At a Glance

Green decking is usually caused by moisture retention, limited sunlight, organic debris and algae growth. Removing loose debris, using appropriate cleaning products and avoiding overly aggressive pressure washing can help restore the surface. Ongoing maintenance and algae treatments can also reduce regrowth, keeping decking safer, cleaner and easier to maintain throughout the year.

Need suitable decking cleaning products for your home? Order from AMB Hygiene now!

What Is the Green Build Up on Decking?

You clean your decking in spring, enjoy it through summer, then suddenly notice green patches creeping across the boards again. It happens in outdoor spaces across the region every year, particularly after long spells of wet weather.

According to data from the UK Met Office, many parts of the country receive over 800mm of rainfall annually, while western regions can see well over 1,500mm. All that moisture creates ideal conditions for algae, moss and other organic growth to settle on outdoor surfaces. Combined with mild temperatures and a shaded garden, decking can quickly become discoloured and slippery.

The green coating you see is usually algae, which thrives in damp conditions and spreads across timber, composite decking, paving and other outdoor surfaces. While it might look like a cosmetic issue at first, algae can make decking dangerously slippery, particularly during autumn and winter.

Understanding why it appears is the first step towards learning how to effectively remove green algae from decking and keep it away for longer.

Why Does It Happen?

Here are the four most common causes of decking turning green.

1. Moisture Retention Creates the Perfect Conditions

One of the biggest causes of green decking is moisture trapped in decking, as deck boards are exposed to rain, morning dew and humidity throughout the year. 

If water can’t evaporate quickly, damp conditions remain on the surface for extended periods. Algae spores only need a small amount of moisture to establish themselves. This is more common on older timber decking, where rougher surfaces can retain water longer after rainfall.

2. Lack of Sunlight Slows Everything Down

Many homeowners notice decking turning green in areas that receive little direct sunlight. Trees, fences, neighbouring buildings and dense planting can block sunlight for much of the day. 

Once shade becomes a regular feature, the surface remains damp longer after rain. These shaded decking problems are prevalent in north-facing gardens where sunlight exposure is naturally reduced throughout much of the year.

3. Organic Growth Builds Over Time

Decking doesn’t turn green all of a sudden and most of the time, the issue starts with tiny algae spores that constantly settle on the surface. Over weeks and months, they begin to multiply, especially when conditions remain damp. 

What starts as a faint green tint can gradually spread across a larger section of the deck. The process is similar to how weeds establish themselves in paving joints. The growth starts small, then gains momentum once conditions become favourable.

4. Dirt and Debris Feed the Problem 

Leaves, pollen, soil and garden debris do more than make decking look untidy. As organic matter accumulates, it creates a surface layer that retains moisture. This layer also provides nutrients that encourage algae growth. 

Gardens surrounded by mature trees tend to experience this issue, mainly during autumn. This is why routine cleaning plays such an important role in preventing future problems.

How to Remove Green Algae from Decking?

If your decking looks green with algae, you probably want to know how to remove green algae from decking without damaging the surface underneath. In most cases, you can successfully address the issue with the right approach and specialised cleaning products formulated by AMB Hygiene specifically for cleaning decking. 

Here’s how to remove green algae from your decking in four simple steps:

1. Start by Removing Loose Debris 

Before applying any cleaning product, clear away leaves, dirt and loose organic matter. A stiff outdoor brush works well at this stage, as it helps expose the affected areas and allows cleaning products to come into direct contact with algae. 

2. Use Gentle Decking Cleaning Methods

When you’re learning how to remove green algae from decking, it’s worth knowing that the cleaning product matters just as much as the technique. Specialist exterior cleaning fluids designed to remove algae and organic growth can break down contamination without causing unnecessary damage to the decking surface. 

AMB Hygiene supplies a range of exterior cleaning products designed to tackle algae, moss and organic staining on outdoor surfaces, including decking, pavings, patios and pathways. Where appropriate, these solutions can help remove existing contamination and support your ongoing maintenance programmes.

We generally find that a targeted decking algae treatment that works provides longer-lasting results than repeated scrubbing alone.

3. Avoid Aggressive Pressure Washing

Pressure washers can seem like a quick solution and sometimes they do remove visible algae. The problem is that excessive pressure can damage timber fibres, leaving the surface rougher than before. 

Once that happens, moss retention may increase and future algae growth can become even easier. A decking algae treatment that works is one that includes a controlled cleaning approach and provides a safer outcome.

4. Treat the Surface to Help Prevent Regrowth 

After cleaning, you’ll want to address any remaining organic contaminants. Some exterior cleaning treatments continue working after application by targeting algae spores that may remain on the surface. This can help reduce the speed at which green growth returns. 

AMB Hygiene offers a range of specialist cleaning products suitable for tackling various kinds of organic growth on exterior surfaces. Products such as Didecyl Dimethyl Ammonium Chloride (DDAC) are specifically formulated to remove and control algae contamination. 

Plus, treatments within AMB’s product range can help maintain clear outdoor surfaces between deep cleans. Using a suitable biocidal treatment after cleaning can also help reduce the likelihood of rapid regrowth, particularly in shaded or moisture-prone areas where algae commonly return.

For homeowners looking for a decking algae treatment that works, selecting products specifically designed for outdoor algae control can make ongoing maintenance much easier.

Contact AMB Hygiene For Decking Cleaning Products 

If green algae keeps returning to your decking, using the right cleaning products can make a noticeable difference. 

AMB Hygiene has been supplying specialist cleaning and hygiene solutions since 1984, helping homeowners tackle algae, moss and organic growth on outdoor surfaces. Our decking cleaning products are designed to remove contamination, improve surface appearance and support ongoing maintenance throughout the year. 

Whether you’re dealing with light algae staining or widespread green build-up, our team can recommend suitable products with the best decking maintenance tips for your situation. 

Place your order now!