Mid-century through 1980’s buildings with lock-strip or “zipper-gasket” glazing systems are an ever present part of the urban landscape in many cities across North America. Although these systems are considered outdated by many and seldom used in new construction, the systems have performance attributes that should merit respect.
For many in the facade community, lock-strip gasket facades are often dismissed as a system to be removed and replaced with modern aluminum curtain wall. While this may be practical in certain situations, it is far from the only option available and not always the right option for the owner’s budget or maintaining the original architecture of a building.
Lock-strip facades continue to endure but age has taken its toll on the functionality of what was once a revolutionary glazing system. By maintaining the lock-strip gasket facade and upgrading glazing when possible, building performance can be restored or even increased as retrofit technology improves.
Remedial options are available for a lock-strip gasket facades that focus on preserving and maintaining the primary elements and appearance of the system from simple remediation efforts such as the installation of exterior “wet-seals” to limit air and water infiltration, to complete replacement and reglazing.
Improved curtain wall performance (reduced air infiltration, lowered solar heat gain and improved acoustical performance) are achieved by introducing modern insulating glass with a low-e coating and emerging technologies, such as vacuum insulating glass (VIG), present possibilities for replacement of an original monolithic glazed system for increased energy performance. Reglazing also provides the opportunity to increase spandrel insulation, or change the aesthetic of the facade by introducing (or removing) existing spandrel panels.
While the benefits of the above are appealing, lock-strip gasket replacement projects are not immune to challenges. As with most remediation projects there are technical considerations to address.
One of the first large scale lock-strip gasket glazing projects was completed in 1952 at the General Motors Technical Center in Warren, Michigan by Architect Eero Saarinen & Associates (Fig
Lock-strip gaskets or “zipper gaskets” are generally described as a two-part neoprene gasket assembly consisting of a main body gasket which is used to capture and support the glazed infill
When replacing gaskets it is critical to understand that RMA (Rubber Manufacturers Association) tolerance for the production of rubber products including lock-strip gaskets are not the same as the tolerances
As previously mentioned, remediation of a lock-strip glazing system should include an evaluation of the current physical condition for structural performance, as well as an evaluation air and water infiltration
Mid-century lock-strip façade buildings can continue to function and even perform better with retrofit technology. By maintaining the lock-strip gaskets and upgrading glazing when possible, building performance can be increased
Michigan State Historic Preservation Office. Michigan Modern. “General Motors Technical Center” http://www.michiganmodern.org/... (accessed July 27, 2017).
Parise C.J. “Evaluation and Test of "Gasket Glazing Systems”, Window and Wall Testing ASTM STP 552. American Society of Testing and Materials, 1974, pp. 46-66.
Pilkington North America, NSG Group. Vacuum Glazing, Pilkington Spacia Catalog, 2017.
“SIGMA Voluntary Guidelines for Commercial Insulating Glass Dimensional Tolerances”, TR-1200-83, Sealed Insulating Glass Manufacturers Association.
“Standard Specification for Lock-Strip Gaskets”, ASTM C542-05, American Society of Testing and Materials, Annual Book of ASTM Standards vol. 4.07.
“Standard Specification for Lock-Strip Gaskets”, ASTM C716-06, American Society of Testing and Materials, Annual Book of ASTM Standards vol. 4.07.
“Standard Specification for Lock-Strip Gaskets”, ASTM C964-07, American Society of Testing and Materials, Annual Book of ASTM Standards vol. 4.07.
“Stanlock Architectural Gasket Systems Catalog”, Griffith Rubber Mills, 2010.
Tremco Commercial Sealants & Waterproofing Structural Lock-Strip Facade Restoration Solutions Catalog, Tremco Commercial Sealants, 2016.