How do installation processes differ for stick-built and unitized curtain walls?

The installation processes for stick-built and unitized curtain walls are fundamentally different, primarily distinguished by where the assembly takes place—on-site versus in a factory. The stick-built installation is a sequential, on-site process. It begins with the delivery of long aluminum extrusions (the "sticks"), which are then individually attached to the building structure to create the curtain wall's grid-like frame of mullions and transoms. This work is done from scaffolding or mast climbers, piece by piece. Once the framework is in place, glaziers install the vision glass and spandrel panels from the exterior. This method requires a significant amount of on-site labor and storage space for materials, and its progress is highly susceptible to weather conditions. In contrast, the unitized curtain wall installation process is defined by pre-fabrication. Large, complete panels—often one story high and one or two modules wide—are manufactured, assembled, and glazed in a climate-controlled factory. These finished units are then transported to the construction site. A tower crane hoists each unit and installers working from inside the building guide it into place, securing it to anchors embedded in the floor slabs. This method is significantly faster, safer for installers who work primarily from within the building, and results in higher quality as assembly is done in a controlled environment. For the rapid construction of high-rise towers across Saudi Arabia, the speed and predictability of the unitized process are invaluable, drastically reducing building enclosure time and reliance on favorable weather.