Although composite decking is fairly low maintenance, its natural exposure to the elements means it will still need routine care to keep it looking new and help it last longer.

To save time and labor you may want to use a pressure washer, but you are unsure if it will cause damage to your composite decking.

In this article, we will see if you can pressure wash a composite deck, what the safest methods are for doing so, and what the best equipment is for the job.

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Can you pressure wash a composite deck?

Yes, you can pressure wash a composite deck, however, you do need to be careful when doing so. Composite decking is made up of primarily plastic and wood materials, which is softer than natural wood and can be marked or damaged more easily. Before pressure washing with any composite decking, it is recommended to get in touch with your manufacturer to get advice on what the best method is for your specific type of deck.

Is it safe to pressure wash composite decking, or is it bad?

If you take the correct precautions, follow user instructions, and apply them carefully, it will be safe to pressure wash your composite deck. It can only damage your decking if you use the pressure washer in the wrong setting, use the wrong type of cleaning agent, or apply the pressure washer incorrectly. In this article, we will address all this and even more!

How to pressure wash a composite deck

To prepare your deck for pressure washing, make sure to clear your deck area of all furniture and decorations. It’s not worth the hassle of trying to clean around them. Then take a sweeping brush, leaf blower, or even a vacuum to clear any loose debris from the deck, making sure to get in the gaps between the boards so there is nothing left on the surface that could mark or scratch the deck when pressure washing. A putty knife can be quite handy for this.

Next, you will cover the deck with a soap detergent, either homemade or through your pressure washer’s soap dispenser setting. Once applied, allow a few minutes for the soap to work on the dirt and grime. Be aware that many soap solutions should not be allowed to dry on the surface, so make sure to periodically spray or mist over the deck if you find this may be an issue.

Take a medium, stiff-bristled brush and scrub over the deck. With a good soap and a little elbow grease, you should be able to remove most of the dirt. Then use your pressure washer to rinse off the deck. Make sure to use a wide nozzle fan tip and keep it a safe distance from the surface (no closer than 8 inches). Always work along the grain of the boards and make sure to remove all soap residue as it can leave a film on the surface. Remember, the majority of the cleaning should be done with the detergent, the pressure washer is mainly to rinse off the deck of all soap and broken up dirt.

Composite deck wash recipe – a DIY cleaner recipe for deck

If your pressure washer does not have a soap dispensing attachment, or you are out of brand detergent, you can make your own cleaner. You can often get great results with a simple mixture of warm water and dish soap (ammonia-free). Another homemade method for deck wash soap is using half a cup of white vinegar and ¼ cup of baking soda with 1 gallon of water, which is good for mold and mildew.

WARNING: The application method for these DIY soaps is most often manually applied. Do not put these mixtures through your pressure washer soap attachment without consulting the manufacturer.

If you find these methods aren’t enough and you need something a little stronger, get in touch with your decking manufacturer for information on what best to use and not use, as bleach products are not always advisable on composite decks.

Pressure washer setting for composite deck

Because composite decking is softer than natural wood, your pressure washer has to be set just right. You will need a wide fan tip nozzle attachment with around a 40°- 60° spread to minimize the concentrated spray. You do not need a high pressure as the majority of the work should be done with the detergent and brush. The pressure settings should be from 1500 pounds per square inch (PSI) to a maximum of 3100 PSI and keeping the tip a safe distance (8inches) from the surface to make sure you do not score or cause damage to the deck.

Best pressure washer for composite decks

The best pressure washer to use for composite decks should be able to have an adjustable tip for a wider spray range, not too much pressure, and a soap dispenser setting, allowing quick and easy coverage. We recommend the Ryobi 2900 PSI, 2.3 GPM Gas Pressure Washer. It’s a popular choice and has good versatility for composite decks, as well as being an all-round pressure washer. This makes it a good value for money. This model is priced at around $300 and available at Ryobi or Home Depot. It’s 5 in 1 changeover nozzle allows you to switch easily from a soft soap dispenser setting to the wide spray setting for rinsing. The durable hand truck frame and it being gas-powered means fewer cables to restrict mobility.

You can also buy a 2300 PSI model for the same price which is electrically powered. Alternatively, if this is out of your price range or you cannot locate this model, speak with the professionals at your local hardware store about different models or even just hiring a pressure washer for your composite deck with the required specifications.

