Cleaning composite decking is simple: sweep off loose debris, hose down the boards, scrub with a composite-safe cleaning solution, and rinse before it dries.
For grease stains, mold between boards, or that chalky white film that shows up after a bad rinse job, there’s a bit more technique involved, and the wrong product can make things worse.
Choosing The Right Cleaner for Composite Decking
If you have a TimberTech deck, start with their care and cleaning guide, which recommends TimberTech DeckCleaner, a bleach-free, non-toxic, biodegradable formula designed for capped composite surfaces.
One gallon diluted 1:3 (one part cleaner, three parts water) covers around 1,000 square feet of deck surface.
For mild routine cleaning, Dawn dish soap mixed with warm water is generally safe for composite surfaces, though TimberTech notes it won’t deliver the same results as their dedicated cleaner.
Important to note that cleaners labeled as “composite deck cleaners” (such as Corte Clean, Thompson’s Water Seal Oxy Action, or Olympic Deck Cleaner) are not recommended for current TimberTech capped products because the capping material on those products is not wood-plastic composite.
You should also avoid cleaners with chlorine bleach as the active ingredient. These can cause discoloration and are not compatible with composite decking finishes.
How to Clean Composite Decking, Step by Step
- Clear everything off the deck first. Furniture, planters, the grill, all of it. Missing a corner because a chair is in the way means you’ll be back out there spot cleaning again within a week.
- Remove loose debris. A leaf blower works quickly, or sweep carefully with a stiff broom. Get into the gaps between boards where pollen and leaves pack in, since that’s where mold takes hold.
- Saturate the first section with diluted cleaner and let it stand for 30 to 60 seconds.
- Scrub in both directions, with the grain and across it, so the bristles work into the board texture. Use a stiff natural-fiber brush for TimberTech Advanced PVC and a medium-to-stiff nylon brush for TimberTech Composite. Using the wrong brush can dull the surface.
- Rinse each section thoroughly before moving on, aiming the hose in the direction of the board grain.
Try to work in sections the entire time, especially in warm weather or full sun, to keep the cleaner from drying on the surface.
If you see a white film after cleaning, it almost always means the cleaner dried before the rinse was complete. Rewetting and rinsing thoroughly fixes it.
For more on why TimberTech is worth maintaining properly, our TimberTech composite decking review covers each product line in detail.
Pressure Washing Composite Decks
A power washer is useful for rinsing on larger decks, but TimberTech’s official cleaning guide is clear that it should be used for rinsing only, not as a substitute for scrubbing.
Keep these parameters in mind:
| Setting | Recommended |
| Maximum PSI | 1,500 |
| Nozzle type | Fan-tip |
| Direction | With the board grain only |
| Power washer position | Keep it off the deck surface while in use |
Spraying across the grain can damage the product. Morning or evening is the better time to clean, since afternoon heat causes the cleaner to dry on the surface before rinsing is done.
Getting Rid of Stubborn Stains
- Grease and oil need immediate attention. Use a paper towel to remove as much as possible first, then apply a compatible degreasing cleaner followed by a thorough rinse and dry. The longer it sits, the harder it gets.
- Mold and mildew respond to a cleaning agent and water with a deck brush worked into the affected area. Consistent cleaning of the board gaps is what prevents it from recurring.
- Tannin stains (from wet leaves or stacked wood) are temporary and can be cleaned using TimberTech DeckCleaner with the appropriate brush.
- White film is dried cleaner residue. Rewet the area and rinse it off.
FAQ
Can I use a pressure washer on composite decking?
For rinsing, yes. TimberTech allows power washing at a maximum of 1,500 PSI using a fan-tip nozzle, always spraying with the board grain. Power washing is not a replacement for scrubbing with cleaner and the correct brush.
How often should composite decking be cleaned?
TimberTech recommends a full cleaning at least twice a year, typically at the transition from winter to spring and from summer to fall, when temperatures are above 55°F. Spot clean spills and stains right away regardless of schedule.
Does composite decking get mold?
Composite boards resist mold growth, but organic debris packed into the gaps between boards creates conditions where it can develop. Cleaning the gaps consistently is the most effective prevention.
Is dish soap safe on composite decking?
Mild dish soap diluted in warm water is generally safe for routine cleaning. For best results, TimberTech recommends using their DeckCleaner.
What causes white film on composite boards after cleaning?
The cleaner dried on the surface before it was rinsed off. Working in smaller sections, avoiding cleaning in direct afternoon sun, and rinsing more thoroughly prevent it. Once it’s there, rewet and rinse again.
You Can Spend Your Weekend Doing Other Things
If you’re not sure what you’re dealing with, or just want a professional set of eyes on the deck before you start scrubbing, we’re happy to help.
Decks on Point works with TimberTech composite decks across Westfield, Fishers, Noblesville, Carmel, and the rest of central Indiana.
A quick consultation can save you from making a cleaning mistake that affects your warranty or leaves the surface in worse shape than when you started.
Call us at (317) 903-2431 or message us here.