Externalframe

Externalframe is a term used in architecture and structural engineering to describe a building system in which the primary structural frame is located on the exterior of the building, while the interior walls and floors form a largely unobstructed space. In this arrangement, loads from the roof and floors are carried by external columns and beams, with the façade contributing to stiffness and stability, rather than only the interior skeleton.

Historical context: The concept has roots in early cantilever and steel-framed skyscraper ideas of the late 19th and early 20th centuries, and modern exterior-frame systems occasionally appear in high-performance facades and exoskeletal designs. It is distinct from curtain-wall construction, where the façade is mainly a non-structural envelope, and from interior-frame systems.

Design and engineering: Externalframe systems require carefully designed connections between the outer frame and the rest of the structure, and they often use steel or reinforced concrete. Thermal performance and weatherproofing are key considerations because elements of the frame are exposed. Building services and interior layouts can be more flexible since interior columns are minimized.

Advantages and challenges: The exterior frame can maximize interior openness, facilitate rapid assembly, and simplify later modifications. However, it can introduce thermal bridging, exterior maintenance needs, and higher initial fabrication costs, and it may impose more stringent wind or seismic design requirements.

Applications: Externalframe has been explored in speculative architecture, large-span pavilions, and some high-rise designs where facade performance or future modification is prioritized. See also: exoskeleton architecture, frame construction, curtain wall.