How long does a properly built custom deck typically take from start to finish?

A straightforward single-level deck usually takes one to two weeks of on-site work once the permit is approved, though permit review time in King County can add several weeks before construction starts. Multi-level or more complex designs take longer. Weather can also push the schedule during the wettest months.

What should I ask a deck contractor before hiring them for a Seattle project?

Ask whether they pull their own permits, what fastener and hardware grade they use, and how they detail the ledger flashing where the deck meets the house — those answers tell you a lot about whether they build for this climate specifically. Also ask for proof of licensing and insurance, and don't be afraid to ask how many decks they've built in the area versus elsewhere.

Is composite decking actually worth the higher upfront cost compared to wood?

It depends on how much maintenance you want to do. Composite and PVC decking cost more initially but skip the annual sealing and staining that wood needs, and they resist moss and moisture damage better in a climate this wet. Wood is the better choice if you want that specific look and don't mind the upkeep.

What's the difference between capped and uncapped composite decking?

Capped composite has a protective outer layer bonded to the board that resists moisture absorption, staining, and fading better than uncapped composite, which is more prone to swelling and algae growth over time. In a climate as wet as King County's, the difference in long-term performance is noticeable enough that we generally recommend capped products.

Does a deck near the water need different materials than one further inland in King County?

Yes — decks closer to Puget Sound are exposed to salt-laden air that accelerates corrosion on standard hardware, so we spec stainless or heavy-coated fasteners and connectors for those builds. Decking material choice matters less for salt exposure than the hardware does, but drainage and ventilation design stay important everywhere in the county given the overall rainfall.

Seattle Custom Decks Built for King County's Wet Climate

Seattle's Climate Is Harder on Decks Than Most Homeowners Realize

A deck in Seattle doesn't fail the way a deck in a dry inland climate fails. It's rarely one big storm that causes the damage — it's the accumulation of moisture that never fully dries out between October and June, combined with salt-laden air near the Sound and a moss season that can run six or seven months a year. Framing that would last decades in Eastern Washington can show rot in half that time here if it was built to a generic spec instead of a Puget Sound one.

King County's marine climate means decks stay damp longer after rain, get less direct sun to dry them out under tree cover (common in a lot of Seattle's older, well-treed neighborhoods), and are exposed to salt air if the lot is anywhere near the water. None of that is exotic information to a local crew, but it's exactly the kind of detail that gets skipped by builders who mostly work drier parts of the state or country and treat every deck the same.

What "Correct" Actually Means for a Seattle Deck

Ledger Attachment and Flashing

The ledger board — where the deck attaches to the house — is the single most common failure point we see on older decks in this area, and it's almost always a moisture problem rather than a structural one. Water gets behind the ledger, the house's sheathing stays wet, and rot sets in where nobody can see it until the deck starts to feel spongy or pull away from the wall. A correct install uses proper flashing (not just caulk) that sheds water away from the house, a moisture barrier between the ledger and the sheathing, and structural screws or bolts rated for exterior wet-service use — not general-purpose deck screws.

Footings and Framing for Saturated Ground

Soil in a lot of King County stays saturated for months at a time. Footings need to be set below frost depth and sized for the soil conditions on that specific lot, not just poured to a minimum code number and called done. Framing lumber should be rated for ground contact or full exterior exposure where it's close to grade, and every cut end and drilled hole needs to be re-sealed — an untreated cut end is where rot starts even on treated lumber.

Fasteners and Hardware

This is where salt air changes the math. Standard galvanized hardware can start showing corrosion within a few years on a deck that gets salt-laden wind off the Sound or is just consistently damp. We spec stainless steel or heavy-coated (like triple-zinc or equivalent) fasteners and structural connectors for anything near the water, and coated fasteners as a baseline everywhere else in King County. It costs a little more up front. It's a lot cheaper than re-decking in eight years because every screw head is bleeding rust streaks into the boards.

Choosing a Decking Material for This Climate

There's no single "best" decking material — there's a best material for a given budget, look, and how much upkeep the homeowner actually wants to do. Here's how the common options hold up under Seattle's wet, moss-prone conditions specifically:

Material	Moisture & Rot Behavior	Moss/Algae Tendency	Maintenance	Typical Lifespan Here
Pressure-treated wood	Resists rot when properly maintained; end cuts and fastener holes are vulnerable	High if shaded or poorly drained	Annual cleaning, re-sealing every 1-2 years	10-15 years
Cedar	Naturally rot-resistant but softer, dents and weathers gray without upkeep	Moderate-high in shade	Cleaning and oiling/staining every 1-2 years	15-20 years
Composite decking	Doesn't rot, but can trap surface moisture if not fully capped	Moderate; capped boards shed algae easier than wood	Periodic washing, no sealing needed	25-30 years
PVC decking	Fully moisture-resistant, doesn't absorb water	Low; smooth capped surface sheds moss more easily	Occasional washing	25-30+ years

For homes under heavy tree cover — common through a lot of Seattle's older residential streets — we lean homeowners toward capped composite or PVC unless they specifically want a wood look and are prepared to keep up with cleaning and re-sealing. Wood isn't a wrong choice; it's a choice that comes with a maintenance commitment that not every household wants to make.

