The Klapwiek building in Rotterdam-Prinsenland is a bold example of urban densification and modular innovation. Originally housing 228 two- and three-room apartments for seniors, the building is now being optopped with 44 additional homes, thanks to a collaboration between SOR, Dura Vermeer Bouw Heyma, and EGM Architecten. These new units are created using a prefabricated Smartbox system: the modular core of each apartment—including bathroom, kitchen, and technical installations—is produced in the factory and lifted onto the existing building. The added floor is built using lightweight wooden construction (HSB) to maintain structural integrity and minimize disruption on site. Our Role & Contribution When we joined the Klapwiek project, we knew it would be more complicated than most — but that offered a chance to prove exactly what our system is made for. We designed the entire electrical installation in 3D, tailored to the modular Smartbox architecture. During the process, there were countless changes, adaptations, and feedback from the construction team and stakeholders. Thanks to our pluggable system, accommodating these changes was far smoother than with traditional wiring. Because of our system’s flexibility, we adapted quickly to design tweaks and last-minute updates without compromising on safety or quality. Why This Project Matters? The Klapwiek optopping project is a smart, circular solution to Rotterdam’s housing needs: 1. It adds value to existing urban assets instead of building completely new structures. 2. By using prefabricated modules, on-site disruption is limited, and construction is much faster. The result? More sustainable, high-quality social housing, with a modern construction method that aligns perfectly with Plug and BIM’s strengths.