Composite decking is a popular choice for modern UK gardens, patios, balconies and outdoor living spaces. It combines the natural look of timber with the durability and low maintenance benefits of plastic. Composite decking boards are designed to resist moisture, splintering and everyday weather exposure, which makes them an attractive alternative to traditional wooden decking.
However, composite decking is not completely maintenance free. Over time, dirt, algae, pollen, leaves, mud and general outdoor grime can build up on the surface. In damp or shaded gardens, green deposits may also develop, making the boards look dull and sometimes slippery. Protecting composite decking from dirt and build-up is therefore an important part of keeping your terrace clean, safe and attractive.
At Nanocoating.co.uk, we sell a specialist cleaning and protection system for composite and plastic surfaces:
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NC Nano Plastic Cleaner for cleaning composite decking, plastic boards and outdoor synthetic surfaces
- NC Nano Coating for Plastic for protecting composite decking against water, dirt and renewed build-up
Together, these products help clean composite decking thoroughly and make the surface easier to maintain for longer.
Quick overview and answer
If you are asking What should you not use on composite decking?, avoid harsh bleach, wire brushes, abrasive pads, aggressive solvents, strong acidic cleaners and very high pressure washing at close range. These can damage the surface, affect the colour or make the boards more vulnerable to dirt.
If you are asking How to clean and protect composite decking?, the best approach is to clean the boards first with NC Nano Plastic Cleaner, allow the surface to dry fully and then apply NC Nano Coating for Plastic. The cleaner removes dirt, algae and build-up, while the coating helps reduce water and dirt adhesion.
This system is suitable for:
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Composite decking boards
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WPC decking
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Plastic decking
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Synthetic patio boards
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Composite garden paths
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Composite steps
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Plastic outdoor flooring
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Plastic garden furniture, subject to testing
- Composite cladding, subject to testing
Using the right cleaner and protector helps prevent slippery green deposits, visible dirt build-up, dull surfaces, staining and more frequent deep cleaning.
What is composite decking?
Composite decking is made from a combination of wood fibres and plastic. It is often referred to as WPC decking, which stands for wood plastic composite. The aim is to create a board that looks similar to timber but performs better outdoors.
Composite decking is popular because it offers:
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A timber style appearance
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Good resistance to moisture
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A splinter free surface
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Lower maintenance than natural wood
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Long service life
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Good dimensional stability
- Suitability for patios, terraces and garden paths
Although composite is more resistant to rot than wood, it still has a surface that can collect dirt. Leaves, pollen, soil, bird droppings and air pollution can settle on the boards. When that dirt remains damp, algae and green build-up can appear. Want to learn more? Read our in-depth guide about cleaning and protecting plastic.
Why composite decking can still get dirty
Many people choose composite decking because it is described as low maintenance. That is true compared with timber, but it does not mean the deck will clean itself. Outdoor surfaces always need care, especially in the UK climate.
Composite decking can look dirty because of:
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Leaves and organic debris
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Rain and damp air
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Pollen and tree sap
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Green algae in shaded areas
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Mud from shoes and pets
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Pollution and dust
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Food and drink spills
- Standing water in grooves or textured areas
Once dirt builds up, the surface can become dull and patchy. If moisture remains on the boards, algae may grow on the dirt layer rather than inside the composite itself. This is why routine cleaning is still important.
What Nanocoating.co.uk sells
Nanocoating.co.uk supplies specialist cleaning and nano coating products for a range of surfaces. For composite decking, the recommended system is NC Nano Plastic Cleaner followed by NC Nano Coating for Plastic.
NC Nano Plastic Cleaner is developed for cleaning plastic and composite surfaces. It helps remove dirt, algae, grime, green deposits and outdoor build-up without using aggressive methods that could damage the decking.
NC Nano Coating for Plastic is applied after cleaning. It creates an invisible protective treatment on suitable plastic and composite surfaces. This helps make the surface more water and dirt repellent, so future cleaning becomes easier.
This system helps with:
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Cleaning composite decking
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Removing green algae and outdoor grime
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Reducing dirt adhesion
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Protecting composite surfaces after cleaning
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Maintaining plastic decking boards
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Improving water repellency
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Making future maintenance easier
- Keeping outdoor surfaces looking cleaner for longer
Who is this solution for?
This composite decking cleaning and protection system is suitable for anyone who wants a cleaner, safer and easier to maintain outdoor space.
It is ideal for:
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Homeowners with composite decking
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Garden owners with shaded patios
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Landlords and property managers
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Restaurants, cafés and pubs with outdoor decking
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Hotels and holiday lets with terraces
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Landscapers and garden maintenance companies
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Facilities teams maintaining outdoor walkways
- Anyone looking for a practical composite decking protector
It is especially useful in damp, shaded or tree covered gardens where algae and dirt build up more quickly.
What should you not use on composite decking?
Composite decking is durable, but it can still be damaged by the wrong cleaning products or tools. The safest approach is to use cleaners designed for composite and plastic surfaces.
