How to Remove Algae from Render Without Damaging the Surface

By Mark Cave May 21, 2025

How to Remove Algae from Render Without Damaging the Surface 🧽✨

Is your rendered wall turning green or discoloured? Algae and other organic growth not only ruin your property's aesthetic but can also damage the render over time. Fortunately, there's a safe, effective method to tackle this issue Soft Washing.

🚨 Algae and Organic Stains on Rendered Walls

Exterior render can make your home look sleek and modern but over time it’s a magnet for algae, moss, and mildew. The issue is especially common in shaded or damp areas where moisture lingers. Traditional cleaning methods, like high pressure washing, often damage the render surface or push moisture deeper beneath the coating, leading to even more issues down the line like cracking and crumbling.

Here’s what you’re dealing with:

Green streaks caused by algae
Black spots due to mould or mildew
Efflorescence and stains from rust or environmental factors

😟 Why Quick Fixes Just Don’t Work

Many homeowners make the mistake of using aggressive techniques like power washing or harsh chemicals only to find that the problem returns quickly, or worse:

The render surface gets etched or stripped
Expensive repainting becomes necessary
Algae comes back faster due to disturbed surface biofilm

While the intention is to clean the render, these methods often do more harm than good. That’s where SoftWash UK comes in with a science backed, surface safe approach. ✅

💡Why Soft Washing is the Best Method for Algae Removal

Soft washing rendered walls involves applying a low-pressure mix of biocidal chemicals and cleaning agents that kill algae at the root without harming the render.

✨ Benefits of Soft Washing Render:

Non-invasive, low pressure application
Removes organic matter thoroughly
Helps prevent rapid regrowth with residual biocide action
Safe for K Rend, Monocouche, and other modern renders

🧴 Recommended Products for Algae Removal

Soft Wash Pro 50 Biocide Long lasting algae and moss killer with 50% DDAC
Clever Wash Surfactant Enhances dwell time and penetration of active agents
SoftWash Training Course Learn to apply treatments safely and effectively

🔄 For application, use a dosing system like the Soft Washing Dosatron or Dosatron Biocide Injector to mix chemicals at the correct ratio. Refer to our full Sodium Hypochlorite Mixing Guide for more details.

🛠️ Pro Tips for Cleaning Rendered Walls Effectively

Identify the type of growth Green = algae, black = mould, white = efflorescence.
Pre-wet any adjacent plant life or cover them Learn more: Can Soft Washing Kill Plants?
Apply your soft wash solution evenlyusing a Water Fed Pole Nozzle for hard-to-reach places.
Let the chemical dwell for 10–20 minutes depending on growth severity.
Rinse if necessary with water See: Should I Rinse When Soft Washing?

Bonus Tip: Use Fresh Wash to neutralise chemical odour for a more pleasant application experience. 🌸

🎧 Want to Go Deeper? Tune In to the SoftWash UK Podcast

Mark Cave, founder of SoftWash UK, shares his expert insights on render cleaning, equipment choices and industry best practices. 🎙️ 👷

📦 Shop All Your Render Cleaning Needs at SoftWash UK

Whether you're a homeowner or a professional exterior cleaner, SoftWash UK has everything you need to perform safe, long-lasting render restoration.

Don’t let algae ruin your home’s kerb appeal. Restore your render safely with SoftWash UK.

🛒 Visit our website today to browse equipment, chemical solutions, and training courses!

📚 Explore Related Resources:

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Soft Wash Calculator App

Now you can say I've got an app for that!

Available NOW Click Here To Download

Softwashing calculator is an indispensable tool for juggling complicated chemical mixes. It helps reduce wastage and keeps operating costs down by giving accurate proportions

If you are having difficulty getting your head around the maths, trying to work out what percentage of softwash you need, how much chemical, surfactant and water to add, then this is the App for you.

The Soft Wash Calculator App allows you to work out your soft wash recipe by telling you exactly how much chemical, how much water and how much surfactant to add to get the desired soft wash recipe.
It doesn't stop there!.
- It can also remix your leftover softwash to a new stronger or weaker recipe.
- all controls in one place for see at a glance operation
- ease of input via pre-loaded dials. no more calculator style typing
- instantly responds to changes of complex combinations
- works in both Litres and US Gallons
- tested for Protan and Deutan colourblind users
- links to SoftwashingUK website

Take this scenario
You started with a 1% soft wash recipe of 50 gal (or litres) for a deck clean and you’re left with 13 gallons.

You get a call from a prospective customer to clean their roof. Past experience tells you a 4% soft wash recipe is needed, but what about your leftover mix at 1%?.

Do you waste time and effort driving back to base to transfer into a standby tank?
You could consider the 13 gal as just water, top up the tank and start again.
But that’s throwing away the value of the mix and raising your overhead.

Soft Wash Calculator App to the rescue.

You get to the new job and it requires 100 gal / litres.
Switch into remix mode , confirming the 13 gal already in the tank
Move the dials to your new recipe and the app immediately updates the different amounts to add in front of your eyes including the correct amount of extra surfactant.

You now have a 100 gal / litres tank of 4% soft wash recipe ready for your roof clean job!

Not forgetting you’ve saved money too, all without stress and uncertainty . Don’t underestimate what confident calmness has on your customer putting out referrals.

The same applies if you have a 4% recipe left in your tank and you need to dilute it down to 2%. Again the app will tell you how.

Softwashing calculator will also work for any chemical recipe. For instance you can use it for Sodium Hypochlorite, Bleach, Biocide , TFR traffic film remover and degreaser. Even the mathematically-challenged rocket scientist can top up their booster tanks to new fuel mixes after launch delays caused by changing weather conditions.

Using this app you will know exactly what chemical strength to put on any surface giving you the confidence and the knowledge of a professional soft washer and you’ll save money as well.

So if you have little knowledge of how to mix a soft wash recipe then this app is for you.
If you have little knowledge of how to remix a soft wash recipe then this app is for you.
If you want to save money when mixing a soft wash recipe then this app is for you.

This app is also backward compatible to devices running iOS7. We've done this so you can re-purpose an old iPhone 4 or iPod Touch 5 for what could be hazardous work environments. Just toss one in your cleaning van's toolkit.

Once you learn the methods and procedures of how to apply the soft wash to the different surfaces that need cleaning you’ll be unstoppable!

The app also has a guide to what percentage for what surface. And if you are the lucky owner of a Clever Injector it will remind you the correct setting for the job.
However you should always consider and risk assess what soft wash recipe you need to clean the surface.

** A major iOS code-base change may require a re-purchase. The appiverse at the time will confirm our promise that we won't do so unless the necessity is apparent.

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