How Are Curtain Walls Manufactured and Quality-Checked?

The difference between a facade that performs and one that leaks is usually decided in a factory, months before anything reaches the building.

Gasket seated correctly or pinched. Thermal break crimped to the right pressure or slightly under. Sealant applied to a clean surface or one carrying release agent from the extrusion line. Corner joint sealed or merely assembled.

None of those are visible once a unit is glazed and wrapped. All of them determine whether the facade passes its field water test, and by the time it fails, the units are on a building and the factory is making something else.

That is why the quality checkpoints matter as much as the process. This article covers both. PRANCE manufactures from an owned facility and publishes production process documentation covering the lines described here.

The Curtain Wall Fabrication Process

Six stages, in order, from raw aluminum to a unit ready for delivery.

1. Extrusion

Aluminum billet is heated to approximately 450 to 500 degrees Celsius and forced through a steel die to form the mullion and transom profiles.

Alloy for architectural extrusion is typically 6063-T5 or 6063-T6, chosen for extrudability and adequate strength. Section geometry determines structural capacity, so profile selection follows from the wind load calculation rather than from catalogue preference.

Dies wear. A worn die produces profiles slightly out of tolerance, which shows up later as gaskets that do not seat properly, so die maintenance records are a reasonable thing to ask about.

2. Surface Finishing

Applied before fabrication, since cutting a finished profile exposes bare aluminum at the cut.

• Powder coating: typically 60 to 80 microns, wide colour range, standard for most commercial work

• PVDF fluorocarbon: 25 microns or greater, tested to AAMA 2605, for severe exposure and long warranty periods

• Anodizing: integral oxide layer, typically 15 to 25 microns for architectural grade, excellent abrasion resistance

Pretreatment matters more than the coating itself. Chromate or chrome-free conversion coating prepares the surface, and inadequate pretreatment produces adhesion failure years later regardless of coating quality.

3. Thermal Break Assembly

Where a thermally broken system is being made, two aluminum profiles are joined by polyamide strips.

The strips are inserted into knurled channels in both profiles, then the aluminum is rolled or crimped to lock them mechanically. Crimping pressure is critical. Under-crimped breaks can allow movement under load, and over-crimped breaks damage the polyamide.

Shear testing on sample lengths verifies the bond. This is a checkpoint worth asking about specifically, since a failed thermal break is invisible until the facade underperforms.

4. Cutting and Machining

Profiles are cut to length and machined for drainage, fixings, and corner connections.

CNC machining centres handle this on modern lines, cutting to tolerances in the order of plus or minus 0.5 mm. Weep slots, screw ports, gasket channels, and anchor holes are all machined at this stage.

Cut ends are where corrosion starts if the finish is breached and the detail is exposed, so end sealing and treatment matter in aggressive environments.

5. Assembly

For unitized systems, this is where a panel becomes a panel.

Frames are assembled with corner cleats, crimped or screwed, and the corners are sealed. Corner sealing is the single most common source of water leakage in a finished facade, which makes it the checkpoint that deserves the most scrutiny.

Gaskets are installed, drainage paths are confirmed clear, and insulation and back pans are fitted in spandrel zones.

6. Glazing

Sealed units are set into the frame with structural or captured glazing.

Structural silicone glazing bonds the glass to the frame with silicone carrying the wind load. Bite dimension and joint geometry are engineered rather than assumed, and the silicone requires controlled temperature, humidity, and cure time. Adhesion testing on samples from each batch verifies the bond.

Captured glazing holds the unit mechanically with pressure plates and gaskets, which is more forgiving and visually different.

Curtain Wall Factory Quality Control Checkpoints

Where a serious manufacturer checks, and what they are checking for.

Checks Worth Asking About Specifically

Three that separate a controlled factory from an assembly shop.

Coating thickness measurement. Done with a calibrated gauge on a defined sampling frequency, recorded against batch numbers.

Structural silicone adhesion testing. Peel or butterfly samples taken from production runs and tested, with records retained.

Sample unit water testing. Some manufacturers water test production units on a sampling basis rather than relying solely on the original mock-up. This catches process drift.