Avoid using:
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Wire brushes
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Steel wool
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Abrasive scouring pads
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Strong bleach solutions
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Paint stripper
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Harsh solvents
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Strong acidic cleaners
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Strong caustic cleaners
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Very high pressure washing close to the boards
- Wood oils or timber stains designed for natural wood
These products and methods can scratch, discolour or weaken the surface. They may also affect the protective cap on some composite boards.
Instead, use NC Nano Plastic Cleaner for cleaning composite decking and NC Nano Coating for Plastic for protection after cleaning.
How to clean and protect composite decking
The best way to clean and protect composite decking is to follow a two step process: clean first, then protect.
A practical method is:
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Remove loose leaves, soil and debris
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Sweep the deck thoroughly
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Apply NC Nano Plastic Cleaner to the surface
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Allow the cleaner to work according to the instructions
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Brush gently with a suitable soft or medium bristle brush
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Rinse the surface with clean water
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Allow the decking to dry fully
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Apply NC Nano Coating for Plastic evenly
- Allow the coating to cure before heavy use
This method removes existing dirt and algae, then helps reduce future build-up.
Best composite decking cleaner
The Best composite decking cleaner should remove grime and algae without damaging the composite surface. It should be strong enough to clean outdoor build-up but gentle enough for plastic based decking boards.
NC Nano Plastic Cleaner is a strong choice because it is designed for plastic and composite materials. It helps clean the surface without relying on aggressive chemicals or harsh abrasion.
A good composite decking cleaner should:
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Remove algae and green deposits
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Remove dirt and grime
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Be suitable for composite and plastic
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Avoid damaging the board surface
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Prepare the surface for protection
- Make the deck safer and cleaner
Using the right cleaner is important because damage from unsuitable cleaning methods can make the surface harder to maintain later.
Composite decking protector
A Composite decking protector is useful after cleaning because it helps reduce dirt and water adhesion. Cleaning removes the existing build-up, but outdoor dirt will always return. A protective coating slows this process and makes maintenance easier.
NC Nano Coating for Plastic helps protect composite boards by making the surface more water and dirt repellent. This means water, dirt and organic matter are less likely to cling strongly to the surface.
Benefits include:
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Reduced dirt build-up
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Easier routine cleaning
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Less chance of algae taking hold quickly
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Improved water repellency
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Longer lasting clean appearance
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Better protection for plastic and composite surfaces
- Reduced maintenance effort
The coating does not mean the deck will never need cleaning, but it helps keep the surface easier to manage.
Cleaning composite decking without damage
Cleaning composite decking should always be done carefully. The goal is to remove dirt and algae without scratching the boards or damaging the finish.
For safe cleaning:
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Sweep first to remove loose debris
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Use NC Nano Plastic Cleaner rather than harsh household chemicals
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Brush gently along the board direction
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Avoid wire brushes or hard scraping tools
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Rinse thoroughly with clean water
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Let the boards dry fully before coating
- Avoid pressure washing too close to the surface
This method protects the appearance and performance of the decking.
Why does my composite decking always look dirty?
Composite decking may look dirty if moisture and organic matter remain on the surface. This is common in shaded gardens, near trees, close to ponds or in areas with poor airflow.
Common causes include:
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Leaves decomposing on the boards
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Pollen sticking to damp surfaces
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Algae growing in shaded areas
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Mud from shoes or pets
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Food and drink spills
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Air pollution settling on the surface
- Water collecting in grooves or textured finishes
Regular cleaning with NC Nano Plastic Cleaner and protection with NC Nano Coating for Plastic helps reduce these problems.
Does composite decking need to be treated?
Composite decking does not need the same treatment as wood. It does not need oiling, staining or painting. However, it still benefits from cleaning and surface protection.
You should treat composite decking if:
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It gets dirty quickly
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Green algae appears
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The surface becomes slippery
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You want easier maintenance
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The deck is in a damp or shaded area
- You want to protect it after cleaning
Treatment with NC Nano Coating for Plastic helps reduce dirt adhesion and keeps the surface cleaner for longer.
Common disadvantages of composite decking
Composite decking has many advantages, but it also has some practical limitations.
Possible disadvantages include:
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Dirt can remain visible on the surface
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Algae can develop in damp areas
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Some boards can become slippery when dirty
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Heat can build up on darker boards in summer
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Stains can occur if spills are ignored
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Poor cleaning methods can damage the finish
- Colour may gradually change with exposure
Many of these problems can be reduced with regular cleaning and protection. Using NC Nano Plastic Cleaner and NC Nano Coating for Plastic helps maintain the appearance and safety of the deck.
Composite decking in shaded gardens
Shaded gardens are more likely to develop algae because the boards dry more slowly after rain. If your deck is under trees, beside a fence or close to a water feature, it may need more frequent care.
