What Is Tempered Glass?
Tempered glass is safety glass made by heating cut glass to over 600 degrees Celsius and cooling the surface quickly with air jets. That puts the surface into compression, which makes the glass about four times stronger than ordinary annealed glass of the same thickness. When it does break, it shatters into small blunt cubes instead of long sharp shards, which is why it is required wherever people could fall or walk into glass.
In Canada, the standard we work to is CSA A440 for safety glazing, with every panel carrying a permanent stamp in the corner. If you cannot find the stamp, assume the glass is not tempered.
Where We Install Tempered Glass
| Location | Typical thickness | Notes |
|---|---|---|
| Doors and sidelites | 6mm | Required within 24 inches of a door |
| Low windows near the floor | 6mm | Safety zone under OBC Part 9 |
| Shower panels and doors | 10mm | Usually frameless |
| Balcony guards | 10-12mm | Laminated or heat-soaked often preferred |
| Stair and deck railings | 10-12mm | Standoff or channel mount |
| Table and desk tops | 10-12mm | Polished edges, radius corners |
| Office partitions | 10-12mm | OBC Part 3 interior safety glazing |
Spontaneous Breakage
Occasionally, tempered glass breaks for no visible reason, often on a hot day. The cause is usually a tiny nickel sulfide inclusion from the glass-making process that slowly changes size and cracks the tensioned core. Balcony guards in lakeside towers in Mimico, Humber Bay Shores and Harbourfront see it most often because of big temperature swings.
You cannot see an inclusion, but you can reduce the risk. Heat-soak testing cycles the tempered glass through a high-temperature oven so most inclusion-prone panels break at the factory. We recommend it for balcony guards and any glass over a walkway.
Why Tempered Glass Must Be Measured Exactly
Tempered glass cannot be trimmed, drilled or notched once it is made. Every hole for a hinge or standoff, every notch for a post, and every radius corner is cut before tempering. That is why our measuring visit is careful: laser measurements, micrometer thickness, and hole positions taken off the existing hardware. A panel that comes back 3mm too big is a panel that has to be remade.
Same-Day Stock
For small door lites, sidelites and simple rectangles, we keep common sizes of 6mm tempered in stock and on the truck, so many jobs are finished on the first visit. Larger and drilled panels take up to 7 business days.
Need a tempered panel replaced? Send a photo of the glass and the stamp, and our Toronto glass repair crew will quote it in writing.
Written by The Elite Glass Repair Toronto Crew. Last updated .
