The performance of a curtainwall system heavily depends on the correct compression setting of glazing gaskets. Gaskets—typically made of EPDM or silicone—are designed to seal the interface between glass panels and aluminum frames. Their primary roles include preventing water and air infiltration, damping vibration, and accommodating thermal expansion and contraction. However, improper compression can lead to system failure, such as glass breakage or sealant extrusion.

Correct compression starts with spacer shim design. The glazing pocket must have a precise depth; typically, a 3-5 millimeter compression gap is recommended for standard 6mm to 12mm glass. The gasket’s cross-section should be slightly larger than the gap it seals, ensuring a positive interference fit. When the glass is pressed into the wet sealant bed, the gasket should be compressed to 50-70% of its original height. This ratio provides sufficient sealing force without crushing the glass edge.

Thermal movement must be factored into the setting. On a hot day, aluminum expands more than glass, reducing the pocket depth. If gasket compression is too high, the glass may experience edge stress, leading to breakage. Conversely, low compression in cold climates can leave gaps, causing air leakage and condensation. A rule of thumb: set the gasket to maintain a 2-3mm free space at extreme temperatures.

Installation sequence matters. The gasket is first inserted into the frame glazing leg. After the glass is placed and centered, the glazing wedge gasket is hammered into the opposite side. This wedge should never exceed the manufacturer’s specified compression limit—usually indicated by a mark on the gasket. Over-driving the wedge can distort the glass or shear the sealant.

In structural curtainwalls, the gasket works in tandem with silicone sealant. The sealant absorbs primary wind load; the gasket serves as a secondary weather barrier and holds the glass in place during curing. For best results, inspect gasket compression with a feeler gauge or digital caliper after each panel installation. Periodic re-torquing of pressure plates may be needed as the gasket relaxes over time—especially during the first year of the building’s life.

Ultimately, mastering gasket compression ensures long-term weathertightness, reduces callbacks, and extends the curtainwall’s service life.