Mould on weatherboard requires careful treatment — too much pressure splits joins and forces water behind boards. Here's the correct approach for timber and fibre cement weatherboard in Queensland.
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Mould on weatherboard house exteriors is extremely common across Queensland, particularly in Redlands and other coastal areas where humidity keeps exterior surfaces moist. Whether your weatherboard is traditional painted timber, fibre cement or modern composite profile, the cleaning approach needs to be appropriately gentle — weatherboard can be damaged by high-pressure washing in ways that create more serious problems than the mould you started with.
Painted timber weatherboard is vulnerable to high-pressure washing in several ways: boards can split at joins if the pressure forces into the gap; water forced behind boards enters the wall cavity and causes internal moisture damage and potentially internal mould; and paint can be lifted on older homes with multiple paint layers, causing more extensive paint failure. For heritage weatherboard particularly, soft washing is the only appropriate method.
Modern fibre cement weatherboard (Hardiplank and similar products) is more robust than timber but still requires care. High-pressure washing can: chip edges and corners of fibre cement sheets; force water behind sheet joins; and over time degrade the paint system more rapidly than gentle cleaning. Soft washing is appropriate for all fibre cement products.
For accessible surfaces with light mould growth, diluted sodium hypochlorite (1 to 3% solution) applied with a soft brush and rinsed with a garden hose is a manageable DIY approach. For extensive mould, multi-storey properties, heritage homes or surfaces with significant join gaps, professional soft washing is significantly safer.
Professional soft washing applies the correct concentration for the mould type and weatherboard material, at low pressure that won't split joins or force water behind boards. For heritage Queenslander weatherboard particularly, professional treatment is strongly recommended.
Not recommended — particularly for timber weatherboard. High pressure splits joins, forces water behind boards and can lift paint on older surfaces. Soft washing at low pressure is the safe method.
A biocidal solution containing sodium hypochlorite at the appropriate concentration. The solution kills the mould at root level rather than just wiping the visible layer off the surface.
For light surface mould on accessible single-storey surfaces, diluted bleach solution with a soft brush and garden hose rinse is a manageable DIY approach. For extensive mould, heritage homes or multi-storey, professional soft washing is safer and produces better results.
House washing starts from $499, including a free gutter clean. Free quote before any work starts.
Serving Redlands and all of South East Queensland. We reply within 2 hours, Mon–Sat.
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