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- Preventing Moisture Damage
Preventing Moisture Damage
The next time you take a shower, consider the damage you
may be causing to your home. Actually, one shower won't cause
moisture damage in itself, but together with washing clothes,
steam from cooking, and dish washing, a good deal of moisture
is added to the atmosphere of your home each day. And on the
outside, rain and snow regularly drop a good deal of moisture
on your house. All these factors can cause extensive damage
both to your home's appearance and structure. Moisture can
cause ugly rusting or decay of building materials, and blistering
or peeling of painted surfaces. It can warp wood, and promote
mildew and other fungi growth on our home.
But moisture need not be a menace, if you are aware of its
threat and take the proper steps to prevent its accumulation
in unwanted areas of your home. You should understand how
moisture damage occurs, learn how to prevent future damage,
and know how to repair present damage.
MOISTURE DAMAGE FROM OUTSIDE
Each year rain, ice and snow can expose the outside of your
home to great quantities of moisture. Moisture has historically
been the cause of damage to building structures, but because
of recent energy-saving measures, environmental factors can
cause more havoc to homes than they used to.
Construction methods and building standards have changed
to accommodate the increased interest in conserving energy.
Houses built prior to the 1930s generally had no effective
insulation in either ceilings or walls. Roofs were usually
steeply pitched and constructed with shingles that had gaps
between them which ventilated attics and cooled the roof deck.
These homes were, of course, heat-wasters -- heat escaped
into the attics and natural ventilation kept the attic air
moving. As a result, roof-snow melted rapidly and did not
accumulate. Ice and icicles formed on the eaves and in the
gutters rather than remaining on the roofs. Snow-water penetrations
into the house were insignificant and gone before they could
But in these days of high fuel costs and the need for energy
conservation, new houses and modernized older homes must meet
new standards. Often, the new standards represent only minimum
requirements and serious moisture damage results.
Because of increased insulation, millions of homes now have
warm attics instead of the hot attics in the old heat waster
houses. The snow accumulation on roofs of houses with warm
attics melts slowly along roof edges causing water pools to
back up behind ice dams.
The water often remains in this area for weeks, penetrating
roof shingles and finding its way into ceilings and wall cavities.
This, of course, can create severe damage, such as soaked
insulation, stained, swollen and cracked plaster and drywall
panels, dampness and rotting in wall cavities and, eventually,
stained, blistered and peeling paint. Interior paint damage
may show up fairly soon. The blistering and peeling of exterior
painted surfaces, however, may not become apparent until summer
weather arrives. Water trapped in insulation and wall cavities
may then penetrate the wood siding and emerge as blisters
under the exterior paint film.
Rooftop ice dams aren't the only exterior moisture culprits.
Water from moisture-soaked ground can seep into a home's basement
through the foundation. Once water has penetrated into the
home, it may continue to do so whenever a heavy rainfall occurs.
Obviously the water will eventually cause damage to interior
and exterior building materials.
EXTERIOR PREVENTION MEASURES
There is little point in repairing damage done to the structure
of your home unless you first take all the necessary steps
to prevent future moisture problems. You should first eliminate
the cause of problems before tackling the result of them.
First, thoroughly inspect your home for clues of moisture
damage. The first days of spring are a good time to check
- Near gutters and downspouts, windows and doors, and the
ground level row of boards or masonry.
- Old caulking materials, where gaps may have occurred.
- Masonry and roofing where hotels or seams may have appeared.
- Gutters and downspouts where there may be backups or leaks.
Once you have sized up the damage, follow these steps to
overcome future problems:
- To prevent future damage from ice dams, remove snow from
the roof, wherever possible. Electric heating cables are
available to melt ice in gutters -- but be sure to melt
and clear downspouts first.
- The best safeguard is a well-insulated, but well-ventilated
- If the attic can be kept near the outside temperature,
ice dams aren't likely to form. Remember, proper insulation
must be done in conjunction with adequate ventilation.
- Repair any damage to your roof as soon as possible and
apply a roof coating if needed.
