Ask House Spouse · Exterior & Weatherproofing · Decks & Outdoor Structures
How much does it cost to build a new deck in the Seattle area?
Short answer
A new deck in the Seattle area typically costs between $75 and $150+ per square foot, fully installed. For a common 14x20 ft (280 sq ft) deck, this means a range of $21,000 for simple pressure-treated wood to over $42,000 for premium composite decking with custom railings. The final price depends heavily on materials, height, railings, and site access.
Material Choices: Wood vs. Composite
The single biggest cost decision is your decking material. Pressure-treated (PT) lumber is the most affordable option but requires annual cleaning and sealing to prevent rot in our damp climate. Cedar offers a classic PNW look but also needs regular maintenance. Composite decking has the highest upfront cost but provides a 25+ year lifespan with minimal maintenance beyond occasional washing, making it a very popular choice in Western Washington.
Structural Costs: Footings, Framing, and Height
A deck is essentially a small building. Decks attached to your home require a properly flashed and waterproofed ledger board. Elevated decks need deep concrete footings dug below the frost line and substantial framing to handle the weight. Washington building code mandates that any deck surface more than 30 inches above the ground must have a guardrail at least 36 inches high, which introduces significant material and labor costs for railings and stairs.
Ancillary Costs: Permits, Demolition, and Railings
Beyond the basic structure, several other items impact the budget. Most new decks require a building permit, which involves creating architectural plans, paying city fees, and scheduling multiple inspections. If you have an old, unsafe deck, the cost to demolish it and dispose of the materials must be factored in. Finally, the railing system itself is a major variable. Simple wood railings are the baseline, while aluminum, composite, and especially cable rail systems can add thousands to the final price.
How House Spouse Manages Deck Projects
As a licensed general contractor, My House Spouse can manage your entire deck project from start to finish. We handle the design, permit application, demolition of the old structure, and complete construction of the new deck, including all framing, decking, and railing installation. We ensure the project is built to code, properly integrated with your home, and finished beautifully, saving you the headache of coordinating multiple vendors.
Why it happens
Deck construction costs are driven by three main factors. First, materials: high-performance composite decking (like Trex or TimberTech) costs significantly more than traditional pressure-treated or cedar lumber, but offers lower maintenance in the wet PNW climate. Second, structural complexity: elevated decks require deep concrete footings, robust framing, and code-compliant guardrails, all of which add substantial labor and material costs. Finally, labor and permitting in King and Snohomish counties are expensive; proper projects require detailed plans, city plan review, multiple inspections, and skilled carpentry.
How to diagnose it
- 1Measure your desired deck footprint (length x width) to calculate the total square footage.
- 2Decide on your preferred decking material by weighing the upfront cost of composite against the long-term maintenance of wood.
- 3Determine if the deck will be over 30 inches high, as this legally requires guardrails and often more complex footings.
- 4Consider your railing preference, as simple wood pickets, horizontal metal, and modern cable rail systems have vastly different price points.
- 5Assess the condition of any existing deck. A full tear-down and haul-away will add cost compared to building on a clear, level site.
- 6Note the accessibility of your backyard for equipment and material delivery, as difficult access increases labor hours.
DIY vs. professional
DIY-friendly if…
A DIY approach may be suitable for building a small, ground-level deck platform that doesn't require a permit or for resurfacing an existing deck where the structure is verified to be sound.
Call a pro when…
Always hire a licensed general contractor for any new deck that is attached to the house, elevated over 30 inches, requires new footings, or needs a building permit to ensure it's safe and code-compliant.
Cost expectations
$21,000–$42,000typical WA labor + materials
For a typical 280 sq ft deck. Price varies significantly with materials (wood vs. composite), height, railing style, 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
Roughly 71% of homes older than 8 years show one or more failed caulk joints letting water into wall assemblies.
Caught early on assessment: $220–$750 · Left until failure: $1,200–$8,500
A Home Health Assessment can evaluate an existing deck's structure, including the ledger board attachment, footings, and framing. This inspection determines if a cost-effective repair or resurfacing is possible, or if a full, safe replacement is necessary.
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.