The Problem With "Standard Size" Windows
PERFORMANCE
Ask most window suppliers for a size outside their catalog, and you'll usually hear one of two things: it's not possible, or it costs significantly more and takes much longer. That constraint has quietly shaped a huge amount of architecture — often in ways clients don't notice until well into a project.
Why standard sizing exists in the first place
Manufacturing to a fixed set of sizes is cheaper and faster for suppliers. Tooling, stock profiles, and glass cutting can all be optimized around a limited catalog. For high-volume, low-differentiation projects, this works fine.
The problem is when it gets applied to projects where the window opening should be a design decision, not a manufacturing constraint.
Where it actually costs you
Facade compromise. An architect designs a specific proportion for a facade — a long horizontal strip window, an oversized corner window, an irregular angled opening — and then has to redesign around whatever the nearest standard size happens to be.
Wasted structural openings. Openings get built to standard sizes during construction to "match what's available," locking in a design decision before the architectural intent is even considered.
Filler and packing at the edges. When an opening doesn't precisely match a standard unit, the gap gets closed with sealant, filler strips, or additional framing — which is both visually inconsistent and a common point of long-term sealing failure (see our piece on lessons from 500+ projects for how this typically fails).
Design flattening. Over enough projects, standard sizing pushes architecture toward a narrower range of window proportions industry-wide, simply because that's what's easy to source.
What custom fabrication actually changes
When windows are fabricated to the exact opening — any size, any shape — the constraint disappears entirely. Architects can design the facade first and have the window system built to match it, rather than the reverse. This matters most on:
Statement residential facades where window proportion is a core design element
Irregular or heritage building openings that don't conform to modern standard dimensions
Commercial projects where a repeated but non-standard module is used across many floors
Corner windows, oversized openings, and non-rectangular geometries
The trade-off worth understanding
Custom sizing isn't automatically the right call for every project — a small residential renovation with standard openings may not need it. But for any project where the window is part of the architectural language rather than just a functional opening, sizing constraints from the supplier shouldn't be the thing deciding the design.
The right question to ask early isn't "what sizes do you offer" — it's "can you build to the size the design actually needs."
