Best Decking Cleaner for Timber Maintenance: 2025 Expert Review
DR Joinery
Expert Joiner & Timber Specialist
If you live in the UK, you know the battle against the 'green slime' on decking is constant. Damp autumns and wet winters turn untreated timber into a dangerous ice rink. Many homeowners make the mistake of immediately reaching for a high-powered pressure washer, which often does more harm than good by stripping the wood grain and encouraging rot.
As a joiner dealing with York's specific climate conditions, I always advise my clients to use a proper chemical cleaner rather than just brute force water pressure. The right cleaner will kill the mould spores and algae at the root, rather than just blasting the surface visible dirt away.
In this review, I'll compare three cleaning solution options I've looked at for effective maintenance: a budget-friendly prep cleaner, a bulk buy for large areas, and a potent concentrate for tackling stubborn algae growth.
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Specs vs. The Real World
The Spec: "Restores Original Colour"
"Marketing often claims a cleaner will bring back the 'new wood' look instantly."
Cleaners remove grey dirt and green algae, revealing the wood beneath. However, if the timber has silvered from UV damage, a cleaner alone won't reverse that—you will need a restorative oil or stain after cleaning.
The Spec: "Spray and Walk Away"
"No scrubbing required—just spray it on and the dirt disappears."
Whilst 'spray and leave' products work well on algae over time, heavily soiled decks with ingrained mud in the grooves usually require a stiff broom and some elbow grease for a truly professional finish.
My Top 3 Recommendations
Three options to cover different needs and budgets
Chemical Trade Store - Decking Cleaner | Deck Algae and Mould Remover - 2.5 Litre
Chemical Trade Store
This 2.5-litre option is excellent for homeowners looking to prep a standard-sized deck before re-oiling. It's formulated to open the wood pores, ensuring that your subsequent finish adheres properly. It's a straightforward, no-nonsense cleaner that gets the job done without breaking the bank.
The Good
- Very affordable price point
- Opens wood pores for better oil adhesion
- Works on softwood, hardwood, and composite
The Bad
- Smaller volume may not cover large garden projects
- Requires manual agitation for best results
Installer Tip:
Use this product specifically when you plan to oil or stain the deck immediately after it dries. The 'pore opening' feature is brilliant for ensuring your expensive decking oil penetrates deep into the timber rather than sitting on top.
Priced at £8.67 at the time of writing
Check Price on AmazonJarder Spray & Leave 4 x 5 Litre Concentrate Cleaner (20L)
Jarder
If you have a large wrap-around deck or manage multiple properties, this bulk pack is the professional choice. With 20 litres of concentrate, it makes a massive amount of solution. The 'spray and leave' formula is designed to prevent regrowth for up to six months, which is essential in our damp UK climate.
The Good
- Incredible value per litre (£2.00/l)
- Prevents algae regrowth for months
- Biodegradable and bleach-free (safe for pets once dry)
The Bad
- Large upfront cost
- You need space to store 20 litres of liquid
Installer Tip:
Patience is key here. Do not rinse this off. Apply it on a dry day when no rain is forecast for at least 6-8 hours. The chemical needs time to desiccate the algae spores properly.
Priced at £39.95 at the time of writing
Check Price on Amazon5 Litre Concentrate Spray & Leave Cleaner - Green Mould & Algae Killer
Jarder
If you don't need 20 litres but still want the heavy-duty power to tackle serious green mould, this single 5-litre concentrate is the answer. It's the perfect middle ground—sufficient for a standard semi-detached garden deck that hasn't been cleaned in a few years and is suffering from slick algae build-up.
The Good
- Powerful concentrate kills lichen and algae
- No scrubbing needed for general greening
- Versatile: works on fencing, patios, and UPVC too
The Bad
- More expensive per litre than the bulk pack
- Results take 2-3 days to fully show
Installer Tip:
For problem areas where the algae is thick (like slippery corners that never see the sun), mix it slightly stronger than the instructions suggest. Use a garden sprayer for even application to ensure you saturate the timber end-grain where rot starts.
Priced at £20.95 at the time of writing
Check Price on AmazonFrequently Asked Questions
Should I use a pressure washer on my timber decking?
How often should I clean my decking in the UK?
Can I use bleach to clean my decking?
Why is my decking slippery even when it looks clean?
Do I need professional help for deck maintenance?
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