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FGIA: Your guide to doing it right

We’ve updated the authoritative standard for glass installation.

April 10, 2024  By Amy Becker

The many benefits of prioritizing daylighting and views in buildings are well established, but guidelines for vetting and selecting glazing systems are essential for unlocking these qualities. Luckily, the Fenestration and Glazing Industry Alliance is here to help with its updated IGMA TM-3000, North American Glazing Guidelines for Sealed Insulated Glass Units for Commercial and Residential Use. The comprehensive guide updated with new technologies walks manufacturers, fabricators, specifiers and contractors through all the glazing system components, addressing important points to consider, and potential concerns. IGMA TM-3000 addresses considerations for glass types, framing, clearances, setting blocks, spacer shims, glazing materials, glazing systems, storage and handling, glass protection and cleaning for both double- and triple-glazed IGUs. The document is all-inclusive, covering every aspect of glazing systems from A to Z. The latest update even addresses vacuum insulating glazing. Here’s a sample of just some of the autoritative advice it contains.

Glazing systems typically include silicones, polysulfides, polyurethanes, acrylics, latex, and butyls applied as gunned-in-place glazing sealants. When evaluating these systems, the selected materials for the glazing system and interior of the IGU must be compatible with all glazing system components. This includes the IGU sealant, which may be in contact with or encased under expected environmental conditions. The guidelines refer to three common types of IGU glazing systems: structural glazing, butt glazing, and dry glazing. Structural glazing or stopless glazing, where the IGU is retained only by a silicone sealant or adhesive joint, requires special care as seal failure of a unit glazed without exterior stops could cause the exterior lite to fall from the building. Butt glazing, which is stopless glazing without a supporting mullion on any IGU edge, is not recommended unless the glass is stiff enough to avoid the high shear stresses caused by wind loads on the unit sealant, which could potentially lead to seal failure. Dry glazing refers to the portion of the glazing system that utilizes a non-mastic compound as the seal between the glass and frame. All major glazing components and materials – glass, gaskets, aluminum, wood, fiberglass, and vinyl – have tolerances. However, tolerances can add up and cause major problems such as glass not fitting and gaskets not sealing. Consequently, individual tolerances must be verified with the fabricators. Structural gaskets, also called zipper gaskets or lock-strip gaskets, are pre-formed, cured elastomeric mechanical seals used to install glass or solid panels in a supporting framework. And boot glazing, also called wrap-around marine glazing material, is available in rolls or strips which wrap around the perimeter length of the IGU. 

Glass type and thickness should be installation-specific, firmly supported and resist applicable loads based upon CAN/CGSB 12.20-M89 or ASTM E1300-16, and the National Building Code of Canada, as determined by code jurisdiction. When manufacturers address pre-glazing considerations, this lends a higher level of quality assurance. This includes manufacturers’ shop drawing review, a pre-installation procedures meeting and inspection of the glazing system, and breather or capillary tubes. The glass fabricator or manufacturer should also be consulted regarding the glass construction, strength and compliance with specifications and glazing details. And the sealant manufacturer should be consulted for assurances of sealant compatibility and strength, approval of spacer shim materials and for recommendations on optimum joint configuration and proper adhesion to glass and support members.

This document is being updated, meaning a new version will soon be available. In the meantime, the current version of IGMA TM-3000 can be accessed at FGIA’s online store. •


Amy Becker is the Fenestration and Glazing Industry Alliance’s glass products specialist. She can be reached at

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