Guide to deck cleaning, restoration and repairs

What you need to know about maintaining decks

How often does a timber deck need treatment?

Operations Trade Manager at RACV Trades Adam Jory, who is an experienced carpenter, recommends cleaning your deck thoroughly and applying a fresh coating every 8-12 months, if using a water-based decking finish, and every six to eight months for an oil-based coating. 

"When the warmer weather is upon us is the perfect time to clean and bring your deck back to life," Jory says. "Decks are at the mercy of the extreme weather conditions we get in Australia - the harsh sun and the rain - so if you don’t maintain them at regular intervals, you run the risk of getting cracked or soft boards and, if left too long, rotting in the subfloor."

How do you clean a timber deck?

Before applying a restorative decking finish, you’ll need to clean your deck thoroughly using a hose or pressure washer, a broom and deck cleaning liquid.

Jory recommends using a quality deck cleaner sourced from your local hardware store as it’s specifically designed to help remove dirt, stains, oils and tannins from both new and weathered timber, creating the perfect surface to then apply a fresh decking coat.

Always follow the manufacturer’s instructions when using a decking cleaner, wearing recommended protective equipment (such as gloves, a mask and safety glasses) and mixing it up and applying the product according to the instructions on the container.

The major steps when cleaning a deck are to:

• Clear the entire deck area rather than trying to work around pot plants, furniture, barbecue, etc.
• Sweep away leaves, loose dirt and any other material with a broom.
• Remove any items under the deck and cover any precious plants nearby.
• Apply the deck cleaner with a broom (ideally a decking broom) across the entire surface area.
• Follow the manufacturer’s instructions carefully, leaving it for the recommended wait time.
• Wash the deck cleaner off using a hose or pressure cleaner.
• Leave the deck to dry.

Jory notes that you may need to wet the deck area before applying the cleaning product (but check the instructions) and that care is needed when using a pressure washer.

"You need to make sure you don’t get too close to the boards using a pressure cleaner because you can actually create some furriness in the timber," he says. "It’s best to only use on a low setting."

He adds that if there’s any peeling or minor cracking along the boards, it might pay to give the deck a light sand (while it’s still dry) before applying the deck cleaner, going along the grain.

More: Tips for the perfect barbecue

How do you restore a timber deck?

Once the deck is thoroughly cleaned, it’s time to restore the boards back to a beautiful finish with a fresh coating.

As Jory explains, there are two main types of timber decking coatings:

• oil-based, which penetrates the wood more deeply and is favoured for its rich, natural appearance; and
• water-based, which creates a protective film on the surface of the boards that restricts water and ultraviolet light, making it more durable while still providing a lovely finish.

Jory says it’s important to stick with the same type of coating rather than switch between the two (remember the old saying 'oil and water don’t mix'), however you can change successfully by stripping and sanding the boards right back at the cleaning and preparation stage. It’s also best to stick with the same colour to ensure you get an attractive, consistent finish every time.

Whichever decking coating you use, the major steps when applying are to:

• Thoroughly mix the coating using a broad paddle
• Pour into an appropriate tray – ideally this will be deeper than a standard paint roller tray given the thinner consistency of decking coatings compared to exterior paint
• Apply the coating using a decking applicator – usually a long-handled brush or a compact ‘mop’ (often made with lambswool) that absorbs plenty of liquid and glides across the deck area
• Not forget to apply the coating to the board ends (a brush will be handy for this).

For optimum results, at least two coats of decking finish are generally recommended each time. Drying times vary, and there are different schools of thought on whether to sand between coats, so always follow the manufacturer’s instructions.

More: How to design the ultimate outdoor kitchen and barbecue area

Do you use a water-based or oil-based deck coating?

The decision to go with an oil- or water-based deck coating is a personal one, with Jory favouring the look that an oil stain provides – but acknowledging that it requires more maintenance.

"If you really love timber and want to bring out the grain in your decking boards, oil provides a beautiful, natural finish," he says. "It looks great, but it doesn’t last as long so you have to be prepared to apply a fresh coat every six to eight months. I like to put a coat on by late spring or early summer so that it’s protected across the hottest months and then do another one in autumn when it’s still warm and means the deck will be protected over winter. Basically, if you can see it starting to fade or getting blotchy, then it’s time to coat."

Jory says most homeowners will opt for a water-based deck coating because they’re generally quicker to dry during the application and typically perform well for 12 months before another coat is needed.

"A water-based coating should still look great and they’re longer-lasting but can be less forgiving if you don’t apply a fresh coat every year," he says. "If you leave it too long the boards can start to crack, and it then becomes more difficult to maintain, and repairs might be needed."

Decking paint also remains a cost-effective choice for homeowners, and Jory says it’s especially suited to treated pine. Paint can become slippery when wet, so be sure to use a specific decking paint for the best results.

More: Regular home maintenance checks to keep your home in top shape

What are the signs that it's time to repair or replace a deck?

Timber naturally deteriorates over time but the rate at which this occurs will depend on how well it’s maintained. That holds true for decks, where the area is routinely called upon to carry high loads and battle the elements all year round.

"If your deck is situated in an area that’s heavily exposed to the sun, or cops a lot of rain, and doesn’t have protection over the top, such as with a pergola, you’ll need to be vigilant in coating the deck and also regularly checking for signs of damage," says Jory. "If it’s getting to the point where you feel bounce in the deck, or if boards are splitting lengthways, and if you notice any soft boards and other signs of rot, then you know you've got an issue, and something needs to be done."

Jory says that replacing one or two boards on a low-mounted deck could be managed by a homeowner who’s confident with DIY projects around the house, however a qualified professional should be called in if more extensive repair work is needed.

"It depends on the scale of the issue," says Jory. "If it’s got anything to do with the subfloor – rot in the subfloor or joists, or lots of moisture under the deck which points to poor drainage, then it’s important to seek the help of a professional. I’ve seen decks where people have fallen through them because they’ve had termites or have simply left the problem they can see go on for too long," he adds.

If the deck needs to be replaced, keep in mind that it must be designed and constructed legally. The Victorian Building Authority has further details on its website, but this process will usually require a building permit, and a registered builder will need to do the work if the cost of the project is more than $10,000.

^{RACV Trades is a trading name of RACV's trade partner, Club Home Response Pty Ltd (Victorian registered domestic building practitioner number CDB-U 100178). All works are performed or arranged by Club Home Response Pty Ltd. trading as RACV Trades. Read the RACV Trades Terms and Conditions.}