How Much Does a Deck Cost in Seattle & the Eastside? 2026 Price Guide

2026 deck cost ranges by material

Installed prices for a professionally built deck in the Seattle–Bellevue area generally land in these ranges:

- Pressure-treated wood: roughly $40–$70 per square foot installed. The budget option — strong and code-compliant, but it needs staining or sealing every few years to look its best in our wet climate.

- Cedar: roughly $55–$90 per square foot. A Northwest classic with natural rot resistance and a warm look, though it still wants regular maintenance to keep its color.

- Composite (Trex, TimberTech and similar): roughly $75–$130 per square foot. The most popular choice we build on the Eastside — it costs more up front but shrugs off Washington rain with almost no maintenance, which is why most of our clients land here.

In practice, a typical 300 sq ft deck runs about $15,000–$25,000 in pressure-treated wood and $25,000–$40,000 in composite. Elevated decks, complex shapes, glass or cable railing, and built-in stairs push budgets higher.

What actually drives the price

Two decks with the same footprint can be $20,000 apart. The biggest swings come from height and structure (a walk-out second-story deck needs engineered posts and footings a ground-level platform doesn't), railing choice (powder-coated aluminum and cable systems cost several times a wood rail), stairs and landings, demolition of an old deck, and whether you add a covered area. If you're considering shelter from the rain, see our patio cover options — combining the two projects in one build is cheaper than phasing them.

Do you need a permit for a deck?

Usually, yes. In Seattle, decks more than 18 inches above grade require a building permit; most other King County cities, including Bellevue, Kirkland, and Redmond, require one when the deck is 30 inches or more above the ground, attached to the house, or serving an exit door. Attached and elevated decks also typically need engineering. Blue Lake handles the drawings, the permit package, and every inspection on your behalf — the paperwork never lands on you.

Is a deck worth it?

Decks consistently rank among the best-returning outdoor projects in resale studies, and in the Seattle area the lifestyle math is even better: a well-built deck effectively adds an outdoor room for most of the year. Pairing a deck with a full outdoor living space — seating walls, lighting, a cooking area — is the most common upgrade our clients ask for once they see the deck framed.

How to keep your deck on budget

1. Pick the material honestly. If you won't re-stain wood every two to three years, composite is the cheaper choice over a decade.

2. Decide on railing early — it's the line item that surprises people most.

3. Build footings for the future. If a patio cover or pergola might come later, engineering it now costs little; retrofitting costs a lot.

4. Use a fixed-price contract. Blue Lake builds decks on a fixed-price, fixed-duration contract, so the number you sign is the number you pay.

Get a real number for your backyard

Browse our deck construction page to see recent builds across King County, or request a free estimate — we'll measure the site, talk through materials, and give you a fixed bid for your deck.