Exterior Problem Solver
a misnomer. It is almost never
the paint that fails. When a paint
film lets go prematurely, it is
usually caused by one of 3 conditions:
moisture, poor preparation, or
In all cases, the cause of paint failure must be identified and cured before
Click on the type of problem for details
Patterned cracking in the surface of the paint film resembling the regular scales of an alligator.
of an extremely
an alkyd enamel,
over a more
like a latex
of a top
is dry. Natural
a loss of
- Old paint
should be completely
heat gun or
can be used
to speed work
on large surfaces,
but take care
to avoid igniting
paint or substrate.
a top quality
of the paint
film from the
- Painting a warm surface in direct sunlight.
- Application of oil-based or alkyd paint over a damp or wet surface.
- Moisture escaping through the exterior walls (less likely with latex paint than with oil-based or alkyd paint).
- Exposure of latex paint film to dew, high humidity or rain shortly after paint has dried, especially if there was inadequate surface preparation.
- If blisters go down to the substrate: try to remove the source of moisture. Repair loose caulking; consider installing vents or exhaust fans. Remove blisters (see Below).
- If blisters do not go all the way down to the substrate: remove them by scraping, then sanding, prime bare wood and repaint with a quality latex exterior paint.
Formation of fine powder on the surface of the paint film during weathering which can cause color fading. Although some degree of chalking is a normal, desirable way for a paint film to wear, excessive film erosion can result from heavy chalking.
- Use of a low-grade, highly pigmented paint.
- Use of an interior paint for an outdoor application.
- First, remove as much of the chalk residue as possible, scrubbing with a stiff bristle brush (or wire brush on masonry) and then rinse thoroughly; or use power washing equipment. Check for any remaining chalk by running a hand over the surface after it dries. If noticeable chalk is still present, apply a quality oil-based or acrylic latex primer (or comparable sealer for masonry), then repaint with a quality exterior coating; if little or no chalk remains and the old paint is sound, no priming is necessary.
The washing down of chalk from an excessively eroding paint onto another area below (a brick foundation, for example), ruining its appearance (see Chalking).
- Use of a lower quality, highly pigmented paint.
- Use of an interior paint for an outdoor application.
- Erosion of factory-finished metal siding.
- Remove as much of the chalk residue as possible (see Chalking). Scrub any stained areas with a stiff brush, using a detergent solution; rinse thoroughly. In cases of severe staining, an acid wash may be necessary. Either way, if the affected area dries to a different color, consider painting it with a quality latex paint. Eroding aluminum siding should be thoroughly cleaned (power washing recommended) before painting with a quality exterior latex paint.
CRACKING / FLAKING
a dry paint
at least one
will lead to
of the paint.
Early on, the
- Use of a lower quality paint that has inadequate adhesion and flexibility.
- Overthinning the paint or spreading it too thin.Poor surface preparation, especially when the paint is applied to bare wood without priming.
- Painting under cool or windy conditions that make latex paint dry too fast.
- It may be possible to correct cracking that does not go down to the substrate by removing the loose or flaking paint with a scraper or wire brush, sanding to feather the edges, priming any bare spots and repainting.
- If the cracking goes down to the substrate remove all of the paint by scraping, sanding and/or use of a heat gun; then prime and repaint with a quality exterior latex paint.
Accumulation of dirt, dust particles and/or other debris on the paint film; may resemble mildew.
- Use of a low quality paint, especially lower grades of satin or semigloss.
Soil splashing onto siding.
- Air pollution, car exhaust and flying dust collecting on house body and horizontal trim.
- Wash off all surface dirt before priming and painting, using a scrub brush and detergent solution, followed by a thorough rinsing with a garden hose. Heavier dirt accumulations may require the use of a power washer. While dirt pickup can't be eliminated entirely, top quality exterior latex paints typically offer superior dirt pickup resistance and washability. Also, higher gloss paints are more resistant to dirt pickup than flat paints, which are more porous and can more easily entrap dirt.
Crusty, white salt deposits, leached from mortar or masonry as water passes through it.
- Failure to adequately prepare surface by removing all previous efflorescence.
- Excess moisture escaping through the exterior masonry walls from behind.
- If excess moisture is the cause, eliminate the source by repairing the roof, cleaning out gutters and downspouts, and sealing any cracks in the masonry with a high quality, water-based all-acrylic or siliconized acrylic caulk. If moist air is originating inside the building, consider installing vents or exhaust fans, especially in kitchen, bathroom and laundry areas. Remove the efflorescence and all other loose material with a wire brush, power brush or power washer; then thoroughly rinse the surface. Apply a quality water-based or solvent-based masonry sealer or primer, and allow it to dry completely; then apply a coat of top quality exterior house paint, masonry paint or elastomeric wall coating.
