What is soft washing?

What Is Soft Washing and When Should It Be Used?

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When people think about exterior cleaning, they often picture powerful pressure washers blasting away dirt and grime. While pressure washing is an extremely effective cleaning method for many surfaces, it's not always the most appropriate solution. In fact, some surfaces can be damaged by excessive pressure, which is why professional exterior cleaning often involves a technique known as soft washing.

 

Soft washing has become increasingly popular in recent years because it allows delicate surfaces to be cleaned safely and effectively while delivering longer lasting results. The Australian soft washing market is in it's infancy compared to the U.S. market but we're slowly catching up.

 

Understanding the difference between soft washing and pressure washing can help homeowners choose the right approach for their property.

 

What Is Soft Washing?

 

Soft washing is a cleaning method that uses chemical cleaning solutions to break down mould, algae, mildew, bacteria and other organic contaminants before the surface is rinsed using low pressure water. Different cleaning chemicals such as degreasers can also be applied using the soft washing equipment and techniques for oil stains or BBQ grease, but soft washing is most commonly used for organics so for the purposes of this explainer, we'll assume we're treating organic build up.

 

Unlike traditional pressure washing, soft washing relies on chemistry rather than force to achieve the cleaning result. The cleaning solutions target and eliminate the organic growth at its source, allowing contamination to be removed without the need for aggressive water pressure. Whilst effective, sometimes high pressure water can be too effective and can damage the surface being cleaned.

 

The soft wash approach not only cleans the surface but also helps prevent the rapid regrowth of mould and algae when we apply our post-treatment of biocide. At The Pressure Washing Company, we include this as a standard part of every job we complete. We use a quaternary ammonium product with benzalkonium chloride as the active ingredient. It's a compound commonly used in disinfectants and food-grade antimicrobial products, and is safe to spray and leave on surfaces to kill any residual fungal spores and act as a future prophylactic. 

 

Why High Pressure Isn't Always the Answer

 

Many exterior surfaces can be damaged if excessive pressure is used during cleaning.

 

While concrete driveways and certain hard surfaces can generally withstand higher pressure, more delicate materials require a gentler approach.

 

Using too much pressure on the wrong surface can result in:

 

• Damage to paint coatings

• Etching of render and soft masonry

• Water intrusion behind cladding or walls

• Damage to some roofing materials

• Premature wear (or "fluffing") of timber surfaces

• Disturbance of mortar joints and sealants

 

Professional exterior cleaning involves selecting the appropriate method for each surface rather than applying the same approach everywhere. We typically assess each job individually, and will make the call based upon the factors at play.

 

Common Applications for Soft Washing

 

Soft washing is particularly effective on surfaces that are prone to mould and algae growth but may be vulnerable to damage from high-pressure cleaning.

 

Tiled roof cleaning and metal roof cleaning where the paint is old or compromised is one of the most common applications for soft washing. Roof tiles, metal roofing and painted roof surfaces can often be cleaned effectively using specialised treatments and low-pressure rinsing. This removes mould, algae and lichen while minimising the risk of surface damage. If the organic build up is extreme, we will often still use a surface cleaner in combination with the soft wash, but with a reduced pressure output which is controlled by the nozzle size. Although roof tiles themselves would generally be fine to pressure wash, we choose not to use high pressure on tiles. The reason for this, is that it's a less consistent finish compared to chemically cleaning them and depending upon the age of the roof, they sometimes do not have a waterproof membrane beneath the tiles. This increases the chances of injecting water into the roof cavity and flooding the property. For these reasons, we choose to solely soft wash tiled roof surfaces.

 

Painted and rendered surfaces can be susceptible to damage when cleaned with excessive pressure. Soft washing removes organic growth and environmental staining while preserving the integrity of the coating. Pre-existing surface cracks or fractures are particularly vulnerable.

 

Weatherboards, cladding and painted exterior walls often respond well to soft washing. The process removes dirt, mould and cobwebs without the risk associated with aggressive pressure cleaning.

 

Timber and painted fences can benefit from soft washing, particularly where mould and algae are the primary contaminants. For timber fences that aren't painted we'll usually clean them using sodium hypochlorite and surfactant, and then brighten them with an application of oxalic acid. DO NOT COMBINE CHLORINE AND ACID.

 

Large buildings often contain a variety of different surface types. Soft washing allows these areas to be cleaned safely while minimising disruption and reducing the risk of damage.

 

The Benefits of Soft Washing

 

One of the biggest advantages of soft washing is that it treats the underlying cause of the staining rather than simply removing the visible contamination.

 

Because the cleaning solutions target mould, algae and bacteria directly, surfaces often stay cleaner for longer compared to cleaning methods that rely solely on pressure.

 

Many homeowners are surprised to learn that the most effective cleaning method is often not the most aggressive one. You can often see the changes happening in real time, and will usually see a big visual improvement in as little as a few minutes.

 

Soft Washing vs Pressure Washing

 

Soft washing and pressure washing are not competing methods. In most professional cleaning projects, they work together. You'll occasionally hear soft washing purists talking negatively about pressure cleaning methods, however this binary mindset is short sighted and unfounded. Different tools are appropriate for different jobs, and that's why we don't beat nails with a spanner.

 

Pressure washing is ideal for hard surfaces such as concrete driveways, pathways and certain paving areas where physical surface contamination needs to be removed. If mould or other organic matter has formed a physical crust over years of build up, soft washing alone is not the best approach.

 

Soft washing is often the preferred choice for roofs, painted surfaces, render, cladding and other delicate materials where mould and algae are the primary concern.

 

The best results are usually achieved by selecting the right method for each specific surface rather than relying on a single cleaning technique.

 

How Professionals Determine the Right Approach

 

Every property is different, which is why professional cleaners assess each project individually. Factors such as the surface material, age of the coating, level of contamination, access requirements and surrounding environment all influence the cleaning method that should be used. It's also majorly influenced by the customer preference. For example, if they're planning to have their roof re-painted after the clean, it may be helpful to them if the pressure cleaner removes old flakes of compromised paint. If they're wanting to preserve the paint but they are aware it is possibly compromised, a more delicate approach would be the best choice.

 

A thorough assessment helps ensure the surface is cleaned effectively while minimising the risk of damage.

 

Choosing the Right Cleaning Method for Your Property

 

Soft washing has become an essential part of modern exterior cleaning because it provides a safe and effective solution for many surfaces that would be unsuitable for high pressure cleaning.

 

While pressure washing remains an excellent option for hard wearing surfaces such as concrete, soft washing is often the better choice for roofs, painted exteriors, render and other delicate materials.

 

By using the appropriate cleaning method for each surface, homeowners can achieve excellent results while protecting the long-term condition of their property.