Anacortes Siding Building a Deck for Guemes Island's Marine Climate
Guemes Island sits just across the channel from Anacortes, reachable only by a short county-run ferry, and that separation shapes more about a deck project here than most homeowners expect going in. Every property on the island is surrounded by salt water, which means salt-laden air, wind-driven rain, and a long moss season aren't occasional weather events — they're the baseline conditions a deck has to live in every single day of the year. A deck is a structure with no roof over it, sitting outside in exactly the conditions that wear exterior work down fastest, and on an island that exposure is constant rather than intermittent.
Building a deck correctly for Guemes Island isn't just a matter of layout and looks, though those matter too. It comes down to material selection, fastener grade, and drainage details that actually hold up to sustained salt exposure and moss pressure, plus a construction schedule that accounts for the fact that materials and crews get to the site by boat. This page covers what a Guemes Island deck actually needs from the build, what correct work looks like, and how our process runs for a deck project on the island specifically — not a generic write-up that happens to mention it.
What Guemes Island's Climate Does to a Deck
Salt Air
Being surrounded by water on all sides means salt-laden air reaches every part of the island, not just the lots with a direct water view. Salt accelerates corrosion in any exposed metal — fasteners, brackets, post bases, railing hardware — and a fastener that starts corroding loses holding strength well before it looks obviously bad from the surface. On a structure people walk and stand on, that's a safety issue as much as a cosmetic one, and it's one of the most common corners cut on decks built with standard, non-marine-rated hardware.
Driving Rain
Storms coming across the surrounding water don't fall straight down — wind pushes rain sideways, driving it up under railings, into ledger connections, and between deck boards that aren't gapped or flashed correctly. A deck built to a minimum standard can shed water fine on a calm day and still trap moisture the moment wind gets involved, which on an exposed island lot is often the norm rather than the exception. Elevated decks and lots with open exposure toward the water see this more than sheltered, tree-lined sites.
A Moss Season That Runs Most of the Year
Mild temperatures and near-constant moisture give moss and mildew a long growing season on Guemes Island, and a deck's horizontal surfaces are usually first to show it — they hold water longer than a wall and stay damp between rain events. Shaded decks and north-facing surfaces are typically hit hardest, and any decking material with even modest surface porosity gives moss something to grip and spread from.
Choosing the Right Decking Material for This Climate
Material choice matters more here than it would on a drier, more sheltered inland lot, because the performance gap between a well-suited product and a poorly-suited one shows up faster on an island surrounded by salt water. The three main categories homeowners weigh are pressure-treated or cedar wood, capped composite, and cellular PVC.
Wood
Pressure-treated lumber and cedar are the traditional choice and look good when new, but both need regular sealing or staining to hold up against sustained moisture, and both are more vulnerable to fastener corrosion issues in salt air over time. Left unmaintained even a season or two, wood on an exposed Guemes Island lot is usually the first material to show moss, graying, and soft spots.
Capped Composite
Capped composite boards have a plastic shell around a wood-fiber composite core, which resists moisture absorption, staining, and UV fade far better than uncapped composite or raw wood. In a salt-air, high-moisture setting like this one, that cap layer is doing real work rather than adding a marketing claim — it's the difference between a board that needs occasional washing and one that needs ongoing sealing.
Cellular PVC
PVC decking has no wood fiber at all, so it doesn't absorb moisture the way even capped composite can at cut edges or fastener holes. It typically costs more up front and can flex more under heavy point loads, but for a deck sitting close to open water or in heavy shade, some homeowners find the added moisture resistance worth the difference in price.
| Material | Handling Salt Air & Moisture | Moss Resistance | Upkeep |
|---|---|---|---|
| Cellular PVC | Excellent — no wood fiber to absorb moisture | Strong, smooth non-porous surface | Occasional washing |
| Capped composite | Strong — cap layer resists moisture and staining | Good on most lines | Occasional washing |
| Uncapped composite | Moderate — some moisture absorption at exposed fiber | Fair; more prone to buildup over time | Periodic cleaning |
| Cedar | Moderate — natural resistance, but needs sealing | Fair when sealed and maintained | Regular oiling or sealing |
| Pressure-treated wood | Weak against sustained salt exposure over time | Poor without regular treatment | Regular sealing or staining |
What a Correctly Built Deck Involves Here
The visible decking surface gets most of the attention when homeowners picture a new deck, but on Guemes Island the framing, fasteners, and drainage details underneath are what actually decide how long it lasts. A build done right for this island includes:
- Framing material rated for sustained moisture exposure — pressure-treated lumber sized correctly for the span and load, not just whatever grade is cheapest to source
- Stainless steel or coastal-grade corrosion-resistant fasteners throughout, not standard hardware that starts corroding in salt air within a few seasons
- Hidden fastener systems on the walking surface where the product allows, reducing exposed metal and giving a cleaner finished look
- Correct board gapping for drainage and material movement, so wind-driven rain and standing moisture can actually drain and dry between boards
- Proper ledger board flashing where the deck ties into the house, since that connection point is one of the most common places moisture gets in on a poorly built deck
- Joist spacing matched to the specific decking product's span rating rather than a generic framing layout
- Railing and post attachment sized for the wind exposure the site actually sees, especially on open or elevated lots
- Ventilation and grading underneath the deck so moisture doesn't sit against the framing between storms
Skip any one of those and the deck usually still looks fine on day one. The problems show up a few winters later — a soft joist, a loosening railing post, or fastener corrosion staining the boards around it.
