What's the difference between composite decking and pressure-treated wood decking?

Pressure-treated wood is chemically treated lumber that needs regular sealing or staining and will eventually split, warp, or rot, especially in a wet climate. Composite decking is made from a blend of wood fiber and recycled plastic, often with a protective cap, so it resists moisture absorption and rot without annual sealing. It costs more upfront but generally needs far less maintenance over its lifespan. Both still need a properly built substructure underneath to perform well long-term.

What should I ask a contractor before hiring them to install composite decking in Whatcom County?

Ask whether they pull permits and build to current Washington state code, what fastener and hardware grade they use for our salt-air exposure, and whether they're a manufacturer-certified installer if warranty coverage matters to you. Ask to see how they handle drainage and under-deck clearance, since that's where a lot of shortcuts hide. Also confirm what's included in their own workmanship warranty versus the manufacturer's, and get it in writing.

Are all composite decking brands built the same way?

No — composite decking varies by manufacturer in whether the board is capped or uncapped, how the core is formulated, and what warranty coverage and installer certification requirements come with it. Capped boards from established manufacturers generally perform better in wet, salt-air climates than older uncapped composite products. We'll walk through the specific product lines that make sense for your project and budget rather than pushing one brand on every job.

Do composite deck boards need gaps between them for drainage?

Yes, composite boards need consistent gapping both between boards and at the ends to allow for drainage, airflow, and material expansion and contraction with temperature changes. Gapping specs vary by manufacturer and board profile, so we follow the product's installation requirements rather than guessing at spacing. Skipping or shorting proper gaps is a common cause of water pooling and premature wear on composite decks.

Does Marietta's salt air actually affect a deck if the boards themselves are moisture-resistant?

Yes — the composite boards resist moisture well, but the fasteners, joist hangers, and other hardware holding the structure together are still exposed to salt-laden air and can corrode faster than they would further inland. That's why we use coastal-rated, corrosion-resistant hardware on every deck we build in this area, regardless of which composite board is chosen. A low-maintenance board doesn't make the whole structure maintenance-free.

Composite Decking Built for Marietta's Salt Air and Rain

Why Marietta's Location Puts Extra Demands on a Deck

Homes in the Marietta area sit close enough to the water that salt air is a constant, low-grade factor in how every outdoor material ages. Add in Whatcom County's long wet season, frequent driving rain off the water, and shade patterns that keep surfaces damp for days at a time, and you have a climate that is tough on wood decking and unkind to any composite product that wasn't built or installed with drainage and airflow in mind. Moss doesn't need much encouragement here — it needs moisture that lingers and a surface it can grab onto, and a lot of Marietta lots provide both.

None of this means a deck can't hold up for decades. It means the material choice and the build details matter more here than they would in a drier inland neighborhood. This page is about what actually works for composite decking specifically in Marietta, not composite decking in general.

What "Correct" Composite Decking Looks Like in This Climate

Composite decking earns its reputation for low maintenance, but that reputation only holds up if the deck underneath it is built right. A composite board sitting on a poorly ventilated substructure in a salt-air, high-rainfall environment will still develop moisture problems — they just show up underneath, out of sight, instead of on the surface.

Substructure and Fasteners

The framing under a composite deck in this area needs corrosion-resistant fasteners and hardware rated for coastal exposure, not the standard-grade hardware that's fine forty miles inland. Salt-laden air accelerates corrosion on ungalvanized or under-rated screws, joist hangers, and post bases. We spec hardware and connectors rated for the exposure, and we flash and tape joist tops so water doesn't sit against bare wood framing under the boards.

Drainage and Airflow

Composite boards don't rot the way wood does, but the framing underneath them still can, and trapped moisture under low-clearance decks is one of the most common problems we find when we're called out to look at an existing deck that's failing early. Correct board spacing, proper slope away from the house, and enough clearance under the deck for air to actually move are not optional details in a climate this wet — they're the difference between a deck that dries out between rain events and one that never does.

Choosing the Right Composite Board for a Marietta Property

Not all composite decking is built the same way, and the differences matter more in a salt-air, high-moisture environment than they would somewhere drier.

Capped vs. Uncapped Composite

Capped composite boards have a shell — usually a polymer cap — bonded around a wood-plastic composite core, which limits moisture absorption, staining, and surface mold growth. Uncapped composite (an older generation of the product) absorbs more moisture at the core over time, which shows up as swelling, surface fuzzing, or mold and moss staining faster in a wet climate like ours. For Marietta homes, we default to fully capped boards. The material costs more up front, but it holds up to the moss-and-moisture cycle this area puts decking through far better, and that's a trade-off we think is worth explaining plainly rather than upselling.

Color and Heat Considerations

Darker composite boards absorb more heat on the rare sunny days we do get, which isn't a major issue in our climate the way it is further south, but it does affect how quickly a deck surface dries after rain. Lighter and mid-tone colors tend to shed surface moisture and dry a little faster, which matters more here than the aesthetic difference alone would suggest. We'll talk through color options with actual drying behavior in mind, not just what looks good in a sample chip.

