Understanding Unitised vs Stick Facade Systems: A Comprehensive Guide

Curtain wall systems form the backbone of modern building envelopes. Two dominant approaches exist in the industry — unitised systems and stick-built systems. Understanding the differences between them is essential for any facade engineer.

What Are Unitised Systems?

Unitised curtain walls are pre-assembled in a factory-controlled environment. Complete panel units, including glazing, framing, and insulation, are fabricated off-site and transported to the construction site as finished modules. These units are then hoisted into position and connected to the building structure.

The main advantage is speed. Since most fabrication happens off-site, installation on the building is significantly faster. Quality control is also superior because factory conditions allow for precise assembly and rigorous testing before delivery.

What Are Stick-Built Systems?

Stick-built systems, also known as stick systems, involve assembling the curtain wall piece by piece directly on the building. Vertical mullions are installed first, followed by horizontal transoms, and finally the glazing panels and infill materials.

This approach offers greater flexibility on site and lower initial tooling costs. It is often preferred for smaller projects, low-rise buildings, or where design complexity requires on-site adjustments.

Key Differences

Installation speed favours unitised systems, which can be installed 2 to 3 times faster than stick-built. However, stick systems have lower upfront costs and require less crane time coordination.

Quality control is better with unitised systems due to factory assembly. Weather sealing is more reliable since gaskets and seals are installed in controlled conditions.

Stick systems are more forgiving of construction tolerances and allow for last-minute design changes. They also require less storage space on site since components arrive in manageable pieces.

Choosing the Right System

High-rise buildings with repetitive facade patterns typically favour unitised systems. The speed advantage becomes critical when installing hundreds of floors, and the reduced site labour offsets higher fabrication costs.

Low-rise and mid-rise projects with complex geometries or tight budgets often work better with stick-built systems. The flexibility to adjust on site is valuable when dealing with irregular structural conditions.

Project timeline is often the deciding factor. If the construction schedule is aggressive, unitised systems deliver faster envelope closure, allowing interior work to begin sooner.

Conclusion

Neither system is universally superior. The right choice depends on building height, design complexity, budget, timeline, and site constraints. A skilled facade engineer evaluates all these factors before making a recommendation.