Birch Bay Siding Lummi Island homes deal with a level of water exposure that most Whatcom County properties don't. Surrounded on all sides by the Salish Sea and reachable only by a short vehicle ferry crossing, the island gets salt air, driving rain, and a long moss season with almost nothing between the weather and the wall. Add in a housing stock that runs heavy on older cabins, additions built onto original small footprints, and newer homes designed around the view, and you end up with a lot of window openings that don't match anything sold off a shelf.
We treat custom windows on Lummi Island as their own category of work. The measuring, the flashing sequence, the ordering lead time, and the delivery logistics all look different once a window stops being a standard size — and on an island reached only by ferry, several of those differences show up before installation even starts.
Why So Many Lummi Island Homes Need Custom Windows
A few patterns come up again and again out here. Older cabins and cottages were framed decades ago to whatever dimensions made sense at the time, long before manufacturers standardized common sizes, so a true like-for-like replacement often means ordering custom rather than forcing a stock unit into an opening it wasn't made for. Additions built onto those original structures create openings with no standard reference point at all. And homes designed or remodeled to take advantage of water views tend toward picture windows, bay windows, or oversized units sized for the sightline rather than for what's easy to stock.
None of that is unusual work for us on this island — it's the routine. What it does mean is that a project starts with careful field measurement and an honest lead-time conversation, since a custom unit is built to order and Lummi Island adds its own scheduling layer on top of that.
What Full Water Exposure Does to a Window Installation
Being surrounded by water rather than just adjacent to it changes the exposure math. Salt-laden air moves across the island from more directions than a single stretch of mainland shoreline sees, and it works on hardware, fasteners, and lower-grade frame components faster than a drier, more sheltered site would. Storms coming off open water drive rain sideways into wall assemblies and window flashing instead of falling straight down, so it finds gaps that a gentler climate would never test. And the shaded, damp conditions common on parts of the island support a moss and mildew season that can run most of the year on north- and west-facing walls and trim.
Custom windows raise the stakes on all of that. A bay window has more perimeter that needs flashing. A large picture window has more glass area for wind load to push against. A wide sill has more surface for water to sit on if it isn't sloped correctly. None of this argues against custom windows — it means the installation has to be built around the added complexity rather than treated like a routine stock swap.
Where the Failures Actually Start
The glass and the frame are rarely the first thing to fail on a well-built custom unit. It's the transition points — where a bay window's roof meets the main wall, where a wide sill meets the siding underneath it, where a resized opening meets the original wall assembly. Those spots need real flashing attention, and they're exactly the spots a rushed job is most likely to shortcut, because doing them correctly takes time that a rushed schedule doesn't allow for.
The Ferry Factor: Why Island Logistics Change the Timeline
Custom windows are already built to order rather than pulled from a warehouse shelf, which means a lead time measured in weeks rather than days. On Lummi Island, that lead time stacks with a second logistics layer: getting an oversized or fragile custom unit, plus a crew and tools, onto the island depends on a ferry with a fixed schedule and limited vehicle capacity. Large glass units and bay window assemblies need careful handling in transit, and a delivery that misses its ferry slot doesn't just wait a few hours — it can push an install date back by a full day or more.
We plan around that from the start rather than discovering it mid-project. That means confirming delivery windows against ferry schedules before committing to an install date, sequencing crew trips so tools and materials arrive together instead of in separate crossings, and building in a realistic buffer rather than quoting a mainland timeline and hoping the ferry cooperates. It's a scheduling detail, not a technical one, but it's the one that most often turns a straightforward custom window job into a frustrating one when it isn't accounted for.
Common Custom Window Situations We See on Lummi Island
- Non-standard replacement sizes — matching an opening in an older cabin that predates modern manufacturer sizing
- Bay and bow windows — projecting units that add interior space and open up a water view, but require their own roof, support, and flashing system
- Picture and large-format windows — fixed units sized to maximize a sightline, with wide glass areas to manage structurally
- Reframed or corrected openings — where the existing rough opening needs work before any new unit can go in cleanly
- Matched sets for additions — new windows sized to align with existing windows on an older or expanded home
- Egress and code-driven openings — additions or bedroom conversions where the minimum opening size is set by code, not preference
What a Correct Custom Window Job Involves
Measuring and Ordering
Custom work starts with precise field measurement, not a catalog lookup. We measure the actual opening, note any out-of-square or out-of-level conditions common in older island homes, and account for what the finished trim and flashing will need for clearance. Because custom units are built to order and then have to reach the island, this is also where we set realistic expectations on total lead time — the manufacturing wait plus the ferry-dependent delivery window — rather than letting a homeowner assume mainland turnaround applies here.
Opening Prep and Structural Considerations
Larger custom units, bay windows especially, sometimes need structural support beyond what a standard opening requires, since they carry more weight and project outward from the wall. We evaluate that during the initial assessment, not after demolition has already started. On older Lummi Island homes, this is also typically where we find out whether the original framing or flashing around an opening needs repair before a new window can go in correctly.
