Can You Power Wash a Composite Deck: Ultimate Cleaning Guide

Table of Contents

When properly cared for, composite decks can last 25 years or more. One of the things that makes him so popular is their durability when compared to natural wood. They are low maintenance, resistant to stains, and resistant to insect damage and rot. A common question people have is whether you can power wash your composite deck. Let’s take a look at what the experts have to say.
Royal Deck Power Wash Composite Deck

Can You Power Wash a Composite Deck?

The answer to this is a little more complicated than a simple yes or no answer. If you wash your composite deck with the PSI set too high, it can damage the surface and cause water to seep into the material underneath.

If you decide that you must power wash your composite deck, there are a few things that you should keep in mind. Composite deck has a coating that seals the wood material on the inside. Using a pressure setting that is too high can break the seal and allow water to sink into the wood underneath. This can cause the composite material to swell and crack.

The first thing to avoid is using harsh brushes on the washing unit. You should always use the softest brush available. Most manufacturers recommend pressures less than 2,500 PSI and that you hold the nozzle at least 12 inches above the deck surface. This is a general recommendation, and you should consult your Owner’s Manual or warranty information for the particular brand of composite deck that is installed.

Once you have your PSI set, it is a good idea to try a test on an area of the deck that is not visible, just to make sure that everything is correct. It is also a bad idea to allow water to stand on your composite deck for long periods of time. Once you have finished power washing your deck, you should use a dry mop to clean up any water as quickly as possible.

Choosing the Right Nozzle

The nozzle you attach to your pressure washer matters just as much as the PSI setting. A 40-degree fan tip is the safest option because it spreads the water over a wide surface area and reduces direct impact on the boards. Avoid zero-degree or narrow-angle tips entirely, as they concentrate pressure in a single point and can permanently scar or gouge the surface.

When washing, always spray in the same direction as the grain of the boards, not across them. Moving against the grain can force water into the seams between boards and lift the material over time. Keeping the nozzle at least 12 inches above the surface and moving at a steady, even pace gives you the best results without risking damage.

What Is the Preferred Method for Washing a Composite Deck?

Even though pressure washing may seem like a quick solution to cleaning your deck, manufacturers often recommend washing your composite deck using a regular garden hose, soap, and a soft brush. You should use gentle, circular strokes and avoid gouging or scratching the surface. Even though this is the more time-consuming method, it assures that you will not inadvertently damage your deck by power washing. Once again, it is recommended that you thoroughly dry your deck and not allow water to stand on it for a long time.

The answer to whether you can use a power washer on your composite deck is, yes you can, but with caution. It is always best to be as gentle as possible, which is why handwashing is recommended by many deck manufacturers. If you inadvertently damage your composite deck while power washing, it could mean voiding its warranty. Royal Deck has a team standing by ready to answer any questions about your composite deck or building a new one.

Frequently Asked Questions

Can I power wash my composite deck railings the same way?

Railings can be rinsed with a pressure washer, but they need even more care than the deck surface. Balusters and post caps are more exposed to direct impact, so keep the PSI low and the nozzle at a wider angle. When in doubt, a garden hose and soft brush is the safer option for railings.

Will power washing void my composite deck warranty?

It depends on the manufacturer. Most brands allow pressure washing under specific conditions, typically under 1,500 PSI with a wide nozzle. Exceeding those limits or using the wrong technique can void your warranty, which is why checking your owner's manual before you start is always a good idea.

Is there a difference between capped and uncapped composite when it comes to pressure washing?

Yes, and it matters. Capped composite boards have a protective outer layer that handles pressure washing better than uncapped boards. Uncapped boards are more porous and more vulnerable to damage if the PSI is too high. When in doubt, stick to the lowest setting and let the technique do the work.

Can power washing remove mold and mildew from a composite deck?

Power washing alone may not fully remove mold. A composite-safe cleaning solution applied before washing works much better than pressure alone. Apply, let it sit briefly, then rinse with the washer on a low setting. Scrubbing with a soft brush first also helps loosen buildup before you rinse.