What composite decking is
Composite decking is made from a blend of wood fibers and plastic, usually with a protective outer layer (capped composite) that resists staining and fading. PVC decking is made entirely of plastic. Both are sold as low-maintenance alternatives to wood: they don't need staining or sealing, won't rot or splinter, and resist insects.
Composite versus PVC
- Capped composite is the most common. It's heavier and feels more like wood underfoot. The cap layer protects against stains and fading.
- PVC is lighter, resists moisture completely, and is often used near water and in damp areas. It can expand and contract more with temperature and may cost more.
Quality varies widely between product lines. Ask to see full-size samples, not just small chips, and read what the manufacturer's warranty covers for fading, staining and structural failure.
Heat
Composite and PVC decking can get hot in direct sun, especially darker colors. In very hot climates, lighter colors and products designed to stay cooler make a noticeable difference for bare feet and pets. Shade structures and orientation also help.
The frame still matters
Composite and PVC decking sit on a structural frame, usually pressure-treated lumber or steel. The decking doesn't make the frame last longer. Framing should be rated for ground contact where it's close to the ground or hard to replace, joists should be spaced as the decking manufacturer requires (often closer for composites than for wood, and closer still for diagonal patterns), and joist tops can be protected with joist tape to slow moisture damage. Ask what the frame will be built from and how it will be protected.
Fasteners
Hidden fastener systems clip into grooved board edges for a clean surface without screw heads. Face screws designed for composite decking are another option. Use the fasteners the manufacturer specifies to keep the warranty valid.
Expansion and gaps
Composite and PVC boards expand and contract with temperature. Manufacturers specify gaps at board ends and edges based on temperature at installation. Boards installed too tight can buckle; too loose leaves wide gaps in cold weather.
Railings and stairs
Railings must be strong enough to resist a person falling against them, at a height and with openings that meet local code. Composite, aluminum, steel cable and glass railing systems are common with composite decks. Stairs need consistent riser heights, proper stringer support, handrails where required and good lighting.
Cleaning
Composite and PVC decks need periodic cleaning with water and a soft brush and a cleaner approved by the manufacturer. Clear leaves and debris from gaps so water drains and mold doesn't grow.
Questions to ask
- What product line do you recommend, and why?
- What will the frame be built from, and will joists be protected?
- What joist spacing does the decking require?
- Which fasteners will you use, and does that keep the warranty valid?
- Does the railing system meet local code, and is a permit needed?
Stairs, fascia and edges
Composite product lines include matching fascia boards to cover the frame's rim joists and stair stringers, which gives a finished look and protects the framing from sun. Stair treads need closer stringer spacing than wood. Picture-frame borders, with boards running around the deck's edge, hide cut board ends and look clean.
Lighting
Low-voltage lighting in stair risers, posts and railings makes decks safer at night. Plan the wiring before the decking goes down.