Soft Washing vs. Biocide: Which One is Better in Roof Cleaning?

Roof cleaning keeps your property looking good and protects your roof for years to come. But when it comes to methods, which is best? Should you choose soft washing or biocide treatment? Let’s break them down so you can decide.

Why Roof Cleaning Matters

Regular cleaning stops moss, algae, and lichen from damaging tiles. It also improves kerb appeal. A dirty roof stands out. A clean roof blends in beautifully.

What is Soft Washing?

Soft washing uses a gentle, low-pressure system. A mix of sodium hypochlorite and low VOC surfactants is applied. This solution breaks down dirt, stains, and organic growth.

Unlike jet washing, soft washing is safe for fragile roof materials. It not only cleans but also sanitises. The treatment kills algae and bacteria at the root, stopping regrowth. In fact, the system is similar to agricultural pest control because it penetrates deep into surfaces.

Benefits of Soft Washing

• Keeps roofs looking fresh and clean

• Lasts four to six times longer than pressure washing

• Kills pests, algae, and bacteria at the source

• Protects the roof’s lifespan with regular treatments

Premature roof degradation can cut life expectancy by up to 50%. With soft washing, tiles stay stronger for longer.

How Soft Washing Works in Practice

We begin by removing surface moss and debris. This is done from access equipment such as a cherry picker or tower scaffold. Once clear, we apply the soft wash blend through a low-pressure pump and hose.

The solution loosens dirt, emulsifies grime, and reduces black streaks. Plants are protected with fresh water and PlantWash. We recommend using a SoftWash-trained company, since the blend strength must be set correctly for safe cleaning.

What is Biocide Roof Cleaning?

Biocide treatments work differently. They use chemical solutions that take longer to react but can be very effective. The main advantage is that biocides use less water and are easier to apply for untrained users.

Over time, biocide breaks down moss, algae, and dirt. Results are not instant. Instead, the roof improves gradually over weeks or months. Proper PPE is vital during application, as fumes can be strong.

Benefits of Biocide

• Uses less water than other methods

• Lower impact on soil and vegetation

• Easier to apply than high-pressure cleaning

• Provides steady, long-term results

Biocide is popular for maintaining roofs after initial cleaning, as it slows down organic regrowth.

Common Misconceptions About Roof Cleaning

One myth is that roof cleaning always damages tiles. This isn’t true. What often looks like damage after cleaning is natural wear that was hidden under dirt. Older cement-based tiles may show patchy colouring due to UV exposure and surface coating differences.

Another misconception is that roofs should be cleaned only in rain or wet weather. This is false. While water loosens dirt, it doesn’t remove organic growth. Professional cleaning works effectively in most weather conditions, provided it’s safe.

Which Method Should You Choose?

Both methods have their place. Soft washing gives faster, deeper results and kills growth at the source. Biocide works slower but is effective over time and uses less water.

The right choice depends on your roof material, age, and the level of moss or lichen present. Slate, clay, and man-made tiles all respond differently. A trained professional can guide you to the best solution.

Final Thoughts

There is no single “best” method for roof cleaning. Both soft washing and biocide treatments work well when applied correctly. What matters most is choosing an experienced, well-trained company. At Alfresco, we use both systems to match your roof’s needs and deliver lasting results.

By 

Mark Toovey 

Alfresco Exterior Cleaning 

Unit K1, Kingston Business Park, Kingston Bagpuize, Oxfordshire, OX13 5FD