Bubbles resulting from localised loss of adhesion, and lifting of the paint film from the underlying surface.

POSSIBLE CAUSES:

• Applying solvent-based paint over a damp or wet surface.
• Moisture seeping into the home through the exterior walls (less likely with water-based paint).
• Exposure of water-based paint film to high humidity or moisture shortly after paint has dried, especially if there was inadequate surface.

SOLUTION:

• If blisters do not go all the way down to the substrate: Removeblisters by scraping, and sanding, and repaint with a quality acrylic water-based interior paint.
• If blisters go down to the substrate: Remove the source of moisture, if possible. Repair loose sealants; consider installing vents or exhaust fans. Remove blisters as above, remembering to prime before applying the top coat.

Formation of fine powder on the surface of the paint film during weathering which can cause colour 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.

POSSIBLE CAUSES:

• Use of a low-grade, highly pigmented paint.

• Use of an interior paint for an outdoor application.

SOLUTION:

• 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 solvent-based or acrylic water-based 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.

Patterned cracking in the surface of the paint film resembling the regular scales of a crocodile.

POSSIBLE CAUSES:

• Application of an extremely hard, rigid coating, like a solvent-based enamel, over a more flexible coating, like a water-based primer. • Application of a top coat before the undercoat is dry.
• Natural aging of solvent-based paints as temperatures fluctuate. The constant expansion and contraction results in a loss of paint film elasticity.

SOLUTION:

• Old paint should be completely removed by scraping and sanding the surface; a heat gun can be used to speed work on large surfaces, but take care to avoid igniting paint or substrates. The surface should be primed with high quality water-based or solvent-based primer, then painted with two coats of a top quality exterior water-based paint.

The splitting of a dry paint film through at least one coat as a result of aging, which ultimately will lead to complete failure of the paint. In its early stages, the problem appears as hairline cracks; in its later stages, flaking occurs.

POSSIBLE CAUSES:

• Use of lower quality paint that has inadequate adhesion and flexibility.
• Overthinning or overspreading the paint.
• Inadequate surface preparation, or applying the paint to bare wood without first applying a primer.
• Excessive hardening and embrittlement of solvent-based paint as the paint job ages.

SOLUTION:  

• Remove loose and flaking paint with a scraper or wire brush, sanding the surface and feathering the edges. If the flaking occurs in multiple layers of paint, use of a face filler may be necessary. Prime bare wood areas before repainting. Use of a top quality primer and top coat should prevent a recurrence of the problem.

Formation of bubbles (foaming) and resulting small, round concave depressions (cratering) when bubbles break in a paint film, during paint application and drying.

POSSIBLE CAUSES:

• Shaking a partially filled can of paint.
• Use of low quality paint or very old water-based paints.
• Applying (especially rolling) paint too rapidly.
• Use of a roller cover with wrong nap length.
• Excessive rolling or brushing of the paint.
• Applying a gloss or satin paint over a porous surface.

SOLUTION:

• All paints will foam to some degree during application; however, higher quality paints are formulated so the bubbles break while the paint is still wet, allowing for good flow and appearance. Avoid excessive rolling or brushing of the paint or using paint that is more than a year old. Apply gloss and satin paints with a short nap roller,and apply an appropriate sealer or primer before using such paint over a porous surface.Problem areas should be sanded before repainting.

Black, grey or brown spots or areas on the surface of paint or sealant.

POSSIBLE CAUSES:

• Forms most often on areas that tend to be damp, or receive little or no direct sunlight (e.g., bathrooms, kitchens and utility rooms).
• Use of a solvent-based paint, or lower quality water-based paint.
• Failure to prime bare wood surface before applying the paint.
• Painting over a substrate or coating on which fungal contamination has not been removed.

SOLUTION:

• Test for fungus by applying a few drops of household bleach to the area; if it is bleached away, the discolourant is probably fungus. Remove all fungus from the surface by scrubbing with a diluted household bleach solution (one part bleach, three parts water) or a fungicidal wash, while wearing rubber gloves and eye protection. Rinse thoroughly. To protect against fungal contamination, use a top quality water-based paint, and clean when necessary with bleach/detergent solution. Consider installing an exhaust fan (which is connected to a light switch) in high moisture areas. Some products,with fungicidal claims are available, which you may consider.

