What are the structural differences between unitized and stick-built curtain walls?

The primary structural difference between unitized and stick-built curtain wall systems lies in their fabrication and installation methods, which significantly impacts project timelines, quality control, and cost. A stick-built system is the traditional method where the core components—the aluminum mullions and transoms—are shipped directly to the construction site as individual pieces or "sticks." These are then assembled frame by frame on the building's exterior, after which the glazing and spandrel panels are installed. This approach is labor-intensive and performed entirely on-site, making it highly dependent on weather conditions and local labor skills. In contrast, a unitized curtain wall system involves fabricating large, pre-assembled panels in a controlled factory environment. Each unit includes the aluminum framing, glazing, and spandrel panels. These completed units are then transported to the site and hoisted into place, interlocking with adjacent units. For large-scale projects and high-rise towers, such as those shaping the skyline of Riyadh, the unitized system offers unparalleled advantages. The factory-controlled fabrication ensures superior quality, tighter tolerances, and better performance of seals and gaskets. It also dramatically speeds up on-site installation, a critical factor for massive developments across Saudi Arabia where efficiency and predictable schedules are paramount. While stick systems offer flexibility for complex geometries on smaller projects, the structural integrity and performance consistency of unitized systems, built with precision-engineered aluminum frames, make them the preferred choice for modern architectural statements.