Composite Decking Seattle
The most popular material in King County — and the most common recommendation we make. Wood look, zero maintenance, no staining or sealing. Trex Transcend, TimberTech Legacy, and Fiberon Paramount all installed by our crew.
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The Most Popular Decking Material in King County
Wood-Look Finishes
Modern composite decking mimics the look of real hardwood with multi-tonal color variations and realistic wood grain textures.
25+ Year Warranty
Industry-leading manufacturer warranties protect your investment. Most composite boards are warranted against fading and staining.
Slip Resistant
Composite decking provides excellent traction even when wet — an important safety feature for Seattle's rainy seasons.
Capped composite is the most popular decking material in King County — and the most common recommendation we make. It provides the natural wood aesthetic that Seattle homeowners want without the maintenance cycle that Pacific Northwest weather demands: no staining, no sealing, no annual treatment. For the majority of residential lots in Bellevue, Redmond, Sammamish, and Kirkland, capped composite at $22–$38/sqft installed is the right answer.
- paymentsCost in King County: $22–$38/sqft installed for a standard residential composite deck. Premium capped boards (Trex Transcend, TimberTech Legacy) run toward the high end; mid-tier capped boards (Fiberon Paramount) deliver equivalent performance at 10–15% less cost.
- location_onBest applications: Standard residential lots in Bellevue, Kirkland, and Sammamish; hillside view decks in Newport Hills and Somerset; forested lots in Issaquah Highlands and Canyon Park Bothell where cedar develops aggressive moss within 2–3 years; any homeowner who wants low maintenance without PVC's higher upfront cost.
- verifiedTop brands: Trex Transcend (most widely specified, 25-year fade and stain warranty) — see our dedicated Trex installation page for full product line details; TimberTech Legacy (deepest wood-grain texture, lifetime warranty on top tier); Fiberon Paramount (fully capped at a lower price point). Specify only fully capped lines — uncapped composite absorbs moisture and fails in Seattle's climate within 5–8 years.
- cleaningMaintenance in Seattle: Annual rinse with soap and water. No staining, sealing, or sanding required. On heavily shaded forested lots in Issaquah or Bothell, clean twice a year to prevent surface organic buildup — a 20-minute task, not a maintenance project.
Composite Decking Product Guide
What “Fully Capped” Actually Means
Every edge of a fully capped composite board — including the grooved underside — is enclosed in a protective polymer shell. This is what keeps moisture, mold, and stain from penetrating the wood-fiber core in Seattle's wet climate. We only specify four-sided-capped products: Trex Transcend, TimberTech PRO, and Fiberon Paramount.
— Seattle / King County
What “Fully Capped” Actually Means
Every edge of a fully capped composite board — including the grooved underside — is enclosed in a protective polymer shell. This is what keeps moisture, mold, and stain from penetrating the wood-fiber core in Seattle's wet climate. We only specify four-sided-capped products: Trex Transcend, TimberTech PRO, and Fiberon Paramount.
| Product | Tier | Material Cost | Warranty | Key Feature | Best For |
|---|---|---|---|---|---|
| Trex Select | Mid-entry | $8–$11/sq ft | 25 yr | Scratch-resistant cap | Value builds, East Hill Kent, Federal Way |
| Trex Transcend | Premium | $14–$18/sq ft | Lifetime | Deep wood grain texture | Kirkland, Bellevue, HOA projects |
| TimberTech Terrain | Mid-entry | $9–$12/sq ft | 25 yr | Solid color cap | Replacement projects, South King County |
| TimberTech Vintage | Premium | $15–$20/sq ft | Lifetime | Variegated grain / realistic look | Highlands HOA, West Bellevue |
| TimberTech Pro (PVC-cap) | Premium hybrid | $18–$24/sq ft | Lifetime | 4-sided PVC protection | High moisture, valley floor, shade |
What Does Composite Decking Cost in King County?
Entry
$18,000–$26,000
300–400 sq ft installed
Products: Trex Select, TimberTech Terrain
Common in: East Hill Kent, Federal Way, basic Renton builds
Mid-Grade
$24,000–$35,000
300–400 sq ft installed
Products: Trex Transcend, TimberTech Legacy
Common in: Sammamish, Redmond, Issaquah
Premium
$35,000–$55,000
350–500 sq ft installed
Products: TimberTech Vintage, premium Trex lines
Common in: Bellevue, Kirkland, HOA communities
Elevated Site Add
+$5,000–$18,000
Any deck size
Applies to: West Hill Kent, Mercer Island, Dash Point — hillside lots requiring engineered post systems
For a complete breakdown of deck project costs across all materials and King County neighborhoods, see our Seattle deck cost guide. We also have a dedicated Trex decking page with full product line comparison and King County pricing.