Moss, Algae, and Drainage — Design Decisions That Matter More Than Material

Even the best decking material will grow moss if the deck is designed without drainage and airflow in mind. A few design choices make a bigger difference than most homeowners expect:

Board spacing wide enough to let water pass through instead of pooling on the surface
Under-deck ventilation so the framing and joists can actually dry out between rain events
Grading and drainage at ground level so water isn't sitting under the deck year-round
Avoiding flat, unpitched surfaces anywhere water can collect — even a slight slope matters
Keeping decking clear of overhanging foliage where practical, since constant leaf litter holds moisture against the boards

A deck built without these considerations will grow moss no matter what it's made of, and moss on a walking surface isn't just unattractive — it's slippery and, on wood, it holds moisture directly against the board.

Permits and Local Code Considerations

Deck permitting requirements vary by jurisdiction within King County, and Seattle has its own permitting process separate from unincorporated King County or neighboring cities. Generally, decks above a certain height off grade, decks attached to the house, and any deck requiring new footings will need a permit and inspection. Guardrail height, baluster spacing, and stair requirements are all governed by code and get checked at inspection — this isn't optional paperwork, it's what keeps the structure safe and keeps the homeowner from problems at resale. We handle the permit process as part of the job rather than leaving it for the homeowner to sort out.

Our Process, Start to Finish

On-site assessment — we look at the lot's grading, sun/shade exposure, proximity to water, and existing structure (for replacements) before recommending anything
Design and material discussion — honest trade-offs on wood vs. composite vs. PVC based on budget and how much maintenance the homeowner wants to take on
Permit handling — we pull and manage the permit where one is required
Build — proper flashing, footings sized for the soil, corrosion-resistant hardware, and drainage/ventilation designed in from the start
Final walkthrough and inspection — we don't consider a deck finished until it passes inspection and the homeowner has walked the job with us

Keeping a Seattle Deck in Good Shape Season to Season

Even a well-built deck needs some seasonal attention in this climate — it's a fraction of the work a poorly built one demands, but it's not zero. A simple annual routine goes a long way:

Sweep off leaves and debris regularly through fall so they don't hold moisture against the boards
Clean moss and algae off the surface before it builds up, using a deck-safe cleaner rather than a pressure washer on wood at close range
Check and clear under-deck ventilation gaps and ground-level drainage before the wet season starts
Inspect the ledger flashing and fastener heads once a year for rust streaking or gaps
Re-seal or re-stain wood decking on the schedule the product calls for — don't wait until it's visibly gray and dry
Check stair and railing connections for looseness, especially after the first hard freeze-thaw cycle of the season

Why It Matters That We Already Work Seattle

A crew that mostly builds decks in drier parts of the country will default to specs that work fine there and fail early here — standard galvanized hardware, tighter board spacing, ledger details that don't account for a marine climate. We work King County year-round, which means we're not guessing about how a deck holds up through a Puget Sound winter — we're the ones who get the call when an old deck built to the wrong spec starts failing, and we build to avoid being that call in ten years. That local track record shapes every material and framing decision we make, not just the ones a homeowner happens to ask about.

Cost Factors to Expect

Factor	Why It Matters Here
Decking material	Wood costs less up front; composite and PVC cost more but reduce long-term maintenance and re-sealing labor
Footings and site conditions	Saturated or sloped soil common in King County can require deeper or additional footings
Hardware grade	Stainless or heavy-coated fasteners cost more than standard galvanized but resist corrosion from salt air and constant moisture
Permit and inspection	Required for most attached or elevated decks; varies by jurisdiction within King County
Size and complexity	Multi-level decks, built-in seating, or stairs add labor beyond a simple single-level rectangle

Exact pricing depends on the specifics of the lot and the scope, which is why we look at the site in person rather than quoting off a phone call.

If you're planning a new deck or replacing one that's showing its age, we're happy to come take a look and walk through the options honestly — no pressure, no upsell script. Request a free estimate below and we'll get back to you to schedule a time.