Semiahmoo Siding New-Construction Windows, Done Right the First Time
When a Bellingham home is being built or added onto, the windows go in before the siding does. That's the whole idea behind "new-construction" windows — they use a nailing flange around the perimeter of the frame that gets integrated directly into the wall's weather-resistant barrier (WRB), then covered by trim and siding. It's a different job than swapping out an old window in a finished wall, and it has to be sequenced correctly with the framer, the WRB installer, and the siding crew or it becomes the weak point in the whole building envelope.
We work new-construction window installs in Bellingham and the rest of Whatcom County alongside builders, GCs, and homeowners managing their own build. Because we also install and repair siding for a living, we see what happens years later when a window was flashed wrong at the framing stage — and we install every window assuming we, or someone else, will eventually be pulling siding off next to it.
Why Bellingham's Climate Doesn't Forgive Shortcuts
Bellingham sits close enough to the Salish Sea and Semiahmoo Bay that salt-laden air is a real factor on fasteners, flashing metal, and exposed hardware — not just a coastal-town talking point. Add Whatcom County's long, wet fall-through-spring stretch of driving rain, frequent wind-driven storms off the water, and the moss and algae growth that comes with months of shade and moisture, and you get a climate that actively hunts for any gap in a window opening.
A new-construction window that's flashed correctly sheds that water outward and down, layer over layer, so it never reaches the framing. One that's flashed even slightly wrong — a missing sill pan, tape lapped the wrong direction, a gap at the head flashing — will usually look fine for a year or two. Then the wall sheathing starts staying damp longer after each storm, and by the time it shows up as a stain, soft trim, or a moss line running down from the corner of a window, the damage is already inside the wall.
What This Means in Practice
- Every horizontal surface on a window opening (sill, head flashing) needs to be sloped or lapped to shed water outward, never trap it
- Flashing tape and building paper must be layered shingle-style — upper courses over lower ones — so water always flows over the next layer down
- Sealant is a backup, not the primary defense; a window that relies on caulk alone to stay dry will eventually fail
- Metal flashing and fasteners exposed to salt air should be corrosion-resistant, not standard interior-grade hardware
What a Correct Install Actually Involves
New-construction window installation is a sequence, and skipping or reordering a step is where most failures start. Here's the order we follow:
- Rough opening check — confirm the framed opening is square, plumb, and sized correctly for the window unit before it ever shows up on site
- Sill pan installation — a sloped, waterproof pan at the bottom of the opening that catches any water that gets past the window and directs it back outside instead of into the wall cavity
- WRB integration — the housewrap or building paper is cut and folded into the opening so it laps correctly with the flashing that comes next
- Flashing tape at jambs and sill — self-adhered flashing membrane sealed to both the sheathing and the window flange, lapped so lower courses are never covered by upper ones out of order
- Setting the window — shimmed level, plumb, and square in the opening, fastened per the manufacturer's schedule (not "wherever there's a stud")
- Head flashing — installed last over the top flange, lapping over the jamb flashing beneath it so water draining down the wall never gets behind the window
- Interior and exterior sealant — a continuous bead where required by the manufacturer, plus low-expansion foam or insulation in the gap between the frame and rough opening (not standard high-expansion foam, which can bow a frame out of square)
- Final check — operate every sash and lock, confirm the unit closes and seals evenly all the way around
None of this is exotic. It's the same handful of steps every reputable window manufacturer publishes in its installation instructions. The difference between a window that lasts and one that leaks is almost always whether every step actually got done, in order, on every opening — not whether the crew knew the steps existed.
Our Process on a Bellingham Job
Most of our new-construction window work comes in one of two ways: a builder or GC brings us in as their window subcontractor for a Bellingham project, or a homeowner managing their own build or addition calls us directly to handle the window package.
Before Installation
We walk the framed openings before windows arrive to catch sizing or squareness problems while they're still cheap to fix. We also confirm the WRB and flashing plan with the builder so there's no ambiguity about who's doing what — window flashing is one of the most common places where a builder assumes the window installer is handling it, and the window installer assumes the framer already did.
During Installation
We install in the sequence above on every opening, using flashing tape and sill pans rated for the exposure. On the more exposed sides of a building — typically the sides facing prevailing wind and rain — we pay extra attention to head flashing overlap and drainage detailing, since that's where driving rain concentrates.