Why Composite Outperforms PT Wood in Seattle's Climate
- water_dropSeattle averages 37+ inches of rainfall annually — pressure-treated wood's exposed grain absorbs moisture in every storm event, accelerating surface degradation and creating conditions for biological growth within 2–3 seasons on shaded lots.
- thermostatKing County's temperature swings (17°F winter lows to 80°F+ summer highs) cause PT boards to cup, check, and split through wood movement cycles. Capped composite is dimensionally stable — it expands predictably and returns without permanent deformation.
- forestIn Kent's valley floor and Mercer Island's dense canopy shade, mold colonizes PT boards within 3–5 years. Capped composite has no organic food source on its surface — mold and moss cannot establish without organic material to feed on.
- calculatePT maintenance over 25 years — annual cleaning, biennial staining, board replacements, hardware replacement — runs $12,000–$30,000 on a typical 400 sq ft deck. This typically exceeds the original premium paid for composite at installation.
Hidden Fastener Installation — No Face Screws
Every composite deck we build uses hidden fastener clips seated between boards on each joist. The result: a clean uninterrupted surface with no screw heads to fill, rust, or back out. The system also maintains consistent gap spacing for drainage and thermal expansion — critical in King County's temperature range.
Q: Does capped composite hold up in Seattle's heavy shade and rainfall?
Yes — if you specify fully capped boards. A polymer shell on all four sides of the board prevents moisture from reaching the wood-fiber core regardless of rainfall or shade. Uncapped or partially capped composite (common in lower-price-point products) allows moisture in and will fail in 5–8 years on shaded Seattle lots. We specify only fully capped lines: Trex Transcend, TimberTech PRO or Legacy, and Fiberon Paramount. Ask any contractor you're evaluating exactly which product line they're quoting before accepting a bid.
Q: How does composite decking perform in Seattle's shade and moss growth?
Capped composite resists moss and mold because its outer shell has no organic food source. Quality products (Trex, TimberTech, AZEK) shed water and dry quickly. However, shade accelerates surface algae on any material — we recommend an annual deck wash with a composite-safe cleaner on persistently shaded surfaces. PVC decking (AZEK/TimberTech Pro) is superior to composite in fully shaded Mercer Island and North Bellevue installations because it has zero organic content on any surface.
Q: What's the difference between capped composite and uncapped composite?
Uncapped composite (older boards, some discount brands) has exposed wood fiber on all four sides — these absorb moisture, stain, and can grow mold. Capped composite wraps the board in a protective polymer shell. Single-side-capped boards have one exposed edge (lower tier). Four-sided-capped (TimberTech Pro) has protection on all surfaces — the best performance in wet Seattle conditions. We only install four-sided-capped products; we don't spec single-cap or uncapped boards.
Q: How long does a composite deck last in King County?
Mid-grade capped composite (Trex Select, TimberTech Terrain) carries a 25-year fade and stain warranty. Premium composite (Trex Transcend, TimberTech Vintage) and PVC (AZEK) carry lifetime warranties. The boards themselves typically outlast the structural framing — we've seen 1990s PT frames fail beneath perfectly serviceable composite boards installed in the early 2000s. The warranty governs appearance, but the physical lifespan in King County's climate is 30–50 years for quality capped products.
Q: Should I choose composite or cedar for my Seattle deck?
For most King County homeowners, composite is the better 20-year investment. Cedar costs less on day one but requires staining every 2–3 years (every 1–2 years on shaded lots) — a professional cycle runs $800–$2,700 per treatment. Over 25 years that's $8,000–$18,000 in maintenance costs, typically exceeding the composite premium. Cedar decking is the right call if you genuinely love the natural wood aesthetic, have a sun-exposed lot, and commit to the staining schedule. Composite is the right call if you want to eliminate that cycle entirely.
We install composite decking throughout King County, including Bellevue hillside view decks, Sammamish HOA communities, Kirkland waterfront properties, and Issaquah forested lots where cedar develops moss within the first season. Complete your project with the right railing system — we install composite, cable, glass, and aluminum options to match every composite build.
Get Your Composite Deck
Built Before Summer
Trex, TimberTech & Fiberon installed by King County's most trusted crew. We pull the permits, handle the demo, and don't leave until it's done right.
No obligation. We'll walk your property, discuss material options, and send a written estimate within 48 hours.