How To Clean Greenish Mould Off Render

We all know that the weather in our Great Britain dances between rain & sunshine. Our homes’ exterior walls often bear the brunt of this moist climate. Render, with its crisp finish and protective qualities, is a popular choice across the UK. However, it is not immune to the unsightly and unwelcome visitor that is green mould. This common blight detracts from the visual appeal of your property. And potentially harms render and the structure it shields.

Green mould—a term often used interchangeably with algae—can appear on render as a result of damp conditions, typically thriving in areas that receive limited sunlight. Left unchecked, it can spread quickly, creating a verdant sheen that seems at odds with the well-kept appearance of a home. In our damp British climate, it’s an issue that many property owners face, raising concerns over aesthetics and property maintenance.

Green mould can be effectively treated to its former glory.

Whether you’re a DIY enthusiast ready to tackle the problem head-on, or you’re considering when it might be time to call in the professionals, this guide will help you with the know-how to address green mould with confidence.

What is Green Mould?

Green mould, which you might often find tarnishing the façade of your home, is actually a bit of a misnomer. More accurately, this green invader is a type of algae, a simple organism that favours damp, shaded areas—much like those found on the north-facing walls of our homes here in the UK. This algae, when left to its own, forms a layer of green film that can spread across externally rendered surfaces, flourishing in our notoriously moist climate.

Algae spores are airborne or can be carried to your walls by rainwater. And they settle into the tiny nooks and crannies of the render. Once these spores have made themselves at home, they need little more than moisture and a lack of direct sunlight to begin their unsightly bloom.

The British weather, with its frequent rain and overcast skies, provides the perfect conditions for algae to thrive, especially during the autumn and winter months when the days are shortest.

While algae itself is not a plant, it shares the ability to photosynthesis, which allows it to grow on surfaces where many other organisms cannot. This means that even on the dreariest of days when the weak sunlight barely seems to penetrate the cloud cover, green algae can continue to grow and spread.

It’s important to note that this growth isn’t just a cosmetic/aesthetic issue. Over time, the presence of algae can lead to further moisture retention and can contribute to the breakdown of the render, potentially leading to more serious issues. Additionally, as it holds onto moisture, algae can encourage the growth of other unwanted visitors, such as mosses, mildew, and lichens, which can be even harder to remove and may cause additional damage.


The Risks of Green Mould

While a verdant lawn is the pride of many a British garden, the sight of green spreading across your property’s walls is, understandably, far less welcome.

Firstly, the presence of algae on render; it’s often a symptom of excess moisture. This dampness, particularly in the cooler months, can penetrate the render and potentially the brickwork beneath. Over time, this can compromise the structural integrity of the walls, leading to issues like cracking and erosion. In the freeze-thaw cycle of our British winters, water trapped within the render can expand when it freezes, exacerbating any existing damage and potentially leading to costly repairs.

Render Cleaning Service Company

Furthermore, green mould can create a vicious cycle of dampness. By retaining moisture, algae-covered surfaces can become breeding grounds for further biological growth. These organisms can cause their own set of problems, including further trapping moisture and potentially leading to the decay of the render.

Lastly, there’s the matter of property value and appeal. Homes with pristine exteriors naturally have better kerb appeal, which can be vital if you’re considering selling or renting out your property. Potential buyers or tenants might view the algae as a sign of neglect or assume there are more serious maintenance issues at play, which could affect your property’s marketability and value.


Preventive Measures

Prevention, as they say, is better than cure, and this rings especially true when it comes to keeping your property. Here are some preventive measures to help you keep green mould at bay:

  • Improve Air Circulation: Good air flow is essential in keeping render dry. Trimming back any overhanging branches or dense foliage can help reduce shaded areas on your walls and allow the sun’s natural antiseptic qualities to combat the growth of algae.
  • Regular Cleaning: A gentle wash of your rendered walls once a year can prevent the build-up of dirt and organic material that algae feast upon. This doesn’t need to be an intensive process – a soft wash with appropriate cleaning agents can suffice.
  • Treat With Algaecide: There are environmentally friendly algaecide treatments available that can be applied to your render after cleaning. These treatments help to prevent the regrowth of algae, keeping your walls cleaner for longer.
  • Repair and Maintenance: Ensuring that your exterior render is in good repair can prevent water from seeping in and providing a damp habitat for algae to grow. Be sure to fill in any cracks and attend to any areas of damage promptly.
  • Guttering & Drainage: Maintain your guttering and ensure that rainwater is effectively channelled away from your walls. Overflowing gutters can create streaks of moisture perfect for algae to colonise.
  • Protective Coatings: Some renders can be treated with protective coatings that resist moisture and biological growth. These are particularly useful in areas prone to high humidity.