Appearance of a denser colour or increased gloss where wet and dry layers overlap during paint application.

POSSIBLE CAUSES:

• Failure to maintain a 'wet edge' when painting.
• Use of a low solids 'economy' paint.

SOLUTION:

• Maintain a wet edge when painting by applying paint toward the unpainted area and then back into the just painted surface. This technique (brushing or rolling from 'wet to dry' rather than vice versa) will produce a smooth uniform appearance. It is also wise to work in manageable size areas; plan for interruptions at a natural break, such as a window, door or corner. Using a top quality acrylic water-based paint makes it easier to avoid lapping problems because higher solids (pigments and binder) content makes lapped areas less noticeable. If substrate is very porous, it may need a primer/sealer to prevent paint form drying too quickly and reducing wet edge time.Solvent-based paints generally have superior wet edge properties.

Accumulation of dirt, dust particles and/or other debris on the paint film; may resemble fungus or algae.

POSSIBLE CAUSES:

• Use of a low quality paint, especially lower grades of satin types.
• Air pollution, car exhaust fumes and flying dust collecting on houses.

SOLUTION:

• Wash off all surface dirt before priming and painting, using a scrub brush and detergent solution, followed by a thorough rinse. Heavier dirt accumulations may require the use of a power washer. While dirt pickup can't be eliminated entirely, top quality exterior water-based paints typically offer superior dirt pickup resistance and washability. Also, higher gloss paints are more resistant to dirt pickup than matt paints, which are more porous and can more easily entrap dirt.
• Regular wash down will give longevity to the paint film.

Crusty, white salt deposits, leached from mortar or masonry as water passes through it.

POSSIBLE CAUSES:

• Failure to adequately prepare surface by removing all previous efflorescence.
• Excess moisture escaping through the exterior masonry walls from behind.

SOLUTION:

• If excess moisture is the cause, eliminate the source by repairing the roof, cleaning out gutters and drainpipes, and sealing any cracks in the masonry with a high quality, water-based all-acrylic or siliconised acrylic sealant. 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.

Premature and/or excessive lightening of the paint colour,which often occurs on surfaces with sunny south facing exposure. Fading/poor colour retention can also be a result of chalking of the coating.

POSSIBLE CAUSES:

• 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 colour 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.

SOLUTION:

• When fading/poor colour 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 colours recommended for exterior use.

A white,salt-like substance on the paint surface. Frosting can occur on any paint colour, but it is less noticeable on white paint or lighter tints. On masonry, it can be mistaken for efflorescence (see Efflorescence and Mottling).

POSSIBLE CAUSES:

• 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-coloured paints that have been formulated with calcium carbonate extender.
• Application of a dark-coloured paint over a paint or primer containing calcium carbonate extender.

SOLUTION:

• Frosting, though not common,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 wire brushing masonry or sanding wood surfaces; rinse,then apply a solvent-based primer before adding a coat of high quality exterior paint.

Reddish-brown stains and spots on the paint surface.

POSSIBLE CAUSES:

• Non-galvanised iron nails have begun to rust, causing bleed-through to the top coat.
• Non-galvanised iron nails have not been countersunk and filled over.
• Galvanisednailheads have begun to rust after sanding or excessive weathering.

SOLUTION:

• When painting new exterior construction where non-galvanisednails have been used, it is advisable to first countersink the nailheads,then seal them with a top quality,water-based all-acrylic or siliconised acrylic sealant. Each nailhead area should be spot primed, then painted with a quality water-based 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 solvent-based paint receive a water-based top coat.

POSSIBLE CAUSES:

• Use of water-based paint over more than three or four coats of solvent-based paint may cause the old paint to "lift off" the substrate.

SOLUTION:

• Repaint using another coat o solvent-based paint; although it is preferable to remove the existing paint and prepare the surface-cleaning, sanding and spot-priming where necessary - before repainting with a top quality water-based exterior paint.

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.

POSSIBLE CAUSES:

• Seepage of moisture through unsealed joints, worn sealant or leaks in roof or walls.
• Excess moisture escaping through the exterior walls (more likely if paint is solvent-based).
• Inadequate surface preparation.
• Use of lower quality paint.
• Applying a solvent-based paint over a wet surface.
• Earlier blistering of paint (see Blistering).

