Curtain wall supports are important to understand because they have a large impact on crucial architectural dimensions and perimeter transitions. Some architects seem to be of the unsupported opinion these connections should somehow resemble the typical window frame attachment. This article’s authors have seen designs that simply disregard the issue of supports; the details feature a curtain wall floating on a perimeter 1312.7-mm (0.5-in.) wide sealant joint. The architects of such projects are then genuinely surprised when anticipated façade module dimensions, alignments, and proportions are lost in the field.
Unfortunately, the designer’s confusion is sometimes reflected in the glass of the actual construction. Figure 1 shows a spandrel of a multi-story curtain wall in a high-rise building. It is important to observe how the live load is transferred from slabs onto the curtain wall.
In other cases, windows and doors are often used in lieu of regular glazed curtain walls. They also become subject to the same limitations and requirements affecting curtain wall assemblies. Figure 2 illustrates the failure of a multi-panel, full-height glass sliding doors, incapable of accommodating the live load slab movement.
Simply put, curtain walls are not designed to carry loads from the slab. Instead, a bulky vertical structure is typically used for that purpose. The supporting elements of curtain walls must be designed to allow the free vertical movement in excess of the calculated movements.
A quick scan of typical warranties shows many curtain wall manufacturers and installers exclude the responsibility for these and other transition details. Consequently, it is the designer’s responsibility to understand the system’s ramifications, and then to properly specify and coordinate its installation.
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