The Common Issues and Solutions Guide from Conco Paints will help you address and solve some of the most common paint and coatings issues for building exteriors.
Text and images courtesy of the Rohm & Haas Paint Quality Institute.
Patterned cracking in the surface of the paint film resembling the scales of an alligator.
Application of an extremely hard, rigid coating, like an alkyd enamel, over a more flexible coating, like a latex primer.
- Application of a top coat before the undercoat is dry.
- Natural aging of oil-based paints as temperatures fluctuate. The constant expansion and contraction results in a loss of paint film elasticity.
Old paint should be completely removed by scraping and sanding the surface. The surface should be primed with a high quality latex or oil-based primer, then painted with a top quality exterior latex paint.
NOTE: Alligatored surfaces may be lead-based paint, so follow precautions for preparing, disposing of and painting lead-based paint.
Bubbles resulting from localized loss of adhesion and lifting of the paint film from the underlying surface.
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).
If blisters go down to the substrate, try to remove the source of moisture. Repair loose caulking; consider installing an exhaust fan. Remove blisters (see below).
If blisters do not go all the way down to the substrate, remove them by scraping, then sanding; prime any bare wood and repaint with a quality 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, using a stiff bristle brush (or wire brush on masonry) and then rinse thoroughly with a garden hose; or by careful power washing. 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 an appropriate quality exterior coating; if little or no chalk remains and the old paint is sound, priming may not be 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).
- Applying oil-based or alkyd paint over a damp or wet surface.
- Moisture seeping into the building through the exterior walls (less likely with latex paint)
- Exposure of latex paint film to high humidity or moisture shortly after paint has dried, especially if there was inadequate surface preparation
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.
The splitting of a dry paint film through at least one coat, which will lead to complete failure of the paint. Early on, the problem appears as hairline cracks; later, flaking of paint chips occurs.
- 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 too cool conditions or in warm, 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. Old, flaking paint may contain lead, so precautions for lead paint should be followed.
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 semi-gloss.
- 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. If unsure whether the problem is dirt or mildew, conduct a simple spot-test (see Mildew). Clean off dirt with a scrub brush and detergent solution, followed by a thorough rinsing with a garden hose. Heavier dirt accumulations may require careful power washing. Dirt may be permanently embedded in the paint.
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 the inside.
- Air pollution, car exhaust and flying dust collecting on house body and horizontal trim.
If excess moisture is the cause, eliminate the source by repairing the roof, cleaning out gutters and downspout, 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 and allow it to dry completely; then apply a coat of top quality exterior house paint, masonry paint or elastomeric wall coating. (Elastomeric wall coatings should not be applied to surfaces that may have excessive moisture coming through, such as soil retaining walls, uncapped walls or interior basement walls).
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 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).
- Application of paint to alkaline masonry without primer or sealer.
- 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 light tints. On masonry, it can be mistaken for efflorescence (see Efflorescence/Mottling).
- Forms mostly in protected areas (such as under eaves and on open porch ceilings) that do not receive the cleansing action of rain and dew.
- 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 higher gloss where wet and dry layers overlap during paint application.
Failure to maintain a “wet edge” when applying paint.
Maintain a wet edge when painting. Avoid painting in dry, breezy conditions. Do not paint in bright, direct sunshine. Avoid painting a surface that is hot from bright sunshine. Minimize the area being painted and plan for interruptions at a natural break, such as a window, door or corner (especially important when applying stain to bare wood). Alkyd paints generally have superior wet edge properties.
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.
Test for mildew by applying a few drops of household bleach to the discolored area, then rinse; if it disappears, it is probably mildew. Remove all mildew from the surface by scrubbing with a diluted household bleach solution (one part bleach, three parts water); wear rubber gloves and eye protection. Power washing is also an option. Rinse thoroughly, prime any bare wood, then apply one or two coats of top quality exterior paint, which typically contains more mildewcide than economy products.
Reddish-brown stains 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 prime, and caulk them with a top quality, water-based 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 paint due to poor adhesion. Where there is a primer and top coat, or multiple coats of paint, peeling may involve some or all coats.
- Seepage of moisture through uncaulked joints, worn caulk or leaks in roof or walls.
- Excess moisture escaping through the exterior walls (more likely if paint is oil-based).
- Inadequate surface preparation.
- Use of lower quality paint.
- Applying an oil-based paint over a wet surface.
- Earlier blistering of paint (see Blistering).
- Applying paint in a very thin coat.
- If blisters do not go all the way down to the substrate: Remove blisters by scraping and sanding, and repaint with a quality acrylic latex interior paint.
- If blisters go down to the substrate: Remove the source of moisture, if possible. Repair loose caulking; consider installing vents or exhauset fans. Remove blisters as above, remembering to prime before applying the finish coat.
POOR ALKALI RESISTANCE
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-resistant sealer or latex primer, followed by a top quality 100% 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 removal of rust or oils.
- 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-resistant primer should be applied (one coat is usually sufficient). Prime bare galvanized with a corrosive-inhibitive latex primer, and apply a top quality latex paint.
Deterioration of the paint film, resulting in excessive 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 sunshine.
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 time, lower quality paints will generally lose gloss much earlier than better grades. The binder in top quality acrylic latex paint is especially resistant 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 with 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. Do not powerwash freshly applied paint. Fortunately, even more stubborn cases will generally weather off in a month or so. Surfactant leaching should not affect the ultimate durability of the coating.
Brownish or tan discoloration on the paint surface due to migration of tannins from the substrate through the paint film. Typically occurs on “staining woods,” such as redwood, cedar and mahogany, or over painted knots in certain other wood species.
- Failure to adequately prime and seal the surface before applying the paint.
- Use of a primer that is not sufficiently stain-resistant.
- Excess moisture escaping through the exterior walls, which can carry the stain to the paint surface.
Correct any possible sources of excess moisture (see Efflorescence / Mottling). After thoroughly cleaning the surface, apply a high quality stain-resistant oil-based or acrylic latex primer. Oil-based stain-resistant primers are the best type to use on severely staining boards. In extreme cases, a second coat of primer can be applied after the first has dried thoroughly. Finish with a top quality latex paint.
Warping or buckling of vinyl siding panels that have been repainted.
May be caused by painting with dark color. Dark paint tends to absorb the heat of the sun, transferring it to the substrate. When vinyl siding expands dramatically from heat, it may not be able to contract to its original dimensions.
- Do not paint vinyl siding or other thin exterior PVC material any darker than its original color unless specifically recommended by the material or paint manufacturer. Whites, off-whites, pastels and other very light colors are good choices.
- Top quality acrylic latex paint is suitable for vinyl siding, because its superior flexibility withstands the stress of expansion and contraction cycles caused by outdoor temperature changes.
- Siding that has warped or buckled should be assessed by a siding or home repair contractor to determine the best remedy. The siding may have to be replaced.
Stains that come from waxy substances 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 coats 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 subject to wax bleed than are higher quality paints.
A rough, crinkled paint surface occurring when paint forms a “skin.”
- Paint applied too thickly (more likely when using alkyd or oil-based paints).
- Painting a hot surface or in very hot weather.
- Exposure of uncured paint to rain, dew, fog or high humidity levels.
- Applying top coat of paint to insufficiently dried first coat.
- Painting over contaminated surface (e.g., dirt or wax).
Scrape or sand substrate to remove wrinkled coating. Repaint, applying an even coat of top quality exterior paint. Make sure the first coat or primer is dry before applying the top coat. Apply paints at the manufacturer’s recommended spread rate (two coats at the recommended spread rate are better than one thick coat). When painting during extremely hot, cool or damp weather, allow extra time for the paint to dry completely.