How Much Does a Deck Cost in Washington?

Price per square foot, by material

In the Seattle–Snohomish County market, professionally built decks generally price out like this, installed: pressure-treated wood at roughly $45–$70 per square foot, western red cedar at about $60–$90, and composite (Trex, TimberTech, and peers) at roughly $75–$130. Premium PVC and tropical hardwoods run higher still. For a standard 300-square-foot deck, that puts a pressure-treated build in the mid teens to low twenties of thousands, cedar in the high teens to high twenties, and composite from the mid twenties into the thirties.

The parts that move the number

• Railings. Often the sleeper line item. Basic wood railing runs roughly $50–$100 per linear foot; cable and glass systems can run $100–$250. On a wraparound deck, railing can rival the decking itself.
• Stairs. Figure roughly $1,500–$4,000 per flight, more for wide or switchback runs.
• Height. Second-story decks price 25–50% above ground-level equivalents — taller posts, beefier framing, harder access.
• Cover. A roof or pergola turns a deck into an outdoor room — and adds structure, footings, and often engineering. Covered outdoor living areas are among the best-performing projects we build in this climate.
• Shape. Curves, multiple levels, and built-in benches or planters add 15–30% over a clean rectangle.

Wood or composite in a Puget Sound climate?

Nine months of moisture is hard on horizontal wood. Cedar is beautiful and local but wants washing, brightening, and resealing on a one-to-three-year cycle. Composite costs more on day one and almost nothing after that — which is why, over a 15–20-year life, most of our Washington clients now land on composite for the walking surface even when they keep real wood elsewhere. Whichever you choose, the parts that matter most here are invisible: footings sized for our soils, correct ledger flashing, and ventilation under the boards.

When you need a permit

In most Puget Sound cities, a deck needs a building permit once it is attached to the house or more than a couple of feet above grade — Seattle draws the line at 18 inches, and many cities use 30. Roof decks and anything in a critical area need permits regardless. Permit cost and review time vary by city; we handle the paperwork and inspections as part of the job, and the price for it sits in your itemized estimate, not in a surprise.

Get a real number for your backyard

Ranges are for articles — your deck deserves an exact figure. Go Far Construction designs and builds decks, patios, pergolas, and outdoor kitchens across Snohomish and King County, with free, no-obligation estimates and itemized written pricing. Walk us through your yard and we’ll tell you what it actually costs.