Why does it grow so fast here?
Humidity, summer rain and shade. Surfaces on the Gold Coast stay damp for long stretches, which is exactly what mould, algae, mildew and lichen need. The first places to go green or black are the ones that see the least sun: south-facing walls, anything under a tree, narrow side passages and the underside of eaves.
Why does it come back after a pressure wash?
Because pressure removes the visible growth, not the spores sitting in the surface. Render, paint and roof tiles are porous. Knock the top layer off and the spores are still there, ready to regrow as soon as the weather turns humid again. On those surfaces, high pressure also roughens or damages the finish, which gives the next lot of growth something to hold on to.
What works better?
Killing it. A soft wash puts a biodegradable solution on at low pressure. It kills mould, algae and lichen, and the dead growth rinses away. In our experience a soft-washed wall stays clean two to three times longer than one that's only been pressure washed.
Roofs work the same way. The treatment kills lichen, moss, algae and mould at the root, and whatever's left washes off with a gentle rinse or over the next few rains. See roof cleaning and house soft washing.
What about black streaks on render?
Those are usually algae or mould growing in the texture of the render, and a soft wash deals with them. White powdery marks are a different thing, often efflorescence, which is salt coming out of the masonry. Washing can tidy it up, but if it keeps appearing there's moisture getting into the wall and that's worth looking into.
Does outdoor mould actually matter?
Beyond the look of it, yes. Algae turns paths, driveways and pool surrounds slippery. On a roof, lichen and moss hold moisture against the surface, which speeds up corrosion on metal and wear on tiles, and the debris ends up blocking valleys and gutters.
How do I slow it down?
Get the house washed before the growth gets heavy. For most Queensland homes that's every two to three years, and more like every 12 to 18 months for shaded, coastal or bushland homes. Roofs need it every one to two years. Keep the gutters clear so water doesn't overflow down the walls (see gutter maintenance), and cut plants and trees back from walls and roofs so sun and air can get in.
Is the treatment safe for the garden and pets?
Yes, done properly. The solutions are biodegradable and safe for plants and animals once diluted. We pre-water and protect garden beds before and after every job. Keep pets inside until everything is rinsed and dry.
Suburbs where this comes up most
Reedy Creek · Tallebudgera · Mudgeeraba · Worongary · Elanora · Capalaba · Wellington Point · Carrara · Merrimac · Nerang
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More guides
- Soft washing vs pressure washing: which does your Gold Coast home need?
- How much does house washing cost on the Gold Coast?
- How often should coastal and beachfront Gold Coast properties be cleaned?
- What does a full exterior clean include, and how do you book one?
- Exterior cleaning before you sell or go to auction on the Gold Coast
- Cleaning pavers, patios and pool surrounds on the Gold Coast
- Exterior cleaning for strata and body corporate properties: a guide for managers and committees
- Roof soft washing on the Gold Coast: tiled, metal and older roofs
- All exterior cleaning FAQs