How to treat decking for a longer-lasting surface

Extend the life of your decking with our step-by-step guide.

It’s that time of year when we look forward to spending more time in our gardens, but is your decking summer-ready? 

Whether you enjoy the social aspect of barbecues with family and friends, eating al fresco in the sunshine or simply sitting peacefully and admiring the view, it’s likely your decking will need some care and attention to get it in ship-shape condition.

Contemporary decking laid at an angleCredit: Shutterstock / Radoslav Cajkovic
The right maintenance can have your decking looking summer-ready

On average you can expect timber decking to last between 15 and 30 years, but according to Ronseal, with the right maintenance it can last much longer. So, with the help of the experts, we’re here to show you how to treat your decking and give it a new lease of life. 

Why you need to treat decking

“If you’re lucky enough to have decking, you’ll know that it requires annual maintenance,” says a spokesperson at Toolstation. “It’s common for decking to become green or discoloured with algae or mildew, particularly after winter or a wet period. It can also become slippery and dangerous if not looked after.” 

Knowing how to clean and treat your decking isn’t difficult if you follow these steps. 

1. Sweep away loose dirt and grime

Get your broom out

Remove any garden furniture, containers or accessories from the decking to give a clear space for working. Take hold of a stiff brush and get sweeping to remove the dirt and leaves. You may find a handheld wire brush is needed to tackle tougher dirt. Be careful to get into all the timber grooves to remove the muck.  

Shop a Roughneck soft-grip carbon steel wire brush, £7.99, Screwfix
Stiff brush being used to clean a dirty timber deckCredit: Shutterstock/Maren Winter
Clear away the dirt and grime with a stiff brush

2. Give it a clean with soap and water

Wash the decks

“You can then use a simple solution of washing up liquid and soap for a gentle clean, or purchase a specialist decking cleaner,” says the Toolstation spokesperson. “Whilst both will do the trick, decking cleaner will be more effective in getting rid of stubborn dirt and grime.” 

Scrub the deck once more, creating a lather with the cleaning liquid (if you’re using a decking cleaner, check the instructions before use), and rinse with clean water before leaving it to dry. 

Shop Barrettine Concentrated Decking Cleaner, £10.99, Toolstation

3. Wash the dirt away with a pressure washer

But don’t use too high a setting

Pressure washing being used to clean a decking areaCredit: Shutterstock/bubutu
Be careful not to damage the timber when using a pressure washer

Once the deck has been cleaned, you can remove the leftover debris with a pressure washer. “It’s a quick and easy way to remove any build-up of moss or grime,” says the Toolstation spokesperson. 

If using a pressure washer, be careful not to use too much pressure, as this can damage the timber. Test the pressure washer on a small area first and hold the hose a good distance from the decking, then start the pressure washer on a gentle setting using a wide spray nozzle. If this isn’t sufficient to clean the deck, increase the pressure gradually.   

But don’t worry if you don’t have a pressure washer, a normal hose will work just as well, although you may need to add a little extra elbow grease with the help of a wire brush. 

“I’m a big fan of Kärcher pressure washers – I’ve owned mine for eight years now and it’s still working perfectly,” says Saga Exceptional’s Amy Cutmore. “I’ve always found it really easy to use thanks to its clever wand system that helps you select the right power for each job, and it’s really good at shifting dirt.”

Shop the Kärcher K4 Power Control Home pressure washer, £250, Amazon

Ronseal warns against using a pressure washer if you have mould on your decking, as it can cause the spores to spread and make it worse. The best plan of action is to make sure the mould has been removed before you start. 

Why you need to banish mould 

Black mould can thrive on damp wood. This makes timber decking in shaded areas a perfect breeding ground for mould, as the timber takes longer to dry out than decking positioned in sunny spots. If left untreated, mould will break down the wood fibre, leading to wood rot.

Cleaning the mould off your decking will prevent further long-term damage that would be harder to repair.

4. Protect your timber from the elements

Choose between a decking oil or a stain

Man with paint brush applying oil to deckingCredit: Shutterstock / ronstik
Apply the oil with a brush to get in between the grooves

Now your decking has had a deep clean, its time to nourish the timber and protect it from the elements. But which product do you choose: decking oil or decking stain? 

