What's the real difference between composite decking and PVC decking?

Composite blends wood fiber with plastic, giving it a more natural look and feel, while PVC is fully synthetic plastic with no wood content at all. Composite generally costs less and handles heat slightly better underfoot, while PVC tends to resist moisture absorption a bit more since there's no organic material in it. Both are reasonable choices in our climate; the right pick usually comes down to look, budget, and how the deck will be used.

How should I vet a contractor before hiring them for composite deck work in Whatcom County?

Ask to see how they handle the ledger board attachment and flashing specifically, since that detail causes most of the water damage problems on attached decks. Confirm they're licensed and insured, ask about their joist spacing standard for composite versus wood, and ask how they handle drainage and airflow under the deck. A contractor who can answer those questions specifically, rather than in generalities, has actually built decks that held up through a few wet winters here.

Do you install specific composite decking brands?

We work with several well-established composite brands and can talk through the options that fit your budget and the look you want during the estimate. We steer homeowners toward products with a solid track record and clear warranty terms rather than pushing one brand over another. The bigger factor in how the deck performs long-term is the installation underneath it, not just which brand of board sits on top.

How far apart do the hidden fastener clips need to be on composite boards?

Spacing follows the manufacturer's installation specs, which typically call for a clip at each joist along the board's length, with joist spacing itself set at 12 or 16 inches on-center depending on the board pattern. Stretching clips further apart than specified to save material is a common shortcut that leads to bounce and loosening over time. We follow the manufacturer's published spacing on every job so the warranty stays intact.

Does Sumas get enough freeze-thaw activity to matter for deck framing?

Sumas sees more frost and cold snaps than areas closer to the coast, since it sits further inland in the valley, so footing depth and drainage around posts matter more here than in milder parts of the county. Water that sits and freezes around a shallow footing can heave it over a few winters. We size footings to handle our local frost conditions rather than using a one-size-fits-all depth.

Composite Decking in Sumas: Built for Whatcom County Rain

Decking in Sumas Has to Answer to the Weather First

Sumas sits at the edge of Whatcom County where the valley holds moisture longer than most people expect. Between the driving rain off the Fraser lowlands, the humid air drifting in from the coast, and a moss season that can stretch from October into May, any deck built here is going to get tested constantly — not just during a storm, but every single week of the year. A deck that looks fine when it's installed in July can be growing algae in the board grooves by the following February if the framing and drainage underneath weren't done right.

We build composite decks in Sumas the way we'd want one built on our own house: with the framing, flashing, and airflow treated as seriously as the decking boards themselves. Composite is a good material choice for this climate precisely because it doesn't rot the way wood does — but "doesn't rot" only holds true if the installation underneath it is doing its job too.

What a Correct Composite Deck Installation Actually Involves

Composite decking gets marketed as low-maintenance, and the boards themselves largely are. But the framing underneath, the fastening method, and the spacing all still have to be right — composite doesn't forgive sloppy substructure the way people assume it does.

Framing and joist spacing

Composite boards flex more than solid wood under load and heat, so most manufacturers call for tighter joist spacing than a traditional wood deck — commonly 12 inches on-center for angled or diagonal board patterns, and 16 inches for standard straight runs. Using wood-deck spacing under composite boards is one of the most common corner-cutting mistakes we see, and it shows up later as bounce, sag between joists, or boards that telegraph the joist lines over a few seasons.

Fastening method

Hidden fastener clip systems are the standard now for a clean, screw-free surface, but the clips have to be seated correctly and spaced to the manufacturer's schedule — not stretched further apart to save material. Face-screwing composite is still done in spots where a clean look isn't the priority (stair stringers, picture-frame borders), but it should be the exception, not the whole deck.

Expansion gaps

Composite expands and contracts with temperature more than real wood does. Board-end gaps and perimeter gaps against the house or a wall need to be sized correctly for our local temperature swings — too tight and the boards buckle in a hot stretch; too loose and you get uneven, sloppy-looking seams.

The Ledger Board: Where Most Deck Problems Actually Start

This is the part of the job that a siding contractor pays closer attention to than a lot of deck-only crews will, because it's the same failure point we deal with on siding calls: water getting in behind the wall where the deck ties into the house.

A composite deck attached to the house needs a properly flashed ledger board — metal flashing that directs water out and away from the wall assembly, installed correctly relative to the house wrap or building paper, with the siding lapped over the top of it, not tucked behind it incorrectly. Get this detail wrong and it doesn't matter how good the decking above it is; water works its way behind the ledger, into the rim joist, and into the wall framing, and by the time it shows up as a soft spot or stain on the siding, the damage has usually been building for a couple of years.

Because we work on siding and wall assemblies every week, this connection point gets the attention it needs from the start of the job — not as an afterthought once the deck boards are already down.

