Composite Decking Types: Capped, Uncapped, PVC, Hollow

Composite decking types differ in three ways: whether the board has a protective cap, whether it contains wood at all (composite vs PVC), and whether the profile is hollow or solid. Wikipedia defines wood-plastic composite as wood fiber combined with a thermoplastic such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) or polylactic acid (PLA), commonly in roughly 50/50 proportions and with cellulose content up to 70 percent. It dates the technology to 1960, when Covema of Milan patented it as "Plastic-Wood".

Manufacturers' recipes vary. Trex, for example, says its composite boards are made in the US from 95% recycled plastic film and reclaimed sawdust.

• Uncapped composite - the original form, wood fiber and plastic all the way through. Ovaeda describes it as budget-friendly and natural-looking but needing more maintenance against mold and mildew, because the wood fiber is exposed.
• Capped composite - the same core wrapped in a protective polymer shell that resists fading, staining and scratching and needs less upkeep (Ovaeda).
• PVC decking - no wood fiber at all. Trex sells Refuge as an ignition-resistant PVC board, and TimberTech sells its AZEK line as "advanced PVC".
• Hollow boards - lighter, cheaper and easier to install (Ovaeda). Trex's Enhance line uses a scalloped underside to cut weight.
• Solid boards - heavier, denser and stronger, but Ovaeda notes they are more prone to expansion and contraction.
• Grooved vs square edge - grooved boards take hidden clip fasteners for a screw-free surface; square-edge boards are screwed or nailed through the face, leaving the fasteners visible (Ovaeda).

The two largest brands sort their lines into tiers, which is what most shoppers are actually comparing.

• Trex (from its decking page, accessed 2026-09-25): Enhance is the "Good" tier with a 25-year limited residential warranty; Select is "Better" at 35 years; Transcend and Transcend Lineage are "Best" at 50 years, with Lineage adding heat-mitigating technology; Signature is the luxury tier at 50 years; Refuge is the PVC line at 50 years.
• TimberTech (collections page, accessed 2026-09-25): advanced PVC collections under the AZEK brand (Vintage and Landmark at the top price level, then Harvest+ and Harvest) and composite collections under the PRO and EDGE brands (Legacy and Reserve, then Terrain+, Terrain and Premier+, then Prime+, Prime and Premier at the entry level).

Warranty length tracks tier, so the warranty is a quick way to compare lines across brands. Read the fade-and-stain terms as well as the structural ones.

Wikipedia lists the advantages of wood-plastic composite as high resistance to rot, decay and marine borers, good workability with ordinary woodworking tools, and color without paint. It also lists the drawbacks: lower strength and stiffness than solid wood, vulnerability to UV degradation and fungal attack (the reason caps exist), damage from freeze-thaw cycles, loss of strength when it absorbs water, and a higher fire hazard than wood alone.

If you prefer real wood, the USDA Wood Handbook's decay table is the guide: ipe is in the "very resistant" group, and western red cedar, redwood (old growth) and black locust rank "resistant" or better. Preservative-treated lumber is the other common option; see our treated wood for decks guide and the ipe and western red cedar pages.

Look at a cut board end, usually at a stair tread or the end of a run:

• Real wood shows growth rings and pores or resin on the end grain. A WoodLens photo of that end will suggest the species.
• Uncapped composite shows the same speckled mix of wood fiber and plastic all the way through.
• Capped composite shows a thin, differently colored shell around a speckled core.
• PVC shows uniform plastic with no wood fiber.
• Hollow boards show open chambers or a scalloped underside.

Knowing which one you have matters for repairs: replacement boards need to match both the material and the edge profile, and a capped board cut on site leaves the core exposed at the cut.

This page was drafted with AI help, and every fact was checked against the sources listed on the page.