- Clear dirt and debris out of gutters and downspouts and
repair them with a patching compound and a coat of the proper
- Make sure that flashing under shingles is secure, does
not leak and covers proper areas.
- Caulk around problem areas such as wall joints or cracks,
pipes through walls, window and door frames, flashing, leaky
gutters and downspouts.
- Keep heavily used decks and porches in good repair, recoating
or repainting every two or three years.
- Trim shrubbery away from buildings to allow air circulation
in ground-level areas.
Once you are sure the moisture has been dried out of the
wall cavities and an adequate ventilation system has been
installed, you should begin repairing exterior paint damage.
Where the paint is blistered, loose, or peeling, it will have
to be removed. Paint damage caused by moisture usually results
in the paint coming loose right down to the bare wood.
All exposed wood surfaces should be sanded and spot primed
with a suitable exterior primer. Many paint manufacturers
recommend a solvent-thinned alkyd type for this purpose. When
the primer is dry, apply a topcoat of either an alkyd or a
latex exterior paint following label directions carefully.
Your paint retailer can help you choose a paint that's right
for your home.
MOISTURE DAMAGE FROM INSIDE
Trapped water and moisture, escaping toward an area of less
vapor pressure is technically the cause for moisture damage.
When excessive moisture is retained in such areas as ceilings
and walls that are not properly ventilated, it will begin
to work its way out through these surfaces, causing a variety
of ills to the materials with which your home is built.
Inside your home, you contribute to this build-up of moisture
in many ways -- bathing, cooking, washing, and even breathing.
Of course you can't call a halt to these basic activities.
But you can make sure the moisture they create is routed safely
to the outside instead of into your walls and ceilings.
INTERIOR PREVENTION MEASURES
As with exterior damage, it doesn't help much to repair the
surface of the interior of your home before you have corrected
the problems that caused the damage in the first place. Check
for interior surface damage in such moisture- prone areas
as kitchens, bathrooms, laundry rooms, attics and basements.
Be sure to look past cosmetic damage and check insulation
to see if it is wet. The key to preventing future moisture
problems inside your home is to make sure your house is tight
enough to prevent moisture from entering but at the same time
adequately ventilated to allow interior-produced moisture
to escape. Most importantly, you want moisture to escape through
vents, windows and other openings created for that purpose
-- not through walls and ceilings where it will eventually
cause structural damage.
- Use ventilating fans or louvers to properly ventilate
your home so that moisture can escape to the outside.
- Waterproof your basement from the outside. Make sure the
basement contains adequate drainage to avoid build-up of
- In homes without basements, rot-proof sub-flooring and
joists are necessary, and the ground under floors should
be covered with a vapor barrier such as polyethylene plastic.
- When insulation gets wet, it conducts cold rather than
inhibits it. Insulation should be completely dried out before
If damage to your walls or ceilings is severe enough to require
replacement of some of the panels, you may need the help of
a professional painting contractor. He can assess the damage
and give you an accurate cost estimate for repair. Many painting
contractors are qualified to do the whole repair and repainting
job for you.
To repair sagging drywall on ceilings, it is recommended
that 5/8 inch panels be used. The old damaged panels can be
removed and replaced or new drywall can be installed in front
of the sagging panels. The thicker, 5/8 inch drywall is recommended
today, since greater amounts of insulation are being used.
On the outside, under exterior overhangs, use waterproof
Sheetrock or exterior grade plywood panels to replace sagging
Once the structural damage has been repaired and you have
determined that wall cavities and areas above ceilings and
under floors have been properly dried out, you should repaint.
Ask your paint retailer to help you choose the correct paint
for your particular purpose and follow manufacturer directions
Stained Walls and Ceilings:
Most stains caused by water are likely to be amber or brownish
streaks or blotches. If plaster or gypsum board has not been
damaged by water, repainting may be a sufficient remedy for
stains. Since water has caused the stain, you can assume that
it is at least partially water soluble. Wash the stained surface
carefully with water and detergent or a household cleaner
intended for cleaning paint. Without soaking the surface,
remove as much stain as possible. Allow the washed surface
to dry thoroughly -- 48 hours or longer.
