Anacortes Window Why Guemes Island Decks Take More Punishment
Guemes Island sits just across the channel from Anacortes, reachable by a short ferry ride, and that short crossing changes more about a construction project than most homeowners expect. The island catches salt air off the surrounding water on every side, not just from one direction the way a mainland lot might, and it takes the same driving rain and long moss season that punishes exteriors throughout Skagit County — with less tree cover and fewer wind breaks in a lot of spots to soften it. A deck has no roofline or siding to shield it from any of that. It sits outside, exposed on top and underneath, in exactly the conditions that wear exterior work down fastest.
Composite decking is a good answer to that kind of exposure, but "composite" covers a wide range of product quality, and a deck's actual performance on Guemes Island depends as much on the substructure, fasteners, and drainage details as it does on the boards themselves. This page covers what a Guemes Island home actually needs from a composite deck, what a correct build involves out here, and why working with a crew that already services the island — ferry logistics included — makes a real difference in how the project goes.
What Guemes Island's Climate Actually Does to a Deck
Salt Air From Every Direction
A mainland deck usually takes salt exposure from one prevailing direction. On an island surrounded by water on all sides, that exposure comes from wherever the wind happens to be blowing that day, which means fasteners, brackets, and railing hardware are working against corrosion more consistently than they would on a comparable inland lot. A fastener that starts corroding loses holding strength well before it looks obviously bad, and on a structure people walk and stand on, that's a real concern, not a cosmetic one.
Driving Rain With Little to Break It
Much of Guemes Island is lower, more open terrain than the wooded mainland shoreline nearby, which means storms coming off the water often arrive with less to slow them down before they reach a house. Wind pushes rain sideways and drives it up under railings, into ledger connections, and between deck boards that aren't gapped correctly for it. A deck that sheds water fine on a calm day can still trap moisture the moment wind gets involved — and out here, wind is involved often enough that it has to be a design assumption, not an occasional exception.
A Moss Season That Runs Most of the Year
Mild, damp conditions give moss and mildew a long growing season across this part of Skagit County, and a horizontal deck surface is one of the first places it takes hold — it holds water longer between rain events than a vertical wall ever does. Shaded decks and north-facing surfaces usually show it first, and any decking material with even a little surface porosity gives moss something to grip onto over a season or two.
Ferry Access and What It Means for the Job
Every board, fastener, and piece of equipment for a Guemes Island deck has to cross on the ferry, which means the project runs on a schedule that a mainland job simply doesn't have to account for. Missing a load or under-ordering a material means waiting for the next crossing, not a quick trip back into town. It also means a well-planned material list and a crew that knows how to sequence a build around ferry timing matter more here than they would on the Anacortes side of the water — a detail that's easy to underestimate until it's actually holding up your project.
What "Composite Decking" Actually Means
Composite decking is generally a blend of wood fiber and plastic, but the ratio, the plastic type, and how the board is finished vary a lot between manufacturers. Two distinctions matter most for an island application:
Capped vs. Uncapped
Capped composite boards have a plastic shell wrapped around a wood-plastic composite core, which protects the core from moisture absorption, staining, and UV fade. Uncapped composite is the older style of the product — the wood-plastic blend is exposed on all sides, so it absorbs more moisture and is more prone to fading and mold growth over time. In a salt-air, high-moisture environment like Guemes Island, that difference shows up faster than it would somewhere drier, which is why we standardize on capped composite for island work.
Cellular PVC as an Alternative
Some manufacturers also offer fully cellular PVC decking, which contains no wood fiber at all. PVC resists moisture absorption completely and some lines run cooler underfoot, but it can flex more than composite under heavy point loads and generally costs more up front. We'll walk through whether capped composite or PVC makes more sense for a specific deck based on sun exposure, budget, and how the space gets used — there isn't one right answer for every lot.
What a Correct Composite Deck Build Involves Here
The decking boards get most of the attention, but on an island site the substructure and fastening details are what actually determine whether a deck holds up. A build done right for Guemes Island conditions includes:
- Framing material suited to sustained moisture exposure — pressure-treated lumber rated for the application, sized correctly for the span and load
- Stainless steel or coastal-grade corrosion-resistant fasteners throughout, not standard hardware that starts corroding within a few seasons out here
- Hidden fastener systems on the deck surface where the product allows, reducing exposed metal and giving a cleaner walking surface
- 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, which on an open island lot can be more than homeowners assume
- Grading and drainage around the substructure that accounts for the property's private well or septic system, since a deck built too close to a drainfield or without proper runoff planning can create problems well beyond the deck itself
Skip any one of those and the deck usually still looks fine on day one. The problems show up a few winters later, as a soft joist, a loosening railing post, or fastener corrosion staining the boards around it.
Composite Decking Compared to the Alternatives
| 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 |
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 the property's well or septic system is laid out relative to where the deck will sit. From there we talk through decking material options that fit the budget and how the space will actually get used.
Permitting on Guemes Island runs through Skagit County, and unincorporated island properties can carry their own set of setback and septic-related considerations that a straightforward mainland lot doesn't. We handle that permitting process as part of the job. Materials and equipment get staged and scheduled around the ferry ahead of time, so the crew isn't waiting on a crossing mid-build. Once everything's on-site, the build itself 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 crew that mostly builds decks on the mainland can still put one together competently, but a Guemes Island job has variables that don't come up as often in Anacortes proper — ferry-dependent scheduling for materials and equipment, salt exposure from every direction instead of one, and permitting and drainage considerations tied to private wells and septic systems rather than municipal utilities. Working this island regularly means we're not learning those requirements on your project. We know how to plan a material list around the ferry schedule, which fastener grades actually hold up out here, and how Skagit County permitting applies to an unincorporated island property.
That familiarity also shows up in the smaller judgment calls — how to sequence a build so the crew isn't stranded waiting on a crossing, or being straightforward about what a deck on Guemes Island realistically needs to last versus what's just an extra line item.
Get a Straight Answer About Your Deck
Whether you're replacing a tired deck, building new, or just want an honest read on what a composite 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.