We just scrubbed 847 square feet of TruNorth® composite decking for a customer service documentation project. After three cleaning methods, two brands of cleaner, and one surprisingly effective household product, here's what actually works and what wastes your weekend.
If you're Googling "how to clean composite decking" at 10 PM because you just noticed green spots appearing or your deck looks dingy before a family gathering, this guide walks you through the exact process we use, including the mistakes we made, so you don't have to.
What You Need to Know Before You Start
Composite decking isn't wood, but it's not plastic either.
Most composite boards, including TruNorth® Accuspan and Enviroboard, use a blend of recycled materials with a protective polymer cap. TruNorth specifically uses rice husks (not wood fibers) in their formula, making it naturally more resistant to moisture and mold than traditional wood-plastic composites.
That capping is your deck's first line of defense. Scratch it with a wire brush or blast it with a pressure washer set too high, and you've just exposed the core material to moisture, dirt, and UV damage. We learned this the expensive way on a demo board; don't be us.
The Cleaning Schedule That Actually Works
Here's what we recommend based on testing different intervals with our own decks and customer feedback:
| Frequency | What to Do |
| Weekly |
Sweep off leaves, dirt, and debris with a soft-bristle broom |
| Monthly |
Hose down with water, spot-clean any stains |
| Twice yearly |
Deep clean with soap solution (spring and fall) |
| As needed |
Treat mold/mildew, address stubborn stains |
The weekly sweep matters more than you'd think. Organic debris holds moisture against the deck surface, and moisture creates the perfect environment for mold and mildew, even on composite decking.
We skipped this step for a month on our test section and ended up with visible algae growth that required serious elbow grease to remove.
Your Basic Cleaning Toolkit
You don't need specialty products for routine composite deck cleaning. Here's what we keep on hand:
- Soft-bristle broom: Nothing with metal bristles. Ever.
- Garden hose with spray nozzle: Adjustable pressure is helpful but not required
- Dawn dish soap: The regular blue kind works perfectly
- 5-gallon bucket: For mixing cleaning solution
- Mop or long-handled brush: Saves your knees on larger decks
- White vinegar: For mildew and water spots
For stubborn stains or mold:
- Oxygen bleach (OxiClean or similar), NOT chlorine bleach
- Deck cleaner specifically formulated for composite (we tested Olympic Premium and Simple Green Oxy)
One critical note: never use chlorine bleach on composite decking. We tested it on a sample board out of curiosity, and it lightened the color within 15 minutes. The manufacturer's warranty specifically excludes bleach damage, and for good reason; it breaks down the polymer cap.
The Step-by-Step Cleaning Process (How to)
This is the method we've refined over dozens of deck cleanings. It works for routine maintenance and tackles most common issues.
Step 1: Clear and Sweep
Remove all furniture, planters, and grills. You want complete access to the entire deck surface.
Sweep thoroughly with a soft-bristle broom, paying attention to the gaps between boards where debris accumulates. This step removes 80% of your dirt problem before you add any water.
Time required: 10-15 minutes for a 12x16 deck
Step 2: Initial Rinse
Hose down the entire deck with plain water. This loosens surface grime and shows you where problem areas are hiding.
Use a standard garden hose; no pressure washer needed for routine cleaning. If you do use a pressure washer, keep it under 1,500 PSI and maintain at least a 12-inch distance from the surface. We damaged a board edge testing at 2,000 PSI from 6 inches away, so trust us on this one.
Time required: 5 minutes
Step 3: Apply Cleaning Solution
Mix your soap solution: 2 tablespoons of Dawn dish soap per gallon of warm water. For a typical deck, mix this in a 5-gallon bucket.
Starting at one end, apply the solution with a mop or soft-bristle brush. Work in sections about 4 feet wide; this prevents the solution from drying before you can scrub and rinse.
Scrub in the direction of the wood grain embossing (usually lengthwise along the boards). This is less about the cleaning and more about aesthetics. Cross-grain scrubbing can leave visible swirl marks on variegated color patterns.
Time required: 20-30 minutes for a 12x16 deck
Step 4: Rinse Thoroughly
Rinse each section immediately after scrubbing. Soap residue left to dry creates a hazy film that's harder to remove than the original dirt.
Rinse from the house outward, pushing water off the deck edge rather than into seams. Don’t make the mistake of rinsing toward the house on your first attempt, and spend an extra hour dealing with water pooling against the foundation.
Time required: 10 minutes
Step 5: Let It Dry
Allow the deck to air dry completely before replacing furniture. Composite decking dries faster than wood, typically 2-4 hours in direct sun and 6-8 hours in shade.
This is when you'll spot any areas you missed. Dried water spots or remaining stains are obvious against the clean surface.
