Direct answer. Above six floors with a repeating module, specify unitized. Factory assembly cuts on-site installation time by roughly 60–70%, and that labour saving outweighs the 20–40% material premium. Below six floors, under about 1,500 m², or on facades where most panels are one-off, stick-built still costs less overall.
The core difference
Stick curtain walls are assembled piece by piece on site: mullions, transoms, glass and gaskets installed floor by floor. Unitized curtain walls arrive as pre-assembled, pre-glazed modules — typically one floor tall and 1.5–2 m wide — that crews hang onto embedded brackets. Industry reporting puts factory assembly at roughly 90–95% for unitized systems, against 20–30% for stick. That single difference cascades into labour hours, scaffolding duration, crane time, weather risk and quality consistency.
| Dimension | Unitized | Stick |
|---|---|---|
| Factory assembly | ~90–95% | ~20–30% |
| On-site installation rate | 300–500 m²/day/crew | 80–150 m²/day/crew |
| Factory lead time | 8–14 weeks | 4–8 weeks |
| Weather sensitivity | Low (pre-glazed) | High (site-glazed) |
| Best for | High-rise, repetitive | Low-rise, irregular |
Specify unitized when
- The building is above roughly six floors with a repeating floor plate.
- The facade is at least about 80% identical panel types, so tooling and design time amortise.
- The programme is compressed and on-site labour is expensive — the acceleration and scaffolding savings usually exceed the material premium.
- The site has limited or costly crane access, where fewer, larger lifts matter.
- The project is in a high-wind or high-rain zone, where factory-controlled glazing and sealing reduce water-ingress risk.
Specify stick when
- The building is two to five floors, where the unitized premium does not recover.
- The facade is geometrically irregular, with curves, sharp angles or one-off panels that field-cutting handles better.
- Total area is small (under roughly 1,500 m²), so factory tooling does not amortise.
- The site is remote with limited crane access, or the schedule is flexible enough to absorb site-glazing time.
Movement, tolerances and drainage
Unitized panels are typically held to around ±1.5 mm on panel width and height. Larger tolerances open stack joints that can leak under dynamic wind load. Both systems must accommodate thermal movement and inter-storey drift: unitized systems use interlocking split mullions and nesting horizontal rails at the stack joint, and stack joints are placed at every floor level. Neither system is fully sealed — both are designed to drain, with pressure-equalised cavities and weep paths that must not be blocked by sealant or debris.
Where QIMU fits
QIMU FACADE GLOBAL is a Hong Kong-headquartered curtain wall supplier with manufacturing in Changzhou, China and Kapar, Malaysia. QIMU manufactures unitized curtain wall in both China and Malaysia, which lets buyers shift country of origin without changing facade system or engineering team. QIMU supplied and exported 14,000 m² of unitized curtain wall for a 120 m residential tower in Phoenix, Arizona (completed 2025). QIMU supplies both unitized and stick / framed curtain wall systems, alongside window wall, so the specification decision can be made on the project's own terms rather than on what a single product line offers.