Capped Composite vs. Uncapped Composite: An Honest Look

Not all composite decking is built the same way, and the difference matters more in a wet climate like ours than it does somewhere dry.

Factor	Capped Composite	Uncapped Composite
Moisture absorption	Low — polymer shell resists water intake	Higher — exposed core can absorb moisture over time
Moss and algae resistance	Smoother surface, easier to keep clean	More porous surface, holds moisture and organic growth longer
Fade and staining	Better long-term color retention	More prone to graying and staining without regular care
Upfront cost	Higher material cost	Lower material cost
Warranty terms	Typically longer, stain/fade coverage included	Usually shorter, more limited coverage

We install both, depending on budget and what a homeowner wants out of the deck. Our standard recommendation for a shaded or north-facing Sumas lot — where moss pressure is worst — leans toward fully capped boards, because the smoother, sealed surface simply sheds moisture and organic buildup better through a wet Whatcom County winter. That's a maintenance-and-moisture judgment call, not a knock on uncapped product; it just performs differently here.

Drainage and Airflow Underneath the Deck

The space under the deck matters as much as what's on top of it. Composite boards don't rot, but the joists, beams, and ledger framing underneath almost always are still wood — so keeping air moving and water draining through that understructure is what actually protects the deck's lifespan.

Grade and slope the ground under a low deck so water runs away from the house instead of pooling under it
Leave real airflow gaps at the skirting or under-deck perimeter rather than boxing it in tight
Use joist tape or a joist-protection wrap on the top of each joist to keep fasteners from creating a water trap
Keep board-to-house gaps clear of debris so water and pine needles don't dam up against the siding
Route downspouts and gutter discharge away from the deck footprint, not onto it

Skip these steps and you can still end up with a rotted substructure under a composite deck that looks brand new on top — which is a worse outcome for a homeowner than a wood deck that at least shows its wear where you can see it.

Our Process for a Sumas Composite Deck

Site walk and assessment — we look at drainage direction, sun exposure, existing siding condition at the attachment wall, and ground conditions before we talk product.
Ledger and structural plan — flashing detail, footing layout, and joist spacing get worked out to match the board pattern and local frost and drainage conditions.
Framing — pressure-treated joists and beams, ledger flashing tied into the house's water-shedding layer correctly, joist protection applied.
Decking installation — hidden fastener system, manufacturer-spec gapping, picture-framing or border detail if wanted.
Railings and finish details — stairs, post sleeves, and any trim work matched to the house.
Final walk-through — we go over basic care with the homeowner before we leave.

Maintenance a Sumas Homeowner Should Actually Expect

Composite is genuinely lower-maintenance than wood, but "low-maintenance" isn't "no-maintenance," especially with our moss season.

Sweep or blow off leaves and needles regularly in fall — trapped organic debris is what starts moss and algae growth on any deck surface
Do a soft wash (composite cleaner or mild soap, soft brush, no pressure washer set too aggressively) once or twice a year, more often on shaded sections
Check the gap between the deck and the house wall each fall and clear out any buildup
Look at the ledger flashing area and the base of any support posts once a year for early signs of moisture staining
Keep gutters and downspouts near the deck clear so they're not dumping extra water onto or under it

What Affects the Cost of a Composite Deck in This Area

Cost Factor	Why It Moves the Price
Deck size and shape	More linear footage of board and framing, more cutting on angled or curved layouts
Height and footing depth	Taller decks need more structural support and deeper footings
Board grade (capped vs. uncapped)	Capped boards cost more upfront but reduce moss and staining maintenance
Railing style	Composite/aluminum rail systems cost more than basic wood rail
Ledger and flashing complexity	Additional siding removal and re-flashing at the attachment wall adds labor
Site access and grading	Sloped or hard-to-reach Sumas lots can add equipment or labor time

We'll walk through these specifics for your property during the estimate rather than quoting off a square-footage number alone — a flat lot with easy access and a straightforward ledger tie-in prices very differently than a sloped yard needing extra footing depth and re-flashing work at the house.

Why Hire a Crew That Already Works in Sumas

Deck problems in this region are rarely about the decking material failing — they're almost always about a detail underneath it that wasn't sized or flashed for our rainfall and moss pressure. A crew that works across Whatcom County regularly sees how decks actually hold up here after a few wet winters, not just how they look on installation day. Because we do siding work throughout this area too, we're already paying attention to the exact wall-and-water intersection that causes the most expensive repairs later — the ledger connection, the flashing lap, the drainage path behind the house wall. That's the difference between a deck that just gets installed and one that's actually built for where it sits.

If you're planning a composite deck in Sumas, we're happy to walk the site with you and talk through what your specific lot, sun exposure, and house attachment point call for. Reach out for a free, no-pressure estimate — the form below gets you started.