Pressure washer marks on composite decks – What to do?

If you have used a pressure washer on your deck, but there are overlap marks left on the deck, you may be wondering how to get rid of them or how to avoid them in the first place. Firstly, check and make sure the washer marks have not damaged the deck in any way. If this is the case, get in contact with the deck manufacturer on what to do next as you cannot usually sand the marks out of composite decks like on wooden ones.

One of the best ways to avoid overlap marks is to use a long sweeping motion. Begin at the start of a board and in a slower methodical movement, walk along the length of the board with your fan tip kept at the same distance from the surface the whole way along. It can be a time-consuming process; however, it will minimize the chance of leaving overlap marks. This method is especially great for decks with no railings or obstacles but should work on all decks if you are careful in your application.

Can you power wash a composite deck?

The difference between a pressure washer and a power washer is heat. Power washers deliver a hot stream of water onto its surface. In much the same way you use hot water when washing dishes, a power washer can be more effective at removing tough stains, including oil and grease. Although you have to be more careful with the surfaces you use it on and how you use it. Check with your deck manufacturer if you can use a hot power washer on your deck.

How to power wash a composite deck

In much the same way you pressure wash a composite deck; a power washer follows the same guidelines. Make sure to use a wide nozzle tip and keep it at least 8 inches from the surface. Should your PSI be closer to the 3100 max PSI limit, a further distance from the surface is recommended. Let the bulk of the cleaning work be done by the soap and brush, the power washer’s heat will help remove the last remnants of dirt and excess soap. Because the water coming from the power washer is hot, take extra caution not to spray yourself or others and wear recommended protective equipment.

Best power washer for composite decks

Power washers are not usually made for composite decks in mind, but that doesn’t mean you can’t find the right one for the job. Be aware though, the price difference between pressure washers and power washers can be vast. Power washers are more heavy-duty and used commercially than domestically. The heat advantage power washers have with grime and dirt on decking is not usually worth the price you pay when a pressure washer and the right soap detergent can be as effective.

If the job does require a power washer, we recommend the North Star Electric, Wet Steam & Hot Water Pressure Washer – 1700 PSI, 1.5 GPM, 115 Volt. From around $2000, order this power washer online or check local hardware stores for stock. The multiple attachment options allow you to fit wide fan tip and soap dispensing nozzles. You can also control the pressure and temperature to suit the task. Because of the expense, it may be better to look into hiring a power washer for your job. Ask at your local hardware stores about prices and availability.

Does power washing get rid of mold on composite decking?

If your deck is able to be power washed, removing all mold from it may take a lot of heat and spraying, increasing the likelihood of damaging the boards. The best method is to first scrub the deck using a two parts vinegar, one-part water solution. Pour this solution directly over the mold, then sprinkle some baking soda on the area afterward. Let it sit and soak in for around 20 minutes before scrubbing it with a gentle bristle brush. Then you can use either the power or pressure washer to thoroughly rinse the deck. This can work just as well with the same solution and a pressure washer.

Can you pressure wash Trex decking

Since Trex is also a type of composite decking, you should take similar care as with other composite decks. Just remember to use no more than 3100 PSI, with a 40° fan tip, work along the grain of the boards and use the right cleaning agents and it will be fine.

If you wanted to power wash your Trex decking though, that is a little more complicated. For standard Trex decking (composite and PVC), they do not recommend power washing as it may damage the deck surface and will void the warranty. However, the Trex transcend products can be power washed to remove dirt and debris at 1500 PSI with a fan tip at least 4 inches from the surface

What is the best cleaner for Trex decking?

Trex company state that a simple DIY cleaning agent of warm, soapy water and a soft-bristle brush should clear away most stains on your Trex decking. Soil and debris, oil/grease/food (cleaned within 7 days) as well as mold and mildew can be taken care of in most circumstances. If you have any worries or issues with cleaning your deck, contact Trex directly or visit their home page for their most up to date advice on keeping your deck looking new.

Can you pressure wash vinyl/PVC decking?

While composite decking is made from a blend of wood and plastic materials, vinyl/PVC decking is most often 100% plastic. This is not an issue when it comes to pressure washing a PVC deck though. As long as you stick to the same guidelines as with composite decking and apply the pressure washer carefully, it should work fine.