Trex Deck Cost in Seattle (2026)
Why Trex Transcend Lineage installs at $80-$130/sqft in the Pacific Northwest, how the January 2026 manufacturer repricing shifted the band, and where each dollar in your quote actually goes.
2026 Deck Cost Estimator
Directional range based on material tier, slope condition, jurisdiction, and current site state. Built from 2026 PNW dealer-installed cost data.
$18,400 – $46,000
Range covers materials and labor before permit fees, Washington 10.35% retail sales tax, and any project-specific engineering. We refine to a single open-book number after site visit and structural review.
Seattle SDCI valuation-based; SFI permits ~40% of plan review fee. Typical deck permit fee band runs $400-$1,800; ECA-overlay decks add geotech review costs separately. 2025-2026 saw inflation-adjusted hourly rates rise materially.
Range includes January 2026 Trex/TimberTech repricing — composite Signature and Transcend lines were lifted +7-15% YoY per manufacturer notices. Cost guides published before Q4 2025 do not reflect this adjustment.
Estimates are directional only. Final pricing requires site visit, structural review, and permit feasibility check. Slope and ECA conditions in particular shift the band substantially after stamped engineering enters the scope.
Trex product tiers & PNW installed bands
Trex sells three working tiers in the Pacific Northwest market: Enhance (entry), Select (mid), and Transcend Lineage (premium capped composite). Each lands in a distinct installed-cost band once PNW labor, slope substructure, and the WA 42-inch guard requirement are layered in. Figures below draw on 2026 national installed-cost medians (HomeGuide / Angi) and PNW dealer-installed benchmarks, biased toward PNW pricing.
- Trex Enhance$40-$70/sqft installed. Entry capped composite; PNW-installed pulls toward the upper end on slope sites and once 42-inch railing is specified.
- Trex Select / Enhance Naturals$60-$100/sqft installed. Mid-tier; the typical “Trex deck” quote a homeowner without slope conditions receives.
- Trex Transcend Lineage$100-$130/sqft installed. The premium capped composite line Trex markets through PNW pro channels; standard on architect-led projects.
Sources: HomeGuide / Angi 2026 installed-cost data; PNW dealer-installed benchmarks.
Why the 2026 number is not the 2024 number
A Trex deck quote in Seattle today is structurally different from the same quote 18 months ago, and not because contractor margins moved. Four discrete shocks landed between Q1 2025 and Q2 2026, each documented in primary sources, each line-by-line visible in current quotes if the contractor is being transparent.
First, permit fees. King County (unincorporated) raised the deck permit fee schedule +49% on January 1, 2025 under Ordinance 19857, then layered another ~14% increase on January 1, 2026 under Ordinance 20021, alongside a new $126 application screening fee. Seattle SDCI inflation-adjusted hourly billing rates rose +12-19% in 2025 and a further +18% in 2026. On a 500 sqft project, permit-line cost shifted from roughly $900-$1,300 in early 2024 to $1,900-$2,500 today in unincorporated KC, before any engineering supplement.
Second, the Trex repricing. Trex announced railing, fastener, and Signature/Transcend line increases of +7-15% effective January 1, 2026. TimberTech AZEK followed with parallel mid-cycle moves. Composite Western Washington installed cost for materials and labor on the substructure plus boards now ranges $28-$45/sqft on standard tiers and $80-$130/sqft on Transcend Lineage. Cost guides that have not been republished since Q3 2025 understate the Trex line items.
Third, framing lumber. Q2 2026 saw a +5.11% move in framing lumber, with the national average around $916/MBF in April. PNW labor and supply constraints amplify the move. Pressure-treated joists and beams carry the increase through to the deck quote whether the finish is Trex, cedar, or PVC.
Fourth, code. Washington adopted the 2021 IRC effective March 15, 2024. The 2021 IRC introduces Section R507.10 (continuous load path: guard loads must transfer to deck joists, no notched 4x4 guard posts at the connection point). Layered on top is the WA-specific 42-inch minimum guard height, against the IRC 36-inch baseline. Both rules shift railing system selection, material quantities, and stamped-engineering scope on any deck above 30 inches.
500 sqft Trex Transcend Lineage replacement, West Seattle slope lot
Representative project: full teardown of an aging 480 sqft cedar deck, replaced with 500 sqft of Trex Transcend Lineage, helical pile substructure on a 20% slope inside the Seattle SDCI ECA overlay, single stair flight, Trex Signature aluminum railing at the WA 42-inch spec.
- Demolition & disposalTear-out of existing 480 sqft cedar deck, debris transfer station fees$2,400 – $4,200
- Footings & substructure12 helical piles (slope-rated), pressure-treated framing to 60-psf live load, IRC R507.10 continuous load path$11,500 – $15,000
- Trex Transcend Lineage boards500 sqft of Transcend Lineage at $9-$11/sqft materials (post January 2026 repricing) + 10% waste$5,000 – $6,100
- Trex Signature railing60 linear ft Signature aluminum at WA 42" guard spec, posts and gates$5,400 – $7,800
- Stairs (one flight)Engineered stringers, Transcend treads and risers, code-compliant landing$2,400 – $3,800
- LaborPNW licensed carpenter crew, ~180 hrs at $50/hr blended, includes finish carpentry$9,000
- Structural engineeringStamped drawings for slope and 60-psf load path; required by SDCI on ECA overlay$1,800 – $3,200
- Seattle SDCI permit & inspectionsValuation-based plan review + SFI inspections + 2026 fee schedule$1,200 – $1,800
- WA 10.35% sales taxApplied to materials portion (Seattle/King combined retail rate)$1,800 – $2,400
- Total — directional range$40,500 – $53,300
Materials cost weighted on Trex’s January 2026 price sheet. Labor at PNW carpenter $50/hr blended. Permit and sales tax per the applicable 2026 jurisdiction fee schedule and WA Department of Revenue combined Seattle/King retail rate.