After Installation
Every window gets operated and checked before we leave the site, and we photograph flashing details before they're covered by siding, since that record is useful if any question comes up later — for the builder, the homeowner, or an inspector.
Choosing the Right Window for a Bellingham Build
Frame material matters more here than in a drier climate, because of the moisture and salt-air exposure. The table below covers the trade-offs on the options most commonly specified for Whatcom County new construction.
| Frame Material | How It Handles Local Climate | Maintenance | Typical Fit |
|---|---|---|---|
| Vinyl | Good moisture and salt resistance; won't rot or corrode | Low — occasional cleaning | Most cost-conscious new-construction builds |
| Fiberglass | Excellent — dimensionally stable in temperature and moisture swings, holds paint well | Low to moderate | Higher-end builds, exposed elevations |
| Wood (unclad) | Requires diligent finishing and upkeep to resist coastal moisture | High — refinishing on a schedule | Historic or period-specific designs where the look is the priority |
| Wood-clad (aluminum or vinyl exterior) | Good — exterior cladding shields the wood core from weather | Moderate — interior wood still needs occasional attention | Builds wanting a wood interior look with less exterior maintenance |
As a matter of our own standard, we lean toward vinyl, fiberglass, and properly clad wood units for openings that get direct weather exposure in this area, and we're upfront with clients about the maintenance commitment that comes with unclad wood in a climate this wet. That's not a knock on any manufacturer — it's just what we've found holds up with the least babysitting on the Whatcom County coast.
Cost Factors Homeowners and Builders Should Know
New-construction window pricing swings on more than just the window unit itself. Here's what actually moves the number:
| Factor | Why It Matters |
|---|---|
| Frame material and glazing package | Vinyl runs less than fiberglass or clad wood; upgraded glass (low-E coatings, triple-pane) adds cost but improves energy performance and comfort |
| Number and size of openings | Larger units and more openings mean more flashing detail work, not just more glass |
| Wall exposure | Elevations facing prevailing wind and rain warrant more careful (and slightly more time-intensive) flashing work |
| Coordination timing | Installing windows on schedule with the framer and WRB crew avoids delay costs; installing out of sequence often means redoing wrap or flashing |
| Site access | Multi-story openings or difficult site access add labor time for safe, careful handling |
We give straightforward, itemized estimates rather than a single lump number, so a builder or homeowner can see what's driving the cost and make informed choices on where to spend.
Mistakes We See on New-Construction Jobs
Because we get called in on both new installs and, later, siding repair work, we end up seeing the failures years after the fact. The recurring ones:
- No sill pan, or a flat one that doesn't slope water back outside
- Flashing tape applied in the wrong order (upper courses tucked under lower ones instead of over them), which channels water straight into the wall
- Windows fastened without shimming, leaving the frame slightly racked and hard to operate or seal
- Siding installed tight against window trim with no reveal or gap for drainage
- High-expansion foam used to fill the perimeter gap, bowing the frame and creating operation problems
Every one of these is avoidable with a crew that treats the flashing sequence as non-negotiable rather than optional.
Working With a Semiahmoo Crew on a Bellingham Job
We're based in and around Semiahmoo, and Bellingham is squarely in our regular service area — not a stretch job we take occasionally. That matters for a few practical reasons on a new-construction timeline: we're not driving hours to reach a punch-list item, we already have working relationships with builders and trades in this part of Whatcom County, and we know which elevations on a typical Bellingham lot take the worst of the weather based on local wind and rain patterns.
We also stand behind the work after the siding goes on. If a flashing detail ever needs a look because of a leak, a settling issue, or a remodel down the road, we're a local call, not a company that's moved on to a different region.
Before You Call — A Quick Checklist
If you're a homeowner or builder lining up window installation for a Bellingham new-construction project, having these ready speeds up an accurate estimate:
- Window schedule or plan set showing sizes, styles, and rough opening locations
- Confirmation of who's supplying the WRB and flashing tape (window installer, framer, or siding crew)
- Target install date relative to framing completion
- Frame material preference, if you already have one, or openness to a recommendation
- Any elevations you know get heavier wind or rain exposure on the lot
If you're planning a new build or addition in Bellingham and want windows installed the way they're supposed to be — flashed correctly, sequenced right with your framer and siding crew, and built for what Whatcom County weather actually throws at a wall — we're happy to take a look at your plans and put together a straightforward, no-pressure estimate using the form below.