Composite Deck Installation in Walnut Creek

Capped vs uncapped composite

Composite boards combine wood fiber and plastic. Capped boards wrap that core in a harder polymer shell that resists stains, fading and moisture far better than early, uncapped boards, which is why most current product lines are capped. PVC boards skip the wood fiber entirely: lighter, more expensive, and very moisture-resistant.

A capped board seen end-on: the darker shell wraps the core, and the grooved edges take hidden fastener clips so no screw heads show on top.

The frame underneath still matters

Composite is decking, not structure. It goes on a pressure-treated wood or aluminum frame, and most products call for closer joist spacing than old wood decks used, tighter still for diagonal patterns or stairs. The ledger flashing, footings and connectors are what keep the deck standing; the boards just decide how it looks and wears.

Hidden fasteners clip into the board edges for a clean surface; face screws color-matched to the boards are used on picture-frame borders and stairs. Ask which system the builder uses and whether it's the one the manufacturer warrants.

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Heat in summer

Concord's NOAA normals put the July average high at about 88°F, and hillside decks often sit in full afternoon sun. Composite and PVC boards, especially darker colors, can get uncomfortably hot underfoot. Lighter colors, shade from a cover or trees, and asking the manufacturer for its heat guidance on the specific line all help.

Fire ratings: product line by product line

"Composite" does not mean fire-rated. Some lines are listed as meeting California's wildfire decking tests (State Fire Marshal Standard 12-7A-4, or ASTM E2632 with E2726) and others are not. If your deck is within 10 ft of a home in a fire hazard zone, ask for the listing or test report for the exact boards in your quote. The rules are explained on the fire-resistant decking page.

Warranties and upkeep

Read the warranty. Many capped composite lines carry 25-year or longer limited warranties. Check what they cover (fade, stain, structural), whether labor is included, and the installation conditions (spacing, ventilation, fasteners).
Cleaning. Soap, water and a soft brush handle most dirt; pollen and oak debris should not sit in the gaps.
Ventilation. Low decks need airflow under the boards to stay within most manufacturers' requirements.

Cost pointer

Composite boards alone run about $12–$22+ per square foot versus $2–$5+ for pressure-treated (Angi). Full installed ranges, size examples and resale data are in the deck cost guide; for the long-run comparison, see composite vs wood decking.

Composite questions

Is Trex fire rated?

Some composite product lines, including some from Trex and other makers, are listed by their manufacturers as meeting California's wildfire decking requirements, and others are not. Ratings belong to a specific product line, not a brand, so ask for the current listing or test documentation for the exact boards being quoted.

How much does composite decking cost installed?

Angi puts composite decking at about $15–$32+ per square foot installed, or $5,400–$11,500+ for a 360 sq ft deck (national). Raised decks, stairs, premium lines and Bay Area labor raise it.

Can composite go over my old deck frame?

Sometimes. The frame must be sound, flat and within the joist spacing the product requires; many composite boards need joists closer together than old wood decking did, especially when boards run diagonally. A builder will check the frame before quoting a resurface.