Best Decking for the Northwest: What Holds Up in Skagit, Island and Whatcom Counties

Updated August 2026 · Alpine Exteriors · WA contractor license ALPINI751OW

The Short Answer

For most homeowners in Mount Vernon, Anacortes, Burlington, Sedro-Woolley, La Conner, Stanwood, Camano Island and Bellingham, the two decking materials that hold up best over time are PVC decking and quality composite decking with a capped, textured surface. Both shrug off the steady winter rain here and resist the moss and mildew that colonize anything shaded and damp, without the yearly sanding-and-sealing cycle wood decking demands. If budget is tight or you want a natural look, cedar is the best wood option — it resists rot better than most softwoods and takes on a handsome silver patina. Pressure-treated fir is the least expensive way to get a deck built, but it needs the most upkeep to stay safe and good-looking here. Aluminum decking is worth a look on waterfront lots on Camano Island or near the Anacortes shoreline. There is no single best material for every lot — a shaded deck under Douglas firs in Sedro-Woolley has different problems than a sun-exposed deck facing the Strait in Anacortes, and the right pick depends on which of those problems you're actually solving for.

How We Judged

We weighed each material against the conditions that actually show up on decks in this part of Washington, not generic marketing claims:

• Moisture and rot resistance. Skagit, Island and Whatcom counties get long stretches of steady winter rain, and decks that don't drain and dry quickly stay wet for days at a time, rotting, cupping, or growing mold faster than in drier parts of the state.
• Moss and algae resistance underfoot. Shaded decks, under mature evergreens or below a covered porch, grow a slick green film on almost any surface if it isn't cleaned regularly. Some deck boards resist this better than others, and texture matters as much as the material.
• Wind exposure. The Skagit flats and the open water around Anacortes, La Conner and the islands see real wind in fall and winter storms, which mostly affects railings and how a deck is attached to the house.
• Salt air tolerance. Camano Island, Anacortes and other shoreline properties deal with airborne salt that accelerates corrosion in fasteners and hardware.
• Cold-weather behavior. The foothills toward the Cascades occasionally see hard frost, ice, and light snow, so materials that expand and contract a lot need careful installation gaps.
• Long-term maintenance and honest lifespan. We care more about what a material looks like after five or ten Northwest winters of neglect than what it looks like brand-new.

Pressure-Treated Wood

Pressure-treated fir or hem-fir is still the most common decking material we install, simply because it's the least expensive way to get a structurally sound deck. The chemical treatment resists insect damage and slows rot, and it's widely available and easy to repair board-by-board.

The honest drawback is that pressure-treated wood needs more upkeep in this climate than it would somewhere drier. Left unsealed, it grays, checks, and develops a slick moss film in shaded spots within a year or two, as we see often on lots tucked under trees around Sedro-Woolley. To stay safe underfoot, it needs a wood cleaner and a fresh coat of sealant roughly every one to two years, more often on the shaded side of a house. Fasteners matter too: treated lumber sold today is more corrosive to plain steel than older formulations, so hardware needs to be hot-dip galvanized or stainless — a requirement the Washington State Building Code already accounts for and one we don't cut corners on.

Cedar

Western red cedar is grown right here in the Pacific Northwest, and its natural oils give it real rot and insect resistance without chemical treatment. It's a softer, more attractive wood than pressure-treated fir, and it takes stain evenly if you want to keep the honey-brown color, or it can weather to a silver-gray.

Cedar's honest weakness is that it's a softer wood — it dents and scratches more easily under furniture legs and dropped tools than composite or PVC. It also isn't maintenance-free: it benefits from a water-repellent sealant every couple of years in our wet winters, though it tolerates going unsealed longer than treated fir without rotting outright. Cost sits above pressure-treated lumber but below most composite and PVC. For homeowners in Bellingham or La Conner who want a real-wood look, cedar is usually our recommendation over treated fir.

Composite Decking

Modern capped composite decking — a wood-plastic core with a protective outer shell — is the material we install most often when a homeowner wants to stop maintaining their deck every year. It doesn't need staining or sealing, resists splintering, and better capped products resist moisture well enough to hold up through our long wet winters without the swelling and cupping that plagued some early composite boards.

That history is worth mentioning honestly: first-generation composite decking from the early 2000s, uncapped and more wood-fiber than plastic, had real problems with moisture absorption and mold staining in wet climates like ours. Today's capped products from reputable manufacturers have largely solved that, but it's still worth choosing a board with a full polymer cap on all sides rather than a cheaper, partially capped product, especially on a shaded deck. Composite can still develop a thin algae film in deep shade, though textured boards shed it better than smooth ones and a seasonal wash keeps it in check. Upfront cost is meaningfully higher than pressure-treated wood, but reduced maintenance over ten-plus years often closes that gap.

