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How to clean colorbond roof

Joan_J
Growing in Experience

How to clean colorbond roof

My Colorbond roof appears to have mould on it which has been there since I purchased the property. I’m wondering if there’s a way to clean it off? I have a pressure cleaner from Bunnings but unsure if that’s enough. Thanks!

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MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: How to clean colorbond roof

Hi @Joan_J,

 

I'd suggest a bit of a combination between 30 Seconds 5L Roof Treatment Concentrate and possibly your pressure sprayer. You can either spray the product and leave it for up to 6 months before the lichen fully decays and washes off in the rain or spray as much as you can off now with your pressure sprayer before applying the product.

 

It's best to get the 30 seconds product on there as soon as possible and let it do its work. I'd recommend doing the work from a ladder if possible, as it would be pretty dangerous to get onto the slippery Colorbond roof whilst it's wet. Your pressure sprayer won't do much to the lichen unless you can get the nozzle up close to it. If that requires you to get on the roof, I would advise you to leave it to the professionals.

 

Unfortunately, you might find that the lichen has secreted destructive acids causing damage to roof materials. This might appear as a discolouration even after the lichen is removed.

 

Please let me know if you have any questions.

 

Mitchell

 

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Cranswick
Building a Reputation

Re: How to clean colorbond roof

l dont think it lichen because because, the spots on my roof is  black, does that mean its more likely mould . does the 30 second product work on mould and is it safe for colorbond roof

Re: How to clean colorbond roof

Hi @Cranswick,

 

It could be mould or mildew, though mould doesn't typically grow on a roof. Looking at the specifications of the 30 Seconds 5L Roof Treatment Concentrate it does say that it is suitable for Coloured steel. However, as mentioned in your discussion, chemical cleaners are not listed for use in the technical specifications of Colorbond steel.

 

This cleaner should work for most organic issues on a roof.

 

Mitchell

 

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Cranswick
Building a Reputation

Re: How to clean colorbond roof

Thanks, l will see if l can take a photo later to post here, its just on one section of the roof about 1 meter wide and 2.5 meters long covered in black spots or streaks . Even though chemical cleaners are not listed , Would a one off spray of that small  roof section be very unlikely to harm the roof, l will only be spraying that section not the entire roof. l was thinking they wouldnt say on the ' 30 second package ' its suitable for colorbond roofs if it can damage the roof, then if people roofs were damaged by it they would get sued. If l give it a spray with ' 30 secod cleaner' how long will it take for the black spots to go away ? should l hose it down afterwards or let the 30 second cleaner sit there overnight 

Re: How to clean colorbond roof

They've likely done testing and found it doesn't damage Colorbond @Cranswick. Given that they are recommending it for that purpose, I would say it's very unlikely that it would damage the roof.

 

However, if you can wait until Monday, I'd like to contact the manufacturer directly to get a definitive answer on Colorbond. The product description notes that it is suitable for coloured steel, though I'm not finding that information on the 30 Seconds website. There, it only states "steel roofs" and not painted steel roofs.

 

I think it would be wise to have this confirmed before applying it to your roof.

 

Mitchell

 

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Cranswick
Building a Reputation

Re: How to clean colorbond roof

Thanks, lm now thinking l might get my plumber who cleans my roof to scrub it with detergent which will be safer, one thing l am a bit worried about is l read about something called " Black Rust" l hope its just some sort of  fungus and not " Black Rust" . Would it be unlikely to be black rust ,? is that common or rare,  if its black rust would that be a series expensive problem,  the roof is 15 years old and 2 km from the ocean. l will try and post some photos later

Re: How to clean colorbond roof

That's typically seen at points where the sheeting is damaged and the inner steel exposed, like on cut edges @Cranswick. It's unlikely to occur mid-sheet. Repair would be a process of sanding the area back, treating the rust and re-coating. I'm not aware of how costly that would be, and you'd likely need to get some quotes.

I wouldn't jump to that conclusion until the area is assessed; it's most likely some organic matter.

 

Mitchell

 

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Cranswick
Building a Reputation

Re: How to clean colorbond roof

Heres a photo , can you tell me what you think the black stuff on the roof is , thanks 20250511_154823 (7).jpg

EricL
Bunnings Team Member
Bunnings Team Member

Re: How to clean colorbond roof

Hello @Cranswick 

 

It appears to be mould and mildew along with a form of dust deposit. It does not appear to be a heavy rust infestation. In regards to the cleaner, Mitchell will be following this up with our supplier of 30 seconds. Let's wait to see what they have to say in regards to making sure that using the cleaner is safe. 

 

If you have any other questions we can help with, please let us know.

 

Eric

 

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