Unitized Versus Stick Manufacturing

The production demands differ considerably.

Unitized panels are complete assemblies, so almost all the quality-critical work happens in the factory under controlled conditions. That is the method's main advantage, and it requires a real assembly line, jigs, handling equipment, and storage space for finished panels.

Stick systems ship as components, so more of the quality outcome depends on site work. Factory demands are lower, which is partly why stick systems are more widely available from smaller fabricators.

Handover from factory to site differs accordingly. Unitized panels arrive ready to hang. Stick components arrive as a kit requiring assembly.

Documentation a Factory Should Produce

Manufacturing quality is only verifiable through records.

• Material certificates for alloy, temper, and glass

• Coating records showing thickness measurements and batch traceability

• Thermal break test results from shear testing on production samples

• Structural silicone adhesion test records by batch

• Dimensional inspection records against approved shop drawings

• Sample unit test results where production testing is carried out

• Packing lists referenced to the erection sequence

Judging a factory before award covers how to assess whether these records exist and are actually used rather than filed.

Where Manufacturing Quality Shows Up Later？

Four failures that trace directly back to the factory.

Water leakage at corners. Inadequate corner sealing during assembly. Found by field testing, expensive to fix once installed.

Thermal underperformance. Poorly crimped thermal breaks allowing conduction, or breaks damaged during handling. Invisible until the building underperforms or condensation appears.

Coating failure. Inadequate pretreatment producing adhesion loss, typically appearing after several years as blistering or peeling.

Structural glazing failure. Incorrect bite, contaminated substrate, or inadequate cure. The most serious failure mode, and the reason adhesion testing records matter.

Proving the finished assembly through laboratory testing catches system design problems. It does not catch process drift on unit 400 of 900, which is what factory quality control is for.

Capacity and Scheduling

Manufacturing capability includes throughput, not just quality.

Ask for monthly output in square meters, what is already committed, and whether lead time runs from order or from approved shop drawings. Those are different dates, and drawing approval frequently consumes more programme than production.

Phased delivery by zone lets erection begin while later floors are still in fabrication, which pulls weeks out of a tall building programme at no additional cost. Where fabrication cost actually sits explains how these decisions affect the facade rate.

For context, PRANCE operates an owned facility with in-house finishing lines rather than subcontracting, which keeps colour consistency and scheduling under direct control. Further detail sits on our curtain wall manufacturing page.

Judging the Manufacturing Behind a Facade

Ask where the extrusion comes from and who applies the finish. Ask how thermal breaks are verified. Ask for structural silicone adhesion records and coating thickness logs. Ask whether production units get water tested on a sampling basis or whether the original mock-up is the only evidence.

The answers separate factories that control their process from shops that assemble parts and hope.

PRANCE manufactures curtain wall and facade systems from an owned facility with in-house finishing, documented quality control at every stage, and full material and test traceability. Send your specification and programme and request a factory capability review.

Frequently Asked Questions

1. What is the most important quality checkpoint in curtain wall manufacturing?

Corner sealing during frame assembly. Corners are where multiple sealing planes meet and they are the most common source of water leakage in a finished facade. The defect is invisible once the unit is glazed and only appears under field water testing or in service.

2. Why does surface finishing happen before fabrication?

Because cutting and machining a finished profile exposes bare aluminum at the cut. Finishing first means the coating covers the full extruded surface, with cut ends treated separately where exposure demands it.

3. How is a thermal break assembled and verified?

Polyamide strips are inserted into knurled channels in the aluminum profiles, which are then rolled or crimped to lock them mechanically. Crimp pressure is critical, and shear testing on production samples verifies the bond, since a failed break is invisible until the facade underperforms thermally.

4. Is unitized manufacturing better quality than stick?

Generally yes, because almost all quality-critical assembly happens in a controlled factory rather than on site in weather. Stick systems place more of the outcome on site workmanship, which is harder to control and verify.

5. What manufacturing records should a supplier provide?

Material certificates for alloy and glass, coating thickness measurements with batch traceability, thermal break shear test results, structural silicone adhesion records, dimensional inspection against approved shop drawings, and packing lists referenced to the erection sequence.