PVC Decking

Fully synthetic PVC decking contains no wood fiber at all, which means it can't rot, and it's about as close to moisture-proof as decking gets. That makes it a strong choice for the wettest, shadiest lots we work on, and for waterfront properties on Camano Island or around Anacortes where salt air and constant dampness are both in play.

The tradeoffs are cost and feel. PVC is generally the most expensive decking option we quote, and some homeowners feel it looks and sounds a bit more plastic underfoot than composite, though newer wood-grain finishes have narrowed that gap. PVC also expands and contracts more with temperature swings, which matters during a cold snap dropping into the 20s — proper gapping at installation is important to avoid buckling, and it's a detail an inexperienced installer can easily get wrong.

Aluminum Decking

Aluminum decking is a less common choice, but it deserves a mention for the right lot. It's essentially immune to rot, mold, and moss growth, and its powder-coated, textured surface stays slip-resistant even when wet, which matters on covered or shaded decks that rarely fully dry out. It also holds up well to salt air, worth considering for exposed shoreline properties on Camano Island or near the Strait.

It costs more than composite in most cases, fewer installers work with it regularly, and some homeowners find the look and feel less like a traditional deck than wood or wood-look composite. It's also a poor match for anyone who wants a warm, natural aesthetic — it reads as modern and industrial rather than rustic.

What to Avoid Here and Why

A few choices we steer homeowners away from, based on what actually fails on Northwest decks:

• Exotic hardwoods like ipe without a real maintenance plan. These woods are dense and rot-resistant, but they need regular oiling to keep their color, they're expensive, and sourcing can be inconsistent. Skip the upkeep and the wood grays out unevenly, so the cost premium isn't worth it.
• Plain steel fasteners in treated lumber. The copper-based preservatives in modern pressure-treated wood corrode standard steel screws and joist hardware over time, especially with our rainfall. Hot-dip galvanized or stainless fasteners cost more upfront but prevent streaking and weakened connections.
• Smooth, uncapped, or partially capped composite boards on shaded decks. These are the boards most likely to develop a slippery moss film in wet months, and most at risk of the moisture problems that gave early composite decking a bad reputation.
• Undersized or under-flashed ledger connections. This isn't about the decking surface, but it's the most common structural shortcut we see on older decks here — a ledger attached without proper flashing lets water into the house rim joist, which rots from the inside out long before the deck boards show a problem.

FAQ

How long does composite decking actually last in the Skagit Valley's wet climate?

A quality capped composite deck, properly installed with good drainage underneath, typically holds up well for two to three decades in this climate. The main variable isn't the winter rain itself — modern capped composites handle that fine — it's whether the deck was built with enough airflow and slope to drain, and whether shaded sections get an occasional wash to prevent algae buildup.

Does cedar decking need to be sealed every year in this area?

Not every year, but it shouldn't go more than two to three years without a fresh water-repellent sealant if you want to preserve its color. If you're fine letting it weather naturally to gray, you can stretch that further, since cedar's natural oils still provide baseline rot resistance even unsealed — it just won't look as rich.

What's the best decking for a deck on Camano Island or another spot near saltwater?

PVC and aluminum decking generally handle salt air and constant dampness best, since neither has wood fiber to absorb moisture. Composite is a reasonable middle option if budget matters, as long as fasteners and railing hardware are corrosion-rated for coastal exposure.

Can a deck be built here so it doesn't get slippery every winter?

Yes, but it depends more on design and maintenance than on picking one non-slip material. Textured composite, PVC, or aluminum boards resist algae film better than smooth wood, and orienting a deck for some sun exposure reduces the shaded, damp conditions moss needs. A seasonal cleaning with a deck-safe cleaner keeps almost any material safe underfoot through the wet months.

Ready to Talk Through Your Deck

Every lot in Skagit, Island and Whatcom counties handles rain, shade and wind a little differently, and the right decking choice depends on your specific site as much as your budget. Alpine Exteriors has built and repaired decks across Mount Vernon, Anacortes, Burlington, Sedro-Woolley, La Conner, Stanwood, Camano Island and Bellingham, and we're happy to walk your property and lay out honest options for a new deck or repair. Alpine Exteriors is licensed in Washington under contractor license ALPINI751OW — reach out for a straightforward, no-pressure assessment of what will actually hold up on your lot.