Tempered glass is glass that has been heat-treated to significantly increase its strength and, critically, to change how it breaks, shattering into small, relatively blunt pieces rather than the large, dangerous shards ordinary annealed glass produces when broken.
This heat-treating process involves rapidly cooling the glass surface after heating it to a high temperature, creating internal stresses that give tempered glass its characteristic strength and distinctive, safer breakage pattern compared to standard glass.
Building codes specifically require tempered glass in certain locations considered hazardous, including glass doors, windows near doors, and glass in bathrooms or near stairways, reflecting the genuine safety benefit this treatment provides in areas with elevated impact risk.
Where Does Code Require Tempered Glass?
- Glass in and adjacent to entry doors
- Shower and bathtub enclosures
- Glass near stairways or landings
- Large windows close to floor level
Why Is Tempered Glass Important?
The safer breakage pattern tempered glass produces, small, relatively blunt pieces rather than large sharp shards, meaningfully reduces injury risk in locations where glass breakage is more likely to occur, whether from accidental impact or other hazards, making this a genuine life-safety consideration rather than simply a code technicality. This is precisely why building codes specifically mandate its use in identified hazardous locations.
Because tempered glass cannot be cut or drilled after the tempering process without shattering, any modifications needed, like adding hardware, must be planned before manufacturing rather than attempted afterward, a consideration relevant during custom window or door glass ordering. This upfront planning avoids costly delays or the need to reorder custom glass units.
Tempered Glass vs. Laminated Glass
Tempered glass breaks into small, relatively safe pieces upon shattering. Laminated glass uses an interlayer holding broken pieces together rather than shattering apart entirely, offering a different safety approach particularly valued for security and sound control applications.