Bellingham Two Engineered Sidings, One Very Different Wet-Climate Track Record
If you're replacing siding in Bellingham, you've probably run into both of these products in your research. James Hardie fiber cement and LP SmartSide engineered wood are both marketed as upgrades over old-school vinyl or unprimed cedar, and both are legitimate, factory-engineered building products — this isn't a case of one being "real" siding and the other being a gimmick. The difference that matters here in Whatcom County comes down to what each product is actually made of, and how that material behaves after twenty winters of Pacific Northwest rain, salt-laden air off Bellingham Bay, and the shade-and-moisture combination that keeps moss growing on north-facing walls nine months a year.
We install James Hardie exclusively. Not because LP SmartSide is a bad product on paper, but because of how the two materials are built at the core, and what that means for a house that has to shed water for decades, not just pass inspection the year it's installed.
What Each Product Actually Is
James Hardie Fiber Cement
Hardie siding is made from a mix of Portland cement, sand, and cellulose fiber, cured under pressure and heat. It's fundamentally an inorganic material — there's no wood fiber for moisture to soak into, and nothing in the board itself for fungus or insects to feed on. It's heavy, dimensionally stable, and doesn't expand and contract with humidity the way wood-based products do.
LP SmartSide
LP SmartSide is an engineered wood product — strand-based wood fiber (similar in concept to OSB) treated with zinc borate for insect and fungal resistance, then coated with a resin-saturated overlay and primed or pre-finished. It's a real improvement over old untreated wood siding and hardboard products that failed badly in the 1990s. The engineering is genuinely better than what it replaced.
Why Wood Fiber Is the Deciding Factor Here
Whatcom County isn't a marginal case for moisture exposure — it's one of the wetter, mossier corners of an already wet state. Bellingham gets sustained fall-through-spring rain, driving rain off the Strait during winter storms, and salt air along the waterfront and Chuckanut corridor that accelerates wear on anything with exposed seams or fasteners. Add in the deep shade many lots get from mature evergreens, and you've got ideal conditions for moss and algae to colonize a wall and hold moisture against it for weeks at a time.
LP SmartSide's borate treatment and resin overlay are specifically engineered to resist that environment, and the company stands behind the product with its own warranty. But it's still a wood-fiber core. The vulnerable points are the same ones that have challenged every engineered wood siding: cut edges exposed during installation, butt joints, and any spot where the factory seal gets compromised — a nail driven wrong, a scratch from a ladder, caulking that fails at year twelve instead of year twenty. Once moisture gets past the surface treatment and into the wood fiber, that's the one failure mode fiber cement doesn't have, because there's no wood fiber to get into.
Fiber cement has its own installation-sensitivity issues — clearances, fastener placement, and caulking matter for both products — but the consequence of a small installation flaw is different. On Hardie, a missed detail is usually a paint or caulking fix. On any wood-based siding, a chronic moisture entry point can mean fiber swelling or breakdown at that specific spot over time.
Moss and Algae Specifically
This is worth calling out separately because it's such a Bellingham-specific issue. Moss holds water against a wall surface far longer than open rain exposure does, and shaded, north- or west-facing walls under fir and cedar canopy are where we see the heaviest growth. On fiber cement, moss is a surface and finish issue — it can be washed off without threatening the substrate underneath. On any wood-based product, prolonged moss coverage means prolonged moisture contact with a material that has an organic core, which is exactly the condition its treatments are designed to fight off, but also exactly the condition that stresses those treatments hardest over the decades.
Finish and Maintenance Over Time
| Factor | James Hardie (ColorPlus) | LP SmartSide |
|---|---|---|
| Core material | Cement, sand, cellulose fiber (inorganic) | Engineered wood strand, resin-treated |
| Factory finish | Baked-on ColorPlus finish, 15-year finish warranty | Primed or pre-finished; field paint common |
| Repaint cycle (PNW conditions) | Typically well beyond 10-15 years before repaint needed | Often 5-8 years depending on exposure and original finish |
| Combustibility | Non-combustible | Combustible (treated wood product) |
| Moisture failure mode | Surface/finish issues only if maintained | Potential fiber swelling/breakdown if seal is compromised |
| Product warranty (material) | 30 years, non-prorated, transferable | Manufacturer-specific, typically shorter and often prorated |
The repaint cycle matters more than it looks on paper. A wood-based product that needs repainting every 5-8 years in a wet climate isn't just a cost line — every repaint is also a maintenance event where caulking, flashing, and joints need to be re-inspected. Skip a cycle and you're not just looking at faded paint, you're extending the window where the underlying material sees unprotected exposure.
Fire Consideration
This matters less for daily weather resistance and more for long-term risk profile: fiber cement is non-combustible. LP SmartSide, being wood-based, is a combustible material regardless of its treatment. For most Bellingham homeowners this isn't the deciding factor the way moisture behavior is, but it's part of the honest comparison and it's one reason insurance carriers increasingly ask about siding material.
Why We Standardized on James Hardie
We don't install LP SmartSide, vinyl, or untreated wood siding. That's not a knock on every homeowner who has it or every crew that installs it well — it's a standard we set for our own work because we're the ones who get called back when siding underperforms in this climate, and we'd rather stand behind one product system we know inside and out. James Hardie's HZ5 product line is formulated specifically for the Pacific Northwest's freeze-thaw and moisture cycle, the ColorPlus factory finish removes on-site painting as a maintenance variable, and the transferable 30-year non-prorated warranty gives homeowners real coverage if something does go wrong — not just a pro-rated schedule that shrinks every year.
None of this means LP SmartSide is a poor product in absolute terms — it's a legitimate step up from the wood siding it replaced, and plenty of installers use it correctly. It means that for a house that has to perform through forty-plus inches of annual rain, coastal salt air, and a moss season that runs most of the year, we'd rather put an inorganic material on the wall than a treated organic one, and we've built our entire installation practice around doing that one product correctly rather than juggling multiple systems.
Questions to Ask Before You Decide
- Is the quoted product HZ5 or HZ10, and is that the correct climate zone rating for a Whatcom County installation?
- What's the actual warranty structure — non-prorated and transferable, or does coverage shrink over time and end at resale?
- Who is responsible for caulking, flashing, and joint maintenance after year one, and is that written down anywhere?
- What's the manufacturer's stated repaint or refinish interval for this specific climate, not the national average?
- Does the installer follow manufacturer-specified clearances from grade, decks, and roof lines — this is where most siding failures actually start, regardless of brand?
- Is the fastening pattern and joint treatment documented, so a future owner or inspector can verify it was installed to spec?
What This Means for Your Project
If you're comparing bids and one contractor is quoting LP SmartSide at a lower price point than a Hardie quote, that price difference is real, but so is the difference in what you're buying long-term in this climate. We'd rather explain that trade-off plainly than pretend it doesn't exist. For a lot of Bellingham homes — especially anything close to the water, under heavy tree cover, or on a north-facing exposure that never fully dries out between storms — the inorganic core of fiber cement is doing real work that a treated wood product, however well-engineered, is still working against.
If you'd like an honest look at your specific house — sun exposure, moss history, existing siding condition — we're happy to walk the property with you and give you a straight answer, not a sales pitch. Reach out for a free, no-pressure estimate and we'll tell you what we'd actually recommend for your home.