That Black Stuff on Your Roof Isn't Just Dirt (And It's Eating Your Tiles)

You've noticed it. Those dark streaks and patches creeping across your roof. Maybe it started in the corners, or under the trees, or on the south-facing side that doesn't get as much sun.

You figured it was just dirt. Bit of grime from the weather. Nothing to worry about - it's a roof, it's supposed to get dirty, right?

Here's the thing: that's not dirt. And ignoring it is costing you money.

What You're Actually Looking At

That black and green growth on your roof is alive. It's a combination of mould, mildew, lichen, and algae - and on the Gold Coast, our warm, humid climate is basically an all-you-can-eat buffet for the stuff.

Algae shows up first. Those dark streaks that look like someone dragged dirty water down your tiles? That's algae. It's not just ugly - it's feeding on the limestone filler in your tiles and slowly breaking down the surface.

Then comes the moss and lichen. These guys are slower, but they're doing real damage. Lichen sends tiny root-like structures into your tiles. Moss holds moisture against the surface. Both of them are literally pulling your roof apart, one microscopic crack at a time.

And mould? That's the gift that keeps on giving. It's not just on your roof - the spores are getting into your roof cavity, your gutters, and potentially your home.

Why It Gets Worse If You Leave It

Here's where people get caught out.

This stuff doesn't just sit there looking ugly. It grows. It spreads. And the longer you leave it, the more damage it does.

Those tiny cracks from the lichen? Water gets in. Gold Coast storms come through, that water expands and contracts, and suddenly you've got tiles that are porous when they should be sealed. Your roof starts holding moisture instead of shedding it.

The algae keeps feeding on your tiles, breaking down the protective surface layer. Your roof ages years in months. Tiles that should last decades start deteriorating.

And here's the real kicker - by the time most people notice it's a problem, the growth has been there for years. What looks like "a bit of black stuff" is actually a mature colony that's well established and has already done damage you can't see.

I've seen roofs where homeowners thought they just needed a clean, but the tiles were so degraded they needed replacing. We're talking tens of thousands of dollars because someone thought "it's just dirt" for too long.

The Fix Isn't What You Think

Your first instinct might be to get up there with a gurney and blast it off. Don't.

High pressure on roof tiles is a disaster waiting to happen. You'll strip the protective coating, damage the tile surface, and potentially crack tiles - especially if they've already been weakened by years of organic growth. You'll make the problem worse, not better.

Roof cleaning is one of those jobs where knowing what NOT to do is just as important as knowing what to do. Different tile types need different approaches. Concrete tiles handle things differently to terracotta. Colorbond is another story entirely.

We use a combination of low pressure and the right cleaning solutions to kill the growth without damaging your roof. It's not about blasting - it's about treating. Kill the spores, remove the dead growth gently, and your roof can actually recover.

The other thing I do is give you a realistic assessment. If your tiles are already compromised, I'll tell you before we start - not after you've paid for a clean that won't fix the underlying problem. Sometimes the honest answer is "you need a roofer, not a cleaner." I'd rather have that conversation upfront.

The Bottom Line

That black stuff on your roof isn't cosmetic. It's biological, it's growing, and it's actively damaging your tiles.

You can keep telling yourself it's just dirt and deal with an expensive roof replacement down the track. Or you can get it sorted now, while it's still a cleaning job and not a tradie's quote.

Your roof. Your call.

Want to know what's actually going on up there? Get your free online estimate or give us a call on 1800 517 402.