Before applying the finish coat of paint, use a special stain-blocking
or stain-killer type of primer sealer. These primers are solvent-thinned
therefore they will prevent further leaching of the water-soluble
staining material. Any type of topcoat or enamel may then
If painted woodwork, doors or paneling are discolored or
stained by water from inside walls or ceilings, they can usually
be refinished with a moderate amount of work. If the painted
surface is blistered or the paint is peeling or chipping,
it may be necessary to remove the paint down to the wood surface
to achieve a smooth attractive finish. Many types of paint
and varnish removers are available at your paint dealer. Be
sure to follow label directions carefully when using paint
If the painted wood surface has not been badly damaged, but
has become dulled, discolored or stained, clean the surface
thoroughly, sand lightly and apply an enamel undercoat. Allow
the undercoat to dry completely, then sand lightly with a
very fine sandpaper. Wipe clean and apply either an alkyd
or latex enamel in any color or sheen you like.
If the wood surface has not been painted but is a finished
natural wood, minor damage may be repaired with a light sanding,
followed by a coat of gloss or semi-gloss clear varnish. When
the damage is extensive, remove the finish, sand the wood
until it is smooth, and refinish. Most paint stores carry
a wide variety of fine wood stains as well as clear varnishes
in a choice of sheens.
If water has caused plaster to swell and crumble, or if sections
have collapsed, it is likely that new plaster will be needed
in some areas. New plaster must be allowed to dry and harden
properly before painting.
Professional contractors often use a moisture meter to determine
whether an area of plaster is dry, wet or very wet. But if
you are doing your own work and cannot readily purchase or
rent a moisture meter, be sure to allow adequate time for
the plaster to dry.
Most plaster can be safely painted in four weeks, if the
temperature in the house or building is above 50 degrees F.
and the relative humidity is not above 70 percent. If your
home does not meet these conditions, or if plaster is applied
directly to a solid wall such as brick, tile, etc., a longer
drying time is necessary before painting.
If you must paint new plaster before adequate drying time
has elapsed, the best procedure is to apply just one coat
of a high quality latex wall paint. The latex paint will not
be affected by any free alkali coming to the surface and the
single coat will allow moisture to continue to evaporate through
the paint without causing blisters. Later, another coat or
two of either latex or alkyd wall paint may be applied.
Once you have determined that your newly plastered walls
are dry enough to paint, you should check them carefully for
chalky areas. These can occur when plaster dries too rapidly
at high temperatures. Chalk should be removed by vigorous
brushing before painting.
Drywall which has become badly soaked by water from inside
the wall will probably need replacement. Once new gypsum board
panels have been installed and the joints have been properly
taped and sanded, painting is a fairly straightforward procedure.
For the first coat on new gypsum board, a latex primer is
recommended. These fast-drying, water-thinned primers prepare
the drywall panels for topcoat painting by providing a smooth,
sealed surface. Following an evenly applied coat of latex
primer, the topcoats can be either latex or alkyd paint in
your choice of color and sheen. Latex wall and ceiling paints
are usually recommended for this purpose because they clean
Certain types of paint can be excellent vapor barriers --
helping to keep moisture from permeating walls and ceilings.
Vapor barriers, when used to coat interior ceilings and walls,
inhibit inside moisture from penetrating these surfaces and
damaging insulation and exterior finishes. Many of the familiar
paint products work well as moisture barriers and there are
now special vapor barrier paints available as well. A topcoat
can be applied over the vapor barrier paint if the latter
is not available in the color of your choice.
By ridding your home of moisture traps, promptly repairing
any damage, and repainting or re-coating properly, your home
will be more energy efficient, protected from harsh weather,
and more attractive.
This information is taken from http://www.paintinfo.org/brochures/moisture.htm
PaintInfo.org -- the web site of the Paint and Coatings Industry
Information Center -- is copyright © 2000-2001, the National
Paint and Coatings Association.
The information provided or referred to as part of the PaintInfo.org/NPCA
Web Site is believed to be reliable and accurate.
However, NPCA cannot warrant any of this information, and
cannot assume any liability for actions taken or reliance
on any of it.