When Not to Sand Composite Decking: Safer Prep Alternatives

Composite decking has become a go-to for homeowners seeking low-maintenance outdoor living spaces. But when boards get weathered or stained, the first instinct is often to sand them smooth. That’s a mistake—sanding can melt the plastic binders, expose fibers, and void the manufacturer’s warranty. Instead, safe prep alternatives keep your deck looking sharp without permanent damage.

Why sanding composite decking is risky

Unlike solid wood, composite decking blends wood fibers with plastics. High-friction sanding heats the surface, causing:

• Melting & glazing: Heat softens polymers, leaving shiny, uneven patches.
• Fiber pull-out: Aggressive grits can yank wood fibers, exposing fuzz you can’t hide.
• Warranty issues: Many brands void coverage if boards are sanded or planed.

Tools & materials you’ll need instead

• Plastic-safe deck cleaner or oxygenated bleach
• Soft bristle brush or broom
• Low-pressure power washer (under 1500 psi, wide fan tip)
• Protective gloves, goggles, and non-slip footwear
• Non-abrasive scrubbing pads for spot cleaning

Safe surface prep sequence

1. Clear & inspect. Remove furniture, sweep debris, and check for mold, mildew, or grease spots.
2. Apply cleaner. Mix a composite-safe deck cleaner per instructions. Apply generously with a pump sprayer or watering can.
3. Agitate gently. Use a soft brush to loosen grime. Scrub with the board grain to avoid fuzzing the fibers.
4. Rinse thoroughly. Use a garden hose or low-pressure washer (wide fan tip). Keep the nozzle at least 12 inches away.
5. Spot treat stains. For grease or tannin stains, use non-abrasive pads with cleaner; avoid sanding.
6. Dry & inspect. Let boards dry fully. Repeat spot treatment if stains remain.

Special cases

• Mold or mildew: Use oxygenated bleach—not chlorine—to avoid damaging plastic.
• Grease/oil stains: Address quickly with a composite-approved degreaser.
• Scratches: Heat guns or replacement boards are safer than sanding.

Pro tips

• Avoid pressure washers above 1500 psi; high pressure can gouge boards.
• Work in cool, shaded conditions to prevent streaking as cleaners dry.
• Always rinse thoroughly—residue left behind attracts dirt faster.
• Keep spare boards for swapping heavily damaged sections.

Aftercare

• Wash the deck twice a year to prevent buildup.
• Use mats under grills to catch grease.
• Avoid dragging furniture; use pads to reduce scratches.

FAQs

• Can I sand lightly with fine grit? No—any sanding risks melting or fuzzing. Stick to cleaning methods.
• What about painting or staining? Most composite boards don’t accept coatings well. If you must, use products specifically labeled for composite surfaces.
• How do I remove deep scratches? Minor ones may fade over time; deeper damage usually requires board replacement.

Video: Cleaning composite decking safely

Bottom line: Don’t sand composite decking. Instead, clean with the right products, scrub gently, and rinse thoroughly. These alternatives protect the surface, maintain your warranty, and keep your deck looking great for years.