2026 Permit Fee Matrix
Four core Greater Seattle jurisdictions, their deck permit thresholds, and the 2026 fee schedules behind every quote you receive.
| Jurisdiction | Permit Threshold | 2026 Fee Structure | Recent Change |
|---|---|---|---|
| Seattle SDCI | >18" above grade; any roof deck; any deck in an ECA overlay | Valuation-based sliding scale. SFI (Subject-to-Field-Inspection) permits run ~40% of the plan review fee. 2026 Fee Code and Fee Estimator published. | +12-19% in 2025, +18% inflation-adjusted hourly rates in 2026 |
| King County (unincorporated) | >30" above ground (uncovered decks at or below 30" outside critical areas exempt) | $772 application review + $2.46/sqft inspection (deck of 500 sqft or less) + new $126 application screening fee | +49% on Jan 1 2025 (Ord. 19857), +~14% on Jan 1 2026 (Ord. 20021) |
| Bellevue | >30" above ground (plan review included in permit) | Valuation-based. Reported by local contractors as relatively faster and less painful than King County unincorporated. | No major fee-schedule shock reported through Q2 2026 |
| Pierce County (unincorporated) | >30" above adjacent grade; guardrail required on all decks >30" | $69 for the first $2,000 of valuation + $12.21 per additional $1,000 up to $25,000. Fast Track available for pre-designed single-level decks up to 14 ft high. | Updated effective Feb 1, 2026 (Pierce County Code 17C.10.070) |
Source: Seattle SDCI 2026 Fee Code; King County Ord. 19857 / 20021; Bellevue Development Services; Pierce County Code 17C.10.070. Threshold and fee data current as of Q2 2026. Final permit cost on any project depends on valuation, site conditions, and whether structural engineering or geotechnical review is triggered.
Frequently asked
- Why is Trex more expensive in Seattle than the national average cost guides suggest?
- PNW labor is the structural floor. Washington carpenter wages run $38-$52/hr on residential framing, against a national contractor mean closer to $32/hr. Add 60-psf live-load engineering on slope and shoreline parcels, the WA 42-inch guard requirement (vs IRC 36-inch baseline), and the January 2026 Trex repricing on Signature and Transcend lines (+7-15%), and the installed band for capped composite shifts up by $15-$25/sqft relative to a Sun-Belt national figure.
- What is the actual installed cost band for Trex in Seattle right now?
- Trex Enhance and Trex Select (standard composite) install at $40-$100/sqft depending on substructure complexity. Trex Transcend Lineage (capped composite, the line Trex actively markets to premium PNW dealers) sits at $100-$130/sqft installed. Below $80/sqft on a Trex Transcend quote, ask hard questions about framing-grade, footing type, and railing system.
- Do I need a permit for a Trex resurface where I am keeping the existing framing?
- Inside the City of Seattle, any deck more than 18 inches above grade, any roof deck, or any deck in an Environmentally Critical Area (ECA) requires a permit regardless of whether you are reusing framing. In unincorporated King County, Bellevue, and Pierce County, the threshold is 30 inches. Resurfacing-only scopes still trigger inspection in many jurisdictions because the work touches the structural load path.
- How much does the WA 42-inch guard requirement add to cost?
- WA State requires a minimum 42-inch guard height on residential decks more than 30 inches above grade, against the IRC 36-inch baseline. The difference is rarely the headline driver, but it adds to material on rail systems, particularly on cable, glass, and aluminum systems where the manufacturer prices per linear foot at the taller spec. A 60-linear-foot perimeter at the 42-inch spec runs roughly $300-$900 above the equivalent 36-inch order on a Trex Transcend railing kit.
- Why does Trex tariff repricing matter on a quote I receive today?
- Trex announced railing, fastener, and Signature/Transcend line increases of +7-15% effective January 1, 2026. Cost guides that pre-date Q4 2025 do not reflect this. Contractor quotes pulled against old supplier price sheets will under-quote materials by hundreds to low thousands of dollars on a 400-600 sqft project — with the gap surfacing as a change order mid-build.
- Is a $40/sqft Trex quote real?
- Almost never on a permitted, structurally engineered deck in Greater Seattle. The number occasionally appears on unpermitted resurfaces where the existing framing is being reused without structural review, or on substructure-only quotes that exclude railings and finish carpentry. Reddit shock posts ($72-$102k on 650 sqft, or $110-$157/sqft) are the upper end of legitimate full-scope quotes; $40/sqft is structurally suspect on the lower end.
Permit pulled in your name. Tracking number on day one.
Every Trex deck we build runs through Seattle SDCI, King County DPER, or the relevant municipal office under your name as the property owner. You receive the permit tracking number on day one. No “no permit needed” shortcuts on slope or ECA work.