FADING / POOR COLOR RETENTION
Premature and/or excessive lightening of the paint color, which often occurs on surfaces with sunny southern exposure. Fading/poor color retention can also be a result of chalking of the coating.
- Use of an interior grade of paint for an outdoor application.
- Use of a lower quality paint, leading to rapid degradation (chalking) of the paint film.
- Use of a paint color that is particularly vulnerable to UV radiation (most notably certain bright reds, blues, and yellows).
- Tinting a white paint not intended for tinting, or overtinting a light or medium paint base.
- When fading/poor color retention is a result of chalking, it is necessary to remove as much of the chalk as possible (see Chalking). In repainting, be sure to use a quality exterior house paint in colors recommended for exterior use.
A white, salt-like substance on the paint surface. Frosting can occur on any paint color, but it is less noticeable on white paint or lighter tints. On masonry, it can be mistaken for efflorescence (see Efflorescence and Mottling).
- Forms mostly in protected areas (such as under eaves and on porch ceilings) that do not receive the cleansing action of rain, dew and other moisture.
- Use of dark-colored paints that have been formulated with calcium carbonate extender.
Application of a dark-colored paint over a paint or primer containing calcium carbonate extender.
- Frosting can be a stubborn problem. It often cannot be washed off readily. Moreover, the condition can recur even as a bleed-through when a new top coat is applied. In extreme cases, it can interfere with adhesion. The best remedy is to remove the frosting by wirebrushing masonry or sanding wood surfaces; rinse, then apply an alkyd-based primer before adding a coat of high quality exterior paint.
Appearance of a denser color or ligher gloss where wet and dry layers overlap during paint application.
a "wet edge" when
a wet edge
from "wet to dry" rather
It is also
at a natural
Black, gray or brown areas of fungus growth on the surface of paint or caulk.
- Forms most often on areas that tend to be damp, and receive little or no direct sunlight (walls with a northerly exposure and the underside of eaves are particularly vulnerable).
- Use of a lower quality paint, which may have an insufficient amount of mildewcide.
- Failure to prime bare wood before painting.
- Painting over a substrate or coating on which mildew has not been removed.
- Test to distinguish mildew from dirt by applying a few drops of household bleach to the discolored area; if it disappears, it is probably mildew. Treat the mildew by applying a mixture of water and bleach, 3:1, and leave on for 20 minutes, applying more as it dries. Wear goggles and rubber gloves. Then scrub and rinse the area. Apply an exterior latex primer, then a top-of- the-line exterior latex paint in flat, satin, semigloss or gloss finish, depending on the desired appearance.
Reddish-brown stains and spots on the paint surface.
- Non-galvanized iron nails have begun to rust, causing bleed-through to the top coat.
- Non-galvanized iron nails have not been countersunk and filled over.
- Galvanized nailheads have begun to rust after sanding or excessive weathering.
- When painting new exterior construction where non-galvanized nails have been used, it is advisable to first countersink the nailheads, then caulk them with a top quality, waterbased all-acrylic or siliconized acrylic caulk. Each nailhead area should be spot primed, then painted with a quality latex coating. When repainting exteriors where nailhead rusting has occurred, wash off rust stains, sand the nailheads, then follow the same surface preparation procedures as for new construction.
Loss of adhesion where many old coats of alkyd or oil-based paint receive a latex top coat.
to "lift off" the
- Repaint using another coat of alkyd or oil-based paint. Or completely remove the existing paint and prepare the surface - cleaning, sanding and spot-priming where necessary - before repainting with a top quality latex exterior paint.
of paint due
to poor adhesion.
Where there is
a primer and
top coat, or
of paint, peeling
may involve some
or all coats.
Where there are
many layers of
old paint (say
about 15 coats),
two peeling problems
can result: peeling
caulk or leaks
in roof or
a wet or
of a new
- Try to identify
source of moisture.
The most common
source of dampness
walls are covered
with dew, and
are out painting
- Prepare surface
all loose paint
or stiff wire
and apply appropriate
with a top
paint for best
For best results
strip old paint
and start fresh
and dry old
Color loss and overall deterioration of paint film on fresh masonry.
- Oil-based paint or vinyl acrylic latex paint was applied to new masonry that has not cured for a full year. Fresh masonry is likely to contain lime which is very alkaline. Until the lime has a chance to react with carbon dioxide from the air, the alkalinity of the masonry remains so high that it can attack the integrity of the paint film.