For shaded decking:
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Sweep leaves regularly
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Improve airflow where possible
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Move plant pots occasionally
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Clean green deposits early
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Use NC Nano Plastic Cleaner seasonally
- Apply NC Nano Coating for Plastic after cleaning
This helps prevent dirt and moisture from building up into a persistent green layer.
Can you pressure wash composite decking?
Some composite decking manufacturers allow low pressure washing, while others advise against it. High pressure can damage the board surface, especially if the nozzle is held too close.
If you use a pressure washer:
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Use low pressure
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Keep the nozzle at a safe distance
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Avoid narrow jet settings
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Do not hold the spray in one place
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Avoid damaging board edges and joints
- Test first in a discreet area
For many homeowners, NC Nano Plastic Cleaner with a brush and hose is a safer and effective alternative.
How often should composite decking be cleaned?
The frequency depends on location and use. A sunny, open deck may only need cleaning once or twice a year. A shaded deck under trees may need more frequent attention.
General guidance:
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Sweep weekly during autumn
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Remove leaves and mud quickly
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Clean with NC Nano Plastic Cleaner once or twice a year
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Clean more often in shaded or damp areas
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Reapply NC Nano Coating for Plastic when water no longer beads well
- Inspect steps and walkways regularly for slipperiness
Regular light cleaning is easier than removing heavy build-up once it has taken hold.
Problems prevented by cleaning and protecting composite decking
Using NC Nano Plastic Cleaner and NC Nano Coating for Plastic helps prevent or reduce:
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Dirt build-up
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Green algae
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Slippery surfaces
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Surface staining
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Dull appearance
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Organic residue
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Harder future cleaning
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Moisture related grime
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Frequent deep cleaning
- Reduced visual appeal
The cleaner removes dirt and algae. The coating helps protect the surface afterwards.
Frequently asked questions (Q&A)
What should you not use on composite decking?
Do not use wire brushes, steel wool, harsh bleach, strong solvents, acidic cleaners, caustic cleaners or high pressure washing too close to the boards. These can damage or discolour composite decking.
How to clean and protect composite decking?
Clean the boards with NC Nano Plastic Cleaner, rinse, allow them to dry fully and then apply NC Nano Coating for Plastic to reduce water and dirt adhesion.
What is the best composite decking cleaner?
NC Nano Plastic Cleaner is a strong option because it is designed for plastic and composite surfaces and helps remove dirt, algae and build-up.
What is a good composite decking protector?
NC Nano Coating for Plastic works as a composite decking protector by making suitable surfaces more water and dirt repellent.
Does composite decking need coating?
It is not required like timber oil or stain, but protection helps reduce dirt build-up and makes maintenance easier.
Why does composite decking get green algae?
Algae grows when moisture, shade and organic dirt remain on the surface. Regular cleaning and protection help reduce this.
Can I clean composite decking without a pressure washer?
Yes. Use NC Nano Plastic Cleaner, a suitable brush and clean water. This is often safer than aggressive pressure washing.
Protect composite decking with Nanocoating.co.uk
Composite decking is durable and low maintenance, but it still needs care to stay clean, safe and attractive. Dirt, algae, moisture and outdoor grime can build up over time, especially in shaded or damp areas.
NC Nano Plastic Cleaner removes dirt, algae and surface contamination from suitable composite boards. NC Nano Coating for Plastic then protects the surface by making it more water and dirt repellent.
Whether you need a Composite decking protector, the Best composite decking cleaner, or practical help with Cleaning composite decking, Nanocoating.co.uk offers a reliable system for cleaner, safer and easier to maintain outdoor decking.
About Nanocoating.co.uk
At Nanocoating.co.uk, our specialists develop high-quality nano coatings and nano cleaners for a wide range of surfaces, helping you protect materials for longer and spend less time cleaning.
Our products are manufactured in the Netherlands and developed with performance, safety and sustainability in mind. They are formulated without intentionally added PFAS and developed in accordance with applicable chemical safety and regulatory requirements, including UK REACH requirements for the Great Britain market.
Whether you want to protect glass, wood, stone, metal, textiles, sanitary surfaces or outdoor materials, Nanocoating.co.uk offers professional-grade nano coating solutions for everyday use at home, in the garden and in commercial environments.
Why customers choose Nanocoating.co.uk
✅ Money-back guarantee if you are not satisfied
✅ Free UK delivery on orders over £40
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✅ Secure purchase protection through Trusted Shops
✅ Safe and reliable payment options, including Klarna and credit card
✅ High-quality nano coatings and nano cleaners manufactured in the Netherlands
✅ Formulated without intentionally added PFAS
✅ Developed with performance, safety and environmental responsibility in mind
✅ Specialist nano coating and nano cleaning solutions for cleaner, easier-to-maintain surfaces
At Nanocoating.co.uk, we believe surface protection should be effective, easy to apply and safe to use. That is why our nano coatings and cleaners are developed to deliver long-lasting performance while avoiding unnecessary substances and supporting responsible product formulation.