Curtain wall selection on most projects comes down to a fundamental choice: unitised or stick-built. Both systems achieve the same end result — a non-load-bearing facade that keeps weather out and provides a finished enclosure — but they get there in very different ways, with different implications for program, quality, cost, and building performance.
This is a practical comparison based on how the two systems work on real projects, where each approach has genuine advantages, and how to make the right call for a given building.
What is the difference between unitised and stick-built?
Stick-built curtain wall is assembled on site, piece by piece. Mullions (vertical members) and transoms (horizontal members) are fixed to the building structure individually, and glazing panels are then installed into the assembled framework. The facade is built in place, from the scaffold or from a swing stage, one component at a time.
Unitised curtain wall is pre-assembled in a factory as complete panels — frame, glazing, seals, and all — then transported to site and installed as finished units. Each panel typically spans one floor height and one module width. On site, the panels are lifted into position by crane and hooked onto brackets fixed to the slab edge. The connections between adjacent panels form the weatherproofing joints.
The distinction is essentially about where the skilled work happens. With stick-built, the precision assembly happens on the scaffold. With unitised, it happens in a controlled factory environment, and the site work is reduced to lifting, placing, and connecting.
How do they compare on installation speed?
This is where unitised curtain wall has its most significant advantage. Because the panels arrive fully assembled, site installation is fast. A well-organised unitised installation can close a floor of facade in a fraction of the time it takes to stick-build the same area. On a 20-storey building, this time saving compounds dramatically.
Stick-built installation is inherently sequential. Mullions go up first, then transoms, then glazing. Each step depends on the previous one being complete and aligned. On a multi-storey building, this sequence plays out floor by floor, and the facade program often becomes the critical path constraint for the follow-on trades.
On projects where the construction program is tight — which, in the current market, is most of them — the speed of unitised installation is often the deciding factor. The facade closes faster, interior trades start earlier, and the project reaches practical completion sooner.
How does quality control differ?
Factory assembly provides inherent quality advantages. The panels are built on jigs, in a dry and controlled environment, with consistent tooling and repeatable processes. Glazing is installed flat, seals are applied under ideal conditions, and every panel can be inspected before it leaves the factory.
Stick-built assembly happens on the side of a building, often at height, in variable weather, with tolerances that depend on the skill of the individual installer and the accuracy of the structural frame they are fixing to. None of this means stick-built facades cannot achieve excellent quality — they can, and regularly do — but it requires more site supervision, more tolerance management, and more reliance on individual workmanship.
For projects where the facade finish quality is critical — landmark buildings, buildings with tight visual tolerance requirements, or buildings where the facade is the defining architectural element — the factory-controlled environment of unitised construction provides a measurable advantage.
How do the two systems handle building movement?
Every multi-storey building moves. Floors deflect under load, the structure shortens over time as concrete creeps, wind causes sway, and thermal expansion changes dimensions daily. The curtain wall needs to accommodate all of this without transferring stress to the glazing or compromising the weather seal.
Unitised systems handle movement through the joints between panels. Each panel is structurally independent, hanging from brackets at the slab edge, with interlocking spigot joints between adjacent panels that allow relative movement in all three axes. The typical design allowance for a unitised system is plus or minus 25mm at the stack head (vertical) and plus or minus 10mm at the mullion split (horizontal). This is built into the panel design from the outset.
Stick-built systems handle movement through expansion joints built into the mullion and transom framework. The mullions are typically fixed at one point and allowed to slide at another, with the expansion joint absorbing vertical movement. Horizontal movement is managed through similar sliding connections. The movement allowances are similar in principle but depend heavily on the detailing and the quality of installation.
Both approaches work. Unitised systems tend to handle movement more predictably because the joints are factory-set and the movement mechanism is inherent to the panel connection. Stick-built systems require more care in setting up the movement joints on site, and the achievable tolerance depends on the installer’s execution.
What about thermal performance?
Thermal bridging — heat transfer through the aluminium frame from the exterior to the interior — is a challenge for both systems. Aluminium conducts heat efficiently, which is useful in many applications but problematic in a building enclosure where you are trying to maintain an insulated boundary.
