Glazing Guidelines

General guidelines:

  • All architectural glass should be glazed in a way that ensures that it is free floating and non-load bearing. The glazing material must remain resilient.
  • To prevent premature failure of fabricated, opacified spandrel and laminated glass , an adequate weep system is necessary, or materials that totally repel the passage of water.
  • Adequate clearance must be provided for bow and warp of heat-strengthenedand tempered glass, as specified in ASTM Standard C-1048.

For more complete information about generally accepted industry standards, consult the Glass Association of North America’s Glazing Manual.

Guidelines for conventional glazing:

  • Framing must be structurally sound, able to support the glass weight without any sagging, twisting or deformation that may impose a load on the glass. No framing member should deflect more than 1/175 of its span. Maximum deflection, under load, is 3/4".
  • Appropriate setting blocks, face gaskets, wedges and edge spacers must meet the current requirements of ASTM Specifications D-395 and C-864 for hardness, deformation, compression set and polymer content.
  • Framing members must be free of any glazing obstructions that would result in glass damage.
  • To reduce the risk of thermal breakage, a minimum framing extension is necessary. If thermal breakage is a potential concern, ask for a thermal stress analysis.
  • If lateral glass movement is anticipated due to wind load, seismic load or other causes, anti-walk blocks should be used.

Guidelines for silicone structural glazing:

  • Remember that glass is not typically used as a structural member. The support framing must be of sufficient strength and dexterity to absorb all loads resulting from wind, thermal expansion or building movement.
  • Back up mullions are recommended when glass is 1/4" thick or less, and in all instances where insulating glass is specified.
  • Coatings that transmit higher amounts of light may show edge read-through. Insulating glass used in structural glazing must be silicone units.
  • Opacified spandrel must have trim in the back of the opacifier to ensure glass-to-silicone adhesion.
  • When structural silicone is used, its compatibility and adhesive characteristics must be confirmed in the early design stages.