Aluminium Curtain Wall (unit)

Overview

A curtain wall is the building's outer skin: a continuous aluminium-and-glass envelope that hangs in front of the floor slabs and carries no part of the building's weight. It only has to resist wind, hold out water, insulate, and pass its own dead load back to the structure. This is a stick system, the simplest kind, assembled on site from individual frame sticks rather than from prefabricated panels.

The frame is a grid. Vertical Mullion members run floor to floor and take the load; horizontal Transom members span between them and divide each bay. Both are thermally-broken aluminium extrusions: an inner and an outer aluminium half linked by a Polyamide Thermal Break of reinforced polyamide so heat cannot conduct straight through the metal. The grid is infilled with two kinds of panel, clear Vision Glazing Unit glazing where people look out, and opaque Spandrel Panel units that hide the floor slab and ceiling void.

How it works

Each infill panel is captured mechanically rather than glued. A continuous Pressure Plate & Cap Set is screwed down the centre of every frame member, clamping the glass edge against the inner gasket with even pressure; a snap-on cover cap then hides the screws and gives the facade its visible grid. The whole seal line depends on the Gasket & Seal Set, inner and outer EPDM gaskets that cushion the glass and form the air and water barrier.

The wall manages water by drainage, not by trying to be perfectly watertight. The glazing rebate is a pressure-equalised cavity; any rain that gets past the outer gasket falls into it and runs back out through the Drainage & Weep Set, whose baffled weep covers let water escape but block wind from driving it inward. Wet-applied Sealant Set silicone closes the perimeter and movement joints. The entire envelope hangs off the building on the Anchor & Bracket Set: one adjustable bracket per mullion bolts to a slab anchor, taking dead load on a single fixing and wind load on the rest while letting the building sway and settle without cracking the glass.