How Do You Stop Decking Being Slippery? 4 Proven Fixes
Why Decking Turns Slippery (And What Actually Fixes It)
If you're wondering how do you stop decking being slippery, the answer comes down to one thing: removing the invisible film of algae, mould and grime that builds up on the surface. That film is what turns a safe deck into a skating rink after rain.
The wood looks fine from the kitchen window. Then someone steps out in the wet and goes down hard.
Slippery decking is caused by biological growth, not by the wood itself. Algae, mould and lichen thrive in damp, shaded conditions. They form a slimy layer that water can't drain through. Timber, composite and painted boards can all suffer. Shaded decks under trees are the worst offenders.
The fix isn't one product. It's a combination of cleaning, treating and preventing regrowth. We'll show you exactly how to do all three.
Watch Out Never pressure wash a timber deck at full force. It gouges the grain, raises splinters and strips any protective finish. That damage makes the deck hold more moisture, which means algae returns faster than before.
How to Clean Slippery Decking Safely
Cleaning slippery decking safely means killing the growth first, then scrubbing it away. Skip the killing step and you'll just spread spores around.
Tools and Products You'll Need
A stiff-bristled deck brush with a long handle
A pump sprayer or watering can
A dedicated deck cleaner or diluted bleach solution
A garden hose
Rubber gloves and eye protection
A bucket of warm soapy water
Step-by-Step Cleaning Method
Clear the deck of furniture, pots and toys.
Sweep off loose leaves and debris.
Apply your cleaner to a small test patch first.
Spray the whole deck and leave it to work for 10-15 minutes.
Scrub along the grain with your deck brush.
Rinse thoroughly with a hose, not a pressure washer.
Let the deck dry fully before walking on it.
Work in sections so the cleaner doesn't dry out before you scrub. On heavily shaded decks, you may need two passes.
Slippery Decking Treatment Options Compared
A slippery decking treatment works in one of two ways: it kills the growth, or it adds grip. Most decks need both.
Here's what most guides miss. A coating alone won't help if the algae underneath is still alive. You have to clean first, then treat. Otherwise you're sealing in the problem.
For timber, a penetrating oil or stain helps water bead and run off. For composite boards, check the maker's guidance before applying anything, as some coatings void the warranty.
Anti-Slip Decking Strips and Grips
Anti-slip decking strips are the fastest fix for a deck that's already dangerous. They bond to the boards and give your shoes something to bite into.
You'll find them in two main types:
Adhesive strips you cut to length and press down
Screw-fixed strips for high-traffic areas
Both work well on steps, ramps and boardwalk edges. Adhesive versions are quick but can lift in frost. Screw-fixed strips last longer and suit decks that get constant use.
Clean the boards thoroughly before fitting. Strips won't stick to a slimy surface. And leave small gaps between strips so water can still drain away.
Pro Tip Fit strips on the parts of the deck people actually walk on: the path from the door, the steps and any slope. Covering the whole deck looks cluttered and traps water between the strips.
How to Prevent Algae on Decking
Stopping algae on decking comes down to light, airflow and drainage. Algae needs damp shade to grow. Take that away and it struggles.
A few habits that make a real difference:
Trim back overhanging branches to let sun and wind reach the boards
Clear leaves and debris from between boards every few weeks
Keep planters and furniture off the deck where possible
Re-treat the surface before winter, not after
Fix any dripping gutters or downpipes nearby
Decks that stay wet are decks that turn green. Airflow is your best defence. If a section never dries out, that's where algae will always return first.
A common mistake is treating the deck once and assuming that's it. Prevention is a routine, not a one-off job.
Common Mistakes That Make Decking More Slippery
Some well-meaning fixes make the problem worse. Here are the ones we see most.
Pressure washing at full power. It strips the surface and opens the grain to moisture.
Using washing-up liquid. It leaves a residue that feeds mould.
Skipping the rinse. Leftover cleaner attracts dirt and regrowth.
Sealing a dirty deck. You trap algae under the coating.
Ignoring the edges. Growth hides in corners and along the wall.
Treating in the rain. The product washes off before it works.
Each of these adds time to your next clean. Do it right once and you'll spend less time on it later.
When to Call a Professional Deck Cleaner
Some decks need more than a brush and a sunny afternoon. If your deck is large, badly shaded or covered in years of growth, professional cleaning saves you the hassle and the risk.
At Cotswold Exterior Surface Cleaning, we use specialist equipment and eco-friendly products to clear algae, mould and grime properly.
We work on residential and commercial decks, and we're fully trained and insured. For holiday lets and hospitality properties, we can schedule around your bookings so the deck is ready for guests.
Key Takeaway The real difference between a deck that stays safe and one that turns green again is the routine: clean, treat, then keep it clear of leaves and shade. Skip any step and the slip comes back.
A slippery deck is more than an eyesore. It's a fall waiting to happen, and it gets worse every wet month you leave it. Cotswold Exterior Surface Cleaning removes the algae, mould and grime at the root, using eco-friendly products and specialist equipment, then helps you keep it that way. Our trained technicians handle residential and commercial decks across the region, so you get a safe, good-looking surface. Get in touch with Cotswold Exterior Surface Cleaning and make your deck safe to walk on again.
Frequently Asked Questions
Why does decking become slippery?
Decking becomes slippery when algae, moss, mould or dirt build up on the surface, especially in shaded or damp areas. Wood and composite boards can also become slick when wet. In the UK, our damp climate speeds up organic growth, so regular cleaning and prevention are key. Without treatment, the risk of slips and falls increases, particularly on steps and ramps.
How do you clean slippery decking?
Start by removing loose debris with a broom. Apply a suitable deck cleaner or a mix of warm soapy water. Use a stiff brush to scrub along the grain, paying attention to grooves and gaps. Rinse thoroughly with a hose, not a pressure washer on full blast, which can damage the wood. For stubborn algae, use a dedicated algae remover. Always test on a small area first and follow safety instructions.
Does pressure washing make decking less slippery?
Pressure washing can remove algae and grime, but it can also damage wood fibres, making the surface rougher and more prone to future growth. It may provide short-term relief, but without a follow-up treatment, algae often returns within months. For best results, use a low-pressure setting and combine with a suitable cleaner, or hire a professional who knows how to clean decking without causing damage.
What can you put on decking to stop it being slippery?
You can apply anti-slip decking strips, which are adhesive-backed and provide immediate grip. Alternatively, use a slippery decking treatment such as an anti-slip coating or sealant that contains grip particles. For a natural look, regular cleaning and applying a preventative algae treatment can help. Choose products suitable for your decking material, wood or composite, and always follow the manufacturer's instructions.