There are two main classifications of curtain wall systems: unitized curtain walls and stick-built systems. Unitized systems are composed of large pre-fabricated units that are erected on the building’s facade. In contrast, stick-built curtain walls are installed piece by piece.
In essence, the key distinctions between these systems lie in their installation methods and, often, their manufacturing techniques. Unitized systems involve the construction and insulation of large units at the manufacturing site, which are then transported and assembled on-site. On the other hand, stick-built systems involve the construction of individual components directly at the work site.

Unitized Curtain Systems

Unitized curtain systems consist of large glass units that are manufactured and glazed within a controlled factory environment before being transported to the construction site. Once on-site, these units can be easily lifted and attached to anchors on the building. This type of system is known for its high quality, achieved through precise fabrication tolerances in a climate-controlled setting. A notable advantage of unitized systems is the speed of installation, as there is no need for on-site glazing.

Compared to stick-built systems, unitized systems can be installed in approximately one-third of the time. This makes them particularly suitable for projects requiring a large number of prefabricated unitized panels and where field labor costs are higher, thus enabling the shift of labor to a more cost-effective factory workforce. Additionally, unitized systems offer enhanced performance in terms of wind loads, air/moisture protection, seismic and blast resistance. They are well-suited for taller structures and projects with more regular conditions that allow for panel optimization.

Stick Built Glass System

If your project doesn’t meet the criteria for a unitized system, the alternative option is to opt for a stick-built system, which is the most common method for installing low to mid-rise curtain walls. In stick-built systems, elongated aluminum pieces (referred to as “sticks”) are inserted vertically between floors and horizontally between vertical members to provide support and transfer the load of the glass back to the structure.

The majority of the assembly and glazing work for stick-built systems takes place on-site. One advantage of stick-built systems is their cost-effectiveness for facades that require lower volumes and involve complex conditions. Lead times for fabricated materials to be delivered to the site are typically shorter compared to unitized systems, and upfront staging requirements are reduced. In contrast, unitized systems may require six months to a year for this process.

However, the trade-off is that on-site installation for stick-built systems takes longer to complete. Additionally, a significant amount of space is necessary for material storage and installation on-site, which can pose challenges in high-traffic cities with limited job site area.