Composite Decking for Guemes Island Homes

Building a Deck That Can Actually Handle Guemes Island

Guemes Island sits right out in Rosario Strait, which means most homes here get more direct weather than a comparable lot a few miles inland in Anacortes. Salt-laden wind off the water, long stretches of driving rain through fall and winter, and shaded, damp corners that stay wet for weeks at a time — all of it works on an outdoor deck harder than most manufacturers' warranty language ever accounts for. Composite decking can handle that environment well, but only if it's specified and installed with the island's conditions in mind, not just built to a generic spec sheet.

We're not talking about swapping wood boards for composite boards and calling it done. The framing underneath, the fasteners, the drainage path, and even the board profile all need to be chosen differently for a waterfront or near-waterfront lot on Guemes than they would for a sheltered backyard deck across the channel in Anacortes proper.

What Salt Air and Rain Actually Do to a Deck

Two separate problems show up on Guemes decks over time, and they call for different fixes:

• Salt air corrosion: Standard coated screws, cheap joist hangers, and mismatched metal fasteners corrode noticeably faster this close to the water. Once a fastener starts rusting, it stains the board around it and eventually loses grip strength.
• Trapped moisture: Skagit County's wet season means a deck's substructure can stay damp for months. Composite boards themselves don't rot, but the wood framing underneath them absolutely can if it's not protected, and ledger connections at the house are a common failure point if flashing is skipped.

A deck built without accounting for both of these will look fine for a year or two and then start showing problems exactly where they're hardest to fix — inside the framing, under the boards.

What a Correct Composite Deck Build Involves Here

Substructure and Framing Protection

Every joist should get a protective tape or coating over the top edge before boards go down — this is standard good practice everywhere, but it matters more on Guemes because the framing spends more days per year genuinely wet. Ledger boards attached to the house need proper flashing so wind-driven rain, which this stretch of coastline gets plenty of, doesn't track behind the siding.

Fasteners and Hardware

We spec stainless steel or marine-rated coated fasteners and hardware for anything within reach of salt spray, rather than the standard-grade fasteners that are perfectly fine on an inland deck. It costs a bit more up front and saves you from rust streaks and loosening connections a few years in.

Board Selection: Capped vs. Uncapped Composite

Capped composite boards — with a plastic protective shell wrapped around a wood-plastic composite core — resist moisture absorption and staining far better than uncapped composite, which behaves more like the older generation of composite product and can take on water at cut ends and fastener holes over time. For Guemes Island's exposure, we default to capped boards and make sure every cut end gets sealed, because an unsealed cut end is the one place moisture can still work its way in.

Ventilation and Drainage

Low-clearance decks need real airflow underneath, not just a gap. On lots with limited crawl space between the deck framing and the ground, we build in venting and grade the ground below to shed water away from the structure rather than letting it pool.

Moss, Algae, and Keeping the Deck Safe Underfoot

Western Washington's long wet, shaded season grows moss and algae on outdoor surfaces that stay damp and don't get much direct sun — and composite decking is not immune just because it doesn't rot. A north-facing deck under fir or cedar cover on Guemes can develop a slick green film the same way a roof or a shaded walkway does. The fix isn't a different product, it's board texture and a maintenance routine:

• Choose a board surface with a textured, slip-resistant finish rather than a smooth or high-gloss profile, especially on shaded or north-facing decks.
• Plan on a rinse-and-soft-brush cleaning once or twice a year, more often under heavy tree cover.
• Keep overhanging branches trimmed back where possible so the deck gets more sun and dries faster after rain.
• Avoid pressure washing at close range on composite — it can etch the surface texture and actually make future moss grip easier.

Composite vs. Wood Decking for This Environment

Factor	Composite (Capped)	Pressure-Treated Wood
Salt air resistance	Strong — surface doesn't absorb salt or moisture	Moderate — needs regular sealing to keep protection
Rot risk	Very low	Present if sealing lapses, especially in shaded/wet spots
Moss/algae growth	Can occur on shaded boards, cleans off easily	Also occurs, harder to fully clean out of grain
Maintenance routine	Occasional rinse/brush, no staining or sealing	Sealing or staining every 1-3 years
Upfront cost	Higher material cost	Lower material cost
Long-term cost	Lower over 15-20 years with minimal upkeep	Ongoing sealing/repair costs add up

Neither option is "wrong" — some homeowners genuinely prefer the look and feel of real wood and are willing to keep up the sealing schedule. But for a lot of Guemes Island homeowners who aren't out at the property every week, composite's lower maintenance burden is the deciding factor.

Cost Factors to Expect

Every deck is different, but the things that move the price on a Guemes Island project specifically are:

Factor	Why It Matters
Ferry-dependent delivery	Material has to be scheduled around ferry runs, which affects lead time and sometimes delivery cost
Site access	Some island lots have longer carries from the road to the build site than a typical Anacortes in-town lot
Existing structure condition	Rebuilding a deck on an older substructure often means addressing hidden moisture or rot in the framing first
Board and hardware grade	Capped composite and marine-rated fasteners cost more than base-grade materials but hold up better here
Deck size and complexity	Multi-level decks, built-in benches, and railing systems add labor and material

We give straightforward, itemized estimates so you can see where the money is going rather than a single lump number.

Our Process

1. On-site walkthrough: We look at the existing deck or build site, note exposure to wind and water, shade patterns, and the condition of any existing framing.
2. Material recommendation: We talk through board options, colors, and hardware suited to the specific spot on your lot — a sheltered deck off the kitchen and an open waterview deck don't need the same spec.
3. Logistics planning: We build the ferry schedule into our project timeline up front so material delivery doesn't hold up the job.
4. Framing and protection: Joist tape, flashing, and stainless or coated hardware go in before a single deck board is placed.
5. Installation: Boards are laid, cut ends sealed, and drainage checked before final fastening.
6. Walkthrough and care guidance: We show you the finished deck and go over the simple maintenance routine that keeps it looking right.

Why a Crew That Already Works Guemes Island Matters

Any contractor can install composite decking on a dry, sunny day inland. Building one that holds up on Guemes Island means already knowing the ferry schedule well enough to plan material deliveries without wasted trips, already knowing which fastener grade actually holds up a few hundred feet from the water, and already having seen what happens to a deck that skipped flashing or ventilation during a wet Skagit County winter. That kind of knowledge doesn't come from a spec sheet — it comes from having built and repaired decks on the island already.

We also know the practical side of working out here: coordinating access with a property that's only reachable by ferry, keeping a tight materials list so we're not making unnecessary extra crossings, and building a schedule that respects that this is an island job, not a standard in-town job with the same logistics.

Simple Maintenance Checklist for Guemes Island Composite Decks

• Rinse and soft-brush the deck surface once or twice a year, more often under tree cover.
• Check and clear gaps between boards where debris and organic matter can collect and hold moisture.
• Inspect visible fasteners and railing hardware annually for early rust, especially after winter storms.
• Trim back overhanging vegetation to improve sun exposure and airflow.
• Confirm under-deck ventilation gaps and drainage paths aren't blocked by stored items or plant growth.
• Address any soft spots or movement in railing posts promptly — they usually point to a framing issue, not a surface one.

Let's Talk About Your Deck

If you're planning a new composite deck on Guemes Island or replacing one that's showing its age, we're happy to walk the site, look at what you're working with, and put together a straightforward, no-pressure estimate. Use the form below to get started.