Every curtain wall tender eventually reaches the same question: unitized or stick? The two systems can produce an identical elevation, an identical U-value and an identical water test result, yet they load the programme, the site labour and the budget in completely different places. This is a working comparison rather than a sales argument — including the cases where we recommend against unitized.
The difference in one sentence
A unitized system assembles the frame, glass, spandrel, insulation and gaskets into a complete panel in a factory, then lifts that panel onto the building as one piece. A stick system ships mullions, transoms and glass separately and builds the wall member by member, on the building, from the inside.
Everything that follows — cost, speed, quality, geometry, access — is a consequence of where the labour happens.
Where unitized wins
- Programme on tall buildings. Installation is a crane-and-crew operation with no glazing at height; the facade closes floor by floor as the structure rises.
- Quality control. Glazing, sealing and torque are done at a bench, under a roof, with an inspection record per unit. Water and air performance depends far less on the weather that week.
- Site labour. A small, trained crew can install a large area. That matters in markets where facade labour is scarce, expensive or inconsistent.
- Movement and drainage. The double-wall interlock gives a designed drainage path and accommodates inter-storey drift without relying on wet seals.
- Testing before site. Mock-up panels can be built and tested from the same line that will produce the job, which is what consultants and facade engineers want to see.
Where stick still wins
- Small and awkward buildings. Below roughly fifteen storeys, the crane time and factory set-up of unitized can outweigh the labour saving.
- Complex geometry in small quantities. One-off curves, raking panels and tight radius work are often cheaper to site-assemble than to jig and transport.
- Tight sites. Unitized needs delivery access and crane time at the face; a stick system works from a mast climber or scaffold with far less laydown area.
- Late design change. Stick tolerates a change to a mullion position far better than a factory that has already built two hundred units.
- Cash flow. Payments follow production in unitized; some owners prefer the slower, smaller site-based spend of stick.
Why the unit rate misleads
Unitized almost always prices higher per square metre at the supply stage. The comparison only becomes meaningful when the whole package is counted: site labour and supervision, crane time, scaffold or mast climber, programme duration, snagging, and the cost of a delay to the building envelope.
On a tall tower in a high-cost labour market, the installed cost of the two systems often converges. On a low-rise building in a market with cheap and experienced facade labour, stick usually stays cheaper. We price both before recommending, because the answer flips with the project.
Our own rule of thumb: we quote unitized when the building is above about fifteen storeys, when the programme is tight, or when the specification requires a tested mock-up. Otherwise we ask the client to let us price stick as well.
A decision table you can take to a meeting
| Condition | Unitized | Stick |
|---|---|---|
| Height above ~15 storeys | Preferred | Workable |
| Two to eight storeys | Rarely justified | Preferred |
| Repetitive module, long elevation | Preferred | Workable |
| One-off curved or raking panels | Workable | Often cheaper |
| Tight site with no laydown | Difficult | Preferred |
| Site labour scarce or costly | Preferred | Risky |
| Mock-up testing required | Preferred | Possible |
| Design still moving | Risky | Preferred |
What to ask a supplier before you commit
- Which system do you actually manufacture, and what is your monthly output of that system?
- Can I see the test reports for air, water and structural performance on that specific profile?
- Who details the units — you, or a third-party consultant, and at what LOD?
- What is your tolerance on the unit and on the interlock, measured how?
- What happens to a damaged unit after delivery has closed — what is the replacement lead time?
- Can you price both systems for this building so the comparison is real?