Windows and doors: made-to-measure fabrication with a glass problem

Bespoke by nature, batched by necessity

No two orders are quite alike, yet the factory has to behave like a production operation. The reconciliation happens in software: order entry that captures sizes and configurations, optimisation that nests cuts across many orders to minimise profile waste, and scheduling that groups by colour, system and glass type. Errors entering that system are expensive because they propagate through cutting, welding and glazing before anyone notices. Fabricators who invest in accurate surveying and disciplined order entry outperform those with better machinery and sloppy data. Remake rates traced back to their root cause tell an owner more about the business than any efficiency dashboard.

You fabricate under someone else's system

Profile systems come from extruders who design the section, publish fabrication instructions and hold the test evidence supporting performance. The fabricator works under that licence, which brings ready-made technical backing but restricts what may be changed. Deviating from the specified reinforcement, hardware or assembly method can invalidate the evidence supporting a performance declaration. It also creates dependency: system suppliers set profile prices, control colour availability and can support a competitor down the road with equal enthusiasm. Choosing a system is therefore a long-term commercial decision, not a purchasing one. Switching systems later means retraining, retooling and rebuilding evidence, so that choice compounds quietly over years.

The glass unit is the awkward component

Sealed units are heavy, break easily, cannot be stocked in useful variety and must match the frame exactly. Fabricators either make them in-house, adding a sealed unit line with its own quality issues around seal integrity and gas fill, or buy from a processor whose lead time then governs delivery. Breakage during handling or installation restarts the clock on a component nobody has spare. Sensible operations measure glass-related delay separately from everything else, because it is usually the single largest cause of failing a promised installation date. Ordering glass at the right moment, late enough to reflect confirmed sizes and early enough to arrive, is a scheduling skill in itself.

Declaring performance for products you assemble

Windows and external doors placed on the market carry declared performance for characteristics such as thermal transmittance, water tightness, air permeability and, where relevant, security. The evidence generally derives from testing of the system, with the fabricator responsible for building within its scope and operating factory production control. Notified body involvement and periodic audit apply. Fabricators sometimes assume the system supplier carries the whole obligation; they do not, and an audit that finds unlicensed modifications on the shop floor is a serious commercial problem. Keeping licence documentation, training records and test evidence current is a small standing cost that prevents a very large one.

The housebuilder and the homeowner want opposite things

New-build supply means large repeat orders at negotiated prices, delivered to a site programme that moves, with retention and slow payment attached. Replacement work through installers means small orders, fast turnaround expectations, higher unit margins and cash that arrives quickly. A single factory serving both fights a permanent scheduling battle, since a site delivery of many units disrupts a flow built for small batches. Most fabricators pick a primary market and treat the other as fill, rather than pretending one operation can optimise for both. Running both without separating scheduling and cash planning usually means the retail customer waits while the site gets served.

Frequently asked questions

Should a fabricator make sealed glass units in-house?

Only at volume and with real process discipline. A unit line controls your worst lead time and removes a supplier from the critical path, but sealed unit quality problems, failed seals, misting and gas loss, appear years later in the customer's home and are expensive to put right. Fabricators below steady volume usually do better maintaining two qualified processors, agreeing service levels, and investing instead in handling practices that stop breakage on site.

Why can a fabricator not modify a profile system to suit a job?

Because performance evidence belongs to the tested configuration. Reinforcement, hardware positions, sealing details and maximum sizes are specified because the system was tested that way. An undocumented change can invalidate a declared performance and leave the fabricator, not the system supplier, holding responsibility for a product that no longer matches its evidence. Where a job needs something outside scope, the correct route is asking the system supplier for supporting evidence or a project-specific assessment.

What causes most missed installation dates in fenestration?

Measurement errors and glass. A survey mistake is discovered at installation, when the frame is already made and the unit already cut, and the replacement takes as long as the original. Breakage in transit or during fitting has the same effect. Fabricators reduce both by tightening survey procedures, checking orders against site drawings before release, and packaging and handling glass as the most fragile item in the load, which it is.