- Allow masonry surfaces to cure for at least 30 days, and ideally for a full year, before painting. If this is not possible, the painter should apply a quality, alkali-resistance sealer or latex primer, followed by a top quality 100 percent acrylic latex exterior paint. The acrylic binder in these paints resists alkali attack.
Paint that has lost its adhesion to a galvanized metal substrate.
- Improper surface preparation, such as inadequate rust removal.
- Failure to apply a primer before application of an oil-based or vinyl latex paint.
- Failure to sand baked-on enamel finishes or glossy surfaces before painting.
- Any rust on the metal should be removed with a wire brush; then, an acrylic latex corrosion-inhibitive primer should be applied (one coat is usually sufficient). Previously painted galvanized metal that is completely rust-free can be painted without applying a primer. A latex metal primer should be applied to unpainted galvanized metal, followed by a top quality exterior acrylic latex paint.
POOR GLOSS RETENTION
Deterioration of the paint film, resulting in execessive or rapid loss of luster of the top coat.
- Use of an interior paint outdoors.
- Use of a lower quality paint.
- Use of a gloss alkyd or oil-based paint in areas of direct sunlight.
- Direct sunshine can degrade the binder and pigment of a paint, causing it to chalk and lose its gloss. While all types of paint will lose some degree of luster over tim, lower quality paints will generally lose gloss much earlier than better grades. The binder in top quality acrylic latex paints is especially resistance to UV radiation, while oil and alkyd binders actually absorb the radiation, causing the binders to break down. Surface preparation for a coating showing poor gloss retention should be similar to that used for chalking surfaces (see Chalking).
Concentration of water-soluble ingredients on latex paint, creating a blotchy, sometimes glossy appearance, often with a tan or brownish cast. More likely with tinted paints than with white or factory-colored paints.
- Painting in cool, humid conditions or just before they occur. The longer drying time allows the paint's water-soluble ingredients - which would normally evaporate, or be leached out by rain or dew - to rise to the surface before paint thoroughly dries.
- Mist, dew or other moisture drying on the painted surface shortly after it has dried.
- Avoid painting in the late afternoon if cool, damp conditions are expected in the evening or overnight. If the problem occurs in the first day or so after the paint is applied, the water-soluble material can sometimes be rinsed off rather easily. Fortunately, even more stubborn cases will generally weather off in a month or so. Sufactant leaching should not affect the ultimate durability of the coating.
or tan discoloration
on the paint
from the substrate
cedar and mahogany,
or over painted
knots in certain
of a primer
that is not
to the paint
apply a high
type to use
coat of primer
can be applied
a top quality
Warping or buckling of vinyl siding panels that have been repainted.
- Most likely cause is that vinyl siding was painted with a darker color paint than the original color. Dark paint tends to absorb the heat of the sun, transferring it to the substrate. When vinyl siding expands dramatically, it is not able to contract to its original dimensions.
- Paint vinyl siding in a shade no darker than the original. Whites, off-whites, pastels and other very light colors are good choices. Top quality acrylic latex paint is the best type of paint to use on vinyl siding, because the superior flexibility of the paint film enables it to withstand the stress of expansion and contraction cycles cause by outdoor temperature changes.
- Siding that has warped or buckled should be assessed by a siding or home repaint contractor to determine the best remedy. The siding may have to be replaced.
Stains that come from waxy substance in the reconstituted wood products used to make hardboard siding. When the substrate is painted, these staining substances bleed through the paint; they can even bleed through some ordinary primers, possibly causing dirt pickup, mildew and/or poor paint adhesion (see Dirt Pickup and Mildew).
- Failure to apply a proper primer to hardboard before applying the top coat.
- Allowing hardboard siding to weather before being painted.
- To treat or prevent, apply a quality exterior acrylic latex primer; follow with a coat of high quality exterior acrylic latex paint. The American Hardboard Association recommends two coat of top quality acrylic exterior house paint for best results. Some hardboard grades have adequate factory primer and need only a quality paint applied. Low quality, highly pigmented flat paints are more prone to wax bleed than are higher quality paints.
forms a "skin."
- Paint is
Sun can cause
the top of
the paint to
bake dry while
the under layer
When the under
and can cause
the upper layers.
or sand substrate
to remove wrinkled
hot to warm
a stiff brush
and wash from
of the house
up, so residue
does not streak
down the siding.
an area, rinse
with a garden
it has a chance
an even coat
of top quality
is dry before
the top coat.
at the manufacturer's
at the recommended
or damp weather,
to dry completely.