What Is Composite Decking Made Of? (Materials)
Composite decking is usually made from wood fibers or flour mixed with a thermoplastic such as polyethylene or polypropylene. Many boards add a protective polymer cap, while some products sold as composite are wood-free PVC. Recipes vary by maker, so check the product specifications. For cleaning, use only a deck-maker-approved detergent and care method.
If a board’s material is unclear, do not guess at the cleaner or scrubbing method. A composite deck is not hardwood flooring, tile, or a single standard material. Its ingredients and surface layer affect how it responds to cleaners, brushes, heat, and pressure. I use the manufacturer’s care instructions as the deciding guide because there is no universal composite-deck recipe or cleaning standard.
Composite Decking Materials and Cleaner Compatibility
Composite decking is a manufactured board, not a single material. Most wood-plastic composite boards blend plant-based fibers with plastic; capped versions add a polymer-rich outer layer. Product formulas differ, so a cleaner or tool suitable for one board may not be approved for another. Check the deck maker’s instructions before washing.
What are composite deck boards made of?
Wood-plastic composite, often shortened to WPC, combines wood flour or fibers with a thermoplastic resin. A thermoplastic is a plastic that can soften when heated during processing and harden as it cools. Common resins include polyethylene (PE) and polypropylene (PP), but brands do not all use the same formula.
Manufacturers may also use pigments for color, UV stabilizers to help limit sun-related damage, processing aids, and coupling agents. A coupling agent helps different ingredients bond. Exact proportions and additives are usually specific to the manufacturer, so one product’s recipe should not be assumed to describe another.
What is a capped composite board?
A capped board has a WPC core covered by a polymer-rich outer layer. The cap is designed to protect the core and may have an embossed grain or textured surface. It does not make all boards identical, nor does the word “capped” establish which cleaners or pressure-washing methods are safe.
Some decking sold in the composite category is made from PVC and contains no wood fiber. PVC is a type of plastic, not a wood-plastic blend. Read the product description and care guide to distinguish PVC decking from WPC and capped WPC.
| Board type | Typical material description | What to verify before cleaning |
|---|---|---|
| Uncapped WPC | Wood flour or fibers mixed with PE, PP, or another specified plastic | Approved detergent, brush type, and any pressure-washer limits |
| Capped WPC | WPC core with a polymer-rich outer shell | Approved cleaners and methods that will not damage the shell |
| PVC decking | PVC-based board; some products contain no wood fiber | Product-specific instructions for cleaners, scrubbing, and rinsing |
The material label is a starting point, not a cleaning recipe. A detergent marked “safe for decks” may still lack approval for a particular board, and a floor-cleaner dilution should not be presumed suitable for outdoor decking. Follow both the deck maker’s directions and the cleaner label.
Which cleaner is compatible with composite decking?
Use a mild detergent approved by the deck manufacturer, diluted as its label directs. There is no universal approved pH, product, or dilution ratio for composite decking. Avoid assuming that “neutral” or “all-purpose” means compatible; verify the product against the deck maker’s care instructions.
Do not use unapproved solvents or abrasive cleaners. Strong chemicals or aggressive scrubbing may alter a surface, especially a capped shell. If you cannot identify the decking product, ask the manufacturer or supplier before applying a cleaner to the full deck.
Brush, Water, and Equipment Setup
Choose tools that loosen dirt without cutting into the board surface. Cool-to-lukewarm water and a soft nylon brush are common conservative choices, but the product maker’s directions take priority. Brush design, pressure-washer settings, and nozzle distance are not universal standards for all composite boards.
A soft brush helps lift loose soil from grain and embossing without relying on a scouring pad. Avoid wire brushes and abrasive pads. They can scratch or change the finish, and damage to a capped shell can leave permanent differences in texture or gloss.
| Equipment | Practical starting point | Important limit |
|---|---|---|
| Broom | Soft bristles for dry debris | Do not grind grit into the boards |
| Brush | Soft nylon bristles | Confirm the maker’s approved brush type |
| Water | Cool to lukewarm | Avoid unapproved hot-water methods |
| Pressure washer | Use only if the maker allows it | Pressure, nozzle, and distance limits vary by product |
| Cloth or mop | Use only if listed as suitable | Microfiber GSM, weave, and mop specifications are not universal deck standards |
Pressure washing deserves particular care. Too much pressure, or a nozzle held too close, can scar a surface or strip a capped polymer shell. If pressure washing is permitted, follow the manufacturer’s exact limits for equipment, nozzle, distance, and technique. If those limits are not available, do not improvise.
Step-by-Step Deck Cleaning Technique
A controlled wash has four parts: remove dry debris, apply approved cleaner, rinse fully, and let the deck air-dry. This order limits the chance of dragging grit across the surface or letting detergent dry on the boards. Follow the deck maker’s instructions if they differ from this general sequence.
- Dry-prep the deck. Sweep away leaves, grit, and loose debris with a soft broom. Clear board gaps and drainage paths so water and debris can move through as intended.
- Mix and apply cleaner. Use a deck-maker-approved mild detergent at the dilution on its label. Do not strengthen the mix or substitute a floor-cleaner ratio.