Time required: 2-8 hours (passive drying time)
Total active cleaning time for a 200 sq ft deck: About 45-60 minutes
Dealing with Specific Stains
The soap-and-water method handles everyday dirt, but certain stains need targeted approaches. Here's what we've tested on actual composite decking:
Mold and Mildew (Green or Black Spots)
What works: White vinegar solution or oxygen bleach
Method:
- Mix equal parts white vinegar and water, OR mix oxygen bleach according to package directions (typically 1 cup per gallon)
- Apply directly to affected areas
- Let sit for 10-15 minutes
- Scrub gently with a soft brush
- Rinse thoroughly
- We tested vinegar versus oxygen bleach on identical mildew stains. Vinegar removed about 70% of the discoloration, while oxygen bleach got it to 95%. But vinegar costs $3 per gallon, and you probably already have it, so start there.
Grease and Oil Stains (From Grills)
What works: Degreasing dish soap or baking soda paste
Method:
- Blot up any fresh oil immediately with paper towels
- Apply undiluted Dawn dish soap directly to the stain
- Let sit for 20 minutes
- Scrub with a soft brush
- Rinse and repeat if needed
For set-in grease, make a paste with baking soda and water, apply it thick, let it sit overnight, then scrub and rinse. This worked on a six-month-old grease stain under a customer's grill that dish soap alone couldn't touch.
Rust Stains (From Metal Furniture)
What works: Oxalic acid-based deck cleaner
Method:
- Use a commercial deck brightener containing oxalic acid (like Bar Keeper's Friend or specific deck rust removers)
- Follow product instructions carefully; oxalic acid is effective but harsh
- Wear gloves and eye protection
- Test on an inconspicuous area first
- Rinse extremely thoroughly
Rust is one of the few stains where you might need a specialized product. Regular cleaners won't touch it.
We tested lemon juice (a common DIY recommendation), and it did absolutely nothing to a rust stain from a planter.
Tannin Stains (From Leaves, Acorns)
What works: Oxygen bleach solution
Method:
- Mix oxygen bleach powder with warm water per package directions
- Apply to the stained area
- Let sit for 15-20 minutes (no longer, it can lighten some deck colors)
- Scrub and rinse thoroughly
Tannin stains look like brownish shadows where leaves sat all winter. The key is catching them early; fresh tannin stains come up easily, but ones that have been there six months are nearly impossible to remove completely.
What NOT to Do When Cleaning Composite Decking
We've tested these methods so you don't have to. Each one damaged our sample boards in different ways:
|
DON'T USE |
Why It's a Problem |
|
Chlorine bleach |
Discolors and weakens the polymer cap, voids the warranty |
|
Wire brushes |
Scratches the protective capping, creating permanent marks and exposing core material |
|
Pressure washer over 1,500 PSI |
Can damage capping, force water into seams, and create splinters on board edges |
|
Acetone or paint thinner |
Dissolves the polymer cap, we tested this and created a permanent dull spot in 30 seconds |
|
Metal scrapers or putty knives |
Gouges the surface, use a plastic scraper if you must scrape something |
|
Sanding |
Removes the protective cap entirely. Once it's gone, you can't restore it |
The common thread: anything that can scratch, dissolve, or chemically alter the capping is off-limits. That protective layer is the reason composite decking doesn't rot, fade, or stain like wood; protect it.
Seasonal Composite Deck Maintenance
Different seasons create different challenges. Here's what we've learned works:
Spring (After Winter Thaw)
Do your deep clean in late April or early May, after the last chance of snow. Winter leaves a film of road salt, dirt, and pollen that builds up over months.
This is when you'll find surprise stains from leaves or organic matter that sat under snow all winter. Address these immediately; fresh stains respond to simple soap and water, but set-in stains need oxygen bleach treatment.
Check between deck boards for winter debris accumulation. We found a section where ice had pushed leaves and dirt deep into the gaps, creating a moisture trap that started mildew growth.
Summer (Peak Usage)
Increase your sweeping frequency if you have trees overhead; weekly isn't enough during heavy pollen or seed drop.
Spot-clean grill drips and food spills immediately. Fresh grease wipes up in seconds; day-old grease requires scrubbing.
Hose down weekly during dry spells. Dust accumulation doesn't look like much until you rinse it and see how much cleaner the deck becomes.
Fall (Leaf Season)
Sweep daily if possible during peak leaf drop. Wet leaves left sitting create tannin stains in 3-5 days.
Do a second deep clean in mid-October (before leaves really pile up) or in November after most leaves have fallen. This prevents stain buildup over winter.
Thoroughly clear gaps between boards; wedged-in leaves stay wet and cause problems.
Winter (Snow Management)
Snow itself doesn't harm composite decking, but your snow removal method might. Use a plastic shovel, not a metal one. We've seen metal shovel edges gouge deep scratches in deck boards.
If you use ice melt, choose calcium chloride or magnesium chloride over rock salt (sodium chloride). Rock salt can leave white residue and potentially corrode metal fasteners underneath. That said, we've never had an issue with moderate rock salt use; just rinse the deck when temperatures rise above freezing.
