2. Heavy prefabrication

When the external air pressure is greater than the pressure inside a facade, the kinetic energy of wind-driven rainwater or run-off water forces it through even the tightest joints.

To achieve a balance between these pressures, a pressure equalization chamber is often provided at the time of construction, in addition to the air and water seals provided by the mastic. A watertight strip, usually made of bituminous felt, is inserted as an additional airtight seal ( [C 3 660] , figure 6a ).

Horizontal joints are generally two-stage. The trim at the top of the panels forms the airtight barrier and the watertight complement [3] ( [C 3 660]...