Free tool
Tempered glass check: does this lite need safety glass?
Two different rules make a lite tempered: your glass supplier's size limit, and the building code's hazardous locations. Enter the glass size and where the window goes, and the check tells you which conditions are met and why.
Inches for sizes. Use the exposed glass of one lite, not the whole window. Leave the annealed limit blank to skip the size check.
What the check looks at
- Size. Many sealed-unit suppliers will only make a lite tempered above a certain area. 30 sq ft is the limit at our launch plant; enter your own supplier's. A lite exactly at the limit stays annealed.
- Large, low windows (IRC R308.4.3). A pane is a hazardous location only when all four are true: larger than 9 sq ft, bottom edge less than 18" above the floor, top edge more than 36" above it, and a walking surface within 36" horizontally.
- Doors and next to doors (R308.4.1, R308.4.2). Glass in a door, and glass within 24" of a door's edge whose bottom is less than 60" above the floor.
- Wet areas (R308.4.5). Glass in walls around tubs, showers, hot tubs, saunas and steam rooms whose bottom is less than 60" above the standing surface.
- Stairs, landings, ramps and pools have their own distances in the code; the check flags them for you to confirm.
Each rule has exceptions (a protective bar, decorative glass, openings too small for a 3" sphere, among others). The reasoning, and how a window configurator should handle each rule, is in our guide: when must window glass be tempered?
Tempered glass — common questions
Does every window over 9 square feet need tempered glass?
No. Under IRC R308.4.3 a large pane is a hazardous location only when all four conditions are met: larger than 9 sq ft, bottom edge under 18" above the floor, top edge over 36" above it, and a walking surface within 36" horizontally.
Does glass next to a door have to be tempered?
Usually, when the glass is within 24" of the door's edge in the closed position and its bottom edge is less than 60" above the floor (IRC R308.4.2), subject to the code's exceptions.
Why would a lite be tempered when no code rule applies?
Because of size. Glass suppliers set limits on how large an annealed lite they will make, so a large lite is tempered for manufacturing reasons even where the code doesn't require safety glazing.