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Why is there Algae on My Render? - And What Types Are There?

Should I Be Worried?

Types of Algae

How We Remove Algae


In damp climates like the UK, algae and moss will always grow on render façades.

Our job is to provide non-damaging algae removal services that offer long-lasting results. By understanding why algae grows and how it can affect a rendered façade, it will mean you can make the best maintenance choices for your property. When render first became a popular building material, it was considered maintenance-free. However, now that many rendered buildings are beginning to age, we can see that this isn’t the case. Green algae on rendered walls is a common sight across buildings in damp climates like the UK. With regular professional maintenance, there is no reason your property should be left looking dull and discoloured.

 If you are looking for specialist render cleaning click here.

Why Is There Algae on My Wall?

An alga is an organism that shares properties with plant life. However, it exists in a category of biological matter of its own. It grows when moisture containing organic matter (from rain, for instance) adheres to your façade, and algae spores land on the wall. Algae spores are carried by the wind, so they can be transported to any outdoor surface.

Over time, algae grow and spread, forming visible discolouration which is typically green, red or black. You may find it especially noticeable on lighter walls, which is why cleaning white render walls from the eyesore of algae is such an urgent matter for property owners.

Any leaks, cracked pipes or blocked drainage systems will contribute to a flow of water down walls, encouraging algae growth on rendered walls. Essentially, the more moisture your property is exposed to, the greater the risk of algae setting in. The textured surface of the render walls and surfaces creates the perfect environment for algae spores to settle and grow.

Buildings that receive less sunlight can also have increased algae growth due to a lack of evaporation of surface moisture. If residual water from rain, humidity or guttering does not evaporate from the surface of a building, it contributes to the ideal environment for algae, supercharging the organic growth and subsequent unsightly stains.

If you would like Spectrum's render cleaners to look at your property, do get in touch. We can offer a sample cleaning to show you exactly how stained your rendered walls are, our team will also take you through our highly effective steam cleaning process.

Should I Be Worried About Algae on My Walls?

Whether you should be worried about algae depends on your plans for the affected property. Are you looking to sell up, attract clients or acquire new tenants? Improve kerb appeal? Then perhaps you should be concerned. Left untreated, algae can leave façades looking discoloured, tired and neglected. It acts as a repellent, immediately causing prospective renters or clients to think poorly of your property.

On the sunnier side, algae on the render will not threaten the building’s structure and won’t show as a serious risk on surveys either. Still, when cleaning algae from render is so easy with modern innovations, you’d be foolish to let algae continue growing unchecked. Or worse, paint over it!

Types of Algae

Three types of algae commonly grow on rendered surfaces: red algae, green algae and black algae. Green algae are the most common type and can often be removed with soft washing. Red algae are common in Northern Ireland and Scotland, and we see more in England as the climate becomes warmer and wetter. Black algae, though less common, is very difficult to remove and generally requires cleaning and biocide application. All types of Algae are best removed with steam cleaning as this kills the organism, sanitises the surface and removes discolouration.

Cleaning rendered walls with white vinegar or bleach is not recommended for long-lasting results, though the acidity will kill the algae for a short time.

How We Remove Algae

All types of modern render, including high-quality products from manufacturers like K-Rend and Weber Saint-Gobain, require regular cleaning to remove algae and prevent the quick regrowth of algae. A scheduled professional algae removal service is the only way to keep these organic growths from staining your property.

Plenty of algae removal services from top companies will do a fine job clearing up your algae problem. However, the additional costs incurred by these companies using traditional access methods make the financial investment difficult for many property owners and managers to stretch to regularly. Spectrum uses in-house designed, specially 3D printed and patented pole equipment that allows us to clean render up to 18 meters high without stepping a foot off the ground.

Spectrum’s Four-Step Algae Cleaning Process

1. Preparation - Our team carries out a thorough assessment of the area to be treated. This involves a property survey and risk assessment for all operatives and personnel due to be present during the operation. If cleaning areas above 18 meters, our abseiling team will decent and inspect these areas.


2. Biocide -  We next apply a specialised biocide solution to the entire render façade using rope access and our unique 3D printed equipment to save clients money. The aWe next apply a tailored biocide solution to the entire render façade using rope access and our unique 3D printed equipment. The application of biocide provides a starting point for the cleaning service and kills any living algae organisms. Appropriate protective materials are used to cover surrounding pathways, vehicles and greenery. As well as PPE for our operatives and on site staff.


3. Steam-based low pressure washing - We then gently remove the remaining algae and biocide with a cloud of super-heated steam (around 150 degrees) instead of pressure washing. Due to the force applied, pressure washing can risk damaging the render, which would be disastrous. The super-heated steam is at a far lower pressure but does not compromise on effectiveness.

Our advanced pressurised steam cleaning equipment allows us to clean up to 5 storeys from the ground instead of using costly cherry pickers or scaffolding, saving our clients money. These access innovations mean the total project cost is reduced significantly, allowing for more regular visits from our team to removal algae.

4. Biocide topcoat - Finally, we apply a diluted surface coating of biocide over the entire render façade to prevent regrowth and extend the amount of time a property can go between cleans.

This staged process allows Spectrum to thoroughly remove the algae from the exterior surface of a rendered building carefully and effectively. On completion, properties that have undergone a thorough clean are restored to their original aesthetic appearance and are protected from future algae growth. This method gives fantastic results.

Our 3D Printed Equipment

To help get to every corner of a building and keep access costs low, we design and 3D print our specialist equipment. This allows our operatives to work from the ground, or ropes instead of cherry pickers and scaffolding, dramatically reducing costs and ensuring the render cleaning is completed as quickly as possible. We have many examples of saving clients thousands by using rope access, like this client who saved 60% on access costs by choosing abseiling and our unique ground-use tools.

Remember, keeping as much moisture away from your property as possible is the key to preventing algae buildup on rendered walls. That means keeping up with any leaks, cracked pipes or gutter issues.

Get In Touch

If you have any questions regarding algae or anything else troubling your property, feel free to contact us! We’d be happy to discuss your needs or concerns.

Visit our render cleaning service page here.


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