Why should We Consider Building Movement When Specifying Perimeter Fire Seals for Curtain Wall Façades?

As more and more sky-high multi-occupancy buildings emerge across India's densely populated megacities, it is not only crucial that curtain wall façades are designed and constructed to withstand constant movement but that the passive fire protection measures incorporated within can accommodate this movement.

- SREENIVAS NARAYANAN

With clean lines, sleek glass surfaces, and technological glazing innovations, curtain walls offer an ultra-modern aesthetic, floor-to-floor natural daylight, and excellent weatherproofing. Unlike more traditional wall constructions, curtain walls are not part of the building's supporting structure. They are a non-loadbearing and self-supporting vertical enclosure or envelope that separates and protects the internal environment from the external climatic conditions. This makes them highly susceptible to movement caused by wind and rain loads, seismic sway, occupancy loads on the floor slab, and thermal loads that cause the structure to expand and distort. Whilst various calculations and computer modelling can help designers to better understand the range of potential movement and work needed to mitigate it, it cannot be designed out completely.

Consequently, curtain-walled buildings are commonly built with a gap between the edge of the floor slab and the façade itself to allow for both vertical and lateral deflection. This is known as the movement gap or the expansion joint and the designed perimeter gap can vary considerably in void size. For instance, this can be wider in certain cases such as where buildings are built in locations with high movement risk (e.g. frequent seismic activity) or include more dynamic, complex design elements (e.g. curved elevations). Whilst vital for allowing free movement without damage to the structure, this gap can present a huge challenge when it comes to ensuring passive fire protection.

Perimeter Fire Seals