Lock-Strip Gasket System Retrofit: A Case History

The facade of the subject 20-year-old, three-story building is comprised of insulating glass units in vision areas and single monolithic glass sheets in spandrel areas. Both products have a reflective metallic coating on the exterior surface and are completely captured by a perimeter lock-strip (zipper) gasket system. The zipper gasket intersections are butted, not vulcanized, causing numerous Oavenues for water penetration. Attempts to seal some of these gaps with sealant had been made in the past, yet active leaks still existed. Furthermore, there was a concern regarding the premature failure of the insulating glass units within the inadequately drained glazing pockets of the zipper gasket system.

In order to address these gasket conditions properly and to protect the insulating glass units for the long-term, custom designed repairs consisting of overlapping preformed silicone shapes and extrusions were utilized to create a watertight barrier. Unique elements of this application include accommodation of undulating gaskets and misalignment of intersecting gaskets, complete coverage of the previously repaired lock-strip gaskets (believed to be contributing to the glass staining) with the preformed shapes and extrusions, sealant pockets within the extrusion to control bond surface area, and selection of sealant adhesive to mitigate future glass staining. Lessons learned from the application of this barrier system, including issues related to sizing and fabrication of the preformed silicone parts, are presented. The experiences gained via the prolific use of preformed silicone products on this project will be beneficial to all those involved in the maintenance of lock-strip gasket systems and other types of building facades.