What's the real difference between new-construction and replacement windows?

New-construction windows have a nailing fin that fastens to the wall sheathing before siding goes on, integrating them into the wall's flashing and water-management system. Replacement windows fit into an existing opening without disturbing the surrounding siding. New-construction is the right approach for new builds, additions, or any project where the wall is open to the studs.

What should I ask a contractor before they install new-construction windows on a Semiahmoo property?

Ask how they detail sill pan flashing, how they sequence flashing with the weather-resistive barrier, and whether they upgrade hardware for coastal exposure. Ask to see how they handle a window opening before trim and siding close it up, since that's the point where flashing mistakes are still easy to catch. A contractor who can answer these specifically, rather than vaguely, has done this kind of work before.

Do you install a specific window brand, or can we choose our own?

We work with several manufacturers and can install a brand you've already chosen, provided it's a quality line with hardware suited to coastal exposure. For clients without a preference, we'll recommend options based on your budget and how exposed the specific opening is to wind and salt air. The installation quality matters as much as the brand name for long-term performance.

What frame material holds up best to salt air near Semiahmoo?

Vinyl and fiberglass both resist corrosion well since they don't have exposed metal to pit or oxidize; fiberglass adds dimensional stability at a higher cost. Aluminum-clad wood can work well but depends heavily on cladding and hardware quality. Bare aluminum is the weakest choice for a waterfront or near-waterfront lot unless it has a high-quality protective coating.

Does Whatcom County's moss season affect how or when new-construction windows should be installed?

The long damp season doesn't change the installation itself, but it raises the stakes on drainage details like sill pans and weep paths, since anywhere water sits will eventually grow moss or mildew. It's also worth scheduling framing and window installation with the wet season in mind so open walls aren't exposed to prolonged rain longer than necessary. Once installed and properly flashed, the windows perform the same year-round.

New-Construction Windows for Semiahmoo Homes

Building or Adding On in Semiahmoo? The Windows Have to Match the Site

Semiahmoo sits right up against Semiahmoo Bay and the Strait of Georgia, which means homes here take a different kind of weather beating than a house a few miles inland in Ferndale or Lynden. If you're framing a new home, an addition, or a room with a full wall opening, the windows you put in during that framing stage are doing more than filling a hole — they're one of the first lines of defense against salt-laden wind, wind-driven rain, and the long, damp stretch of the year when moss and mildew take hold on anything that stays wet too long.

New-construction windows are built and installed differently than replacement windows, and getting that installation right the first time matters even more on a site like this. This page covers what that job actually involves, what Semiahmoo's coastal microclimate demands from the materials and the install, and how we approach the work.

What "New-Construction" Actually Means

New-construction windows have a nailing fin (also called a flange) built into the frame. That fin gets fastened directly to the wall sheathing before siding goes on, which lets the window become part of the wall's water-management system rather than being retrofitted into an existing opening later. This is the right window type for:

New home builds, from the ground up
Additions where you're framing new exterior walls
Room conversions or bump-outs with a fresh rough opening
Projects where the siding and weather-resistive barrier (WRB) are also being installed or replaced

If you're simply swapping out an old window in an existing wall without touching the siding around it, that's a replacement or "pocket" window project — a different scope with different techniques. We handle both, but this page is specifically about the new-construction side, because the sequencing and flashing details are different and worth understanding before you start a project.

Why Semiahmoo's Climate Changes the Calculus

Whatcom County gets its share of Pacific Northwest rain no matter where you build, but Semiahmoo's exposure adds a few specific stressors:

Salt Air

Being this close to saltwater means airborne salt reaches window frames, fasteners, and hardware year-round, not just during storms. Salt accelerates corrosion on unprotected metal components — screws, hinges, cranks, and cheaper hardware finishes — and it can dull or pit certain frame coatings over years of exposure. This doesn't mean every window fails; it means frame material and hardware quality matter more here than they would on a build twenty miles inland.

Driving Rain

Open water exposure means wind-driven rain hits window openings at an angle, not just straight down. A window can be perfectly weathertight in a still rain and still leak in a sideways storm if the flashing and sill pan weren't detailed for wind-driven conditions. This is a flashing and sequencing issue more than a window-brand issue — we'll get into that below.

A Long Moss and Mildew Season

Whatcom County's damp season runs long, and anywhere moisture sits — window sills, trim returns, low-slope headers — moss, algae, and mildew will eventually take hold if drainage isn't built in from the start. That's a maintenance and appearance issue as much as a performance one, and it's easiest to prevent at the install stage rather than fix later.

