How to Power Wash Composite Decking


Since your decking is right outside the front of your home, it makes sense that maintaining it in good condition is high on your list of priorities. 

However, when it comes to composite decking, you can’t just use any cleaning method. Composite decking is not the most durable type of decking.

Can You Power Wash Composite Decking

That means you need to be careful not to accidentally damage it in the process of trying to keep it clean. 

The fact that composite decking can be easily damaged has led a lot of people to ask: ‘can you power wash composite decking?’ This is a question with a complex answer, so we’re going to discuss it in depth today. 

Read on to find out what composite decking actually is, the risks associated with power-washing this type of decking, how to power-wash your composite decking safely, and more. 

What Is Composite Decking?

Composite decking is a type of decking made from a combination of different materials. Most composite decking is made from plastic and wood fibers, with some bonding agents mixed in to hold these materials together. 

The point of composite decking is that it looks more like realistic wooden decking than purely plastic alternatives, but compared to wooden decking, it doesn’t need as much maintenance. 

With that being said, due to the fact that composite decking is made from different materials held together by bonding agents, it’s not as durable as wooden decking. 

Why Power Wash Composite Decking?

As you might already have figured out from the introduction of this article, there are some risks involved in power washing composite decking due to the fact that it’s not the most durable material. 

So, why would anyone want to power wash their composite decking while knowing that to be the case?

Well, first of all, power washing is an incredibly effective way to clean decking.

Due to the force of the water coming out of the pressure washer, the cleaning task can be done with minimal effort, in a very short amount of time, and you can be sure that all the moss and grime will be removed completely. 

Additionally, power washing is a very cost-effective cleaning method for any kind of decking (so long as you don’t cause any damage in the process).

While it’s true that composite decking doesn’t need as much maintenance as other types of decking, meaning that it costs less to maintain anyway, it’s still tempting to use cost-saving methods where possible. 

The Risks Of Power-Washing Composite Decking 

Before we discuss how to power-wash composite decking (because yes, it’s possible), you should be aware of the risks associated with cleaning your composite decking in this way. 

The most common problem that occurs when power-washing composite decking is damage to the surface of the deck due to the power setting being too high or the nozzle being held too near the deck.

This kind of damage is known as etching, and it’s where pressure damage causes scratches in the surface.

Even if the material of the composite decking itself doesn’t get damaged during the pressure washing process, you could still end up damaging the finish.

This can cause further issues down the line because the purpose of the finish is to protect the material underneath from moisture damage. If the finish is worn away, moisture can easily damage your decking, and this can lead to mould, which isn’t something anyone wants to deal with. 

At the end of the day, if you damage your composite decking by trying to pressure wash it, you’ll end up having to spend money repairing the damage. This negates any advantage of pressure-washing from a financial perspective.

Power-Washing Composite Decking: Step-By-Step 

If you do choose to pressure-wash your composite decking, the good news is that you can do it without causing damage, but you’ll need to be careful. 

Here’s a step-by-step guide to pressure-washing your composite decking without damaging either the finish or the material underneath: 

1. Buy A Fan Tip Nozzle 

If you don’t have one already, you should purchase a fan tip nozzle for your pressure washer. This is important because it will help to lessen the direct pressure of the water on your composite decking. 

Using a fan tip nozzle will still provide an amazing standard of cleaning, but it will stop excessive, direct pressure from etching your composite decking. 

Make sure to order your fan tip nozzle or pick it up from the store in advance of when you’re planning to clean your decking. 

Can You Power Wash Composite Decking (1)

2. Clear The Decking 

You’ll want to remove any furniture from your decking before you pressure-wash it since the furniture will only get in the way. You might also damage your deck furniture if you pressure-wash it by accident, so it’s best to get it all out of the way first. 

Once you have done this, make sure to sweep away any debris before you get out of the pressure washer. Leaves and bits of dirt left on your decking will interfere with your ability to clean properly. 

3. Read Your User Manual 

We’re going to be giving you lots of tips for how to use a pressure washer safely on composite decking, but the best way to make sure you’re using your pressure washer correctly is to check the user manual that came with it. 

If you can’t find the manual that came in the box, you may be able to find a digital copy online. In the manual, there should be instructions on how to use the different settings, and ideally, there should also be tips for using the pressure washer on various surfaces. 

See if there’s anything in the manual about pressure-washing composite decking. If there is, follow these instructions above any other instructions you find online (including the information in this article) since the information in the manual will be model-specific, which is important. 

4. Keep 12 Inches Of Distance 

Before you turn on your pressure washer, you should make sure that the nozzle is not held closer than 12 inches to the surface of the decking. 

The closer you hold your pressure washer relative to the deck surface, the more likely you are to damage it because you’re effectively increasing the pressure by holding it closer.

5. Test A Small Area 

It’s a good idea to test your pressure washer on a small area of your decking before you get started with cleaning the entire thing. Ideally, this should be a small patch of decking in the corner or somewhere that’s not clearly visible just in case it goes wrong. 

Before you do this, read through the other steps below since you’ll need to follow all the precautions, even for the test run. This will give you an accurate idea of how you can expect your deck to hold up when you use the pressure washer correctly. 

6. Check What is the Maximum Pressure

Pressure washers have some pretty intense pressure settings, but when it comes to your composite decking, you want to stay away from the higher settings. The higher PSI settings are likely to damage your decking even with the fan nozzle attachment.

We recommend sticking with a maximum of 1500 PSI – even less if possible. 1500 is the absolute most you should use in terms of pressure.

It’s best to start at a lower setting than this (say, 1000 PSI) and only go up to 1500 if the lower settings aren’t delivering an effective clean. 