Decking oil

Toolstation tells us: “Decking oil is great for repairing and nourishing wooden surfaces as it helps to bring out the natural features in the wood. The oil is designed to penetrate the wood and protect the decking from within, helping to prevent it from warping, splitting, or cracking. If you’d like to keep the natural look of your wooden deck, oil is the preferable choice.” 

Oil also has another advantage. “It’s less slippery than stains,” says Toolstation, “as it doesn’t coat the wood with a plastic-like film.   

“Its final colour is influenced by the natural colour of the timber – meaning the finish could slightly alter from the image on the packaging.” 

However, the spokesperson has a warning: “One thing to remember is that stains will not take to a deck that’s been previously oiled, meaning it’s best to choose between one or the other.”

Decking stain

While oil is the best option for a natural look, a stain will change the colour of your timber to create an entirely different effect.

Stain will still work as a preservative, but it will need some maintenance. It can crack and peel over time if not maintained or applied correctly,” says Toolstation, so make sure to prepare your surface before applying the correct amount.”  

Person applying stain to a deckCredit: Shutterstock/Grusho Anna
Decking stains can add a bold statement to your garden

Try these decking oils

Ronseal ultimate decking oil in natural 2.5l, £29.99 at Screwfix 

Cuprinol UV guard decking oil in natural 2.5l, £29 at Wickes 

Try these decking stains 

Ronseal ultimate protection decking stain in slate 2.5l, £34.99 at Screwfix 

Cuprinol anti-slip decking stain in Hampshire Oak 2.5l, 2.5l, £29 at Wickes 

5. How to treat decking with oil

It’s best to put it on plank by plank

Before applying either decking oil or stain make sure the timber is completely dry.  

When applying oil, Liberon recommends giving the oil a good stir before starting to apply it in thin coats using a brush, roller or spray gun.  According to the website: “It’s best to apply the decking oil in sections or plank by plank to provide your wood floor oil protection evenly.” 

Apply another thin coat after 20 minutes, then remove the excess oil with a cotton cloth (check the instructions on your product for specific application advice). The area should be left to dry for at least 24 hours before use.

6. How to treat decking with stain

The technique will depend on the age of the deck

Applying stain to a new deck

Ronseal advises checking to see if there’s any pre-treatment on your new decking, as this can prevent the stain from sticking, leaving your timber unprotected. If it’s untreated, you can either allow the deck to weather naturally for six months or give the decking a good clean (see above).

Before you start, give the stain a good stir and apply it with a brush along the lengths of the decking, in the direction of the grain. Check the label for the correct drying time before applying another coat.  

Applying stain to an old deck

When applying a stain to an existing deck, there’s more preparation required than when staining a new deck. Ronseal advises removing any previous treatments of oil or stain with a deck stripper. Although it may seem like an arduous process, it provides a better surface for the new stain to adhere to.  

Shop Ronseal Decking Stripper, £31 for 2.5ltrs, Wickes

Wait for a warm before getting to work. Remove any debris from the decking then give the deck stripper a good mix before pouring it onto the deck. Work the stripper into the timber using a stiff handheld brush and apply more stripper to any areas that dry out.

Then wait 30 minutes, or however long it details on the instructions, before scraping the surface with a sharp implement, such as a paint stripper or putty knife.

You may need to wait a few more minutes if the stripper hasn’t worked, however, if it’s ready, get a stiff brush, add some water and get scrubbing. Then, wash the whole area with a pressure washer. 

Leave the deck to completely dry before applying the stain – 48 hours is a good guide.

Camilla Sharman

Written by Camilla Sharman she/her


With her 30 years of experience, Camilla Sharman has covered a wide range of sectors within the business and consumer industries both as a feature, content, and freelance writer.  As a business journalist, Camilla has researched articles for many different sectors from the jewellery industry to finance and tech, charities, and the arts. Whatever she’s covered, she enjoys delving deep and learning the ins and out of different topics, then conveying her research within engaging content that informs the reader.