What's the difference between a "custom" window and a standard replacement window?

A standard replacement window comes in fixed factory sizes that fit into an existing, properly sized opening. A custom window is built to match a non-standard opening — common in older homes, additions, or unusual shapes — so it fits without forcing the wall framing to change or hiding gaps with extra trim.

How do I know if a contractor is actually qualified to install custom windows, not just standard ones?

Ask how they handle flashing and weather barrier integration specifically, not just the window brand they carry — that's the part that determines whether the install holds up. A qualified contractor should be able to explain their tear-out and inspection process and show they check the framing before installing, not just swap boxes.

Does it matter if my siding contractor also installs the windows, or should those be separate jobs?

It matters. Windows and siding meet at the same joint, and if two different crews handle them without coordinating, that joint is often where leaks start. Having one crew responsible for both means the flashing, barrier, and siding tie-in are treated as one continuous system instead of two separate scopes.

Are vinyl windows good enough for a coastal Washington climate, or do I need something higher-end?

Quality vinyl windows perform well in salt air and rain as long as the frame and weld quality are good and the installation flashing is correct — the window itself is rarely the weak point. Fiberglass is a step up in dimensional stability for larger openings, but vinyl is a solid, lower-maintenance choice for most homes here.

How does Whatcom County's rain and moss season actually affect window lifespan compared to drier parts of the state?

Extended damp periods and moss growth keep moisture in contact with sealant, trim, and frame joints far longer than in a drier climate, which accelerates seal breakdown and, if flashing is inadequate, hidden rot. Homes here typically need earlier attention to caulking and drainage details than the same house would in a drier region, even with the same window product installed.

Custom Windows for Sehome Homes: Built for Coastal WA Weather

Why Windows in Sehome Take More Than a Catalog Size

Sehome sits close enough to Bellingham Bay that salt-laden air, wind-driven rain, and a moss season that can run half the year all work on a home's exterior at once. Windows take the worst of it. Frames absorb moisture at the joints, hardware corrodes faster near the water, and any gap in the seal around a window becomes an entry point for water that has nowhere to evaporate to during our wetter months. On top of that, a lot of homes in this part of Whatcom County were framed decades before today's window sizes existed, so openings have settled, shifted, or were never standard to begin with.

That combination — an aggressive coastal climate plus non-standard openings — is exactly why "custom windows" is its own service, not just a bigger box store order. Get the sizing or the flashing wrong and you're not looking at a cosmetic problem later; you're looking at rot in the wall framing.

What "Custom" Actually Means

Custom doesn't automatically mean expensive or exotic. It means the window is built to the actual opening in your house, rather than the house being forced to fit a standard window. In practice, that covers a few common situations we run into around Sehome and Fairhaven:

When a Custom Window Is the Right Call

Older homes where the rough opening has settled slightly out of square over the years
Additions or bump-outs where the wall framing wasn't built to a standard window module
Unusual shapes — arched tops, odd transoms, or oversized picture windows
Openings where a previous remodel left an in-between size that no stock window fits cleanly
Homes where you want to change the window style (adding grilles, changing operation type) without rebuilding the whole wall opening

The goal is always the same: a window that sits square, seals correctly, and doesn't need trim tricks or shims to hide a bad fit.

The Part That Gets Skipped: Window-to-Siding Integration

Most window problems we get called out to fix in this area aren't failures of the window itself — they're failures of how it was tied into the wall. A window is only as weathertight as the flashing and siding detail around it. In a climate with steady driving rain off the water, water will find any shortcut in that assembly.

Because we install siding as our core trade, we treat the window opening as part of the wall's water management system, not a separate task handed off between crews. That means:

Sill pan flashing under the window to catch and direct out any water that gets past the sash, rather than letting it sit on bare sheathing
Correct shingle-lap order between the weather-resistive barrier, the flashing tape, and the window flange, so water sheds down and out — never behind the barrier
Head flashing above the window that ties back into the siding's drainage plane
Sealant used as a backup, not a substitute for proper flashing — caulk fails eventually, especially with UV exposure and the freeze-thaw cycling we get in winter; the flashing underneath is what actually keeps the wall dry

This is also where moss season matters more than people expect. Moss and organic buildup hold moisture against trim and sealant joints for weeks at a time. If the underlying flashing is sound, that's a maintenance issue. If it's not, that trapped moisture finds the first weak seam and starts rot behind the siding where you can't see it.

