Welcome to this categorized glossary of Wood-Plastic Composite (WPC) decking terms. This guide is designed for homeowners, contractors, and designers to use a consistent professional language when selecting materials, installing, and maintaining WPC-dekken. Each term includes a concise definition to facilitate quick reference.
Board Types and Profiles
- WPC / Wood-Plastic Composite: A decking material composed of wood fiber and plastic, offering the appearance of wood with enhanced durability and outdoor performance.
- Capstock / Capstock Thickness: The outer protective layer on WPC boards that provides UV resistance, color stability, and surface durability; thickness influences longevity and cost.
- Capstock Colors: The color options applied to the capstock to achieve desired aesthetics and fade resistance.
- Core: The internal material composition of a board, typically a mix of wood fibers and plastics, determining strength and stability.
- Hollow Core: A board with hollow cavities inside to reduce weight and cost, usually with lower stiffness than solid cores.
- Solid Core: A board with a continuous solid interior, offering higher stiffness and impact resistance but greater weight.
- Extruded: A manufacturing process where the board is formed by pushing material through a shaped die, producing uniform cross-sections.
- Coextruded: A process where the core and capstock are extruded separately and then bonded, often yielding thicker capstock and more uniform weathering.
- Embossed / Textured / Brushed: Surface textures created to mimic wood grain and/or enhance slip resistance.
- Anti-slip Surface: Surface treatment or texture designed to improve traction, especially when wet.
- Grooved Board: A board with grooves on the underside or back to accommodate hidden fastening systems.
- Solid Edge / Square Edge: Edges finished as full thickness without grooves, seams, or chamfers.
- Tongue-and-Groove (T&G): A cladding/interlock system where boards interlock via a tongue on one board and a groove on the adjacent board for a tight seam.
- Board Profile: The overall cross-sectional shape and edge design of a board (grooved, solid edge, T&G, etc.).
- End Grain Sealer: Treatment applied to board ends to reduce water uptake and potential end-splitting (included on some products).
Installation and Substructure
- Substructure: The supporting framework beneath the decking surface, including joists, beams, and supports.
- Joists: Horizontal members that directly support the decking boards.
- Beams: Primary structural members that support the joists and distribute loads to footings.
- Joist Spacing: The distance between adjacent joists, affecting board support, stiffness, and sag resistance.
- Aluminum Framing: Aluminum substructure components offering durability, corrosion resistance, and reduced weight.
- Timber / Waterproof Substructure: Traditional wood substructure or treated wood designed for outdoor exposure.
- Hidden Fasteners: Fastening systems that attach boards without visible screws on the surface for a cleaner look.
- Face Fasteners: Screws or fasteners that are visible on the board face.
- Starter Clip / End Clip: Hidden fasteners used to secure the first and/or last row of boards for alignment and stability.
- Clip System: The complete family of hidden fastening components used with a WPC deck.
- Clip Compatibility: How well a fastening system works with a given brand or board profile.
- Plug: Decorative or protective caps that cover screw or clip holes for a clean finish.
- Expansion Gap: The intentional spacing between boards to allow for thermal expansion and moisture movement.
- Alignment / Start / End Alignment: Ensuring consistent gaps, angles, and board orientation during installation.
- Alignment Tools: Tools used to help achieve uniform spacing and alignment during layout.
- Substructure Drainage: Design features that promote drainage beneath the deck to prevent water pooling and wood/board damage.
Fasteners and Connectors
- Screws: General term for fastening hardware used to secure boards to substructure members.
- Stainless Steel Screws / Coated Screws: Corrosion-resistant screws suitable for outdoor use with WPC.
- Flush Installation: Mounting boards so the screw heads sit flush with or below the board surface for a smooth top.
- Face Fasteners: Screws that are installed on the face of the board, visible from above.
- Hidden Fasteners: Fasteners that are not visible on the surface, providing a cleaner appearance.
- Starter Clip / End Clip: Hidden edge fasteners used to secure the first and last rows.
- Clip System: The full set of hidden fastening components used with a board profile.
- Plug Color Matching: Using plugs that match the deck color for a seamless look.
- Hardware Corrosion Resistance: The durability of fasteners and metal components in outdoor, humid, or saline environments.
- Deck Screw Size: Typical lengths vary by board thickness and spacing (e.g., 1-1/4″ to 2-1/4″ or ~32–57 mm).
- Sealant / Edge Sealant: Sealants used at board edges or joints to improve water resistance and airtightness.
Surface and Aesthetics
- Embossed / Textured / Brushed: Surface treatments that imitate wood grain and enhance tactile/visual appeal.
- Texture: Visual and tactile surface characteristics of the board.
- Grip: The degree of slip resistance provided by surface texture, especially when wet.
- Fade Resistance: The ability to maintain color over time under UV exposure.
- UV Stabilizers: Additives that slow color fading and material degradation due to sunlight.
- Color Consistency / Batch Variation: Differences in color/appearance between boards or batches.
- Nosing: A decorative or protective edge piece at the end of a deck board for safety and finish.
- Fascia / Skirting: Decorative or protective boards used along the outer deck edge to provide a finished look.
Performance and Material Properties
- Moisture Content (MC): The percentage of moisture contained in the board, affecting dimensional stability.
