How long does a composite deck installation typically take?

A straightforward composite deck replacement on an existing footprint usually takes several days to about a week, depending on size and whether framing repairs are needed. New builds or larger decks with custom rail systems can take longer. Weather windows around San Juan Island's wetter months can also affect scheduling.

What should I ask a contractor before hiring them for deck work here?

Ask whether they'll inspect and address the substructure and flashing, not just install new boards over existing framing, and ask what fastener and hardware grade they use given the salt air exposure. Also ask for their approach to ledger flashing at the house connection, since that's a common failure point in wind-driven rain. A contractor who can answer these specifically, rather than generically, is a good sign.

Are all composite decking brands basically the same?

No — composite lines vary in cap material, core composition, and how they handle moisture and UV exposure over time, and those differences matter more in a marine climate than a dry one. We recommend specific lines based on how they've performed in coastal Pacific Northwest conditions rather than picking one product for every job. We're glad to walk through the options and trade-offs during an estimate.

What's the difference between capped and uncapped composite boards?

Capped composite boards have a polymer shell wrapped around the composite core, which resists moisture absorption, staining, and fading better than uncapped boards where the raw composite material is exposed. In a damp, salt-exposed climate like San Juan Island's, that cap layer meaningfully reduces how much moss, staining, and surface wear the deck picks up over time. It's generally worth the modest cost difference here.

Does San Juan Island's damp climate mean composite decking needs different spacing or drainage than a drier area?

Yes — we typically hold tighter expansion gaps and pay closer attention to under-deck ventilation and drainage slope than you'd see in installation guides written for drier climates. The extended damp season and driving rain here mean water needs a clear path off and out from under the deck, or it lingers longer than the material is designed to tolerate. Getting this right at installation avoids moisture-related issues showing up years later.

San Juan Island Composite Decking Installation & Replacement

Composite Decking Built for San Juan Island Conditions

A deck on San Juan Island lives a harder life than the sales brochures suggest. It sits under a marine layer that rolls in and out through much of the year, takes on salt-laden air off the surrounding water, and spends long stretches of fall and winter under a film of moisture that never fully dries between storms. Add a shoulder season where moss and algae take hold on any shaded, north-facing, or tree-covered surface, and you've got a decking material problem that's different from what a contractor in a dry inland climate deals with. Composite decking, installed correctly, holds up well to this — but "installed correctly" is doing a lot of work in that sentence, and it's where a lot of decks on this island run into trouble.

This page covers what composite decking actually needs to perform here, what a correct installation looks like from the substructure up, and how we approach the work as a crew that's out on San Juan Island regularly rather than passing through once.

Why the Local Climate Changes the Decking Conversation

Salt Air and Metal Fasteners

San Juan Island's proximity to salt water means airborne salt settles on every exterior surface, including deck framing, fasteners, and hardware. Standard fasteners corrode faster here than they would twenty miles inland. That corrosion doesn't just stain the board around the screw head — over years it weakens the connection between the board and the joist, which is a structural issue, not a cosmetic one. Fastener and hardware selection matters more here than in most parts of the state.

Driving Rain and Drainage

Rain on the islands doesn't always fall straight down. Wind-driven rain gets pushed sideways into ledger connections, under rail posts, and into any gap where flashing was skipped or done as an afterthought. A deck that sheds water fine in a calm rain can still take on water at the house connection during a wind event. Drainage detailing at the ledger board and around post bases is one of the first things we check on both new builds and repair calls.

Moss, Algae, and Shade

Between the tree cover common on island lots and the extended damp season, moss and green algae film show up fast on any deck surface that doesn't get regular sun and airflow. This is mostly a surface and maintenance issue on composite decking rather than a structural one, but the board's surface texture and the substructure's ventilation both affect how bad it gets and how hard it is to keep ahead of.

What Correct Composite Decking Actually Involves

Composite boards themselves are a relatively forgiving, low-maintenance product — that's the whole appeal. But the board is only as good as what's underneath and around it. A correct composite deck installation here includes:

A structurally sound substructure — joists, beams, and posts sized and spaced to the composite manufacturer's specs, which are often tighter than dimensional-lumber spacing because composite boards flex differently than wood
Proper ledger flashing where the deck ties into the house, so wind-driven rain can't work its way behind the siding or into the rim joist
Corrosion-resistant fasteners and hardware rated for coastal/marine exposure, not standard exterior-grade hardware
Joist tape or another moisture barrier on top of the framing to slow rot at the fastener penetrations, which is cheap insurance against the damp season
Correct board spacing and expansion gaps, since composite material expands and contracts with temperature and moisture more than people expect
Ventilation underneath the deck so trapped moisture and shaded, damp air don't accelerate substructure rot or feed moss growth on the underside and edges
Hidden fastener systems or manufacturer-approved face-screwing, done to spec so board edges stay tight and don't telegraph fastener lines over time

Skip any one of these and the composite boards can look fine on the surface while the framing underneath is quietly failing — which is exactly the kind of problem that shows up as a soft spot or a loose rail three or four years later, well after the original installer is gone.

