Seattle Siding What "New-Construction Windows" Actually Means
New-construction windows are a different product and a different installation method than replacement windows, and the distinction matters if you're building in Redmond or adding onto an existing home. A new-construction window has a nailing fin around its perimeter that gets fastened directly to the wall sheathing before siding goes on. That fin, combined with proper flashing, is what ties the window into the home's water-management system. Replacement (or "pocket") windows, by contrast, are designed to slide into an existing frame with no fin at all, relying on the old frame and trim to do the water-shedding work.
If you're framing a new home, finishing an addition, converting a garage or bonus room, or doing a full re-side down to the studs, you want new-construction windows installed the correct way the first time. Redo work on a window that was never properly flashed means tearing into siding and sheathing that's already closed up — a much bigger job than getting it right during the build.
Why Redmond's Climate Puts This Installation to the Test
Redmond sits in the Puget Sound lowlands, and like the rest of King County it deals with a long, wet fall-through-spring stretch where rain doesn't just fall straight down — it drives sideways against west- and south-facing walls during storms. Add in the region's marine-influenced humidity, shaded and tree-heavy lots common in Redmond neighborhoods, and a moss season that can stretch for months, and you have conditions that punish any weak point in a window's water-management detail. A window that's slightly out of plumb, under-flashed, or sealed with the wrong material may look fine on move-in day and still leak two winters later.
Driving Rain and Wall Assemblies
Wind-driven rain pushes water up and under laps in housewrap and flashing that would never see moisture in a drier climate. New-construction windows have to be integrated into the weather-resistive barrier in the correct shingle-lap sequence — head flashing over the barrier, side and sill flashing under it — so water is always directed outward and down, never trapped behind the siding.
Moss, Mildew, and Shaded Lots
Many Redmond properties carry mature tree cover, which keeps siding and trim damp longer after a storm passes. That extended dampness is exactly what moss and mildew need to take hold around window trim and sills. Correct sill pitch, drainage gaps, and quality caulking at the right joints (and no caulk at the joints that need to breathe) reduce how long water sits against the window assembly.
What a Correct Installation Involves
A new-construction window installation is really a sequence, and skipping or rushing any step is where problems start.
Rough Opening and Flashing
The rough opening has to be framed square, plumb, and sized correctly for the window unit with the right amount of shim space. Before the window goes in, a sloped sill pan is set so any water that gets past the window has somewhere to go besides straight down into the wall cavity. Housewrap or building paper is then integrated with the window flashing in the correct overlap order, and self-adhered flashing tape seals the jambs and head.
Setting and Sealing the Window
The window unit is set into the opening, checked for level, plumb, and square, and fastened through the nailing fin per the manufacturer's schedule — not just at a few points, but at the full spacing the warranty requires. The gap between the window frame and the rough opening gets insulated (typically with low-expansion foam, not standard high-expansion foam that can bow the frame) and sealed with backer rod and sealant on the interior side.
Tying Into Siding
Trim, casing, and the surrounding siding then need to lap correctly over the flashing so the whole assembly sheds water the way it's designed to. This is where a crew unfamiliar with the region's detailing tends to cut corners — treating window trim like a cosmetic finish step instead of the last link in the water-management chain.
Materials We Work With
Builders and homeowners in Redmond typically choose between vinyl, fiberglass, and wood-clad windows for new construction. Each performs differently in a wet marine climate, and the right choice depends on budget, the home's design, and how much long-term maintenance you're willing to take on.
| Material | Moisture Performance | Maintenance | Typical Fit |
|---|---|---|---|
| Vinyl | Won't rot; seams and welds matter for water tightness | Low — no painting or sealing needed | Budget-conscious new construction and additions |
| Fiberglass | Dimensionally stable, holds paint and seals well over time | Low to moderate | Homes wanting durability with a more refined look |
| Wood-clad | Exterior clad protects wood, but any breach in the cladding invites rot | Highest — cladding seams and sealant joints need periodic checks | Traditional or high-end architectural designs |
We're not going to tell you one brand is the only right answer — the correct choice depends on the project. What we will say is that whatever unit goes in, the installation detailing matters more than the label on the window in a climate like ours.
Our Process for Redmond New-Construction Projects
Whether we're working directly with your builder or you've brought us in as the window and siding contractor for an addition, the process looks the same:
- Review the plans and window schedule with the builder or homeowner, confirming sizes, egress requirements, and window types before ordering.
- Coordinate the install timing with the framing and weather-resistive barrier install so windows go in at the right point in the sequence — not too early, not after siding prep has already started.
- Set sill pans, flash, and install each window per manufacturer specifications, with the sequencing built for Redmond's rain patterns.
- Integrate flashing with housewrap and trim so the assembly is ready for siding.
- Walk the completed openings before siding closes them up — this is the last chance to catch a flashing or sealant issue before it's hidden behind finish materials.
Mistakes We See on New-Construction Window Jobs
Most window leaks we get called out to inspect on newer Redmond homes trace back to a handful of recurring issues:
- No sloped sill pan, so incidental water has nowhere to drain except into the wall
- Housewrap lapped in the wrong order over the flashing instead of under it at the head
- Nailing fin fastened at only a few points instead of the full manufacturer schedule
- High-expansion foam used in the shim space, bowing the frame and causing the sash to bind
- Caulk applied at joints that are supposed to allow drainage, trapping moisture instead of releasing it
- Trim installed before the flashing sequence was verified, hiding a mistake that surfaces years later
None of these show up on a walkthrough the day the siding goes on. They show up during the first hard driving rain, or slowly, as rot, once moss and moisture have had a season or two to work on a weak spot.
Why a Crew That Already Works in Redmond Matters
Redmond has its own permitting process through the City of Redmond, and new-construction window work on a permitted addition or new build typically needs to pass inspection as part of the building envelope. A crew that regularly pulls permits and works with Redmond building inspectors knows what they'll be checking for at the flashing and rough-in stage, which avoids the delays and rework that come from failed inspections.
Beyond permitting, a crew familiar with Redmond's mix of lot conditions — heavily treed lots, newer developments with tighter setbacks, older Eastside neighborhoods being added onto — has already seen how local drainage patterns and shade affect a wall assembly's exposure. That local pattern recognition is worth more than a generic install checklist, especially on a job where the mistakes don't show up until the next wet season.
Cost Factors for New-Construction Windows in Redmond
Pricing for new-construction window installation depends on more than just the window unit itself. The table below covers the main variables that move the number up or down on most Redmond projects.
| Factor | Why It Affects Cost |
|---|---|
| Window material and size | Fiberglass and wood-clad units cost more than comparable vinyl; larger and specialty shapes (arched, oversized) add labor and material |
| Number of openings | Per-window cost typically drops as the total count on a project goes up |
| New build vs. addition | Additions often involve tie-in work to existing siding and flashing that new builds don't |
| Site access and lot conditions | Steep, wooded, or tight-access Redmond lots can add setup and staging time |
| Coordination complexity | Projects requiring close scheduling with a general contractor or other trades add planning time |
As a broad range, homeowners in this area typically see new-construction window installation run somewhere in the low-to-mid hundreds per opening up through well over a thousand dollars each for larger or higher-end units, before siding and trim. The only way to get a real number is to look at your specific plans and window schedule.
Get a Free Estimate
If you're building new, finishing an addition, or planning a project in Redmond that involves new-construction windows, we're glad to walk through the plans with you or your builder and give you a straightforward, no-pressure estimate. Use the form below to get started.