How to Clean and Remove Moss on Decking

Why Does Moss Love Your Decking?

Decking creates the perfect environment for moss growth. The wood traps moisture, sits in shade for parts of the day, and provides endless tiny grooves for moss spores to anchor into. Add in some fallen leaves and a bit of British rain, and you’ve got yourself a moss farm.

The real problem? Moss on decking isn’t just unsightly – it’s dangerous. That green layer becomes incredibly slippery when wet, turning your outdoor entertaining space into a liability. Worse still, moss holds moisture against the wood, accelerating rot and reducing your deck’s lifespan.

How to Remove Moss from Decking: The Right Way

Step 1: Clear and Prepare (10 minutes)

Remove all furniture, plant pots, and BBQ equipment from the deck. Give it a good sweep with a stiff broom to clear loose debris, leaves, and surface dirt.

Safety first: Moss-covered decking is incredibly slippery. Wear shoes with good grip and consider placing non-slip mats in areas you need to walk on during cleaning.

Step 2: Choose Your Cleaning Method

Professional moss killer (recommended): Spray a decking-safe moss treatment over the entire affected area. Let it work for 24-48 hours, then rinse away. This method kills moss at the root and prevents regrowth.

DIY vinegar solution: Mix equal parts white vinegar and water. Apply liberally, let sit for 2-3 hours, then scrub with a soft-bristled brush. Rinse thoroughly. (Note: Vinegar can darken some woods and needs frequent reapplication.)

Pressure washing: Can be effective but risky. If you must pressure wash, use the lowest setting (under 1500 PSI), keep the nozzle at least 30cm from the wood, and use a fan spray pattern. Never use high pressure on softwoods or older decking – you’ll cause permanent damage.

What NOT to use: Bleach (damages wood fibres and kills plants), wire brushes (gouges the surface), or harsh chemicals not designed for decking.

Step 3: Rinse and Dry (30 minutes active time)

Once the moss is dead or loosened, rinse the entire deck thoroughly with a garden hose. Work systematically to ensure no cleaning solution remains.

Crucial drying tip: Let the deck dry completely before applying any treatments or sealants. This typically takes 2-3 days in dry weather. Walking on damp wood can cause staining and embedding dirt.

Preventing Moss from Coming Back

Cleaning moss is only half the battle. Without prevention, you’ll be doing this all over again in a few months.

Improve Air Circulation

Trim back overhanging branches and bushes that create shade and drop debris onto your deck. More sunlight means less moss. If your deck is permanently shaded, consider installing shade-tolerant decking or using moss-resistant treatments more frequently.

Regular Sweeping

A quick sweep once a week removes leaves and organic matter before they decompose and create moss-friendly conditions. This 5-minute habit is the single best prevention method.

Annual Treatment

Apply a decking oil or sealant annually. This creates a barrier that makes it harder for moss spores to establish themselves. Choose products with built-in algae and moss inhibitors for extra protection.

Check Your Drainage

Standing water is moss heaven. Ensure your deck has proper drainage and isn’t retaining water in low spots. If you notice puddles after rain, you may need to adjust the deck’s slope or improve drainage underneath.

Different Decking Types: What You Need to Know

Wooden decking: Most susceptible to moss. Requires gentler cleaning to avoid damaging wood grain. Annual oiling is essential to maintain water resistance.

Composite decking: More resistant to moss but not immune. Can typically handle slightly more aggressive cleaning. Check manufacturer guidelines before using any chemicals.

Treated timber: The treatment helps resist rot but doesn’t prevent moss. Clean regularly and reapply treatment every few years as it wears away.

Quick Troubleshooting

Q: Can I use a pressure washer on old decking?
A: Generally not recommended. Older wood is softer and more prone to splintering. Stick to soft brush cleaning or low-pressure rinsing.

Q: My deck is still slippery after cleaning. Why?
A: You may have algae as well as moss. Apply an algae treatment after moss removal. Also check if your deck has developed a smooth, worn surface that needs texturing or anti-slip treatment.

Q: How often should I clean my deck?
A: Light sweeping weekly, deep clean once or twice a year depending on moss severity. Shaded decks need more frequent attention.

Q: Will deck cleaning harm my plants?
A: Cover nearby plants during cleaning and rinse the area thoroughly afterward. Most moss killers designed for outdoor use are safe once dry, but always check the label.

Related Moss Problems

If you have moss on your decking, you may also notice it appearing on other outdoor surfaces. Check nearby paths and fencing for early signs of moss growth – treating all affected areas at once prevents cross-contamination. If your deck sits beneath a flat roof or overhang, check that surface too as moss spores can drop down from above.

The Bottom Line

Moss on decking is more than a cosmetic issue – it’s a safety hazard and a threat to your deck’s structural integrity. The key is addressing it quickly and preventing it from establishing in the first place.

DIY methods can work for light moss coverage, but they require regular reapplication and risk damaging your deck if done incorrectly. Professional moss treatments offer faster results with less risk and longer-lasting protection.

Whatever method you choose, consistency is key. Regular maintenance beats occasional deep cleaning every time. A weekly sweep and annual treatment will keep your deck looking great and safe for years to come.