How is a deck contractor different from a general contractor for a project like this?

A dedicated deck and exterior crew works with framing, flashing, and decking materials daily and knows the failure points specific to coastal exposure, like ledger flashing and fastener corrosion. A general contractor may build a structurally sound deck but miss the moisture and weather details that matter most in this location.

What should I ask a contractor before hiring them for composite decking work?

Ask whether they inspect and address the existing framing (not just resurface over it), what fastener and hardware grade they use, and whether they follow the manufacturer's installation specs closely enough to keep the product warranty valid. Also ask for references from other coastal or waterfront properties, since inland deck experience doesn't always translate.

What's the actual difference between capped and uncapped composite decking?

Capped composite boards have an outer polymer shell wrapped around the core that blocks moisture absorption and resists staining and fading. Uncapped or partially capped boards are more prone to moisture getting into the core over time, which matters more in a wet, salty climate like this one than in a drier region.

Do all composite decking brands perform the same in a marine environment?

No — board density, cap thickness, and how well a product resists color fade under UV and salt exposure vary by manufacturer and product line. We can walk through the options and explain the honest trade-offs for a property this close to the water rather than pushing one brand.

Does Semiahmoo's proximity to the water actually change how a deck should be built compared to other parts of Whatcom County?

Yes — closer proximity to salt water means more corrosion-resistant hardware, more attention to wind-driven rain at flashing points, and often more shade and dampness depending on the lot, all of which affect material choices and detailing. It's not a different deck, just a more exposure-conscious build.

Composite Decking Built for Semiahmoo's Coastal Climate

Decking That Has to Work in a Marine Climate

Semiahmoo sits close enough to the water that homes here deal with a different set of conditions than decks built ten or twenty miles inland. Salt-laden air, wind-driven rain that gets pushed sideways under normal flashing details, and a long wet season that keeps surfaces damp for months at a time all add up to faster wear on outdoor living spaces. A deck that would hold up fine in a drier part of Whatcom County can start showing problems within a few years out here if it wasn't built with this specific environment in mind.

Composite decking has become the material of choice for homeowners in this area for good reason, but "composite" isn't one product — it's a category, and how it's installed matters as much as which brand you pick. This page walks through what Semiahmoo homes actually need from a deck, what a correct installation looks like, and how we approach these projects.

What Salt Air, Rain, and Moss Actually Do to a Deck

Salt Air and Metal Fasteners

Airborne salt accelerates corrosion on anything metal — fasteners, joist hangers, screws, railing brackets. On a standard wood deck, corroding fasteners eventually stain the boards, weaken connections, and create the streaking you sometimes see running down from screw heads. Composite decking doesn't eliminate this risk on its own; the substructure underneath is still typically wood-framed with metal hardware, so the fastener and hardware specification matters just as much as the decking material itself.

Driving Rain and Hidden Moisture

Rain that comes in at an angle finds its way into places vertical-only flashing details were never designed to handle — ledger board connections, stair stringers, the gap where decking meets a house wall. Moisture that gets trapped against framing without a way to dry out is what leads to rot, even under boards that look fine from above. This is arguably the single biggest factor in how long a deck lasts in this climate, and it has almost nothing to do with the decking brand and everything to do with the build underneath it.

Moss and Extended Dampness

Whatcom County's moss season is long, and a deck that stays shaded or doesn't get much airflow underneath will grow moss and algae on its surface just like a roof does. On wood decking this means regular cleaning and eventually resurfacing. On composite decking, moss and mildew mostly stay on the surface rather than working into the material, but surfaces still need airflow and periodic cleaning to keep from becoming slick — a real safety issue on stairs and near doorways.

Why Composite Decking Fits This Environment

We install composite decking on Semiahmoo homes because it holds up to this specific combination of conditions better than the alternatives, without pretending it's maintenance-free. Here's how the common options compare for a coastal, high-moisture property:

Material	Moisture Behavior	Maintenance	Typical Lifespan Here
Pressure-treated wood	Absorbs and releases moisture repeatedly; prone to warping, splitting, and rot at fastener points in wet climates	Annual cleaning, periodic staining/sealing	10-15 years before major repair or replacement
Cedar	Naturally rot-resistant but still absorbs moisture; surface checking common with repeated wet/dry cycles	Regular sealing to maintain color and water resistance	15-20 years with upkeep
Composite decking	Capped boards shed water at the surface and don't swell, splinter, or absorb moisture the way wood does	Periodic washing; no staining or sealing	25-30+ years, backed by manufacturer warranty
Uncapped/older composite	Can absorb moisture at the core over time if not fully capped; more prone to staining and mold on the surface	More frequent cleaning; some products require sealing at cut edges	Shorter than fully-capped composite; varies by product

We generally recommend fully-capped composite boards for Semiahmoo projects rather than older uncapped composite products. The extra cap layer is what actually resists the moisture and salt exposure this location sees — it's not a marketing detail, it's the part doing the work.

