Deck Building Cost in Seattle, WA
A 16×20 ft deck in Seattle costs $8,800 (pressure-treated) to $18,800 (composite) — 26% above the national average.
Seattle — PT Wood Deck (16×20)
$8,800
$28/sqft installed
Composite (Trex)
$18,800
$59/sqft; low-maintenance
vs National Average
26% above
Seattle labor market
Deck Cost in Seattle by Material — 2026 (16×20 ft, 320 sqft)
| Material | Total Cost | Per Sqft | Lifespan |
|---|---|---|---|
| Pressure-treated wood | $8,800 | $28/sqft | 15–20 yrs |
| Cedar / Redwood | $13,200 | $41/sqft | 20–30 yrs |
| Composite (Trex, Fiberon) | $18,800 | $59/sqft | 25–30 yrs |
| PVC / capped composite | $21,300 | $67/sqft | 30–50 yrs |
Includes framing, decking, 1 set of stairs, basic railing, and permit. Second story or rooftop decks add 25–50%. Seattle labor rates are 26% above the national average.
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FAQs — Deck Cost in Seattle
How much does a deck cost in Seattle?
A standard 16×20 ft deck (320 sqft) in Seattle, WA costs $8,800 for pressure-treated wood, $13,200 for cedar, and $18,800 for composite (Trex) — 26% above the national average of $8,500. Per-sqft rates: PT wood $28/sqft, composite $59/sqft. Costs include framing, decking boards, stairs, and basic railings.
Is composite or wood decking better in Seattle?
In Seattle's moderate climate, pressure-treated wood ($8,800) is cost-effective if you're willing to seal it every 2–3 years. Composite ($18,800) is the no-maintenance premium choice. Break-even on composite vs. PT wood maintenance savings is typically 10–12 years.
Do I need a permit to build a deck in Seattle?
Yes — most deck projects in Seattle require a building permit if the deck is attached to the house, over 30 inches off the ground, or over 200 sqft. Permits cost $200–$500 in Seattle and require structural drawings and a post-installation inspection. A licensed WA contractor will handle permits as part of the project. Unpermitted decks must be disclosed at sale and may need to be removed or permitted retroactively.
How much does a 12×12 deck cost in Seattle?
A 12×12 ft deck (144 sqft) in Seattle, WA costs: PT wood $4800–$5700, cedar $7300–$8600, composite $10300–$12200. Smaller decks have higher per-sqft costs since fixed costs (footings, framing, stairs) spread over fewer square feet. A 12×12 is popular for smaller yards and costs approximately 55–65% of a 16×20.
What is the ROI on a deck in Seattle?
A wood deck in Seattle recoups approximately 65–75% of cost at resale according to Remodeling Magazine's Cost vs. Value report. A $8,800 PT wood deck adds $6200–$6600 to your home's value. Composite decks often recoup a similar dollar amount to wood but at a higher cost, so the percentage ROI is lower. In Seattle's market, outdoor living spaces are increasingly valued — a well-built deck is one of the top outdoor ROI projects.