Unitised systems typically incorporate thermal breaks within the framing, using polyamide strips or similar low-conductivity materials to separate the interior and exterior aluminium sections. These thermal breaks can be factory-installed with precision, ensuring consistent performance across every panel.
The V&G 165CW unitised curtain wall, for example, uses thermally broken glazing adaptors with polyamide strips and aluminium nose caps. The 165mm frame depth provides space for insulated glazing units from 24mm to 40mm, allowing the facade engineer to select the IGU configuration that meets the project’s Section J energy performance requirements.
Stick-built systems can also incorporate thermal breaks, but the assembly is done on site, and the consistency of the thermal break installation depends on site execution. On projects with demanding energy performance requirements, the factory-controlled thermal break installation of unitised systems offers a reliability advantage.
When does unitised win?
Unitised curtain wall is the stronger choice when several of these conditions are present:
High-rise buildings. Above roughly 10 to 15 storeys, the program advantage of unitised installation becomes substantial. The faster the facade closes, the earlier interior fit-out can begin, and on tall buildings this cascading benefit is significant.
Tight construction programs. When the project cannot afford a slow facade enclosure, unitised delivers. Panels can be manufactured while the structure is still going up, and installation begins as soon as enough structure is available, progressing floor by floor behind the jump form or climbing crane.
Quality-critical facades. When the architectural design demands tight visual tolerances, consistent joint widths, or a high-quality glazing finish, factory assembly provides the control environment that site assembly cannot match reliably.
Complex geometry. Unitised panels can be manufactured to accommodate curves, angles, and non-standard module sizes, with the complexity absorbed in the factory rather than managed on the scaffold.
Difficult site access. On urban sites with limited laydown area and constrained access, unitised panels can be delivered and installed directly from the truck to the building face, reducing the on-site storage and handling that stick-built systems require.
When does stick-built win?
Stick-built curtain wall has genuine advantages in other project contexts.
Low-rise buildings. On buildings below five or six storeys, the program advantage of unitised is smaller, and the higher unit cost of factory-assembled panels may not be justified by the time savings.
Simple geometry. On buildings with straightforward rectangular facades and repetitive module sizes, stick-built systems can be installed efficiently without the additional cost of factory unitisation.
Budget-constrained projects. Stick-built systems generally have lower per-square-metre material and fabrication costs, though this comparison is project-specific and needs to account for the longer installation program and associated site costs.
Late design changes. Stick-built systems are more adaptable to changes during construction, because the components are assembled individually and adjustments can be made on site. Unitised panels, once manufactured, are committed to their designed configuration.
Limited crane availability. Unitised installation requires a crane for lifting panels into position. On projects where crane access is constrained or the crane is shared with other trades, stick-built installation — which relies on scaffold access rather than crane lifts — may be more practical.
What does the V&G 165CW system offer?
The V&G 165CW is a unitised curtain wall system designed, engineered, and extruded in Australia. The key specifications are:
- 165mm frame depth with IGU capacity from 24mm to 40mm
- Primary framing in 6060-T6 alloy, secondary in 6060-T5, structural members in 6005A-T6
- Stack head movement allowance of plus or minus 25mm
- Mullion movement allowance of plus or minus 10mm
- Three-part structural bracket with three-dimensional installation adjustment
- Hook-on bracket system for efficient panel placement
- Thermally broken glazing adaptors with polyamide strips
- Four-side structural silicone glazing
- Integrated sunshade brackets with concealed nutplate fixing
- LogiKal software database for estimating, cutting optimisation, and CNC output
The 86mm mullion width (including 10mm nominal gap) provides a clean sightline, and the system supports both anodised and powder coat finishes. The hook-on bracket and three-dimensional adjustment allow installers to achieve precise alignment efficiently, which is where the practical benefit of unitised construction shows up most clearly on site.
If you are assessing curtain wall options for an upcoming project, our team can provide technical specifications, project references, and advice on which system suits your building.
Evaluating curtain wall options for a project? Talk to our team for 165CW specifications and project references.
Related Reading
- 165CW Curtain Wall System: Australian-Designed Specification Guide
- Aluminium Facades for Office Buildings
- Aluminium Facades for Hotels and Hospitality Buildings
- High-Rise Facade Trends in Australia: 2026
Last updated: 4 April 2026