Flashing and Weatherproofing
This is the step that matters most given the exposure out here. Every custom shape changes how flashing has to be sequenced — a bay window's roof needs its own weatherproofing separate from the wall flashing below it, a wide sill needs to shed water outward rather than pool it, and a resized opening needs new flashing tied cleanly into the surrounding wall rather than patched around the old detail. We build the flashing plan around the specific opening in front of us, not a generic sheet pulled from a manufacturer's average-climate installation guide.
Finish and Trim Integration
Custom windows often sit in the most visually prominent spot on the house — a bay window facing the water, a picture window centered on a view — so the trim and finish work needs to match the rest of the exterior cleanly. We plan that integration before the window even arrives, so the finished result reads as intentional rather than added on later.
Frame Material Choices for Full Water Exposure
Frame material matters more on a custom unit, since a larger or more exposed window has more surface for salt air and sustained moisture to work against over time. We'll walk through the honest trade-offs for your specific opening rather than defaulting to whatever's fastest to install. In general, fiberglass and vinyl frames hold up to sustained coastal moisture with less ongoing upkeep than an all-wood exterior finish, which is why we lead with them on weather-facing custom installs on Lummi Island. Wood-clad interiors paired with a low-maintenance exterior cladding can still be the right call when the interior look matters and the exterior is properly protected — that's a trade-off worth discussing against your specific opening and budget, not a default answer we give everyone.
Our Process, Start to Finish
- On-site assessment — we measure the opening, check square and level, and flag any structural or flashing concerns tied to its shape or size
- Honest recommendation — custom order, modified stock size, or opening reframe, explained with the reasoning behind it
- Ordering and lead-time planning — a realistic timeline that accounts for both manufacturing and ferry-dependent delivery
- Removal and opening prep — the old unit comes out carefully, and any hidden framing or flashing issues get addressed before the new window goes in
- Installation and flashing — the new unit is set, shimmed, and flashed to a sequence built for its specific shape and size
- Trim and finish — exterior trim is integrated to match the surrounding siding and architecture
Costs and Trade-Offs: Stock vs. Custom on Lummi Island
| Factor | Stock Window | Custom Window |
|---|---|---|
| Lead time | Often available quickly, ferry logistics aside | Built to order — weeks, not days, plus ferry-dependent delivery scheduling |
| Fit | Standard sizes only; reframing needed if the opening doesn't match | Matched to the exact opening or design intent |
| Flashing complexity | Straightforward, well-documented rectangular details | Shape-specific — bay roofs, resized openings, or wide sills each need their own plan |
| Delivery coordination | One ferry trip, minimal handling risk | Larger, more fragile units need trips timed to the ferry schedule and each other |
| Cost | Lower, especially for common sizes | Higher, reflecting manufacturing, labor, and logistics complexity |
| Best fit | Simple replacements in standard, already-correct openings | Older cabins, additions, view-driven design, or non-standard framing |
What actually moves price on a custom job is fairly consistent: overall size and glass area, shape complexity, whether structural framing needs correction, frame material, the condition of the existing opening, and how many units are ordered together. We won't quote a number without seeing the opening in person, but we'll walk through which of those factors apply to your project before you commit to anything.
Practical Checklist Before You Order
- Confirm the opening was field-measured, not estimated from old plans or a rough guess
- Ask what the flashing plan looks like for your specific opening shape, not a generic answer
- Get a total lead time in writing that accounts for both manufacturing and ferry delivery, not just the manufacturer's quoted build time
- Ask whether the opening needs structural review, especially for bay or oversized units
- Confirm what's covered under warranty — the window unit and the installation labor are often separate
- Ask how trim and finish will be matched to the surrounding siding
Why a Crew That Already Works Lummi Island Matters
Manufacturer installation guidance is written for average, standard-size conditions in a moderate climate — not full water exposure on an island reached by ferry. A crew that has actually built bay windows, reframed odd-sized cabin openings, and flashed large view windows here knows which parts of that guidance are non-negotiable in this exposure, and which extra step is worth the time even when it isn't strictly required elsewhere. Just as important, that crew already has ferry logistics figured out — they're not learning the schedule, the vehicle limits, or the timing math on your project's dime.
That experience shows up in decisions that never come up in a sales conversation: how a bay window's roof ties into the main wall's drainage plan, how much lap a flashing course needs on a resized opening, when a sill needs a sloped composite cap instead of relying on caulk alone, and how to sequence a delivery so a missed ferry slot doesn't turn into a missed install day. Those are the details that decide whether a custom window is still performing cleanly in fifteen years or showing drafts and soft trim in five.
What to Ask Before Hiring for Island Window Work
- Ask to see examples of custom shapes or sizes they've actually installed, not just standard replacements
- Ask how they sequence flashing for your specific opening shape
- Ask how they plan delivery and crew logistics around the ferry schedule
- Confirm current Washington contractor licensing and insurance
- Get a written scope of work and a realistic total lead time before signing anything
- Ask how labor and the window unit are each covered under warranty
If you're weighing a custom window for an older Lummi Island cabin, planning an addition, or looking at a bay or picture window to make the most of a water view, it's worth having someone look at the actual opening before you start pricing units. We offer free, no-pressure estimates for custom window projects on Lummi Island — use the form below to get a time on the schedule.