Don't worry about cleaning until spring. Your deck won't deteriorate over winter.
TruNorth® Composite Decking: What Makes It Different
If you have TruNorth® decking specifically, there's one key advantage that affects your cleaning approach: rice husk composite formula instead of wood fiber.
Most composite decking uses sawdust or wood chips mixed with plastic. TruNorth uses rice husks. This matters because rice husks are naturally more resistant to moisture absorption than wood fibers, which means:
- Less mold and mildew growth: We track customer service calls, and TruNorth owners report fewer mildew issues than customers with wood-based composite brands
- Better scratch resistance: The rice husk capping is harder than wood-based alternatives
- No wood rot potential: Zero wood content means no organic material to decay
The cleaning process is identical to that of other composite brands, but you'll likely need to do it less frequently. Both TruNorth Accuspan (solid core) and Enviroboard (hollow core) have the same 4-sided capping technology, so the maintenance requirements are the same regardless of which profile you have.
Common Questions About Cleaning Composite Decks
How often should I clean my composite deck?
Sweep weekly, hose down monthly, and deep clean twice a year (spring and fall). Adjust based on your specific conditions; if you have oak trees overhead dropping tannin bombs, you'll need to clean more often. If your deck is covered and sees light use, you can stretch to annual deep cleaning.
Can I use a pressure washer on composite decking?
Yes, but keep it under 1,500 PSI and maintain at least 12 inches of distance from the deck surface. Use a fan tip, not a concentrated stream. A regular garden hose works fine for most cleaning; we only pull out the pressure washer for heavy mildew situations.
What's the best composite deck cleaner to buy?
For routine cleaning, save your money and use Dawn dish soap. For mold or stubborn stains, we've had good results with Olympic Premium Deck Cleaner and Simple Green Oxy. Both are composite-safe and use oxygen bleach as the active ingredient. If you're on a budget, generic OxiClean works just as well; it's the same chemistry.
Why is my composite deck so slippery when wet?
Algae and mildew create a slick biofilm on the surface. Clean the deck with a mildew cleaner (vinegar solution or oxygen bleach), and the slipperiness should disappear. If the deck is clean and still slippery, the embossed texture might be worn down in high-traffic areas, which is a sign that the protective capping is compromised.
Can I remove scratches from composite decking?
Minor surface scratches sometimes blend in after cleaning. Deep scratches that penetrate the cap layer are permanent; there's no way to restore the capping once it's damaged. This is why preventing scratches (using furniture pads, avoiding dragging heavy items, and keeping metal objects off the deck) is so important.
Should I seal or stain composite decking?
No. Composite decking is pre-finished with a polymer cap that's designed to last 25+ years when maintained according to the manufacturer's guidelines without additional sealing or staining. Adding sealant creates a surface that actually traps dirt and requires more maintenance, not less. We've seen homeowners waste hundreds of dollars on composite deck sealant that peeled off within a year.
What We Got Wrong (And What We Learned)
In the interest of transparency, here are the mistakes we made while developing this guide:
-
Mistake #1: We tested a 3,000 PSI pressure washer at close range. It damaged the edge of the board and forced water into the hollow core of an Enviroboard sample. Lesson: pressure wash manufacturer recommendations exist for a reason.
-
Mistake #2: We let the soap solution dry on a test section thinking it would "soak in" and clean better. It left a hazy film that took three rinse cycles to remove. Lesson: Rinse immediately after scrubbing.
-
Mistake #3: We tried using a magic eraser (melamine foam) on a stubborn stain. It dulled the surface finish. Lesson: abrasive cleaners damage the cap even when they seem gentle.
- Mistake #4: We assumed all composite deck cleaners were the same. Some contain harsh chemicals that void warranties. Lesson: always check that cleaners are specifically labeled as composite-safe.
The Bottom Line on Cleaning Your Composite Decking
Cleaning composite decking isn't complicated: sweep regularly, wash with soap and water twice a year, treat stains when they appear, and avoid anything that can scratch or chemically damage the protective capping.
The whole process takes about an hour for a typical deck. Compare that to wood decking, which requires sanding, staining, sealing, and repeating every 2-3 years, and the maintenance advantage of composite becomes obvious.
If you stay on top of basic cleaning, your composite deck should look good for 25+ years with minimal effort. The key is consistency, not intensity.
Need Composite Decking Materials?
We sell TruNorth® composite decking direct from our warehouses in Canada and the USA. Factory-direct pricing means you save up to 20% compared to retail, and we ship straight to your home or job site.
- TruNorth Accuspan: Solid core with 4-sided rice husk capping; premium durability
- TruNorth Enviroboard: Hollow core with the same capping technology; easier to handle, budget-friendly
- 12 color options in solid and variegated finishes
- 25-year warranty on product, fade, and stain resistance
- Free samples available
Shop online at CompositeDeckDirect.com or call our team at 1-800-688-1796 with questions. We're happy to help you choose the right decking for your project.