Wooden or composite decking can be the jewel in your garden’s crown, but a life spent out in the elements can take its toll on even the most hardy of finishes. Like patios and paths, decking accumulates dirt, algae, bird droppings – and it can even be a home to mould. Four seasons of exposure can leave your decking looking awful, but with help from a pressure washer, it only takes a couple of hours to get it as good as new.
In this guide, I’m going to explain how to quickly and safely rejuvenate your decking, without causing damage. We’ll cover how to prepare and clean wood or composite finishes, and what you can do to help prolong the life and appearance of your newly washed deck.
What you’ll need
- An outdoor broom
- A pressure washer
- Decking cleaner (suitable for your decking/pressure washer type)
- Stiff brush
- Old towels (optional)
- Wood stain/protector (optional but recommended)
The short version
- Prepare your decking
- Apply detergent
- Set up your pressure washer
- Pressure wash the deck
- Aftercare
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Step 1.
Prepare your decking
Before you start, clear all furniture and other objects off the deck to give you full access. Next, take a broom and give it a sweep, ensuring you remove all loose material like leaves and dirt. Examine the deck for any rotted or damaged wood – you’ll want to avoid pressure-washing these parts. You should also remove any moss or other plants growing on, or extending over the decking.
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Step 2.
Apply detergent
Make sure you buy a detergent that’s formulated for your decking material. You can buy wood and deck detergents suitable for a pressure washer’s dispenser, but you’re likely to get better results if you buy a decking cleaner that’s applied by hand before washing. Check the instructions on your detergent to be sure which it is: the latter are usually poured or rolled onto the deck, followed by a bit of brushing.
Where brushing is required, you’ll typically work by scrubbing the length of one decking board at a time, working along the grain. While you’ll need a bit of elbow grease to lift out stubborn stains, don’t brush too hard – it’s easy to damage the finish on wood and plastics. Leave the cleaner to work for a few minutes if necessary according to the manufacturer’s instructions. -
Step 3.
Set up your pressure washer
Connect your pressure washer up to water and power, ideally using an RCD-protected plug socket, and a non-return valve to prevent water backflow. Wear foot, eye and ear protection, then follow the manufacturer instructions to prime your machine with water. Keep children and pets away from your work area, and remember that the decking will become slippery once wet.
Fit a patio cleaning attachment if you have one, otherwise attach a fan nozzle, or select a wide fan spray for your pressure washer. If you’re using dispenser detergent, fill the bottle or fit the detergent nozzle as appropriate. It’s easy to damage softwood decking, so choose the lowest power setting and widest nozzle setting you can. Hardwood decking is more robust, but avoid using high power settings on anything except a composite deck. Don’t use a narrow jet of water – it’s more likely to damage the deck, or leave an uneven finish.
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Step 4.
Pressure wash the deck
If you’re working on hardwood decking, choose a low-medium pressure if you can. Spraying from around 15-20cm away, work along the grain of the board in a smooth, straight action. Overlap passes to get an even finish, but don’t dwell in any one spot – try to be consistent to get an even finish. If you’re using a patio attachment, work methodically in the same way, focusing on one board at a time.
In this way, cover the whole deck to rinse off the detergent you applied by hand. Or, if you’re using the machine’s detergent dispenser, complete one moderately powerful pass with detergent, then follow it up with a second pass at low power to rinse the deck clean. Now use a broom or old towels to sweep or soak up standing water if you can, and leave the deck to fully dry.
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Step 5.
Aftercare
You can improve the look and extend the life of wooden decking by applying an oil, stain, or other treatment – it’s especially important after pressure-washing, which can remove existing treatments. While this step is optional, I’d highly recommend it.
Apply treatments as soon as the deck has dried fully after cleaning, which may take a day or so. Decking protectors add some water resistance, reducing the chances of splitting. They usually also help prevent damage from strong ultraviolet light in summer. Decking stains do the same, but add colour, so it’s important to match them to the existing shade of your wood.
Softened or rotten wood may need further treatment. Wood fillers can help fill unsightly gaps left by rotted wood, but they’re unlikely to last long on a deck. Similarly, a rotted wood hardener can help slow down decay, but it won’t stop it forever. Sometimes it’s best to just replace decayed boards – staining the whole deck afterwards can help disguise any replaced sections.
Troubleshooting
Yes, but you should stick to low pressure, and avoid any rotted or softened areas. Hardwood decks can usually withstand higher pressure washing, but always use a wide fan spray, or a specialised patio or decking attachment.
The trick is consistency. Always use a wide fan nozzle or patio attachment, and work along the grain with smooth, consistent motions. Don’t dwell in any one area, even if it’s heavily stained. Overlap several passes to avoid leaving visible patterns.
Pressure washing can remove previous stains or treatments, leaving the wood more vulnerable to the elements. It’s best to re-treat the deck to help prolong its life between cleans.
