. Avoid the temptation to just
wipe the mold away and forget about it—find and stop the water source.
If mold is growing on an exterior wall
or ceiling, first look for a leak in the wall
or roof. Measure from the moldy area
to a reference point like a door, then
find the spot on the other side of the
wall or ceiling.
Closely inspect nearby vents, roof
flashing, decks, window wells and anywhere
wood is rotting. Look for ground
sloping toward the house and downspouts
emptying next to the wall. If the
ground around the house gets too wet,
moisture will wick into the foundation
or slab and become persistent dampness.
If mold forms on the ceiling under a duct or register and
there's no sign of a roof leak, badly insulated ductwork may
be the cause. Warm, moist air condenses and forms water on
ducts carrying cold air through the attic or crawl space. The
condensation is a sign that the duct is uninsulated or missing
a vapor barrier. Eventually the water saturates the insulation
and drywall and mold spores (which are everywhere)
In cold weather, the reverse happens. Moisture forms anywhere
warm air escapes—for instance, at unsealed joints
between duct sections.
Most mold is unmistakable, but sometimes
small or largely hidden growths just
make a surface look dirty.
For a quick test, dip a swab in diluted
bleach (1 part bleach, 16 parts water) and
dab it on the wall. If the spot quickly
lightens (or keeps coming back after
cleaning), assume it's mold.
Mold test kits are available that detect
the presence and identify the type of
mold, but they won't help determine the
cause or what to do about it.
If you need to build or rebuild an
area where moisture has been a problem,
use materials that resist mold
growth and aren't affected by
water. Construct walls with
pressure-treated wood and
rigid insulation and cover the
walls with paperless drywall,
which has nothing for mold to
In areas where mold
might grow, such as basement walls,
spray the surfaces with an antimicrobial
treatment. Paint walls with
mildew-resistant primer and paint or
add mildewcide to your paint.
Warm air seeks gaps in the insulation,
and when it hits colder surfaces as it
flows out of or into the house, water
condenses—which then feeds mold.
These spots often occur on outside
walls near floors or windows, at corners
and around outlets and lights. If
the mold disappears after cleaning it
and lowering indoor humidity with a
dehumidifier or vent fan, just keep an
eye on it. If it recurs, open the wall and
fix the problem.
To prevent mold around the tub or shower,
spray the wall
with an antimicrobial treatment, then
seal the grout with two coats of grout
sealant to keep water from wicking in.
If the mold is extensive and tiles come
off, rebuild the wall with cement board
tile backer and new tile.
If the wall is sound but the mold
stains won't go away, try
regrouting. Scrape out the caulk
and stained grout, spray the wall
with antimicrobial treatment, regrout
and caulk and then coat the whole
wall with grout sealant.
Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.
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