Decking Cleaning Tips: How to Clean and Maintain Your Deck

Updated February 2026 • 8 min read

Green, slimy decking isn't just ugly – it's dangerous. Algae-covered decks are a slip hazard, especially when wet. But decking is also easy to damage if you clean it incorrectly. Here's how to safely clean your deck and keep it looking good year-round.

Why Does Decking Turn Green?

That green coating on your deck is algae – microscopic plant life that thrives in damp, shaded conditions. In the UK's climate, most decking will develop algae growth within 6-12 months of installation, especially:

In shaded areas or under trees
On north-facing aspects
Where water pools or drains slowly
When leaves and debris accumulate

Left unchecked, algae creates a slippery biofilm that makes decking genuinely dangerous to walk on, particularly when wet.

Wooden vs Composite Decking

Wooden Decking

Softwood (pine, spruce) or hardwood (oak, ipe)
More susceptible to damage from pressure
Can splinter if cleaned incorrectly
Benefits from oiling/staining after cleaning
Grooves trap dirt and algae

Composite Decking

Wood fibres and plastic mixed
More durable but still needs care
Won't splinter but can scratch
Usually doesn't need treatment after cleaning
Textured surface can trap dirt

Safe Decking Cleaning: Step by Step

Step 1: Clear and Sweep

Remove all furniture, pots, and items
Sweep away leaves, twigs, and loose debris
Clear debris from between boards where possible

Step 2: Apply Decking Cleaner

Don't rely on pressure alone – a decking cleaner makes the job easier and safer:

Choose a product suitable for your decking type
Apply according to instructions (usually diluted with water)
Scrub with a stiff brush to work it into the surface
Leave to work for 10-15 minutes

Step 3: Pressure Wash Carefully

This is where technique matters most:

Pressure: Use LOW pressure – 1000-1500 PSI maximum for wood
Nozzle: Wide fan (40°) or a dedicated deck cleaning attachment
Distance: Keep at least 30cm from the surface
Direction: Always wash along the grain, never across it
Angle: Work at 45° angle to the boards, not straight down
Speed: Keep moving – don't linger in one spot

⚠️ The Danger of Too Much Pressure

High pressure on decking causes:

Splintering – Wood fibres lift and create a rough, dangerous surface
Furring – Surface becomes fuzzy and traps more dirt
Etching – Visible marks where pressure was too concentrated
Erosion – Soft parts of wood erode faster than hard parts

Once wood is damaged by pressure washing, it cannot be repaired – only replaced.

Step 4: Rinse Thoroughly

Rinse away all cleaning solution
Wash dirt towards edges/drainage
Rinse adjacent areas that got splashed

Step 5: Allow to Dry

Let the deck dry completely – at least 48 hours in good weather
Don't replace furniture until fully dry
Avoid walking on it more than necessary while drying

Step 6: Treat if Needed (Wooden Decking)

After wooden decking is clean and dry:

Consider applying decking oil, stain, or preservative
This protects the wood and can improve slip resistance
Follow product instructions carefully
Usually needs reapplying every 1-2 years

💡 Anti-Slip Treatments

If your decking is prone to becoming slippery, consider anti-slip products. These include textured deck paints, anti-slip strips that attach to each board, or grip additives that mix into decking oil. Prevention is easier than constantly cleaning.

Decking Maintenance Tips

Sweep regularly – Weekly sweeping prevents debris buildup
Clear between boards – Use a thin tool to clear gaps periodically
Trim back plants – Overhanging vegetation drips moisture and drops debris
Move furniture occasionally – Allows air circulation underneath
Address spills promptly – Don't let stains set in
Annual clean – A yearly clean is much easier than major restoration
Check for damage – Replace damaged boards before they become hazards

Common Decking Problems

Mould and Mildew

Black spots or patches indicate mould. Requires specialist treatment beyond simple cleaning – look for products containing fungicide.

Grey Weathered Wood

Untreated wood naturally weathers to grey. This isn't harmful but can be reversed with deck brightener/restorer products, followed by oiling.

Raised Nails/Screws

Fixings can work loose over time. Hammer or screw them back down before they become trip hazards.

Wobbly or Bouncy Boards

Indicates structural issues with the frame beneath. Address before it becomes dangerous.

Need Your Decking Professionally Cleaned?

Hulkzilla uses the right pressure and techniques to clean decking safely and effectively. We'll transform your slippery deck into a usable space again.

Call 07725 542334 Get a Free Quote

Summary

Decking cleaning requires more care than cleaning hard surfaces like driveways. Use low pressure, the right nozzle, and always work along the grain. A decking cleaner makes the job easier and safer. After cleaning wooden decking, allow it to dry completely before applying protective treatment. Regular maintenance – sweeping, clearing debris, and annual cleaning – keeps your deck safe and looking good while extending its lifespan.