Cleaning a colorbond roof incorrectly voids warranties and causes permanent coating damage. Here's what Bluescope Steel recommends — and the professional method that's safe for all colorbond roofing.
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Colorbond steel roofing is Australia's most widely used residential roofing material, and it's also one of the most commonly cleaned incorrectly. The factory-applied paint system on colorbond is designed for weather resistance, not mechanical pressure — meaning that high-pressure washing, abrasive cleaning and incorrect chemicals can all cause irreversible damage to the coating. This guide covers what Bluescope Steel (colorbond's manufacturer) recommends for cleaning, the risks of DIY and pressure washing approaches, and the professional method that delivers a clean colorbond roof without any damage to the coating.
Bluescope Steel's official guidance for cleaning Colorbond steel recommends: washing with mild detergent and water; using low pressure or hand washing with a soft brush; avoiding abrasive cleaners, solvents or acids; and rinsing thoroughly with clean water. High-pressure washing is contrary to these recommendations and voids most colorbond product warranties.
Avoid: high-pressure washing (strips coating, causes micro-fractures, voids warranty); abrasive brushes or pads (scratch coating permanently); acid-based cleaners (corrode the paint system and the steel substrate); and solvent-based products (can lift and dissolve the paint coating). Any of these approaches can cause permanent, irreversible damage to colorbond roofing.
Professional soft washing for colorbond uses: a pH-balanced cleaning solution specifically selected for painted metal surfaces; application at 50 to 100psi (compared to 2,000 to 4,000psi for pressure washing); adequate dwell time for the solution to kill biological growth; and a thorough low-pressure rinse. This approach is consistent with Bluescope's recommendations and produces a clean colorbond roof without any coating risk.
For single-storey colorbond with minimal biological growth — light dust and general grime only — gentle DIY cleaning with mild detergent and a soft brush is possible but working on a roof safely requires appropriate equipment. For any biological growth (moss, algae, lichen), professional chemical treatment is required to kill the organism at root level. For two-storey or elevated colorbond, professional access equipment is necessary.
Low-pressure soft washing with a pH-balanced cleaning solution — applied at 50 to 100psi with appropriate dwell time for biological growth, then rinsed at low pressure. This is consistent with Bluescope Steel's care recommendations.
Household bleach is not recommended at full strength — the pH and concentration can affect colorbond coatings. Professional soft wash solutions use sodium hypochlorite at calibrated concentrations with surfactants specifically formulated for metal surfaces.
Yes — high-pressure washing strips and micro-fractures the factory paint coating on colorbond roofing, voids warranties and can expose the steel substrate to corrosion.
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