Roof Restoration
Roof Mould Removal in Sydney
Those black streaks aren't dirt -- they're living mould, and we treat them at the source.
The dark streaks and blotches spreading down a roof are usually mould and algae, not simple dirt or staining. They're living organisms feeding on the film of grime, spores and moisture that builds up on a roof surface, and they flourish in Sydney's humid, subtropical stretches -- especially on shaded, damp roofs and in leafy or coastal suburbs. Hosing them off does nothing lasting because the growth is alive; it needs treating so it dies and lifts, then the roof stays clean far longer.
What those black streaks really are
The classic dark streaking, often running in vertical lines down the slope, is typically a mix of algae and mould. It takes hold where moisture lingers -- shaded slopes, under overhanging trees, and areas that stay damp because of poor airflow. On lighter tiles and metal it shows up starkly as grey-black staining; on painted roofs it can make a good coating look tired years before its time.
It's not just cosmetic. The growth holds moisture against the surface, and on a coated or painted roof that dampness slowly undermines the finish. Left unchecked, mould keeps spreading and the roof needs recoating sooner.
Treating mould at the source
Mould has to be killed, not just rinsed away, or it regrows from what's left behind within months. We apply a treatment that kills the mould and algae through the growth, let it work, and then clean the roof down. Killing it first means we can clear it at a lower, tile-safe pressure rather than blasting at living growth and damaging the surface or forcing water under the laps.
On a painted or coated roof we take care to lift the mould without stripping the coating -- the aim is a clean surface, not a damaged one. We rinse thoroughly and clear the runoff from gutters and downpipes.
Keeping mould from coming back
Mould returns quickest where the roof stays damp and shaded. Improving airflow and sunlight by trimming back overhanging branches, keeping gutters flowing so water doesn't back up, and applying an anti-fungal treatment after cleaning all buy you much longer between cleans. If your roof is due for recoating anyway, a coating with anti-fungal additives resists regrowth well.
What's Included
- Application of a treatment that kills mould and algae through the growth
- Dwell time before cleaning so the growth dies and releases
- Tile-safe, controlled-pressure cleaning that protects any coating
- Careful lifting of mould from painted or coated surfaces without stripping them
- Thorough rinse-down and clearing of runoff from gutters
- Anti-fungal treatment and advice to slow future regrowth
Frequently Asked Questions
Are the black streaks on my roof mould or just dirt?
They're almost always living mould and algae rather than dirt. Dirt washes off; mould regrows because it's alive and feeding on the film on your roof. That's why hosing it down doesn't keep it away. It needs treating to kill it at the source before cleaning.
Is roof mould a health risk?
Mould on the outside of the roof isn't the same concern as mould inside your home, but the spores can wash into gutters and around the property, and persistent damp can eventually affect the roof structure. It's worth clearing, and we do it without spreading spores through the house.
Will cleaning damage my painted or coated roof?
Not the way we do it. We kill the mould with a treatment first so it can be cleared at a low, controlled pressure that lifts the growth without stripping the coating. Blasting living mould off a painted roof at high pressure is what damages the finish -- we avoid that.
How long until the mould comes back?
It depends on shade, moisture and airflow. On a damp, shaded roof it can return within a year or two; a sunnier, well-drained roof stays clean much longer. Trimming trees, keeping gutters clear and an anti-fungal treatment after cleaning all extend the time between cleans.
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