How Much Does It Cost to Build a Deck in Seattle? (2026 Guide)

Thinking about adding a deck to your Seattle home before the 2026 season? Whether you’re envisioning summer BBQs in Ballard or morning coffee overlooking Lake Washington, the first question is always: What is this going to cost me?

At Kolmo Construction, we believe in radical transparency. As we move into 2026, we are seeing shifts in labor rates and material costs. Instead of vague "ballpark" figures, we use digital tools to provide real-time estimates based on the current PNW economy.

Based on our updated 2026 data, let’s break down the actual cost to build a deck in Seattle.

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The Case Study: A 400 Sq. Ft. Composite Deck

To give you a clear picture, let’s look at a standard high-quality project: a 20’ x 20’ (400 sq. ft.) rectangle deck, elevated 2 feet off the ground, using premium materials.

The 2026 Estimated Total: ~$26,550

1. Materials: ~$8,550 (approx. 32%)

In Seattle’s damp climate, we almost always recommend Composite Decking. While the upfront cost is higher than cedar, it won’t rot, warp, or require staining every two years.

• Framing: Pressure-treated 2x6 lumber is the industry standard for longevity.
• Railing: A classic wood railing system adds safety and aesthetic value without the massive price tag of custom glass.

2. Labor: ~$18,000 (approx. 68%)

Seattle remains one of the most expensive labor markets in the country.

• Expertise: A 400 sq. ft. deck takes roughly 200 labor hours to complete correctly—from setting footings to precise composite miters.
• The Rate: For 2026, professional labor rates in Seattle are approximately $90/hr, reflecting the rising cost of living and specialized skills required for PNW building codes.

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Advice for 2026 Seattle Homeowners

• The "18-Inch Rule": In Seattle, any deck with a walking surface more than 18 inches above the ground requires a building permit. Factor this into your timeline!
• Design for Rain: Ensure your contractor uses joist tape and proper flashing. In our climate, moisture management is the difference between a 10-year deck and a 30-year deck.
• Plan for Lighting: With 4:30 PM winter sunsets, integrated LED stair lighting is no longer a luxury—it's a safety essential.
• Maintenance: Even "maintenance-free" composite decks need a bi-annual wash to prevent moss and pollen buildup, which can become slippery in the rain.

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Why Digital Estimates Matter

The traditional way of getting a quote involves a contractor "guessing" prices. At Kolmo, we’ve digitized the process to break down every hour and every dollar before the first board is cut. This tech-driven approach allows us to move faster—completing a project like the one above in about 25 days.

Ready to get your 2026 quote? Use our Interactive Deck Calculator.