Composite vs. Wood vs. PVC — An Honest Comparison for This Climate

We install more than one decking material, and each has real trade-offs. Here's how they compare specifically for San Juan Island's conditions:

Material	Moisture/salt air behavior	Maintenance	Upfront cost
Composite decking	Resists rot and swelling well; surface can still grow moss/algae in shaded, damp spots without cleaning	Periodic washing to stay ahead of moss; no staining or sealing required	Mid to upper range
Pressure-treated wood	Prone to warping, splitting, and rot acceleration in prolonged damp; treatment slows but doesn't stop it	Regular sealing/staining needed, more often in this climate than inland	Lowest
Cedar	Naturally rot-resistant but still weathers and grays quickly in salt air and rain	Sealing or staining to maintain appearance; more upkeep than composite	Mid range
PVC/capped polymer	Fully resists moisture absorption; performs very well in wet, salty conditions	Lowest maintenance; occasional washing	Highest

For most San Juan Island homeowners, composite hits the practical middle ground: it handles the moisture and salt exposure far better than uncapped wood, doesn't demand a sealing schedule, and costs less than full PVC systems — with the honest caveat that it still needs occasional cleaning to stay ahead of moss and surface grime in shaded spots.

Repair, Resurface, or Full Replacement?

Not every deck on the island needs to be torn out. When we get a call about a tired or damaged deck, we're figuring out which of three categories it falls into:

Repair

Isolated board damage, a few failed fasteners, or a soft spot in one section of framing can often be repaired without replacing the whole deck — as long as the rest of the substructure tests sound.

Resurface

If the framing underneath is still structurally solid but the old decking (often wood, or an early-generation composite) has reached the end of its life, we can often reuse the substructure and install new composite boards on top, which saves demolition cost.

Full Replacement

If the joists or ledger connection show rot, if the deck was undersized or under-flashed from the start, or if the framing spacing doesn't meet current composite manufacturer specs, resurfacing isn't an honest option — we'll tell you that rather than screw new boards onto a bad foundation.

We'll always tell you which category your deck falls into before we quote anything, and why.

Our Process, Start to Finish

On-site evaluation. We walk the existing deck or the build site, check framing condition and moisture exposure, and talk through what you actually use the space for.
Material and layout plan. We recommend a composite line and color based on your home, sun/shade exposure, and budget, and lay out board direction and rail style.
Framing and flashing work. Any needed substructure repair, ledger flashing, and moisture barrier work happens before a single composite board goes down. This is the step that gets skipped by rushed installs and it's the one that determines how the deck ages.
Composite installation. Boards, fasteners, and rail systems go in to manufacturer spec, with attention to expansion gaps and fastener corrosion resistance.
Final walkthrough. We review the finished deck with you, including basic care guidance for keeping moss and algae off the surface through the wet months.

Maintenance Checklist for Composite Decks in This Climate

Composite decking is low-maintenance, not no-maintenance, especially given San Juan Island's damp shoulder seasons. A simple annual routine goes a long way:

Rinse or sweep debris and organic buildup off the deck surface regularly, especially in shaded areas
Wash the deck with a soft-bristle brush and a composite-safe cleaner once or twice a year to remove moss and algae film before it sets in
Check that gaps between boards and along the deck perimeter stay clear so water can drain rather than pool
Inspect fastener heads and railing hardware once a year for early rust or corrosion staining
Trim back overhanging branches and vegetation that keep sections of the deck shaded and damp longer than the rest
Confirm under-deck ventilation gaps and vents (if present) stay clear of debris

Why Hire a Crew That Already Works San Juan Island

Ferry scheduling, material logistics, and site access on the islands are different from a mainland job, and it shows in how a project gets planned and staged. A crew that regularly works San Juan County already has these logistics worked out, already knows which composite lines and hardware hold up to local salt exposure, and isn't learning the region's drainage and moss issues on your project. We also stand behind the work with a local presence — if something needs a look after the fact, we're not a ferry-and-a-half away with no history on the job.

If you're weighing a new composite deck, a resurface, or a repair on San Juan Island, we're happy to take a look and give you a straight read on what your deck actually needs. Reach out for a free, no-pressure estimate using the form below.