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

New-construction windows have a nailing fin or flange that fastens directly to the wall framing and gets integrated with the weather-resistive barrier before siding goes on. Replacement windows are designed to fit into an existing finished opening without disturbing the surrounding siding, which is a different flashing approach entirely. New builds should always use new-construction units so the flashing sequence can be done correctly from the start.

How do I vet a contractor for new-construction window installation specifically?

Ask them to walk you through their flashing sequence in detail — sill pan, jamb, head flashing order — because a contractor who can't explain it clearly usually isn't following one. Ask whether they coordinate directly with your framer and WRB installer, and ask for their experience on coastal sites specifically, since inland installs don't always account for wind-driven rain. A contractor who welcomes a pre-siding walkthrough of every opening is a good sign.

Do you install windows from a specific manufacturer, or can we choose our own brand?

We install whatever window product a homeowner or builder specifies, as long as it's suited to the site's exposure. We'll give you honest input on frame material trade-offs for a coastal location, but the brand and product decision is yours.

What's a sill pan and why does it matter on a new build?

A sill pan is a flashing component installed at the bottom of the rough opening before the window is set, sloped outward with a back dam so any water that gets past the window sheds out and away from the framing instead of pooling or running backward. It's one of the most commonly skipped or poorly installed details on new builds, and it's especially important on sites that see driving rain like Birch Bay does.

Does Birch Bay's salt air really affect window hardware and fasteners?

Yes — ongoing exposure to salt-laden coastal air can accelerate corrosion on exposed fasteners and certain hardware finishes faster than an inland site would see. It's a reason to be deliberate about fastener type and frame material on a Birch Bay build rather than defaulting to whatever's standard for an inland Whatcom County job.

New-Construction Windows in Birch Bay, WA | Bellingham Exterior Contractor

New-Construction Windows Are a Different Job Than a Replacement

Replacing a window in an existing wall means working around what's already there — old flashing, settled framing, finished siding. New-construction window installation is the opposite: you're building the water management system from scratch, in the right order, before siding and trim ever go on. Done correctly, it's one of the most important steps in the entire building envelope, because every mistake made here gets sealed behind siding for the next 20-plus years before anyone notices a problem.

On a new build in Birch Bay, that first-time-right installation matters more than almost anywhere else in Whatcom County. This stretch of coastline gets a steady mix of salt-laden air off the Strait of Georgia, wind-driven rain that hits walls sideways rather than straight down, and a wet season that runs long enough to grow moss on north-facing surfaces most winters. New windows installed here need to be flashed, sealed, and integrated with the wall assembly with that exposure in mind from day one.

What Birch Bay's Climate Actually Does to a Window Opening

Salt Air

Proximity to saltwater accelerates corrosion on exposed fasteners, hinges, and hardware, and it can degrade certain sealants and finishes faster than they'd wear inland. It doesn't mean windows fail — it means the fastener types, frame finishes, and hardware specified matter more here than on a build twenty miles inland.

Driving Rain

Storms coming off the water routinely push rain sideways under wind pressure, not just straight down. A window that would stay dry in a calm rain event can take on water at the sill or head flashing if the wind-driven component wasn't accounted for. That changes how we detail head flashing, sill pans, and the housewrap laps around each opening.

The Long Moss Season

Whatcom County's wet season stretches long enough that anything holding standing moisture — a poorly sloped sill, a flashing lap installed backward, a gap in the weather-resistive barrier — gets tested repeatedly before summer ever dries it out. Moss and mildew growth around window trim is often the first visible sign of a water management problem that started at installation.

Getting the Installation Right: Flashing, Nail Fins, and the WRB

The window unit itself is rarely the point of failure on a new build — the flashing and integration with the weather-resistive barrier (WRB) is where problems start or get prevented. On a proper new-construction install we follow a shingle-lap sequence so water is always directed outward and downward, never trapped:

Sill pan flashing installed first, sloped to drain outward, with back-dam protection so water can't run back toward the framing
Window set into the pan, checked for level, plumb, and square before a single fastener goes in
Jamb flashing lapped over the sill pan legs, never under
Head flashing installed last, lapped over the WRB above the opening so water sheds onto the building paper, not behind it
All flashing tape and housewrap seams checked for full adhesion — no fish-mouths, no gaps where wind-driven rain can find a way in
Nail fin or flange fastened per the manufacturer's schedule — the right fastener spacing and type for the frame material and this coastal exposure

Skip or reverse any one of these steps and the window can look perfect for years while quietly letting moisture into the wall assembly. That's the risk with new construction: the mistakes are invisible until the siding comes off.