- Acclimation: Allowing material to adjust to ambient site conditions before installation to reduce movement after installation.
- Dimensional Stability: The ability of the material to maintain dimensions with changes in moisture and temperature.
- Thermal Expansion / Heat Build-Up: Expansion and contraction behavior with temperature changes and potential heat buildup on sunny days.
- Rapid Drying: Fast moisture loss after installation that can lead to cracks or warping if not managed properly.
- Moisture Equalization: Balancing moisture across components to minimize differential movement.
- End Grain Treatment: Finishes or coatings at board ends to reduce water uptake and end-splitting.
- Warping / Distortion: Any deviation from a flat, true plane; includes cupping, bowing, twisting, and crowning.
- Cuping / Bow / Twist / Crown: Specific warp forms—cup (concave), bow (arch along length), twist (torsion), crown (convex along length).
- Warp: General term for any deviation from true flatness in a board.
- Check / Split: Surface or internal cracks; checks are often cosmetic, splits can affect structural performance if severe.
- End Splitting: Cracks that originate at the end of a board and propagate inward.
- Gapping: Gaps between boards that widen with expansion and shrink with contraction.
- Lipping: A raised edge or burr along a joint between boards.
- Joint Tightness: The snugness of joints and gaps between boards and fasteners.
- Surface Planarity: The flatness of the finished deck surface.
- Heat Build-Up: Excessive surface temperatures that can exacerbate expansion and distortion.
Maintenance and Care
- Cleaning Methods: Recommended cleaning approaches (mild cleaners, water, non-abrasive tools) to preserve surface finish.
- Routine Maintenance: Regular inspection, cleaning, sealing, and treatment as needed.
- Staining / Mold / Algae Control: Preventive and remedial measures for discoloration, mold, and algae growth.
- Repair Options: Solutions for minor cracks, surface damage, or warped boards.
- Replacement Considerations: Guidelines for when to replace boards due to damage or extensive wear.
Standards, Certification and Brand Compatibility
- Warranty / Warranty Terms: Coverage details for materials, workmanship, and installation.
- Certification: Compliance with standards (e.g., ASTM) or quality certifications.
- Batch Variation: Small color/texture differences between production lots.
- Brand Compatibility: How well components from different brands work together (especially clips and fasteners).
- Colorfastness Certification: Verification of color stability under UV exposure and environmental conditions.
Selection and Construction Considerations
- Slope / Drainage Guidance: Recommended deck slope ranges and drainage considerations to prevent water pooling.
- Ventilation / Air Gap: Adequate space for air movement to prevent moisture buildup.
- Drainage Under Deck: Design features to improve water drainage beneath the deck structure.
- Maintenance Windows: Optimal timeframes for cleaning and maintenance activities.
- Installation Direction: The recommended direction for laying boards for visual effect and drainage efficiency.
- Substructure Material Choice: Balancing durability, cost, and environmental considerations when selecting the structural framework.
ADDITIONAL WPC DECKING TERMS (UPDATED)
• Span / Maximum Span: The maximum allowable distance between supporting joists.
• Load Rating / Live Load / Dead Load: Structural load capacities of decking systems.
• Bearing Strength: The load a board can support without failure.
• Screw Holding Strength: The resistance of material to screw pull-out.
• Modulus of Elasticity: A measure of board stiffness under load.
• Poolside Rating / Wet Area Suitability: Suitability of decking for wet environments.
• Fire Rating (EN 13501 / ASTM E84): Fire performance classification standards.
• Anti-Scratch Coating: Surface treatment improving scratch resistance.
• Sound Absorption / Acoustic Property: Noise-reducing characteristics of the decking.
• Linear Expansion Rate: The rate at which boards expand or contract with temperature.
• Creep: Long-term deformation of material under sustained load.
• Spanning Deflection: The amount a board bends under load.
• Joist Tape: Waterproof tape applied to joists for longevity.
• Pedestal / Adjustable Pedestal: Height-adjustable deck support systems.
• Flashing: Metal or waterproof material used to prevent water intrusion.
• Ledger Board: Support board connecting deck structure to a building.
• Rim Joist: Outer framing joist supporting the deck perimeter.
• Joist Hanger: Metal bracket supporting and securing joists.
• Embossing Depth: Depth of wood-grain embossing for texture realism.
• Color Streaking: Multi-tone streak patterns common in capped decking.
• Heat Reflective Technology: Surface technology reducing heat absorption.
• Multi-tone Finish: Color variation within a single board for realism.
• Matte / Satin / Gloss Finish: Surface sheen levels for aesthetic choice.
• Slip Rating (R10 / R11 / P4 / P5): International slip-resistance classifications.
• Bending Strength: Maximum bending force a board can sustain.
• Impact Resistance: Ability to withstand sudden impacts.
• Power Washing Guidelines: Safe pressure limits for cleaning.
• Ice Melt Compatibility: Whether de-icing salts can be used safely.
• Under-deck Drainage System: System directing water away from under the deck.
• Drip Edge: Trim preventing water runoff from damaging underlying materials.
• Water Absorption Rate: The percentage of moisture a board can absorb.
• Heat Retention: How much heat the deck surface retains under sunlight.
