Curtain wall (continuous façade)

A lightweight, continuous external envelope, hung in front of the structure: a grid of aluminium mullions and transoms carrying glazing and panels without bearing the building's loads. The curtain wall «clads» the floors, running uninterrupted past their edges and fixed back with point brackets; it only has to carry its own weight and resist the wind, leaving the rest to the structure. It is the transparent envelope of office and tower buildings.

The curtain wall is a non-load-bearing envelope: a thin, largely glazed skin hung in front of the floors. It does not carry the building's loads — the inner structure does that — but it must carry its own weight, the wind and the thermal movement, and ensure tightness to water and air. It is «continuous» because it runs uninterrupted past the floor edges, giving the building a smooth, uniform surface.

The skeleton is a grid of aluminium profiles: the mullions, vertical, carry the weight of the glass and shed it onto brackets anchored to the floors; the transoms, horizontal, complete the frames. Into the openings go double (or triple) glazing units and opaque panels, held by pressure plates and gaskets. The profiles are thermally broken — aluminium interrupted by an insulating strip — so as not to act as a thermal bridge.

Water and air are controlled by chambers and upstands, not by a single outer seal. Rain that gets past the first upstand enters small chambers and is drained back out through calibrated holes, while the inner gasket makes the air seal (the pressure-equalised principle). So the façade stays tight even under strong wind, without relying on a silicone that, alone, eventually fails.

The façade is hung from the structure with point brackets, one per floor: one fixed point carries the weight, the others slide to follow the thermal movement (aluminium moves a lot in heat) and the floor deflections. The joints between modules are open and movable. The fire barrier at each floor edge must be detailed, to stop flames and smoke running in the gap between façade and floor from one storey to the next.