FUNGAL / ALGAL CONTAMINATION:
Black, grey or brown areas of fungal or algal growth on the surface of paint or sealant.

POSSIBLE CAUSES:
• Fungus forms most often on areas that tend to be damp, and receive little or no direct sunlight (north facing walls and the underside of eaves are particularly vulnerable). Algae forms in the presence of light and moist environments.

• Use of a lower quality paint, which may have an insufficient amount of fungicide or algicide.

• Failure to prime bare wood before painting.

• Painting over a substrate or coating on which fungus or algae has not been removed.

SOLUTION:
• Test to distinguish fungus or algae from dirt by applying a few drops of household bleach to the discoloured area; if it disappears, it is probably fungus or algae. Treat the contamination with either a fungicidal wash or 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 water-based primer, then a premium exterior water-based paint in matt, silk, satin or gloss finish, depending on the desired appearance.

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