Seattle What "New-Construction Windows" Actually Means
The term trips people up, so it's worth clearing up before anything else. A new-construction window isn't just a window destined for a brand-new house. It's a specific product type: one built with a nailing fin (also called a nail flange) around the perimeter of the frame, designed to be fastened directly to the wall sheathing and integrated into the weather-resistive barrier before siding goes on. That's different from a replacement or "insert" window, which is built without a fin and sized to slide into an existing frame that's staying in place.
In West Seattle, we install new-construction windows in a few different situations: ground-up new homes, additions and dormers, full remodels where a wall is opened down to the studs, and the accessory dwelling units (ADUs) and backyard cottages that have become common on West Seattle's smaller infill lots. In every one of those cases, the opening is framed rough, there's no existing window to work around, and the installation has to be built correctly from the sheathing out — because once the siding and trim go back on, there's no easy way to fix a flashing mistake.
West Seattle's Climate Puts Windows to the Test
West Seattle sits on a peninsula bordered by Puget Sound and the Duwamish waterway, and that proximity to salt water shapes how windows age here. Salt-laden air accelerates corrosion on unprotected metal — hardware, screws, and lower-grade aluminum components are the first things to show it. It's not dramatic or fast, but over years it's the difference between hardware that still operates smoothly and hardware that seizes up or streaks with rust.
Driving rain is the bigger day-to-day concern. Storms coming off the Sound push rain sideways against west- and southwest-facing walls, which is exactly the exposure a lot of West Seattle homes have thanks to the water views people build toward. A window that's only "pretty well sealed" will eventually let wind-driven rain find the one weak point in the flashing, and that moisture doesn't show up as an obvious leak — it shows up months or years later as soft sheathing or stained drywall below the sill.
Then there's moss. Seattle's long, wet, mild winters keep surfaces damp for months at a stretch, and shaded or north-facing walls in West Seattle's tree-covered neighborhoods grow moss and algae on sills, trim, and anything with a flat horizontal surface that holds moisture. That growth isn't just cosmetic — it holds water against wood trim and can accelerate rot if the window and its surrounding trim weren't detailed with proper drainage and slope in the first place.
What a Correct Installation Involves
Flashing and Water Management
This is where most window failures actually originate, and it has nothing to do with the window itself. A correct install starts with a sloped sill pan flashing at the bottom of the rough opening — this gives any water that gets past the window a way out, instead of a place to collect. The weather-resistive barrier gets cut and integrated in a specific shingle-lap sequence around the opening, jamb flashing goes on before the window, and head flashing goes on last, lapped over the housewrap above the window so water sheds down and over, never behind.
Air Sealing and Insulation
Around the frame, we use backer rod and low-expansion foam rather than packing the gap solid — overfilled foam can bow the frame and cause the window to bind or fail to seal correctly. The nailing fin gets fastened at the pattern and spacing the manufacturer specifies, not just "enough nails to hold it," because uneven fastening is a common cause of a window racking slightly out of square after the wall settles.
Structural Fit
The rough opening has to be sized correctly, square, plumb, and level before the window ever goes in. We shim to true the frame rather than relying on the wall framing being perfect — because it rarely is — and we check operation (opening, closing, locking) before final fastening, not after, so any adjustment happens while it's still easy to make.
Framing Considerations for New Builds, Additions, and ADUs
West Seattle's building stock is a mix: older homes being added onto, teardown-rebuilds on view lots, and a growing number of ADUs on lots that were subdivided or built out under updated zoning. Each comes with its own wrinkles. View-oriented homes on the bluffs above Alki or along the western shoreline often call for larger window openings and taller units, which means the header and rough opening framing has to be engineered for that load — something to confirm with your builder or architect before windows are ordered, not after.
ADUs and additions on tight infill lots often sit closer to property lines and neighboring structures, which can affect wind exposure in ways that aren't obvious from the street. And because much of West Seattle sits on sloped terrain, drainage around foundations and low walls matters as much as the window flashing itself — water that isn't directed away from the building can find its way up and behind a perfectly well-installed window from below.
Choosing a Frame Material for a Marine Climate
There's no single "best" frame material — it depends on budget, maintenance appetite, and how exposed the wall is. Here's how the common options hold up under West Seattle's salt air, rain, and moss conditions:
| Frame Material | Marine Climate Behavior | Maintenance |
|---|---|---|
| Vinyl | Doesn't corrode; performs well in salt air; can flex slightly in temperature swings | Low — occasional cleaning |
| Fiberglass | Very stable dimensionally, resists corrosion and moisture well, holds paint if desired | Low |
| Aluminum-clad wood | Attractive exterior, but exposed aluminum hardware or trim can show salt-air corrosion over time if not a marine-rated finish | Moderate — watch hardware and any exposed wood interior |
| Bare wood | Handsome but the most vulnerable to the combination of driving rain and prolonged damp/moss conditions if not maintained | High — regular refinishing and sealant checks |
For most West Seattle new-construction projects, vinyl and fiberglass are the practical default because they hold up with the least ongoing attention. Where a homeowner wants a wood interior look, we'll talk through realistic maintenance expectations rather than just selling the upgrade — it's a real trade-off, not a downgrade to talk you out of.
Our Installation Process
New-construction window work is scheduled work — it has to line up with the framing and siding timeline on a job, so we treat coordination as part of the job, not an afterthought.
- Measure and order: We take field measurements off the actual rough openings, not just plans, since framing tolerances vary. Lead times on ordered units can run several weeks, so we build that into the schedule early.
- Coordinate with the builder: On additions, ADUs, and remodels, we work directly with the general contractor or homeowner-builder on sequencing so windows go in at the right point relative to the weather-resistive barrier and siding.
- Install per the flashing sequence: Sill pan, jamb flashing, window, head flashing, in that order — no shortcuts, no skipped layers.
- Check operation and seal: Every unit gets opened, closed, and locked before we call it done, and the interior/exterior seals are finished to be both weathertight and inspection-ready.
Permits and Inspections in Seattle
New construction, additions, and most ADU projects in Seattle require permits through the Seattle Department of Construction and Inspections, and window installations are typically covered under that permit rather than pulled separately. Washington's state energy code sets performance requirements for new windows — how much heat they let through — and that's checked as part of the inspection process on new builds and additions. We install to the specification called for on the approved plans and make sure the work is ready to pass inspection the first time, since a failed inspection on a closed-up wall means opening something back up.
Why a Crew That Works West Seattle Regularly Matters
Exposure varies block by block here more than people expect. A wall on Beach Drive facing open water takes a different beating than a sheltered lot a few blocks up the hill, and knowing that difference changes how we think about flashing details and sealant choices on a given job. Working in the neighborhood regularly also means we're familiar with the permitting process through King County and the City of Seattle, we have a working relationship with local general contractors, and if a punch-list item comes up after the siding crew finishes around a window, we're not driving across the county to handle it.
Checklist: What to Confirm Before Installation Day
- Rough openings are framed to the exact dimensions the ordered windows require
- Weather-resistive barrier is installed and ready for flashing integration
- Sill pan flashing material and slope are specified before the window arrives
- Frame material and glazing package are confirmed against the energy code requirement for the project
- Site access and weather protection are arranged so openings aren't left exposed overnight
- Permit and inspection milestones are known so window work lines up with the schedule
If you're framing an addition, building an ADU, or working through new construction anywhere in West Seattle, we're happy to walk the site, look at the rough openings or plans, and put together a straightforward, no-pressure estimate. Use the form below to get started.