What a Correct Composite Deck Installation Involves

The decking boards get the attention, but the framing underneath is what determines whether a deck lasts. On every Semiahmoo composite deck we build or replace, the following gets real attention, not a shortcut:

Ledger board flashing — a proper self-adhered flashing membrane and metal drip cap where the deck attaches to the house, sized to shed wind-driven rain rather than just vertical rainfall
Joist tape on top of every framing member, to keep rain from sitting directly on cut wood and driving rot from the top down
Corrosion-resistant fasteners and hardware rated for the coastal exposure, not standard interior-grade hardware
Proper board spacing and hidden fastener systems that allow composite boards to expand and contract with temperature without buckling
Ventilation underneath the deck so trapped moisture and shaded, damp air don't sit against the framing year-round
Drainage away from the foundation so water shed off the deck doesn't pool against the house

Skip any one of these and you can end up with a deck that looks new on top while the frame underneath is quietly failing — a problem we see often on older decks we're asked to replace in this area.

Our Process for Semiahmoo Composite Decking Projects

Every property is a little different depending on how exposed it is to wind and salt spray, how much shade it gets, and the condition of any existing structure. Our process:

On-site assessment — we look at the existing deck or build site, note exposure to weather and moisture patterns specific to that lot, and check for any existing rot or drainage issues.
Framing evaluation — if we're replacing an existing deck, we inspect the substructure rather than just building over it. Compromised framing gets addressed before new decking goes down.
Material and layout selection — we walk through board options, colors, and railing choices suited to a coastal setting, with honest input on which products handle this climate best.
Installation — flashing, joist tape, ventilation, and hardware specified for the exposure, then the composite decking itself, installed to the manufacturer's spacing and fastening specs so the warranty stays valid.
Final walkthrough — we go over basic care so the deck is easy to keep looking good through the wet months.

Keeping a Composite Deck Looking Good Through Moss Season

Composite decking is genuinely lower-maintenance than wood, but "low-maintenance" isn't "no-maintenance," especially this close to the water. A simple seasonal routine keeps a Semiahmoo deck performing the way it should:

Sweep off debris and standing pine needles or leaves regularly — trapped organic matter holds moisture against the board surface
Hose down or wash the deck surface a few times a year to clear salt residue and prevent surface mildew from taking hold
Check that gaps between boards and around posts stay clear so water keeps draining rather than pooling
Rinse railings and hardware periodically — salt buildup on metal components accelerates corrosion faster than on the decking itself
Watch shaded, low-airflow areas under overhangs for moss growth and clean those spots more often than sun-exposed areas

Cost Factors for a Semiahmoo Composite Deck

Every project is different, but the same handful of factors drive most of the cost difference between one composite deck and another in this area:

Factor	Why It Affects Cost
Deck size and shape	More square footage and more angles/cuts increase material and labor
Framing condition	Replacing rotted or undersized framing adds cost but is not optional if the substructure is compromised
Board tier	Fully-capped, higher-end composite boards cost more upfront than base-tier composite or wood, but cost less over the life of the deck
Height and railing requirements	Elevated decks need code-compliant railing and sometimes additional structural support
Site access	Waterfront and hillside lots common around Semiahmoo can add labor time for material staging and equipment access

We provide a written estimate that breaks these factors down so you know exactly what you're paying for, rather than a single lump number.

Why Hire a Crew That Already Works in Semiahmoo

A contractor who mostly builds decks inland doesn't always account for salt exposure, wind-driven rain angles, or how much moss growth a shaded, damp deck will see in a full Whatcom County winter. Building to a dry-climate standard in a coastal setting is one of the more common reasons we get called out to look at decks that are failing well before they should. Working regularly in this specific area means we're not guessing at flashing details or hardware specs — we're applying what we already know holds up here.

Ferndale Roofing Co has built its reputation on doing exterior work right the first time, and composite decking is an extension of that same standard: correct flashing, correct drainage, correct materials for the exposure, done by people who show up and stand behind the work.

If you're planning a new composite deck or need to replace one that's showing its age, we're happy to take a look and put together a free, no-pressure estimate. There's no obligation — just an honest read on what your project needs. Use the form below to get started.