Please wait ...

Causes of roof algae and how to remove it

bark profile image

Mika, Staff Writer

Tuesday, 4 May 2021

When a roof is first installed it makes the whole property look brand new. But, similar to how your windows and driveway need cleaning over time, your roof will also be prone to dirt and stains as it ages. 

Most commonly, algae will appear on your roof which are a non-flowering type of aquatic plant. Some might think algae add character and charm to a roof, especially if it's an older home. However, algae can indicate a serious problem that requires immediate attention. 

That’s why you should address the issue as soon as you notice it. Here's what you need to know about roof algae.  

Causes of roof algae

Roof algae or fungus usually starts by a single spore blowing onto your roof, where it settles and grows. As well as the weather, tree branches close to your roof, clogged gutters, standing water or an inferior roof material can all cause the spores to thrive. 

Algae will grow fastest in shaded areas such as under trees as well as humid environments. Therefore, almost all roofs are at risk of developing algae, especially if the roof and guttering aren’t regularly maintained. 

Whatsmore, limestone filler which can be found in some roof tile types nourishes the algae making it quickly spread. Though, different types of moss can also develop on your roof which can be problematic too. Before you know it, your whole roof is covered in algae. 

How to recognise roof algae

  • Green or black streaks on your roof

  • Green or white spots

  • Round lichens

  • Moss 

Why is roof algae a problem?

Algae might seem harmless but are anything but. Over time, algae can start to damage not just the roof tile but the underlying structures, potentially affecting the integrity of the roof itself. If the algae work their way into your home, then this can also cause health problems to both humans and animals, similar to mould and other bacteria. 

On a cosmetic level, roof algae can seriously diminish your property’s curb appeal. That’s because it signifies it’s been years since your roof has been maintained which doesn’t give a good first impression, especially if you are trying to sell the property. It could also lower its value as a result, as your roof could require costly repairs if the algae are particularly bad. 

Removing algae from your roof

Not only do you need to remove algae for the sake of your roof, but given how quickly algae spores can spread it’s also for the benefit of your neighbours too. 

There are a few options you can consider to do this. On a basic level, pressure washing or soft washing may rid the problem, though is only suitable for certain roof types. The roof may also require a disinfectant applied to rid the bacteria growth and help prevent it from reappearing. 

Given it’s a roof you’re dealing with, consulting a roofer is a very sensible option, as only they can get up there to inspect the damage properly. A roofer will advise on the best treatment for your particular roof material, along with whether any more serious damage needs repairing.

Also, be sure to carry out a check of your roof at least once a year. As well as algae, look for any broken or loose roof tiles. Ensure your gutters are not blocked, as this can also affect how well your roof will perform. 

Find a Roofer near me

Is something not looking quite right with your roof? Whether you’ve noticed algae growing on your roof or have a worrying leak, find a trusted roofer to come and fix the problem for you.

The sooner you sort it, the quicker you can put it out of your mind. Plus, consulting a roofer will prevent you from having to shell out more money for costly repairs if you leave your roof to deteriorate any longer. 

Find a Roof Repairer near you

The average rating for Bark Roof Repairers is 4.71, based on 383,438 reviews


based on 383,438 reviews

Get quotes from Roof Repairers near you