Anacortes Siding What Cap Sante's Exposure Does to a Deck
Homes on the bluff above Anacortes' marina and Guemes Channel get some of the best water views in Skagit County, and some of the toughest conditions for an outdoor deck. Wind comes straight off the water with nothing to slow it down, salt air rides that wind up the hill, and the wet season stretches from October into May most years. A deck built for an inland lot doesn't necessarily hold up the same way on Cap Sante, and we've seen decks up here fail early simply because the exposure wasn't taken seriously at the design stage.
Salt Air and Fastener Corrosion
Salt-laden air off the channel doesn't just affect boats and railings — it works on every piece of exposed metal in a deck: screws, joist hangers, post bases, and railing hardware. Standard coated fasteners can start showing rust streaks on a deck surface within a couple of seasons in this location. Once that happens, the staining is often permanent on the board itself, even if the fastener gets replaced.
Driving Rain and Moisture Cycling
Storms coming off the water tend to drive rain sideways rather than straight down, which means ledger connections, end grain, and any horizontal surface get wetted and dried far more often than a sheltered lot would see. That repeated wet-dry cycling is what causes wood to cup, splinter, and open up at fastener holes. It's also what makes flashing details at the house connection more important here than almost anywhere else in Anacortes.
The Long Moss Season
Many Cap Sante lots have mature evergreen cover, which is part of the appeal but also means shaded, damp deck surfaces for a good chunk of the year. Combined with our long Skagit County wet season, that shade is exactly what moss and algae need to take hold. On a low-drainage deck surface, moss doesn't just look bad — it turns a deck slick and genuinely dangerous underfoot by late winter.
Why Composite Makes Sense for This Climate
We install both wood and composite decking, and we're upfront with Cap Sante homeowners about the trade-offs. For a lot exposed to salt air, driving rain, and heavy shade, composite decking generally holds up with less ongoing work than wood. It won't stop moss from landing on the surface — nothing does — but it doesn't give moss and rot the same foothold that untreated or under-maintained wood does.
| Factor | Wood Decking | Composite Decking |
|---|---|---|
| Moisture absorption | Absorbs and releases water, swells and shrinks | Minimal absorption on capped boards |
| Salt air / fastener staining | Rust streaks show clearly on light wood | Same risk if fasteners are wrong, but boards resist staining better |
| Moss and algae | Takes hold quickly on damp, untreated wood | Grows on surface but doesn't penetrate; easier to remove |
| Maintenance | Annual cleaning, periodic staining or sealing | Occasional washing; no staining or sealing |
| Upfront cost | Lower material cost | Higher material cost |
| Expected life in this exposure | Shorter without consistent upkeep | Longer with correct installation and boards |
Not All Composite Handles Salt Air and Moss the Same
"Composite decking" covers a wide range of products, and the difference matters more on an exposed, shaded lot like Cap Sante than it would on a dry, sunny inland site.
Capped vs. Uncapped Composite
Fully capped composite boards have a polymer shell wrapped around the wood-fiber core, which is what keeps moisture out and gives the surface its moss and stain resistance. Uncapped or partially capped boards leave more of the core exposed at the edges and grooves, which is exactly where moisture sits longest and where moss gets a start first. For this climate, our standard is fully capped product — we'll explain why if a lower-cost uncapped option comes up during a bid.
Board Profile and Drainage
Grooved boards for hidden-fastener systems are the norm now, but the groove itself can become a debris and moisture trap under heavy tree cover. We pay attention to board spacing and substructure slope so water actually gets off the deck instead of sitting in those grooves, since a flat or poorly sloped composite deck in a shaded spot is a moss farm no matter how good the boards are rated.
What a Correct Installation Looks Like Here
Composite decking is often sold as low-maintenance, and it is — but that assumes the installation underneath it was done right. A lot of the problems we get called out to fix on Cap Sante decks aren't about the boards at all; they're about what's underneath and behind them.
The Substructure Matters More Than the Boards
Composite boards are heavier than wood and behave differently under load and temperature swings, so joist spacing and blocking need to match the manufacturer's span tables for this specific product, not generic deck-framing habits. We also use corrosion-resistant hardware throughout the substructure — hangers, post bases, structural screws — because that's the hardware doing the real work of holding the deck up in salty air, long after the deck boards themselves are fine.
Ledger Flashing and Fastening
Where the deck attaches to the house is the single most common failure point we see on wind-and-rain-exposed lots. Proper ledger flashing that sheds water away from the band board, correct structural screws or bolts (not just deck screws) at the ledger connection, and a gap or flashing detail that keeps water from wicking behind the siding are non-negotiable on a Cap Sante install, given how much sideways rain this hill sees in a given winter.
Spacing, Picture-Framing, and Airflow
Board spacing needs to account for composite's expansion and contraction with temperature, and we leave enough airflow underneath the deck for boards to dry out between storms — a tight, unventilated substructure traps moisture and speeds up moss growth on the underside as well as the top. Picture-framed edges (a perimeter border board) look sharp and also protect the exposed end grain of field boards, which is one of the more moisture-vulnerable spots on any composite deck.
Our Process for a Cap Sante Deck Project
- On-site assessment of the lot's specific exposure — wind direction, shade cover, and how water currently moves across the existing deck or ground
- Structural check of any existing framing or ledger connection, since many of these homes have decks added or modified over the years
- Material selection based on budget and exposure, with an honest comparison of capped composite options rather than a single default product
- Installation following manufacturer span and fastening specs, with corrosion-resistant hardware and proper ledger flashing throughout
- Final walkthrough covering drainage, railing hardware, and basic care so the deck starts its life set up correctly
Keeping a Composite Deck Clean Through the Wet Season
Composite decking cuts down on maintenance, but "low-maintenance" doesn't mean "no maintenance," especially under Cap Sante's tree cover. A few habits go a long way toward keeping moss from getting a foothold in the first place:
- Sweep leaves and needles off the deck regularly in fall — trapped organic debris holds moisture and feeds moss
- Wash the surface once or twice a year with a soft-bristle broom and a composite-safe cleaner, not a wood deck cleaner or straight bleach
- Keep a pressure washer on the lowest safe setting and a wide-fan tip if used at all — high-pressure, narrow-tip spray can damage the capped surface
- Check railing posts and fastener heads once a year for early rust staining, especially on the side of the deck facing the water
- Clear gutters and downspouts near the deck so roof runoff isn't adding extra water directly onto the deck surface
- Trim back overhanging branches where practical to cut down on shade and debris without stripping the lot of its tree cover
Why Hire a Crew That Already Works This Hill
Cap Sante isn't a typical building site. Wind loading on railings and structural connections is higher here than on a sheltered inland lot, several homes have view considerations or HOA guidelines that affect railing style and deck placement, and the City of Anacortes permitting process has its own requirements for deck work depending on height and location. A crew that's already done work on this hill knows what inspectors here are looking for, knows how the wind and salt air actually behave on specific streets and elevations, and isn't learning these lessons on your project. As a siding contractor first, we also pay close attention to how a new deck ties into existing siding and trim at the house connection — that's often the detail that gets rushed by decking-only crews and ends up causing water problems years later.
If you're planning a new composite deck or replacing an aging one on Cap Sante, we're happy to come take a look, walk the site with you, and give you a straightforward estimate — no pressure, no upsell, just what your home actually needs. Use the form below to get started.