Choosing Window Products for a Birch Bay Build

There's no single "best" window material — the right choice depends on the wall assembly, the home's exposure, and the owner's maintenance expectations. What we can speak to honestly is how each common option holds up in a coastal Whatcom County environment specifically.

Frame Material	Coastal / Salt-Air Performance	Maintenance	Notes
Vinyl	Good — won't corrode or rot, handles moisture well	Low — occasional cleaning	Most cost-effective; good all-around choice for exposed sites
Fiberglass	Very good — dimensionally stable, resists warping in temperature swings	Low	Higher upfront cost; strong long-term value on exposed walls
Aluminum-clad wood	Depends heavily on cladding quality and installation detail	Moderate to high — exposed wood interior needs upkeep, clad exterior needs monitoring at joints	We install these when specified, but we're upfront that clad-wood asks more of the flashing detail and the owner's long-term maintenance near saltwater
Aluminum (uninsulated)	Prone to corrosion and thermal performance issues in this climate	Moderate	We generally steer new builds away from this option here — it's not a fit for the exposure or Washington's energy code

We're not tied to one brand. Our job is to install whatever product the homeowner or builder specifies correctly, and to be honest during the selection conversation about which options carry more long-term maintenance burden on a site this close to the water.

Our Process on a New-Construction Job

1. Plan Review and Rough Opening Verification

We review window schedules against the actual framed rough openings before installation day. Catching a sizing or orientation issue on paper is a lot cheaper than catching it after the crane's gone.

2. Sequencing With the WRB

Windows go in after the weather-resistive barrier is installed on the surrounding wall but before siding starts, so every flashing lap can be built in the correct shingle order with nothing covered up prematurely.

3. Install and Flash Per Opening

Each window is set, shimmed, and flashed individually — sill pan, jambs, head flashing, and WRB integration as outlined above. We don't batch-install and flash later; each opening is finished before we move to the next.

4. Interior Air Sealing

Gaps between the frame and rough opening are sealed on the interior side with an appropriate low-expansion foam or sealant, both for energy performance and to prevent interior condensation at the frame.

5. Walkthrough Before Siding

Before siding crews cover the walls, we do a final check of every opening — flashing laps, fastener seating, operation of the sash or vent — because this is the last point anyone can see the work without opening the wall back up.

Coordinating With Builders and Trade Schedules

New-construction window installs live in the middle of a tight trade schedule — framers before us, WRB and siding crews right behind us. Windows installed too early get damaged by other trades; installed too late and they hold up the whole exterior schedule. We work directly with general contractors and framers on Birch Bay builds to slot into the schedule at the right window (no pun intended) — after rough framing and WRB are ready, before siding starts.

We also flag rough opening issues back to the builder immediately rather than forcing a window to fit an opening that's out of square or mis-sized. On a coastal site, an install that's forced to compensate for a bad rough opening is exactly the kind of shortcut that shows up as a leak two winters later.

Common Mistakes We See on New Builds Near the Water

Head flashing installed under the WRB instead of over it, which funnels water behind the barrier instead of onto it
Sill pans with no back dam, letting wind-driven rain run backward into the framing
Housewrap seams around the opening taped in the wrong lap order
Fasteners inconsistent with the frame material and coastal exposure, leading to premature corrosion or fin damage
Windows installed before the WRB is fully lapped and sealed, forcing awkward field patches instead of a clean shingle sequence

None of these are visible from the street once siding goes on — which is exactly why the installer's process matters more than the finished look on install day.

What to Confirm Before Your Windows Go In

If you're a homeowner working with a builder in Birch Bay, or building yourself, these are worth confirming before window installation day:

Rough openings have been verified against the window schedule
WRB is installed and lapped correctly on all walls receiving windows
Sill pan flashing with a back dam is part of the install plan, not an afterthought
Fastener type is appropriate for the frame material given the coastal exposure
There's a plan for a pre-siding walkthrough to check every opening while it's still visible
The installer has worked coastal Whatcom County sites before and can speak specifically to wind-driven rain detailing

Why Hiring a Crew That Already Works Birch Bay Matters

New-construction window installation is unforgiving of guesswork, and a crew that's only ever installed inland doesn't always think about wind-driven rain, salt exposure, or a wet season that runs as long as ours does here in Whatcom County. We've installed windows on new builds up and down this coastline and we bring that site-specific judgment to every opening — not a generic checklist, but a process built around what Birch Bay's weather actually does to a wall assembly.

If you're planning a new build or working with a builder in Birch Bay, we're happy to walk the plans, talk through window selection for your specific site exposure, and give you a free, no-pressure estimate. Use the form below to get started.

New-Construction Windows in Birch Bay, WA