Ask House Spouse · Exterior & Weatherproofing · Decks & Outdoor Structures
How much does it cost to build a deck in the Seattle area?
Short answer
In the Seattle area, a professionally built deck typically costs between $75 and $125 per square foot, depending on materials, height, and features. For a common 14x20 foot (280 sq ft) deck, this means a budget of $21,000 to $35,000. Composite materials, complex stairs, and cable railings will increase the cost.
Breaking Down Deck Costs in the Pacific Northwest
When budgeting for a new deck, materials and labor are the largest expenses. In the PNW, we exclusively use ground-contact rated pressure-treated lumber for posts and framing for longevity. For decking boards, pressure-treated pine is the most affordable, cedar offers a classic Northwest look with natural rot resistance, and composite decking provides the ultimate in durability and low maintenance, though at a higher initial cost. Labor costs reflect the skill needed to build a structure that can withstand our wet winters for decades, including critical flashing details where the deck meets your house.
How Decking Materials Impact Your Budget
Pressure-Treated (PT) Lumber: Lowest cost option. Requires annual cleaning and staining/sealing every 2-3 years to prevent splintering and rot. Life expectancy is 15-20 years with proper care. Cedar: Mid-range cost. Prized for its beauty and natural resistance to insects and decay. It will weather to a silver-gray if left untreated or can be stained to maintain its rich color. Life expectancy is 20-25 years. Composite Decking: Highest upfront cost. Made from a blend of wood fibers and recycled plastic, it's highly resistant to rot, insects, and fading. It requires only occasional soap-and-water cleaning and often comes with 25+ year warranties.
Don't Forget Permits, Demolition, and Design
Most cities in King and Snohomish County require a building permit for decks attached to a house or over 30 inches in height. This process involves creating code-compliant drawings, submitting them for review, and scheduling inspections. While this adds to the cost and timeline, it is a non-negotiable step for safety and legality. If an old deck needs removal, demolition and disposal costs will also be part of the total project budget.
Adding Power or Gas to Your New Deck
Want to add outdoor outlets for string lights, a heater, or a built-in natural gas line for your grill? For that scope of work, House Spouse coordinates a trusted licensed electrician or plumber. We manage the project and handle all the finish work and restoration after their specialized work is complete, ensuring a seamless integration. (/disclaimers)
Why it happens
Deck pricing is driven by three main factors: materials, labor, and complexity. Material costs vary dramatically between standard pressure-treated lumber, mid-range cedar, and premium composite or PVC decking. Labor in the Puget Sound region is a significant portion of the budget, covering demolition of an old deck, site prep, skilled carpentry, and cleanup. Complexity adds hours and cost. A simple ground-level platform is much cheaper than a second-story deck with long staircases, intricate railings, and built-in features like benches or planters. Additionally, all decks attached to a home in Washington must be properly flashed to prevent water intrusion, and most require permits, which involve design, fees, and inspections.
How to diagnose it
- 1Measure your desired deck area to get a rough square footage. This is the primary number used for initial estimates.
- 2Decide on decking material. Get quotes for pressure-treated wood, cedar, and at least one brand of composite to understand the price tiers.
- 3Determine the height. A deck more than 30 inches off the ground requires more robust railings and support, increasing costs.
- 4Choose a railing style. Simple wood balusters are standard, while horizontal metal, cable, or glass panel systems are significant upgrades.
- 5Check with your local city (e.g., Seattle, Bellevue, Kirkland) about permit requirements for your specific project size and location.
- 6Factor in demolition. If you have an existing deck that needs to be removed and hauled away, include that in your budget.
DIY vs. professional
DIY-friendly if…
A small, freestanding, ground-level platform deck (not attached to the house and under 30 inches high) can be a DIY project if you have advanced carpentry skills and tools.
Call a pro when…
For any deck attached to your home, over 30 inches tall, or requiring permits, you must hire a licensed general contractor like House Spouse to ensure it is structurally sound, code-compliant, and safely flashed.
Cost expectations
$21,000–$45,000typical WA labor + materials
For a typical 200-300 sq. ft. deck. Price varies significantly based on materials (wood vs. composite), height off the ground, railings, and site complexity.
Every House Spouse job is quoted in writing before we start. 12-month workmanship warranty included.
What we see on Home Health Assessments
About 58% of homes we assess have dryer vent lint buildup at the exterior cap — a documented fire risk (US Fire Admin).
Caught early on assessment: $120–$220 · Left until failure: $500–$25,000
A Home Health Assessment evaluates your existing deck's structure, checking for rot, loose railings, and unsafe footings. This inspection clarifies if repairs are sufficient or if a full replacement is the safer, more cost-effective long-term solution.
How the Home Health Assessment worksServices we'd bring to this job
Where we handle this
We answer this question on real Home Health Assessments across Snohomish and King County.