What a Correct New-Construction Install Actually Involves

The window itself is only part of the job. What separates a window that performs for decades from one that leaks within a few winters is almost always the sequencing of materials around the opening. A correct installation, in order, looks roughly like this:

Rough opening check — verified square, plumb, and sized correctly before anything goes in
Sill pan flashing — a sloped, sealed pan at the bottom of the opening so any water that gets past the window drains back out, not into the framing
Window set and leveled, fastened through the nailing fin per the manufacturer's pattern
Jamb and head flashing, integrated with the weather-resistive barrier in the correct shingle-lap order — head flashing overlaps the WRB above it, side and sill flashing tuck underneath
Sealant at critical joints only — not a bead around the entire perimeter, which can trap water rather than let it drain
Interior air sealing with low-expansion foam or backer rod, separate from the exterior weatherproofing layer

Skip or reorder any of these steps and you can end up with a window that looks fine for a year or two and then shows staining, soft trim, or interior moisture — usually well after the crew that installed it is gone. On a Semiahmoo site, where wind-driven rain tests these details more than most, we don't shortcut this sequence.

Frame Material: What Holds Up Near Saltwater

There's no single "correct" frame material for every project — it depends on budget, the home's style, and how much upkeep you want to do. But salt air exposure is a real factor in the decision, so here's how the common options compare for a Semiahmoo build:

Frame Material	Salt Air / Corrosion Resistance	Maintenance	Notes
Vinyl	Good — won't corrode	Low; occasional rinse to clear salt film	Cost-effective; verify hardware is upgraded, not base-grade
Fiberglass	Very good — dimensionally stable, resists pitting	Low	Higher upfront cost; holds paint well if color changes are wanted later
Aluminum-clad wood	Depends on cladding finish quality	Moderate — interior wood needs normal upkeep	Attractive option for higher-end builds; verify cladding warranty covers coastal exposure
Bare aluminum	Weakest in salt air without a quality coating	Higher — watch for pitting and oxidation over time	We steer clients toward clad or coated options this close to the water

Whatever frame material you land on, we pay close attention to hardware — the cranks, hinges, and fasteners are usually where salt exposure shows up first, and upgraded stainless or coated hardware is worth the modest added cost on a waterfront or near-waterfront lot.

Glass and Weatherstripping Considerations

Beyond the frame, a couple of details matter more on an exposed coastal lot like Semiahmoo:

Dual or triple-pane glass with a quality seal — the seal is what fails first in coastal wind exposure; a compromised seal shows up as fogging between panes years before the glass itself is a problem
Weatherstripping designed for wind-driven rain, not just draft-sealing — this affects how well the window resists water intrusion under pressure, not just air leakage
Low-E coatings for year-round comfort, which matter as much for grey winter heat retention as summer glare on open-water lots

Our Process on a Semiahmoo Project

We approach new-construction window work the same way regardless of scale, but a few things get extra attention on Semiahmoo sites specifically because of the exposure:

We check the rough openings against the specific window sizes before ordering — reduces on-site surprises and delays
We install sill pan flashing on every opening, no exceptions, given how much this one detail affects long-term performance in driving rain
We coordinate flashing sequencing with whoever is installing your WRB and siding, whether that's our crew or another trade, so the layers actually shingle correctly
We flag hardware and frame upgrades where the site's exposure justifies the added cost, and explain the trade-offs honestly rather than upselling by default
We walk the finished openings with you before trim and siding close them up, since that's the last point where a flashing issue is easy to fix

Common Problems We See (and Prevent)

Most window failures we get called out to inspect on coastal Whatcom County homes trace back to a handful of recurring issues:

Missing or improperly sloped sill pans, letting water sit against the sill instead of draining out
Sealant applied around the entire window perimeter instead of at specific joints, trapping moisture that gets in some other way
Flashing installed out of shingle-lap order, so water runs behind a layer instead of over it
Base-grade hardware on a waterfront lot that starts showing corrosion within a few years
Trim and cladding installed tight against the sill with no drainage gap, encouraging moss and mildew buildup

None of these are exotic problems — they're all preventable with correct sequencing and reasonable material choices at install time, which is exactly why the framing stage is the right time to get it right rather than the stage where you're patching a leak later.

Why Local Experience on Semiahmoo Specifically Matters

A crew that's worked other Semiahmoo and greater Ferndale properties already knows how this stretch of Whatcom County behaves — which sides of a house typically catch the worst wind-driven rain, how fast moss establishes on north-facing trim, and which hardware upgrades are worth the cost versus which are unnecessary for a given lot's exposure. That's not something you can fully substitute with a generic installation checklist. It shows up in small decisions made on-site — how a flashing detail gets adjusted for a particular roofline, or where an extra bead of protection is worth adding — that a crew unfamiliar with this specific coastal exposure might not think to make.

Keeping New-Construction Windows Performing Long-Term

A correctly installed window still benefits from basic upkeep in this climate:

Rinse frames and sills periodically to clear accumulated salt film, especially on wind-exposed elevations
Check weep holes and drainage tracks each fall to make sure they're clear before the wet season sets in
Watch for moss or algae starting on sills and trim, and clean it early rather than letting it establish
Have caulking and sealant joints inspected every few years — sealant is a wear item, not a permanent fix

If you're planning a new build, addition, or any project that involves framing new window openings on or near Semiahmoo, we're happy to walk the site, talk through material options for your specific exposure, and put together a straightforward, no-pressure estimate using the form below.