Choosing a Window Material for This Climate

There's no single "best" window material — it depends on how much upkeep you want to do and what the house calls for. Here's how the common options hold up in a marine, salt-air environment like ours:

Material	Moisture Behavior	Maintenance	Typical Fit
Vinyl	Won't rot or corrode; seams and welds are the weak point if poorly made	Low — occasional cleaning	Most homes, budget-conscious replacements
Fiberglass	Very stable dimensionally, resists moisture and salt air well	Low	Larger openings, custom shapes, longer-term ownership
Aluminum-clad wood	Good exterior protection, but any breach in the cladding exposes wood to rot	Moderate — cladding needs to stay sealed at joints	Historic-style homes wanting a wood interior look
Bare wood	Attractive but the most vulnerable to our rain and salt exposure	High — regular painting/sealing required	Restoration work where matching original detail matters most

For most Sehome homes we recommend vinyl or fiberglass for straightforward replacements, and reserve wood or clad-wood for cases where matching an older home's original look is the priority and the owner understands the upkeep involved. We'll walk through the honest trade-offs for your specific house rather than push one product line.

Our Process for a Custom Window Installation

On-site assessment — we check the existing opening, sheathing condition, and how the current window ties into the siding before quoting anything
Precise measurement — for custom sizing, the opening gets measured at multiple points since older framing is rarely perfectly square
Tear-out and inspection — once the old window is out, we inspect the sheathing and framing underneath for hidden water damage before installing anything new
Flashing and barrier integration — sill pan, jamb flashing, and head flashing are installed and tied into the existing or new weather-resistive barrier
Window installation — set, shimmed level and plumb, and fastened per the manufacturer's specification, which matters for keeping any warranty valid
Siding tie-in and trim — siding and trim are cut and fitted back around the window so the whole wall sheds water as one system
Final seal and walkthrough — sealant applied where specified, hardware checked, and the finished opening reviewed with you before we consider the job done

Signs Your Current Windows Need Attention

Fogging or a hazy film between the panes of a double-pane window (seal failure)
Noticeable drafts near the frame even when the window is fully latched
Windows that stick, won't stay open, or are hard to lock
Soft or discolored wood at the sill, jamb, or exterior trim
Moss, algae, or dark staining building up around the frame faster than the rest of the siding
Condensation forming on the inside of the glass during cold, wet weeks
Paint or caulking cracking and peeling specifically at the window edges

Any one of these on its own might just be a maintenance item. Several of them together, especially on the sides of the house that catch the worst of the driving rain, usually mean it's time for a proper inspection rather than another round of caulk.

What Drives the Cost

Factor	How It Affects the Project
Number of custom (non-standard) openings	Each one requires individual measurement and often individual fabrication, which adds time and cost per unit
Material choice	Vinyl is generally the most economical; fiberglass and wood-clad run higher
Condition of the framing and sheathing	Hidden rot found during tear-out adds repair work before the new window can go in
Siding tie-in complexity	Matching or patching siding and trim around the new opening takes more labor than a like-for-like swap
Access and height	Upper-story or hard-to-reach windows take longer to stage and install safely

We give straightforward, itemized quotes rather than a single lump number, so you can see exactly what you're paying for and where the custom work adds cost versus a standard replacement.

Why It Matters That We Already Work in Sehome

Window work in this part of Whatcom County isn't the same as window work inland. A crew that mainly installs in drier climates can still put in a technically fine window and have it fail here within a few years, simply because the flashing detail wasn't built for the amount of driving rain and prolonged dampness Sehome gets. Working siding and windows together as one trade, in this specific area, means we're not guessing at how the assembly needs to handle water — we see the results of good and bad installs on homes like yours regularly. That local pattern recognition is worth more than a lower bid from a crew that isn't from around here.

If you're weighing a window replacement, dealing with a stubborn draft, or planning a larger renovation that involves changing an opening size, we're happy to take a look and give you a straight answer — including telling you if a repair makes more sense than a full replacement. Reach out for a free, no-pressure estimate using the form below.