How We Approach a Composite Decking Project in Marietta

We treat every deck build as a small structural project first and a finish-material install second, because that order is what actually determines how long the deck lasts.

Site and drainage assessment — we look at grading, downspout discharge, existing moisture damage, and how much shade and airflow the deck footprint actually gets.
Structural evaluation — ledger attachment, footing condition, and joist spacing are checked against current code and against what the composite board manufacturer requires for span and fastening.
Framing and flashing — corrosion-resistant hardware, joist tape, and proper ledger flashing to keep water out of the wall assembly and off bare framing.
Board installation — correct gapping for expansion and drainage, hidden or exposed fastening per the product's specification, and picture-framing or trim details where they make sense.
Railing and finish work — matched to the board system, with the same corrosion-resistant hardware standard applied throughout.
Final walkthrough — we go over maintenance expectations specific to this climate before we consider the job done.

Permits and Code Considerations for Marietta Decks

Most deck projects that involve new footings, structural framing, or attachment to the house at any meaningful height require a building permit under Washington State building code, and both Whatcom County and the City of Ferndale have their own permitting process depending on where the property sits. Decks above a certain height generally need guardrails at a minimum required height, and stair and railing details have to meet code spacing requirements regardless of what decking material sits on top.

We pull the required permits and build to current code as a matter of course, not as an upsell — it protects you at resale, and it means the structure underneath the composite boards was actually inspected, not just assumed to be sound. If you're replacing an old deck, this is also when problems like undersized footings or outdated framing from a prior build usually surface, and it's better to catch them before new decking goes down than after.

Living With Composite Decking in a Moss-Prone Climate

Composite decking is low-maintenance compared to wood, but "low-maintenance" doesn't mean "no maintenance" in a place with a moss season as long as ours. Organic growth — moss, algae, lichen — feeds on the same trapped moisture and shade that causes structural problems, and it will colonize composite boards the same way it colonizes wood, concrete, or roofing if conditions favor it.

The good news is that composite boards clean up far easier than wood, since there's no bare grain for moss to root into and no need to reseal or restain afterward.

Sweep or rinse debris off the deck surface regularly through fall and winter so organic matter doesn't sit and compost against the boards.
Clean visible moss or algae with a soft-bristle brush and a mild soap-and-water or manufacturer-approved deck cleaner — avoid pressure washing directly into board seams, which can force water into the substructure.
Keep gutters and downspouts clear so runoff isn't discharging directly onto or under the deck.
Trim back overhanging vegetation where practical to cut down on shade and leaf litter that keep the surface damp longer than it needs to be.
Check under-deck clearance periodically to make sure airflow paths haven't been blocked by stored items, plantings, or added skirting.

What Affects the Cost of a Composite Decking Project

Composite decking costs more per square foot than pressure-treated wood up front, and the total project cost depends on more than just board choice. Here's what typically moves the number for a Marietta project:

Cost Factor	Why It Matters Here
Board tier (capped vs. uncapped, or premium composite lines)	Capped, coastal-rated boards cost more but resist the moss-and-moisture cycle far longer
Existing structure condition	Rot or corrosion found in old framing during tear-out adds repair scope before new decking can go on
Deck height and footing type	Taller decks and elevated designs need more substantial footings and railing to meet code
Drainage and grading work	Regrading or adding drainage under a low-clearance deck adds labor but prevents early failure
Fastener and hardware spec	Corrosion-resistant hardware for salt-air exposure costs more than standard-grade hardware
Railing and trim details	Composite or metal railing systems, picture-framed borders, and stair details all add to material and labor

We'll walk through these factors specifically for your property during an estimate rather than quoting off a generic per-square-foot number, because the condition of what's already there usually matters more than the size of the deck.

Why Hiring a Crew That Already Works in Marietta Matters

A lot of decking problems we get called to diagnose weren't caused by bad composite material — they were caused by a build that didn't account for the site's actual moisture and salt exposure. A crew that mostly works inland or in drier parts of the county may not default to coastal-rated hardware, may under-spec drainage, or may not think twice about clearance and airflow because it hasn't bitten them yet. Those shortcuts don't show up as a problem on install day. They show up two or three winters later.

Working regularly in Ferndale and the surrounding Whatcom County shoreline communities means we're not guessing at what this climate does to a deck over time — we're building to account for it from the start, and we stand behind that work with warranty coverage on both materials and installation.

Composite Decking Checklist for Marietta Homeowners

Confirm the board is fully capped composite, not an older uncapped product, if long-term moisture resistance matters to you.
Ask what fastener and hardware grade is being used and whether it's rated for coastal/salt-air exposure.
Make sure the plan includes proper board gapping, slope, and under-deck clearance for drainage and airflow.
Get manufacturer warranty terms in writing, and confirm the installer is a certified or approved installer if that affects warranty coverage.
Ask how ledger flashing and joist protection will be handled where the deck meets the house.
Discuss a realistic maintenance routine for moss and algae control before the project starts, not after.

If you're weighing composite decking for a Marietta property and want a straight answer on what your specific site needs — no pressure, no generic quote — we're happy to walk the property with you and put together a free estimate.