Unitised vs stick curtain wall systems explained

ToughGlaze supplies processed glass for both unitised and stick curtain wall systems. Explore the differences between them.

Curtain walls can be categorised in different ways. They can vary by framing material (typically aluminium or steel) and performance requirements, with specialist systems designed for fire resistance, security or enhanced thermal performance.

They can also be split into two main types according to how they're assembled: unitised curtain walls and stick curtain walls.

The primary difference between these two types of curtain wall systems is simple. Unitised curtain walls are built as large, pre-assembled panels in a factory before being shipped to the construction site.

Stick curtain walls, by contrast, are supplied as individual components and assembled piece by piece on site.

They serve different purposes and come with their own advantages and disadvantages. Both can incorporate a wide range of glass types, including insulated glass units (IGUs), toughened glass and laminated glass.

If you're looking for high-quality processed glass for a unitised or stick curtain wall system, we've got you covered.

At ToughGlaze, we cut and process glass to suit a wide range of facade applications. Depending on the specification, this can include toughened or laminated glass, low-e and solar-control glass and other specialist products.

With that said, let's look at the differences between unitised and stick curtain walls in more detail.

What are the differences between stick curtain walls and unitised curtain walls?

Assembly

The fundamental difference between stick curtain walls and unitised curtain walls is how they're assembled.

Stick curtain walls are assembled piece by piece on the building site. Unitised curtain walls are largely pre-assembled and glazed in factory conditions before being shipped ready for installation.

When supplied with a stick curtain wall, construction teams install individual mullions (vertical framing members) and transoms, the horizontal members that run between them. They then install the glazing and other infill panels on site.

This process is generally more labour-intensive than installing a unitised system.

With a unitised system, large modular panels arrive on site substantially complete. They can then be lifted into place and attached to the building structure. Because much of the glazing, sealing and assembly happens in the factory, on-site workers can install it considerably faster.

Factory assembly also benefits quality control. Glazing, seals and other components can be fitted in controlled conditions rather than being exposed to changing on-site weather.

That doesn't mean stick systems are inherently prone to failure. When correctly designed and installed, they can offer highly reliable weather and thermal performance.

However, because more assembly and sealing takes place on site, workmanship and site conditions can have a greater influence on the finished result. Unitised construction tames some of these variables by completing more of the work in factory conditions.

Cost

There's a cost difference, too. However, this depends heavily on the project.

Stick systems can have lower fabrication and transport costs, particularly on smaller projects, but installation generally requires more work on site.

Unitised systems require greater factory fabrication and may involve more demanding transport and lifting arrangements. The installation process, however, is typically faster and less labour-intensive once the units reach site.

Project suitability

These differences affect the kinds of projects for which each system is commonly chosen.

Generally speaking, stick systems are widely used on low- to mid-rise developments and projects where flexibility is important. Unitised systems are particularly well suited to high-rise buildings, large facades and projects with repetitive modular layouts.



Does my project need a unitised or stick curtain wall system?

There's no straightforward answer to this question. It all depends on the nature of the building project, programme, facade design and budgetary priorities.

Broadly speaking, unitised systems lend themselves particularly well to tall, repetitive and fast-moving installations. Stick systems can offer greater flexibility for smaller buildings and more complex or irregular facade layouts.

Unitised systems are therefore often chosen for high-rise projects where the façade has a regular repeating pattern and rapid installation is important.

Quality control can also play its part. Because much of the system is assembled and glazed in controlled factory conditions, unitised construction can make it easier to maintain consistent fabrication and sealing standards across large numbers of panels.

The key factor isn't always upfront cost.

Unitised curtain walls can be more expensive to manufacture, transport and handle, but may reduce the labour required on site. Stick systems can be economical and flexible but generally require more on-site assembly.

The right choice therefore depends on the design, scale, access requirements, programme and economics of the individual project.

You're more likely to encounter a stick system on a low- to mid-rise building or a facade with complex geometry. Its component-based construction can also provide flexibility where site conditions or interfaces require adjustment during installation.

Unitised systems become particularly attractive where there are large areas of repetitive facade and where reducing installation time, scaffolding or on-site labour is a priority.

Do unitised and stick curtain wall systems use the same kinds of glass?

Both unitised and stick curtain walls can accommodate many of the same types of architectural glass. The main distinction lies in how the curtain wall is fabricated and installed rather than in a completely different family of glazing products.

Both systems can incorporate double- or triple-glazed IGUs where the project requires thermal insulation, solar control or acoustic performance.

Safety glass may also form part of the specification.

Toughened glass (also known as "tempered glass") is made by heating and rapidly cooling annealed glass. This creates internal stresses that make it significantly stronger and change the way it breaks.

When toughened glass fractures, it breaks into many small fragments rather than the large, sharp shards associated with ordinary annealed glass. This reduces the risk of serious injury and makes it suitable for many safety-glazing applications.

Laminated glass works differently. It consists of two or more panes bonded together using an interlayer.

If the glass breaks, that interlayer is designed to hold the fragments together. This can provide valuable post-breakage retention and, depending on the make-up, can also contribute to safety, security, acoustic or structural performance.

Laminated glass can itself incorporate toughened or heat-strengthened panes where the project specification requires them.

Both types of curtain walls can also incorporate low-e or solar-control coatings where improved energy performance or control of solar gain is required. The exact glazing specification will depend on the façade design and the building performance targets.

How is glass installed in each system?

The glazing installation process differs between the two systems.

In a unitised system, glazing is typically installed into the facade panels in factory conditions. With a stick system, the framing is assembled on site, and the glazing is then fitted into the completed grid.

There can also be differences in how tolerances and site variation are managed. Unitised panels must be manufactured accurately so that prefabricated modules align correctly when installed. Stick systems offer greater scope for adjustment within the framing system during installation.

The glass itself, however, still needs to be manufactured to the correct finished dimensions. Toughened glass, laminated glass and finished IGUs cannot simply be cut down on site if they don't fit.

How we can help

Are you sourcing processed glass for a curtain wall project? ToughGlaze supplies toughened, laminated, coated and specialist architectural glass for a wide range of facade applications, as well as fixings for frameless structural glazing.

Get in touch with our team to discuss your specification or request a quick, competitive quote.