You have to expect some level of drippage anywhere you station your grill. Sometimes it leaves deep set stains in paint. In unfinished surfaces, oily spots will linger for years. 

Luckily, composite decks are built to handle outdoor living (and are much easier to clean than a traditional wood deck).

Basic Instructions: How to Clean Grease Off a Composite Deck

"Composite decking, such as Trex, is purposefully engineered to resist staining," shared Dave Kile, Owner and Deck Expert at Trex Protect. It's made from recycled plastic and wood fibers, which makes it more resistant to stains than natural wood.

  1. Get your supplies. You don’t need harsh cleaning products or heavy pressure washing to get the job done. In most cases, a bucket, access to a hose, mild soap, and a soft-bristled brush will be your go-to cleaning solution.
  2. Upgrade to a specialized deck cleaner if the grease has been there awhile. You won't always need it, but don't hesitate to try a composite deck cleaner designed for these decking materials.
  3. Scrub, scrub. Composite is durable; scrub away.
  4. Rinse when complete. "Rinse the area thoroughly with clean water to avoid leaving behind residue that can attract dirt or leave the surface looking dull," notes Kile. "For tougher spots, a mild household degreaser can help lift stubborn grease.”
Trex deck on the back of a house.
Cleaning and maintaining your backyard living spaces helps more than appearances; it'll keep the joists in better condition, too. Credit: Trex Protect

What's Hidden Beneath? A Deeper Cleaning Process to Protect Your Deck Surface

Homeowners are quick to treat the surface, but some grease spills run deep. Sometimes the greatest risk lies in the gaps between the boards, where they make contact with underlying joists and footers.

“It’s also important to check beneath the decking as grease and oils can seep through the gaps between boards and drip onto the wooden joists of the foundation," shares Kile. "If left untreated, this buildup can cause damage to the structure, so make sure the area underneath the deck is cleaned as well.”

  1. Spray between each board. A simple garden hose is usually enough to rinse away dirt and debris. Use a targeted hose nozzle to blast each gap in the board. Avoid using a power washer/pressure washing the boards; if you do try a pressure washer, use a high-angle tip, lower PSI, and keep the nozzle at least 8 inches from the boards.
  2. Treat visible mold and mildew. For a deeper clean, use a composite deck cleaner or an oxygenated cleaner that’s environmentally friendly.
  3. Rinse with clean water. Get rid of any soaps, allow it to dry, then reinspect for issues.

NOTE: Avoid chlorine bleach or sodium hypochlorite. These cleaning agents can damage composite materials over time!

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Don't Overlook Additional Deck Maintenance

Grease is just one part of deck maintenance. Seasonal cleaning helps prevent black stains, oak leaf stains, pollen and sap, and hard water marks from dulling your deck’s look.

Using a deck brightener or baking soda paste can help with tougher marks without harming composite materials.

For homeowners comparing options, it’s worth remembering that composite & vinyl decking often costs more upfront than wood; however, it saves time and money long-term because it doesn’t need regular staining or sealing.

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If you’re curious about cost, ask locally: how much is a Trex deck? Obviously, pricing for any structure can vary depending on size, design, and extras like fascia boards or deck post caps, but expect Trex composite decking to run higher than pressure-treated wood deck options. The trade-off that makes it worthwhile to many homeowners? Lower maintenance and longer lifespan.

FAQ

Can I use a pressure washer on composite decking?

Yes, but with caution! If you decide to pressure wash, keep it under 3,100 psi and use a fan tip at least 8 inches away from the deck surface. Too much pressure can damage composite wood. 

Many experts, including the ones we spoke with, recommend sticking with a garden hose and a soft-bristled brush unless you need a deeper clean.

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What’s the difference between composite decking and natural wood when it comes to grease stains?

Composite decks don’t absorb grease like natural wood. The recycled wood fibers and plastic materials resist stains, so spills stay more on the surface. With wood decks, grease can soak into the pores, often requiring wood deck cleaner or even sanding. That’s one reason composite decking has become a popular choice for outdoor living spaces and home improvement projects.