Looking after your decking

Updated July 11, 2018

Whether you have composite or real wood decking, it lasts longer if you take care of it. Chris Cohn has been building and repairing decks for over 30 years, and he knows the importance of proper upkeep. "Keeping your deck clean is more than a matter of aesthetics," he says, "it's also a way to protect your investment. Many of the repair calls I make could have been avoided by regular maintenance." He offers a few tips to help homeowners avoid the need for his services.

"Keeping your deck clean is more than a matter of aesthetics, it's also a way to protect your investment. Many of the repair calls I make could have been avoided by regular maintenance."

Chris Cohn -- Builder and decking expert

Basic regular cleaning

Decks need basic cleaning, and while it doesn't have to involve a lot of work, you should do it regularly and often. A basic sweeping is essential, because it clears away leaves than branches that can leach tannins into the wood and stain it. "While you're doing that," says Cohn, "clear leaves and debris from between the decking boards. They prevents drainage and cause rot, even if you have composite decking; it's one of main reasons why major repairs, such as joist replacement, become necessary."

• Keep a broom on the deck or in your shed, and use it to sweep the deck at least once a week.

• Clear debris from between the boards with a paint scraper or putty knife. Scrape all organic matter -- especially if it's wet -- from the tops of the joists.

• Make a convenient scraping tool that can save your knees by pushing a putty knife into a 1.2 m (4 foot) length of PVC pipe to extend the handle.

Washing and deep cleaning

"A pressure washer is a super-convenient tool when your decking boards are mouldy and grey, but it can cause a lot of damage. I use one only when a deck is too dirty to clean with soap and water. Oh...and remember. Never pressure-wash composite decking boards; you'll void the warranty." Cohn is a fan of oxalic acid wood bleach, which he uses to remove tannin stains and grey discolouration caused by ultraviolet sunlight.

A strong detergent solution can take care of most dirt, especially if you follow it up with a rinse. Some decking cleaners contain oxalic acid and will bleach while they clean, but you can always apply oxalic acid wood bleach separately.

• Sweep the deck and clean out the debris from between the boards.

• Apply the decking cleaner with a roller or a rag. Spread it liberally and allow it to sit on the wood to give it time to soak in and do its work, then scrub with a scrub brush.

• Rinse with a garden hose or pressure washer. Your pressure washer should have a wide-angle tip. Keep the pressure low and the tip at least 15 cm (6 inches) from the wood to avoid chipping and gouging.

Making basic repairs

No matter how well you maintain your decking, you can't avoid the need for small repairs, such as replacing lifting boards, replacing the odd board and scraping and filling rot. "I always use screws when I lay decking boards, says Cohn, "but many builders don't, and when you see a lifting board, it's almost always because it was nailed. Pull the nails, replace them with screws and board won't lift again -- guaranteed."

• Replace lifting decking boards with 7.5 cm (3 inch) galvanized or coated decking screws. Pull out the nails and drive a screw into fresh wood about 1.3 cm (1/2 inch) from each nail hole. Fill the nail holes with epoxy wood filler.

• Inspect the underside of the decking for rot once a year. If you find any, scrape out the damaged wood with a screwdriver or putty knife and fill the cavity with epoxy filler. Sometimes removing a few decking boards makes rot repair easier.

• Give the railing a good shake, and if it feels loose, look for rot around the bases of the posts. Some posts may have just worked themselves loose -- tighten the bolts with a spanner.

• Replace boards that are severely cracked. The cracks will only get worse, and walking on the deck could become dangerous.

Protective sealing

Without a protective finish, wood dries out more quickly in sunlight and it's more susceptible to stains and fungus. "The best sealers are semi-transparent ones that block sunlight" says Cohn, "but many people prefer clear sealers. Clear ones need frequent updating -- sometimes once a year -- while you can usually leave a pigmented sealer for three years or more." Cohn usually applies sealer as part of a deep-cleaning package he offers. "Sealing is a two-day procedure," he advises. "Two thin coats are better than one heavy one."

Before sealing, the decking must be clean and dry. Work on a day with clear skies and moderate temperatures and on which no rain is in the forecast.

• Sand the deck lightly with a pole sander and 120-grit sandpaper. Sweep away sanding dust with a broom.

• Seal the railing before you do the decking boards, using a paintbrush or sprayer. Some sealers are thin enough to spray with a garden sprayer.

• Apply a thin coat sealer to the decking with a roller, brush or sprayer. Run a paint brush along each board to force material into the gaps on either side.

• Let the sealer dry overnight, then apply a second coat. Avoid walking on the deck for at least 24 hours.

Composite decking care

Composite decking boards are "low-maintenance", but they aren't "no-maintenance." Although manufacturers have largely corrected the problems with mould that affected early products, surface mildew can still be a problem, and you should wash the decking regularly to control it. Moreover, tannin stains from leaves and twigs can also mar the surface. Never try to remove these stains with abrasive materials, such as sandpaper -- doing so voids the manufacturer's warranty, as does pressure-washing. Cleaners designed specifically for composite decking are your best bet.

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About the Author

Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.