- Brush gently. Use a soft nylon brush, working along the board grain or embossing. Apply enough pressure to loosen soil, not enough to abrade the surface.
- Rinse thoroughly. Rinse with clean water before the cleaning solution dries. Remove visible suds and loosened soil. Repeat only as the manufacturer permits.
- Allow the deck to dry. Let it air-dry while keeping drainage and ventilation paths clear. There is no universal deck dry-time limit; weather, shade, airflow, and board design all affect drying.
If a patch remains dirty after one wash, first check whether cleaner dried on the boards or rinse water left soil behind. Do not respond by switching to a harsher chemical or increasing pressure without checking the product instructions. A test in a small, inconspicuous area can help reveal an unwanted surface change, but it does not replace manufacturer approval.
Cleaning-Tool Rinsing and Maintenance
Clean tools after each wash so they do not carry grit or detergent into the next job. Rinse the brush, bucket, and any washable cloth with clean water, then let them dry. A dirty tool can reapply loosened soil or scratch a surface, even when its bristles were suitable at the start.
Inspect the brush for trapped grit, damaged bristles, or embedded debris before using it again. Replace a tool if it has become abrasive or contaminated with an incompatible cleaner. Store products in their original containers and follow their labels; never mix cleaners unless the manufacturers specifically direct it.
Material-Based Examples: Choosing the Safer Method
These are practical decision scenarios, not claims about a particular brand or tested deck. They show how to apply material information before cleaning. The correct final method still depends on the board maker’s care guide, especially when a cap, finish, or cleaner is involved.
Scenario: The board is identified as capped WPC
A homeowner finds a product label that identifies a wood-plastic core and protective cap. The cap matters because abrasive brushing or excessive pressure may leave a visible change. The homeowner checks the manufacturer’s approved detergent and brush, then uses those directions rather than a generic deck-cleaning recipe.
Scenario: The product is identified only as “composite”
A builder has no brand or model information, and the word “composite” does not say whether the board contains wood fiber, has a cap, or is PVC-based. The builder avoids solvents and pressure washing, then contacts the supplier or maker for identification and care instructions before choosing a cleaner.
Scenario: A rinse leaves a dull or hazy patch
A homeowner sees a dull area after washing a capped board. That appearance alone does not identify the cause. The homeowner avoids scouring it, checks whether detergent dried on the surface, and consults the product care guide before repeating the wash or trying another cleaner.
Conclusion: Identify the Board Before Choosing a Cleaner
Composite decking may be WPC, capped WPC, or a PVC-based product, and its additives and surface treatments vary. Start with the product label and manufacturer’s maintenance guide. Use the approved mild detergent, labeled dilution, permitted tools, and specified rinse method. Do not treat a general cleaning tip as a product-specific instruction.
Frequently Asked Questions
Is composite decking made of wood or plastic?
Most wood-plastic composite decking combines wood flour or fibers with a thermoplastic such as PE or PP. However, formulas vary, and some boards marketed alongside composite products are PVC-based and contain no wood fiber. Check the product specifications rather than relying on the category name alone.
Does every composite deck have a protective cap?
No. Some WPC boards are capped with a polymer-rich outer layer, while others are not. A cap may change the board’s surface and care needs. Check the product guide for the board type and approved cleaning methods before choosing a brush, detergent, or pressure washer.
What additives can be in composite decking?
Depending on the product, makers may use pigments, UV stabilizers, processing aids, and coupling agents. These can support color, production, or bonding between ingredients. The exact additives and amounts are manufacturer-specific, so a general ingredient list cannot confirm the recipe of a particular deck board.
What pH cleaner should I use on composite decking?
There is no universal approved pH for composite-deck cleaners. Use a mild detergent approved by the deck manufacturer and follow the cleaner’s labeled dilution. Do not assume that a neutral floor cleaner, household cleaner, or product marketed for decks is suitable for every board.
Can I use a floor cleaner on composite decking?
Not without checking the deck maker’s instructions. Floor-cleaner dilution and surface-care directions are not automatically suitable for outdoor decking. A cleaner may leave residue or affect a board’s surface. Choose a product approved for the identified deck and follow its label.
Can I pressure-wash composite decking?
Only if the deck manufacturer permits it and you follow its limits. Pressure, nozzle type, and nozzle distance vary by product. Excessive pressure or a nozzle held too close can scar a board or damage a capped shell, causing a lasting texture or gloss difference.
Which brush is safest for composite decking?
A soft nylon brush is a cautious general starting point, unless the deck maker specifies another tool. Avoid wire brushes and abrasive pads because they can scratch or alter the surface. Brush along the board grain or embossing, using only enough pressure to loosen dirt.
Does composite decking need to air-dry for a set time?
There is no single dry-time limit for all composite decks. Drying depends on conditions such as airflow, shade, weather, and drainage. After rinsing, allow the deck to air-dry with gaps and drainage paths clear, and follow any product-specific directions.
Can I use the same cleaning method on WPC and PVC decking?
Do not assume so. WPC may contain wood fibers and plastic, while PVC decking may contain no wood. Surface texture and coatings also differ. Identify the product and follow its care instructions, including the approved detergent, tools, and any limits on pressure washing.
(This article was written by one of our staff writers, Gregory Hayes. Visit our Meet the Team page.)
