Patterned cracking in the surface of the paint film resembling the regular scales of an alligator.
- 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 topcoat 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; a heat gun can be used to speed work on large surfaces, but take care to avoid igniting paint or substrate. The surface should be primed with a high quality water-based primer, then painted with a top quality exterior water-based paint. Dulux recommends Dulux Weathershield.
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).
- 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, first try to remove the source of moisture. Remove blisters by scraping, then sanding the surface.
Prime any bare timber with a high quality water-based primer, and repaint with a high quality water-based exterior paint. Dulux recommends Dulux One Step Acrylic Primer Sealer Undercoat and Dulux Weathershield.
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 in 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 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 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 and the surface can be repainted with a quality exterior paint. Dulux recommends Dulux Weathershield.
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.
- Over thinning the paint or spreading it too thin.
- Poor surface preparation, especially when the paint is applied to bare timber without priming.
- Painting under hot or windy conditions that make water-based paints 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 water-based paint. Dulux recommends Dulux Weathershield.
Accumulation of dirt, dust particles and/or other debris on the paint film; may resemble mildew.
- Use of a low quality paint.
- Soil splashing onto the substrate.
- 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 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. Dulux recommends Dulux Weathershield Gloss.
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.
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 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. Dulux recommends Weathershield Matt.
Fading/Poor Colour Retention
Premature and/or excessive lightening of the paint color, which often occurs on surfaces with a sunny exposure. Fading/poor colour 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 over tinting 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 colours recommended for exterior use. Dulux recommends Dulux Weathershield.
Appearance of a denser colour 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 by applying paint toward the unpainted area and then back into the just-painted surface. This technique (brushing from "wet to dry," rather than vice versa) will help produce a smooth, uniform appearance. It is also wise to minimise 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). Solvent-based paints generally have superior wet edge properties.
Black, gray or brown areas on the painted surface.
- Forms most often on areas that tend to be damp, and receive little or no direct sunlight (the underside of eaves are particularly vulnerable).
- Use of a lower quality paint.
- Failure to prime bare wood before painting.
- Painting over a substrate or coating on which mould has not been removed.
Test for mould by applying a few drops of household bleach to the discoloured area;
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 timber, then apply one or two coats of top quality exterior paint. Dulux recommends Dulux Weathershield.
Nail Head Rusting
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 nail heads 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 nail heads, then caulk them with a top quality, water-based all-acrylic caulk. Each nail head area should be spot primed, then painted with a quality latex coating. When repainting exteriors, where nail head rusting has occurred, wash off rust stains, sand the nail heads, 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 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).
Try to identify and eliminate the cause of moisture (see Efflorescence and Mottling). Prepare surface by removing all loose paint with scraper or wire brush, sand rough surfaces, prime bare timber. Repaint with a top quality water-based exterior paint for best adhesion and water resistance. Dulux recommends Dulux One Step Primer Sealer Undercoat and Dulux Weathershield.
Poor Alkali Resistance
Colour loss and overall deterioration of paint film on fresh masonry.
Coating 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, apply a quality, alkali-resistant sealer or water-based primer, followed by a top quality 100 percent acrylic exterior paint. The acrylic binder in these paints resists alkali attack. Dulux recommends Dulux Weatehrshield.
Poor Gloss Retention
Deterioration of the paint film, resulting in excessive, or rapid loss of lustre of the topcoat.
- Use of an interior paint outdoors.
- Use of a lower quality paint.
• Use of solvent-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 lustre 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 solvent-based 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 in chalking surfaces (see Chalking).
Concentration of water-soluble ingredients on water-based paint, creating a blotchy, sometimes glossy appearance, often with a tan or brownish cast. More likely with tinted paints than with white or factory-coloured 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.
- Contact of mist, dew or other moisture with 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. 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 timbers,' such as redwood, cedar and mahogany, or over painted knots in certain other timer 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 and Mottling). After thoroughly cleaning the surface, apply a high quality stain-resistant solvent-based or 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 dried thoroughly. Finish with a top quality water-based paint. Dulux recommends Dulux One Step Oil Based Primer Sealer Undercoat and Dulux Weathershield.
A rough, crinkled paint surface occurring when paint forms a 'skin.'
- Paint applied too thickly (more likely when using solvent-based paints).
- Painting a hot surface or in very hot weather.
- Exposure of uncured paint to rain, dew, fog or high humidity levels.
- Applying the topcoat 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 topcoat. 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 humid, cool or damp weather, allow extra time for the paint to dry completely.