Ferndale Siding Composite Decking in Cordata: Built for What This Climate Actually Does
Cordata sits in the same weather pattern as the rest of our Whatcom County service area: long stretches of driving rain from fall through spring, a marine air layer that carries salt and moisture even well inland, and a moss season that can run eight months or more if surfaces stay shaded and damp. A deck out here isn't just outdoor furniture — it's a structure that sits low to the ground, collects standing water in the wrong details, and gets almost no break from moisture between October and May.
Composite decking handles that environment better than most alternatives, but only if it's installed with that environment in mind. A composite deck installed the way a contractor might build one in a dry inland climate will still grow moss in the gaps, trap water at the ledger, and loosen fasteners within a few seasons. The material is only half the equation — the build is the other half.
Why Composite Makes Sense for This Area
Wood decking isn't a bad product, but it asks a lot of a homeowner in a climate like this: annual sealing, sanding, and constant vigilance against rot at fastener holes and board ends. Miss a year of maintenance and moss takes hold fast, especially on north-facing or shaded sections of a deck, which describes a lot of yards around here.
Composite decking — a blend of wood fiber and plastic, either capped with a protective outer shell or left uncapped — doesn't absorb water the way solid wood does, so it doesn't swell, cup, or rot from the inside. That doesn't make it maintenance-free, but it removes the single biggest failure point we see on wood decks in this region: moisture getting into the board itself.
What Composite Doesn't Fix
Composite won't stop moss from growing on the surface if it stays wet and shaded — moss doesn't care what the board is made of, it cares about moisture and lack of sun. It also won't compensate for a bad substructure. If the frame underneath is undersized, poorly spaced, or missing proper drainage, the deck will still perform poorly no matter how good the decking material is.
What a Correct Composite Deck Build Involves
Substructure and Joist Protection
The joists carrying a composite deck take on more, not less, moisture exposure than the decking itself, since they sit underneath and rarely dry out between rain events. We use joist tape or an equivalent moisture barrier on the top of every joist to keep water from sitting on bare wood under the boards. Skipping this step is one of the most common shortcuts we see on decks that show early rot at the frame while the composite surface still looks fine.
Ledger Board and Flashing
Where a deck attaches to the house, the ledger board and its flashing are doing the most important water-management work on the whole structure — and this is where our background in siding and building envelopes matters. A ledger that isn't properly flashed and integrated with the house's water-resistive barrier will let water track behind the siding and into the wall framing, which is a far more expensive problem than anything happening on the deck surface. We treat this connection with the same care we'd use on any siding-to-structure transition.
Fastening System
Hidden fastener systems are standard on most composite decking today and give a cleaner look with no exposed screw heads for water to pool around. We match the fastener spec to the specific composite product being installed — spacing, gap width, and fastener type all affect how the deck handles seasonal expansion and contraction, which is more pronounced in composite than in wood.
Capped vs. Uncapped Composite
Most composite decking on the market today falls into one of two categories, and the difference matters more in a wet climate than in a dry one.
| Feature | Capped Composite | Uncapped Composite |
|---|---|---|
| Moisture resistance | Protective shell resists surface moisture absorption | More exposed to moisture at the surface over time |
| Moss/mildew resistance | Smoother surface, generally easier to keep clean | Can hold onto surface grime and organic growth more readily |
| Fade resistance | Better long-term color retention | More prone to fading and graying over years |
| Upfront cost | Higher | Lower |
| Best fit here | Recommended for most Cordata-area installs given the wet season length | Workable for covered or partially protected decks |
We'll walk through both options honestly during an estimate rather than defaulting to the more expensive product — the right call depends on sun exposure, whether the deck is covered, and budget.
Moss, Mildew, and the Long Wet Season
Moss growth on composite decking is a surface issue, not a structural one, but it's the complaint we hear most from homeowners in this area once a deck has been in a year or two. A few build-stage decisions make a real difference:
- Board orientation and gap spacing that lets water actually drain instead of pooling in low spots
- Keeping the deck surface a proper height above grade so airflow underneath can help things dry out
- Choosing a capped product with a textured, non-glossy finish in shaded or north-facing areas, where moss pressure is highest
- Avoiding tight board-to-siding or board-to-foundation gaps that trap leaves and debris where they hold moisture
None of this eliminates the need for occasional cleaning, but a deck built with drainage and airflow in mind needs far less scrubbing than one that wasn't.
Our Process
We keep the process straightforward because most of the value is in getting the details right the first time, not in a complicated sales process.
- On-site assessment — we look at sun exposure, grade, drainage, and how the deck will attach to the house before recommending a product.
- Product and layout recommendation — capped or uncapped, board pattern, and railing options based on your site conditions and budget, not a one-size-fits-all package.
- Framing and moisture protection — joist tape, proper ledger flashing tied into the existing wall assembly, and a substructure sized for the load and span.
- Decking installation — hidden fasteners, correct gapping, and attention to how each board handles water at the edges.
- Walkthrough and care guidance — what to expect from the product, cleaning recommendations, and what a normal amount of seasonal color change looks like versus something worth a call back.
Cost Factors
Every deck is different, so we won't quote a number without seeing the site, but these are the main variables that move the price:
| Factor | Why It Matters |
|---|---|
| Deck size and shape | Square footage and complexity (angles, cutouts, multiple levels) drive material and labor |
| Capped vs. uncapped composite | Capped products cost more upfront but generally hold up better in a wet climate |
| Height above grade | Taller decks need railing and often more substantial framing and footings |
| Ledger vs. freestanding | Ledger-attached decks require careful flashing work tied into the house; freestanding decks avoid that but need their own footing layout |
| Site access | Sloped yards or limited equipment access can add labor time |
Why a Crew That Already Works Cordata Matters
A lot of what makes a composite deck last in this part of Whatcom County isn't on the spec sheet — it's knowing how the salt-laden marine air, the length of the rainy season, and the moss pressure on shaded lots actually play out over a few years, not just at installation. We build decks the same way we approach siding: with the assumption that this structure needs to shed water correctly for the long haul, not just look good on day one. A crew that works this area regularly has already seen which details hold up and which ones cause callbacks two winters later — and builds accordingly from the start.
Maintenance Checklist for Composite Decks in This Climate
- Sweep debris off the deck regularly, especially in fall when leaves and needles accumulate
- Rinse the surface a few times a year to discourage moss and mildew buildup, more often in heavily shaded areas
- Check that gaps between boards and along the house line stay clear of trapped debris
- Inspect railing and fastener points annually for movement
- Confirm the area under the deck stays ventilated and isn't collecting standing water
If you're weighing a new composite deck or replacing an aging wood one in the Cordata area, we're happy to take a look and give you a straightforward, no-pressure estimate — just fill out the form below.