Cleaning Green Mould Off Render: Step-by-Step Guide

If the green spectre of mould has already made an unwelcome appearance on your home’s exterior, worry not. With the right approach, you can banish this blight and restore your render’s natural charm. Here’s a step-by-step guide to cleaning green mould off render:


Preparation is Key

Begin by ensuring that you have all the necessary equipment at hand. You’ll need a soft-bristled brush, a bucket, protective gloves, goggles, and a suitable cleaning solution. Cover any nearby plants with a tarpaulin to protect them from runoff.
Safety First

Always wear protective gear to shield yourself from splashes of cleaning agents. If you need to use a ladder, make sure it is securely positioned and consider having someone to spot you.


Choosing the Right Cleaning Solution

Opt for a cleaning agent specifically designed for treating algae on render. These are formulated to be effective without damaging the render. Always follow the manufacturer’s instructions regarding dilution and application.


Gentle Cleaning

Moisten the affected area with water before applying the cleaning solution. Then, using your soft-bristled brush, gently scrub the render to lift the mould. Avoid vigorous scrubbing, which can damage the surface.

Related: how to clean k render?

Let the Solution Do the Work

After scrubbing, apply the cleaning solution to the area and let it sit for the time recommended by the product’s instructions. This allows the solution to penetrate and kill the algae at its roots.

Rinse Thoroughly

Once the solution has had time to work, rinse the area with clean water. A garden hose with a spray nozzle is ideal – avoid using high-pressure washers, as these can be too harsh on render.


Repeat if Necessary

If traces of green mould remain, you may need to repeat the cleaning process. It’s better to perform gentle, multiple cleanings than one overly aggressive scrub.


Post-Clean Care

After the area is clean and dry, consider applying an anti-fungal treatment to discourage the return of the mould. Some treatments can offer long-term protection against algae and other biological growths.


Regular Inspections

Keep an eye on the previously affected areas and address any new growth promptly. A quick response can prevent algae from becoming a persistent issue.

By following these steps, you should be able to effectively remove green mould from your render and maintain the clean, attractive appearance of your home. Remember, when dealing with chemicals and cleaning solutions, always prioritise safety and environmental considerations.

Red stain rust removed by render cleaning in Cheshire

When to Call a Professional

While the can-do spirit is much admired, there are times when a dab hand from a professional is not just recommended, it’s essential. Knowing when to call in the experts can save you both time and potential mishaps. Here are a few scenarios where professional render cleaning services are your best bet:


Height & Accessibility

If the affected areas are out of reach and would require more than a standard ladder to access, it’s time to call in the pros. At Render Cleaning Co. we are equipped with the necessary and safety equipment to tackle high and awkward spaces safely.


Extensive Infestation

Should the green mould cover a substantial portion of your render, our professional team can handle the scale of the problem more effectively and efficiently than a solo effort might achieve.


Delicate or Aged Render

Older or heritage properties with delicate rendering need a specialist’s touch. Our professional render cleaners have the expertise and experience to clean without causing damage to these more vulnerable surfaces.


Recurring Growth

If you’ve cleaned your render but find that the green mould returns with a vengeance, there might be an underlying issue that needs expert attention. Our experienced team can diagnose the root cause and provide solutions for you to prevent future growth.


Time Constraints

Our lives are often busy enough without the added burden of extensive home maintenance. Calling in a professional render cleaning company can free up your time while ensuring the job is done right.


Health Considerations

If you have health concerns that could be exacerbated by the physical exertion of cleaning or by exposure to the cleaning agents, it’s wise to leave the task to those who are trained and equipped to handle it safely.

If you’re in any doubt about tackling the task yourself, it’s a safe bet to consult with a professional – we will be happy to advise you on the best course of action.


Maintenance After Cleaning

Once you’ve bid farewell to the unsightly green mould on your render, keeping it at bay becomes the next order of business. Here are some maintenance tips to help you keep your render looking fresh and free from regrowth:


Regular Inspections

Make it a habit to periodically inspect your render, particularly after bouts of inclement weather. Early detection of any algae reappearance can make subsequent cleanings much more manageable.


Prompt Repairs

Address any cracks or damage to the render as soon as possible. This prevents water ingress, which creates a hospitable environment for algae and mould to flourish.


Gutter Maintenance

Keep gutters and downpipes clear to avoid overflow and streaking on the render. Regularly check for leaks, as these can cause damp patches where green mould could re-establish itself.


Trim Vegetation

Ensure that surrounding trees and bushes are kept trimmed back from your home’s walls. This will improve airflow and reduce the damp, shaded conditions that algae love.


Soft Washing

Consider scheduling a gentle soft wash of your render annually. This preventative measure can remove the early stages of algae before it becomes visible.


Biocidal Treatments

After cleaning, applying a biocidal treatment can help prevent the growth of algae and mould. Opt for a high-quality product that provides long-term protection without damaging the render.

soft washing service

Professional Advice

If you’re unsure about the best maintenance routine for your specific type of render, don’t hesitate to seek advice. We are just a call or email away. Or you can fill in the form.

We are ready to assist in keeping your home looking its absolute best through the seasons.