Ferry Access and What It Means for a Deck Project
Every board, bag of fasteners, and piece of equipment for a Guemes Island deck project has to make the same short ferry crossing the crew does. That's a manageable fact of building here, but it only works smoothly when it's planned for rather than discovered mid-project. Material orders need to be placed with enough lead time to land on the island in the right sequence — framing lumber before decking, decking before railing components — instead of a crew standing around waiting on a delivery that missed a sailing. Crew scheduling works the same way: a well-run island job accounts for ferry timing in the daily plan so the workday isn't cut short by a boat schedule nobody planned around.
None of this changes what the finished deck needs to be built correctly, but it does change how a project gets managed day to day. A crew that treats the ferry as a routine part of the job, not an inconvenience, tends to keep an island project on schedule far better than one working out here for the first time.
Design Considerations for Guemes Island Properties
Beyond material and structure, a deck on Guemes Island has a few site-specific design questions worth working through before anything gets built. Wind exposure affects how open a railing design can be versus how much wind-break value a partial screen or glass panel adds, and that exposure varies a lot from a sheltered, tree-lined lot to an open shoreline site. Sun and shade patterns affect which decking colors and materials will hold up best against fading and moss, since a heavily shaded deck needs different moss-resistance priorities than one that gets sun most of the day. Elevation and grade around the house affect drainage design, stair placement, and whether the substructure needs extra attention for standing water — relevant on a lot of island properties where the house sits well above or below the surrounding grade. None of these are one-size-fits-all decisions, which is part of why a deck designed for a specific Guemes Island lot performs differently than a stock layout dropped onto any site.
How Our Process Works
We start with a site visit to look at what's actually there — existing structure condition if it's a replacement, drainage and grade around the deck area, sun and wind exposure through the day, and how exposed the lot is to open water versus tree cover. From there we talk through decking material options that fit the budget and how the space will actually get used, whether that's a quiet spot off the kitchen or a larger deck built for entertaining.
Permitting for Guemes Island generally runs through Skagit County and follows standard setback, structural, and elevation requirements; we handle that as part of the job rather than leaving it for the homeowner to sort out. Material orders and crew days are scheduled with ferry timing built into the plan from the start, not treated as an afterthought once the job is underway. Once permitted, the build follows the sequence above — substructure and framing first, sized and fastened for the site's actual exposure, then the decking surface, railing, and any stairs or trim work. We finish with a walkthrough covering what the specific material you chose actually needs going forward, which for most modern decking is minimal, but not nothing.
What Your Deck Still Needs From You
Even a well-built deck in the right material needs some routine attention in this climate to get its full lifespan. A short list worth keeping in mind:
- Rinse or wash the deck surface periodically to clear salt residue, pollen, and organic buildup before it works into the surface or cap layer
- Keep gaps between boards clear of leaves and debris so water and airflow can move through the way the design intends
- Check railing posts and hardware once a year for early corrosion or loosening, especially heading into the wet season
- Trim back overhanging branches or plants that hold moisture against the deck or block sun and airflow across the surface
- Address any soft framing or standing water underneath right away — that's a structural issue, not a cosmetic one, and it doesn't improve with time
Why It Matters That We Already Work Guemes Island
A deck crew that mostly builds on the mainland can still put a deck together competently, but a Guemes Island job has variables that don't come up as often elsewhere in Skagit County — corrosion-grade fastener requirements from constant salt exposure on every side of the property, wind loads tied to open water exposure, and a moss season that runs longer here than it does in more sheltered inland towns. Working this island regularly means we're not guessing at those requirements or figuring out ferry logistics for the first time on your project. We've seen which decking lines actually hold up against the island's specific combination of salt air, driving rain, and moss, and which fastener grades and framing details are worth the extra time rather than an upsell.
That familiarity also shows up in the smaller judgment calls — how to orient a deck for the wind a particular lot actually sees, how to sequence material deliveries around the ferry so the job doesn't stall, and being straightforward about what a deck here realistically needs to last versus what's just an extra line item.
Whether you're replacing a tired deck, building new, or want an honest read on what a custom deck would take on your Guemes Island property, we're happy to walk the site with you and lay out the options plainly. Reach out below for a free, no-pressure estimate.