30×30 Deck Cost in Washington
A 30×30 (900 sqft) deck in Washington costs $57,600-$91,800 in mid-tier composite with the state's 1.28× labor multiplier (West). A 30×30 deck (900 sqft) is an estate-class build — needs P.E. stamp, multi-tier framing, and 8+ months in many AHJs. Washington labor 1.28× national. Pacific Northwest rain + moss — composite recommended over PT.
5 finish tiers — 30×30 in Washington
National $/sqft × Washington's 1.28× labor multiplier × 900 sqft = total installed cost. Materials + labor + standard railing included.
Excludes permit ($218-$537 typical in Washington), demolition (if replacing), and exceptional framing for 18″ frost depth. WA permits $250-400. Seattle moss + rain notes.
30×30 framing notes for Washington
Washington considerations
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FAQ — 30×30 deck in Washington
How much does a 30×30 deck cost in Washington?▾
In Washington, a 30×30 (900 sqft) deck costs $28,800-$45,900 in pressure-treated, $57,600-$91,800 in mid-range composite (Trex Transcend / Fiberon Sanctuary), and $86,400-$126,900 in luxury composite/PVC (TimberTech AZEK / Trex Signature). Numbers reflect Washington's 1.28× labor multiplier on 2026-Q1 retail.
What's the cheapest way to build a 30×30 deck in Washington?▾
Cheapest = ground-level pressure-treated pine with no railings (where exempt under 30″ height) — ~$23,040-$34,560 in Washington. Add stairs + railings + above-grade framing and the build goes to ~$32,256-$46,080. DIY saves 30-50% on labor but requires permit + inspection coordination yourself.
How long does it take to build a 30×30 deck in Washington?▾
Permit timeline in Washington: 2-6 weeks depending on jurisdiction. Construction time for a 30×30: pro crew = 8-14 days for framing + boards + railings + stairs. DIY = 5-8 weekends for experienced DIYer. Allow extra time for permit approval + inspections.
What framing do I need for a 30×30 deck in Washington?▾
IRC R507-compliant framing for a 30×30 deck typically uses 2×8 joists at 16″ OC for spans up to 12 ft, 2×10 joists for spans 12-16 ft. Washington's frost depth is 18″ — footings must extend below that per IRC R403.1.4. Sonotube 10-12″ diameter at 18″ depth is typical. Verify with your local building department.
Is composite worth it for a 30×30 deck in Washington?▾
Over 25 years in Washington: PT pine = ~$34,560 install + ~$72,000 maintenance (stain every 2-3 yr) = $106,560 total. Mid composite = ~$66,816 install + $0 maintenance = $66,816 total. Composite wins by 59-81% over 25-yr lifecycle PLUS better resale value in Washington's market.