Composite decking — Trex, TimberTech, Fiberon, and the rest — is marketed as "low maintenance." That doesn’t mean "no maintenance."

In the PNW, rain, shade, and algae can turn a composite deck slippery fast. Homeowners grab a pressure washer, crank it to max power, and blast away… and by spring, the deck is scarred, streaked, or the warranty is void.

Let’s walk through what actually works, what doesn’t, and how to keep your deck in great shape for years.

First Rule: Always Check the Manufacturer’s Recommendations

Composite decking isn’t all the same. Different brands have different materials and different cleaning limits.

Trex, for example, allows up to 3100 PSI on their newer boards — but their older boards will void the warranty if you pressure wash them at all.

Every brand publishes cleaning guidelines on their website. That’s the first place you should look before you touch a pressure washer, bleach, or chemical cleaner.

What Trex Says (The Most Common Brand)

Trex’s cleaning guidance: A pressure washer up to 3100 PSI can be used with a fan tip and kept at least 8 inches away. They recommend soap + a soft bristle brush + a full rinse so dirty water doesn’t dry and leave a film.

For mold: Trex recommends a cleaner containing detergent + sodium hypochlorite (standard bleach). It works — but it may lighten the surface color.

For older Trex decking: They explicitly say do NOT pressure wash it. Doing so can damage the surface and void the warranty.

So the age of your deck matters.

Each Brand Has Its Own Rules

Here’s a simplified homeowner-friendly chart comparing common brands:

This is why homeowners get confused — every brand is different.

So Let’s Answer the Questions Homeowners Ask Most

How do you clean composite decking?

Typically with one of these methods:

Soft washing with the right cleaner
Low-pressure rinsing
Soap + water + a soft bristle brush
Light pressure washing only if allowed by the manufacturer

The right method depends on the brand, the age, and the condition of your deck.

And always — always — test an inconspicuous spot first.

Can I use bleach on a Trex deck?

Yes — but with caution.

Trex allows cleaning with sodium hypochlorite (bleach) to remove mold, but it can lighten the color of the boards. This is why test spots are so important.

Start with a light mix and increase strength only if needed.

Is it safe to use high pressure on composite decking?

Not always.

Some brands allow 1500–2500 PSI. Some allow 3100 PSI. Some allow none. Too much pressure can:

Etch the surface
Leave permanent streaks
Strip protective layers
Void the warranty

Most homeowners simply don’t know how quickly composite can be damaged.

Will pressure washing or soft washing void the warranty?

Yes, it can if you go outside their guidelines.

If a brand says “no pressure washing” and you do it anyway, any damage that shows up later won’t be covered.

This is the biggest reason homeowners call us — they want it done right and safely.

Bottom Line for Homeowners

Cleaning a composite deck isn’t complicated, but it is easy to mess up if you don’t know the brand’s limits.

If you want a safe, long-lasting clean without risking damage or voiding the warranty, we can help.

Spring Clean uses manufacturer-approved methods for every brand, and we always start with test spots to protect your deck’s finish and color.

If you want your composite deck cleaned the right way, let us know!

How to Clean Composite Decking the Right Way