Also, check the composite decking brands’ instructions regards to water pressure and distance from the decking. Brands may vary in their recommended settings.

BrandMax PSI of Pressure WashingMinimiumDistance from Decking
DeckoratorsOpens in a new tab.“Lowest Setting”8″
FiberonOpens in a new tab.2500 psi12″
FortressOpens in a new tab.1500 psi18″
MoistureShieldOpens in a new tab.1300 psi10″
Tangent’sOpens in a new tab.Not recommended
TimbertechOpens in a new tab.1500 psi?
TrexOpens in a new tab.3100 psi8″
TruNorthOpens in a new tab.1100 psi10″
WearDeckOpens in a new tab.1500 psi?
WolfOpens in a new tab.2500 psi12″
ZuriOpens in a new tab.2700 psi?
Composite Decking Pressure Washing Levels

The chart shows a large variance among composite dekcing brands.

The lowest is TruNorth with a max pressure of 1100 psi while keeping the tip 10″ from the surface.

On the higher range is Trex with a max of 3100 psi as close as 8″.

The outlier is Tangent, which is a good reminder to always check with the manufacturer. Some do not recommend cleaning their decking with a pressure washer at all.

7. Clean With The Grain 

It’s important to clean in the direction of the grain, not against it. Cleaning against the grain using a pressure washer is a recipe for disaster (read: etching) when washing composite decking. 

Before you start cleaning, take the time to check the direction of the grain and plan out how you’re going to clean methodically with the grain, from one side of the decking to the other. 

Can You Power Wash Composite Decking (1) (1)

8. Allow To Air Dry 

There’s no reason to rush the drying process after cleaning your composite decking, and there’s no effective way to do so, either. Therefore, the best way to dry your decking after power washing is simply to allow it to air dry. 

This ensures that you won’t cause any heat or friction damage trying to dry it in other ways.

If you decided that pressure washing is for you and your deck but don’t have a pressure washer.

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Stanley SHP2150 Portable Electric Pressure Washer, 2150 PSI, 1.4 GPM, 13 AMP, with Metal Lance, Foam Cannon, Quick Connect Gun, 25' Hose, 25lbs
  • HIGH PRESSURE FOAMER INCLUDED: The specially designed detergent bottle doubles as a high pressure foamer to get tough stuff loose or remove deep-down stains.
  • POWERFUL CLEANING FORCE: Perfect for siding, decks, cement, pavement, pools, outdoor furniture, cars, trucks, RVs, ATVs, garbage cans, animal cages and more.
  • LEAKPROOF CONNECTIONS: Professional grade brass garden hose connector and 22mm connections. The connection of choice for professional level accessories.
  • ATTACHMENTS FOR MOST COMMON PROJECTS: Pressure washer gun, pressure washer wand, 25 foot high pressure hose, foam cannon/detergent tank, 4 quick connect nozzles and o-ring replacement kit.

The Stanely is small, quiet (for a pressure washer) and light to move around. comes with multiple tips for many applications around the house.

Alternatives To Power-Washing For Composite Decking 

If you just don’t want to take the risk of damaging your composite decking with your pressure washer, or if the test clean doesn’t go well, the good news is that there are some alternatives. 

For a safe cleaning option that uses no water pressure but will be highly effective at removing dirt and moss, you could try a solution of water and vinegar.

You can apply this by hand with a sponge, which will take longer than power washing, but it will also be much less abrasive and the results will be worth it. 

Alternatively, if you want to use something even gentler (ideal for composite decking that isn’t particularly dirty) regular soap and water should do the trick. A common brand is Dawn which can be used to clean composite decking. Opens in a new tab.

Again, it’s best to apply this with a sponge, but make sure to use the soft side of the sponge rather than the scouring pad. 

While you might be tempted to remove tough dirt using a solution containing bleach or chlorine, this is not a good idea when it comes to composite decking because the harsh chemicals can damage the finish on your decking, leaving it exposed to water damage and mould. 

Frequently Asked Questions 

Can I Use A Bristle Brush To Clean Composite Decking?

If you’ve decided against power washing your composite decking and want to use either a soap or vinegar cleaning solution instead, you can use a bristle brush to apply it.

Just make sure you use a soft bristle brush because firm bristles may damage the finish of your decking and open up the material underneath to water damage. 

How Do You Get Green Algae Off A Composite Deck?

Green algae is one of the most stubborn types of buildup to remove from composite decking, so it’s one situation where using a power washer or pressure washer is a good idea. 

Clear your deck first, set your pressure washer to a maximum of 1500 PSI and put the fan nozzle on.

Then, apply a cleaning solution and leave it to sit for a few minutes before using the power washer to rinse it off. Once all the green algae is washed away, simply let your deck air dry. 

Can I Use Bleach On Composite Decking?

While it can be tempting to use bleach on your composite decking if it’s very dirty, we don’t recommend doing so because bleach is a very harsh chemical that can not only damage the finish of your decking but actually eat into the structure of the material. 

This can discolour your deck at best, but it can actually damage it structurally, which will be unsightly and costly to repair. 

Final Thoughts 

It is possible to power wash composite decking, but there are risks involved in doing so. 

If you power wash your composite decking on a high setting, hold the nozzle too close, don’t use a fan attachment, or clean against the grain, you could damage the finish on your decking and even etch the decking itself. 

To avoid damaging your composite decking with a power washer, you must set it to below 1500 PSI, use a fan attachment, hold the nozzle at least 12 inches away from the surface, and clean with the grain. We recommend doing a test clean on a small area of the decking first. 

Ryan Nickel

A Red Seal carpenter, passionate about building decks to be enjoyed.

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