SOLUTION:

• Try to identify and eliminate source of moisture. Prepare surface by removing all loose paint with scraper or stiff wire brush,sand rough edges,and apply appropriate primer. Repaint with a top quality acrylic water-based exterior paint for best adhesion and water resistance.

Colour loss and overall deterioration of paint film on fresh masonry.

POSSIBLE CAUSES:

• Solvent-based paint or water-based paint (vinyl acetate copolymers type) was applied to new masonry that has not cured for a fullyear.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.

SOLUTION:

• 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 water-based primer, followed by a top quality pure acrylic exterior water-based paint.The acrylic binder in these paints resists alkali attack.

Paint that has lost its adhesion to a galvanised metal substrate.

POSSIBLE CAUSES:

• Improper surface preparation, such as inadequate rust removal.
• Failure to apply a primer before application of a solvent-based or water-based paint (vinyl acetate copolymer type).
• Failure to sand baked-on enamel finishes or glossy surfaces before painting.

SOLUTION:

• Any rust on the metal should be removed with a wire brush; then,an acrylic water-based corrosion-inhibitive primer should be applied (one coat is usually sufficient). Previously painted galvanised metal that is completely rust-free can be painted without applying a primer. New galvanised iron should be allowed to weather for at least 6 months or washed down with turpentine to remove any oil.A water-based metal primer should be applied to unpainted galvanised metal, followed by a top quality exterior acrylic water-based paint.

Deterioration of the paint film, resulting in excessive or rapid loss of lustre of the top coat.

POSSIBLE CAUSES:

• Use of an interior paint outdoors.
• Use of a lower quality paint.
• Use of a gloss solvent-based paint in areas of direct sunlight.

SOLUTION:

• 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 lustre over time, lower quality paints will generally lose gloss much earlier than better grades. The binder in top quality acrylic water-based paints is especially resistance to UV radiation, while solvent-based paints 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 the surface of a water-based paint, typically on a ceiling surface in rooms that have high humidity (e.g., shower, bathroom, kitchen); may be evident as tan or brown spots or areas, and can sometimes be glossy, soapy or sticky.

POSSIBLE CAUSES:

• All water-based paint formulas will exhibit this tendency to some extent if applied in areas that become humid (bathrooms, for example), especially in ceiling areas.

SOLUTION:

• Wash the affected area with soap and water, and rinse. Problem may occur once or twice again before leachable material is completely removed. When paint is applied in a bathroom,it is helpful to have it dry thoroughly before using the shower. Remove all staining before repainting.  

A rough, crinkled paint surface, which occurs when uncured paint forms a 'skin'.

POSSIBLE CAUSES:

• Paint applied too thickly (more likely when using solvent-based paints).
• Painting during extremely hot weather or cool damp weather, which causes the paint film to dry faster on top than on the bottom.
• Exposing uncured paint to high humidity levels.
• Painting over a contaminated surface (e.g., dirt or wax).

SOLUTION:

• Scrape or sand substrate to remove wrinkled coating. If using a primer, allow it to dry completely before applying top coat. Repaint (avoiding temperature/humidity extremes), applying an even coat of top quality interior paint.

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, such as pine.

POSSIBLE CAUSES:

• 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.

SOLUTION:

• Correct any possible sources of excess moisture (see Efflorescence and Mottling). After thoroughly cleaning the surface,apply a high quality stain-resistant solvent-based or acrylic water-based primer. Solvent-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 died thoroughly. Finish with a top quality water-based paint.

Stains that come from waxy substance in the reconstituted wood products such as chipboard or MDF.When the substrate is painted,these staining substances bleed through the paint; they can even bleed through some ordinary primers,possibly causing dirt pickup, fungal/algal contamination and/or poor paint adhesion (see Dirt Pickup and Fungal/Algal Contamination.

POSSIBLE CAUSES:

• Failure to apply a proper primer to hardboard before applying the top coat. We recommend a quality water-based acrylic primer followed by two coats of quality acrylic paint.

SOLUTION:

• Wash the affected area with soap and water, and rinse. Problem may occur once or twice again before leachable material is completely removed. When paint is applied in a bathroom,it is helpful to have it dry thoroughly before using the shower. Remove all staining before repainting.