Should You Build a Deck in Seattle?
Here's What You Need to Know

Seattle summers are short — and there's no better way to make the most of them than with a well-built outdoor deck. Whether you're envisioning a quiet morning coffee spot or a space to host family and friends, a new deck adds real living space to your home. But before you start, here's what every Seattle homeowner should know.

Wood vs. Trex: The Most Important Decision You'll Make

The first question we get from almost every client: wood or composite?

Pressure-treated wood is less expensive upfront, but in Seattle's wet climate it warps, cracks, and needs regular sealing or staining every 2–3 years. Left untreated, it rots — especially in shaded areas or near soil.

Trex composite decking costs more upfront, but in the Pacific Northwest it's almost always the smarter long-term choice:

• No painting, staining, or sealing — ever
• Resistant to moisture, mold, and fading
• Looks great after 10+ years with minimal maintenance
• Backed by a 25-year warranty

At Wanaka, we build most of our decks with Trex composite decking on pressure-treated framing — the best of both worlds. The framing is structural and built to code; the surface stays beautiful for decades.

Composite decking holds up beautifully in the Pacific Northwest climate

Don't Skip the Deck Tape

One detail that separates a quality deck build from one that fails early: flashing tape on the framing.

Before any decking goes down, we wrap all framing joists with deck flashing tape. This creates a moisture barrier between the composite decking and the wood framing, dramatically extending the life of the structure underneath. It's a small step most homeowners never see — but it matters a lot in Seattle's rain.

What Does a New Deck Cost in Seattle?

Deck pricing varies based on size, materials, elevation, and complexity. Here's a rough range to set expectations:

Project Type	Estimated Range
Small deck (100–150 sq ft), ground level, Trex	$8,000 – $12,000
Medium deck (200–300 sq ft) with stairs & railing	$12,000 – $20,000
Large or elevated deck with custom features	$20,000+

These ranges include labor and materials. The biggest cost variables are deck size, height above grade, and whether you're adding stairs, extensions, or a custom railing system.

Do You Need a Permit?

In most Seattle and Eastside cities, yes. Requirements vary, but generally:

• Decks attached to the house or over 30 inches off the ground typically require a permit
• Permits ensure the structure is code-compliant and safe
• Permit fees are separate from the construction quote and billed if applicable

We advise every client on what's required for their specific project before work begins — no surprises.

Replacing an Existing Deck

If your current deck is past its prime, a full demo and rebuild is often the cleanest path. We remove the old structure entirely, dispose of all materials, and start fresh — which also gives us the chance to catch hidden issues with ledger boards, posts, or footings before they become your next problem.

On a recent project in Seattle's Phinney Ridge neighborhood, we demoed an aging wood deck and rebuilt it with Trex decking, a new Trex railing system, and added a 4–5 ft extension — same footprint the homeowner loved, just bigger and better.

Why the Railing Matters More Than You Think

Railings aren't just a code requirement — they're a major part of how your deck looks and feels. Trex railing systems give you clean, modern lines that complement the decking without the maintenance headaches of wood. We match railing to decking for a cohesive, properly anchored, code-compliant finish.