While pressure washing is an effective cleaning method for composite decks, it’s not always the best DIY task, especially for larger or delicate surfaces. When in doubt, it’s best to call a pro to avoid costly damage. Regular cleaning of composite decks, especially after seasonal climate shifts, will prevent stains and other damage from setting in and staining from happening.
There are multiple methods to clean composite decking, and each has its benefits. But pressure washing is the go-to choice for every professional. Why? Pressure washing quickly removes deep-set grime, mold mildew, and stains without damaging the composite surface when done correctly.
Pressure Settings
Some areas may require more rigorous scrubbing with a scrub brush than others, but regular cleaning of all these residues should be performed using power washers at appropriate pressure settings. So, the most important factor is adjusting the pressure. Here are the details:
- Recommended PSI: 1,500 to 2,000 PSI
- Maximum Safe PSI: Do not exceed 3,100 PSI
- Nozzle Type: Use a fan tip (25- or 40-degree)
- Distance: Keep nozzle 8–12 inches from the surface
- Angle: Spray at a slight angle, not directly downward
- Test First: Always test on a small, hidden area before full cleaning
Precaution: Too much pressure could damage the deck surface, causing potential issues to arise. This is especially important to consider with capped composite decking, which, while being one of the most efficient decking materials available, requires careful handling to maintain its protective outer layer.
Nozzles
There are lots of benefits for pressure washing your house, but it will need some considerations. Your choice of nozzle can have an enormous effect on how forcefully water hits your deck surface. A narrower spray pattern concentrates power, while wider patterns disperse it more evenly. When selecting a nozzle, always choose one with the widest coverage for the gentlest approach.
So, 40-degree fan nozzles will work great for most situations and won’t scar or etch soft surfaces like wooden decking surfaces. Using the wrong nozzle or applying too much pressure can easily damage composite decks. If you’re unsure, a professional service can safely assess the right equipment for your specific deck.
Precaution: Be mindful not to damage the exterior building material by overusing too high of a pressure setting or getting too close. Getting too close could cause etching that exposes it to moisture or sun damage that voids its warranty.
Water Temperature
When it comes to cleaning composite decking, water temperature matters more than you might think. While cold water works fine for light cleanups, warm or hot water can make a big difference when you’re dealing with grease, mildew, or ground-in grime. Just don’t go overboard—extreme heat can damage the trex decking surface.
Why water temperature matters:
- Helps break down oily or sticky residues
- Improves detergent effectiveness
- Loosens tough grime more easily
Temperature tips based on cleaning needs:
- Cold water (under 80°F): Light dirt and quick rinse jobs
- Warm water (100–120°F): General cleaning and mildew removal
- Hot water (120–140°F): Grease, sap, or stubborn buildup
As the temperature matters, you should know the best time to pressure wash your house.
How to Pressure Wash a Composite Deck?
As we have now learned the primary settings of pressure washers, let’s jump to the process of pressure washing a composite decking. When cleaning composite and wood decking, it is important to use the appropriate pressure settings and techniques to avoid damage while removing dirt, mold, and stains. Proper care ensures the longevity and appearance of both types of decking materials. We use a soft washing method to clean the composite and wood deckings so that they don’t get damaged by high pressure of water.
Sweep
Like all outdoor surfaces, the best way to keep a composite deck in excellent condition is to sweep it regularly. This prevents dirt from getting trapped between individual deck boards, where it may be harder for even a deck brush alone to clear away.
For routine maintenance, soap and water cleaning is highly effective and gentle on the decking material. For minor spots or spills, using a dry paper towel to blot the area can help prevent stains before they set in.
Once your deck has been cleaned, use your pressure or power washer to give it an in-depth scrub. Be sure to use low-pressure settings and avoid getting too close to its surface. High-pressure washing could strip away its outer vinyl layer and leave moisture-prone core material exposed.
Apply The Cleaner
Next, apply a small amount of your manufacturer-recommended cleaner to a brush or broom and begin cleaning the deck. Working the cleaner into the surface using soft bristle brushes. Be careful to scrub stained areas or mold spots thoroughly with it.
You should then rinse your deck thoroughly using a garden hose in order to get rid of any remaining cleaning agents. Clean your deck regularly after extreme and seasonal changes to avoid hard water stains, mildew growth, and even rust formation. Routinely cleaning with a hose and brush also prevents food and beverage stains.
Avoid harsh chemicals, acidic cleaners, and bleaches, as these can damage the surface of your deck and void its warranty. For stubborn stains or deeper cleaning jobs, check with your deck manufacturer’s approved list of stronger cleaners for additional support.
Rinse
Once you’ve scrubbed the deck with a cleaner, it’s time to rinse everything off the right way. Skipping this step or doing it too quickly can leave behind residue that attracts dirt or causes discoloration over time. When you power wash composite decking, proper rinsing is essential to avoid buildup and maintain the deck’s appearance.
Here’s how to rinse your composite deck properly:
- Use a garden hose or a pressure washer on the lowest setting
- Start at one end of the deck and work your way across in sections
- Keep the nozzle 8–12 inches from the surface at all times
- Rinse along the grain of the boards to help flush out residue
- Make sure to fully remove all soap or cleaner—don’t let it dry on the surface
- Pay extra attention to cracks and board gaps where cleaners might collect
A thorough rinse ensures your deck not only looks great but stays protected long-term.
Conclusion
Pressure washing is one of the most effective ways to restore the appearance of your composite deck—when done right. Before you start, clear away any loose debris using a broom or a plastic shovel to avoid scratching the surface. When you spray deck boards with a pressure washer, be sure to keep the nozzle at the recommended distance and use a fan tip to gently clean without damaging the wood fiber core beneath the protective layer.
Let the Pros Handle the Dirty Work
Don’t risk damaging your deck with DIY mistakes—leave it to the experts. At Blueline Pressure Washing, we know how to clean composite decking safely and thoroughly. Our trained technicians use the right tools for pressure washing, pressure levels, and cleaning solutions to make your deck look brand new without compromising its integrity.
Call today or book online to schedule your pressure washing service and let your deck shine again—without the guesswork!
