Tempered Glass Requirements for Windows: When Safety Glazing Is Actually Required

Almost everyone asks this question backwards. “Does this window need to be tempered?” sounds like a question about the window — its size, its price tier, the room it is in. The code does not work that way. It identifies hazardous locations and requires safety glazing in them. Tempering is the answer to a location, not to a window.

Getting that backwards costs money in both directions: homeowners get told a large window “has to be tempered” when it does not, and openings that genuinely are hazardous locations get quoted without it and have to be re-ordered. Below is what the residential code says and the measurements that decide it.

A note on scope: this is homeowner education, not a code ruling. Your city adopts, amends and enforces the code, and the final determination on any opening belongs to its building inspections department. The sections quoted here are from the Texas edition of the 2021 International Residential Code as published on UpCodes. Our guide to egress window requirements in Texas covers how code adoption works here and why editions differ from city to city.

How the Requirement Is Structured

Section R308.4 does one thing: it names the places where safety glazing is required. In its own words, the locations specified in Sections R308.4.1 through R308.4.7 “shall be considered to be specific hazardous locations for the purposes of glazing.” Seven provisions, each describing a situation rather than a product: glass in doors, glass next to doors, glass in windows, glass in guards and railings, glass near wet surfaces, glass next to stairs and ramps, and glass at the bottom of a stairway. The question on any opening is which of those seven, if any, describes where it sits.

The Window Rule: All Four, Not Any One

For a window that is not near a door, a tub, a stairway or a guard, the governing provision is Section R308.4.3, Glazing in Windows. It applies to glazing in an individual fixed or operable panel that meets all of the following conditions:

• “The exposed area of an individual pane is larger than 9 square feet.”
• “The bottom edge of the glazing is less than 18 inches above the floor.”
• “The top edge of the glazing is more than 36 inches above the floor.”
• “One or more walking surfaces are within 36 inches, measured horizontally and in a straight line, of the glazing.”

The word doing the work is all. These are not four separate triggers but four conditions that must be true simultaneously, so failing any one takes the opening out of this section — which resolves most quote-stage confusion:

• A 12-square-foot window with its sill 24 inches above the floor fails the 18-inch condition. Section R308.4.3 does not apply, however large the pane is.
• A low window of 8 square feet fails the area condition, even sitting right at the floor.
• A tall, low unit with no walking surface within 36 inches of it fails the fourth condition.

The section also carries three exceptions. The first is decorative glazing. The second covers glazing adjacent to a walking surface where a horizontal rail is installed 34 to 38 inches above that surface; the rail “shall be capable of withstanding a horizontal load of 50 pounds per linear foot without contacting the glass and have a cross-sectional height of not less than 1 1/2 inches.” The third covers outboard panes in insulating glass units where the bottom edge of the glass is 25 feet or more above grade, a roof or a walking surface — relevant on a second-story elevation, not on anything you can reach.

Doors, and the Glass Beside Them

Doors are the strictest case, and the one most likely to catch a sidelite nobody thought about. Section R308.4.1 makes glazing in fixed and operable panels of swinging, sliding and bifold doors a hazardous location outright — no size test. Its two exceptions are glazed openings too small for a 3-inch-diameter sphere to pass through, and decorative glazing.

Section R308.4.2, Glazing Adjacent to Doors, is the one worth reading closely if your entry has sidelites. It applies where the bottom exposed edge of the glazing is less than 60 inches above the floor or walking surface and either the glazing is within 24 inches of either side of the door in the plane of the door in a closed position, or it is on a wall less than 180 degrees from the plane of the closed door and within 24 inches of the hinge side of an in-swinging door. Its exceptions include decorative glazing, an intervening wall or permanent barrier, access through the door to a closet or storage area 3 feet or less in depth, and glazing adjacent to the fixed panel of patio doors.

A word on that recurring decorative glazing exception, which shows up in three of these provisions: it is a defined term in the code, and whether a specific decorative unit meets the definition is a determination for the building official, not an assumption for a buyer or a salesperson. Our guide to exterior door glass options covers the configurations and privacy side of door glass; this is the code side of the same decision.

Bathrooms: The Rule Most Often Stated Wrong

Section R308.4.5, Glazing and Wet Surfaces, covers glazing in walls, enclosures or fences “containing or adjacent to hot tubs, spas, whirlpools, saunas, steam rooms, bathtubs, showers and indoor or outdoor swimming pools where the bottom exposed edge of the glazing is less than 60 inches measured vertically above any standing or walking surface.” It adds that this “shall apply to single glazing and each pane in multiple glazing.”

Three details get lost almost every time this rule is summarized:

• It is measured above any standing or walking surface — not above the floor. The bottom of a bathtub is a standing surface. That is precisely why a window set over a tub is usually captured even when it looks high off the bathroom floor.
• There is a horizontal exception. Glazing more than 60 inches, measured horizontally, from the water’s edge of a bathtub, hot tub, spa, whirlpool or swimming pool, or from the edge of a shower, sauna or steam room, is excepted. In a large bathroom, distance can take a window out of the provision.
• The list is fixtures you stand or bathe in. Tubs, showers, spas, saunas, steam rooms and pools. A window across the room above a vanity is not automatically captured by this section.

None of which means a bathroom window should be specified casually — most bathroom openings in DFW homes do sit within reach of a tub or shower, and bathroom window replacement is one of the places we expect safety glazing on the order. It means the determination turns on the geometry of your room, applied by your building official.

Stairs, Landings and Railings

Two-story DFW homes very often have a window in the stairwell, and that is its own provision with a different number than the others.

• Section R308.4.4 makes glazing in guards and railings — including structural baluster panels and nonstructural in-fill panels — a hazardous location “regardless of area or height above a walking surface.” No tests at all.
• Section R308.4.6 captures glazing where the bottom exposed edge is less than 36 inches above the plane of the adjacent walking surface of stairways, landings between flights of stairs and ramps. Note 36, not the 60 used next to doors. Its exceptions are the same 34-to-38-inch horizontal rail described above, and glazing 36 inches or more measured horizontally from the walking surface.
• Section R308.4.7 covers glazing adjacent to the landing at the bottom of a stairway where the glazing is less than 36 inches above the landing and within a 60-inch horizontal arc less than 180 degrees from the bottom tread nosing. It is excepted where the glazing is protected by a compliant guard and the plane of the glass is more than 18 inches from that guard.

How to Tell What You Already Have

You do not have to guess, because the code requires the glass to tell you. Under Section R308.1, each pane installed in a hazardous location must carry a manufacturer’s designation “specifying who applied the designation, the type of glass and the safety glazing standard with which it complies, and that is visible in the final installation.” The section also governs how that mark is made: “acid etched, sandblasted, ceramic-fired, laser etched, embossed, or be of a type that once applied cannot be removed without being destroyed.” A label is permitted in lieu of the designation.

In practice: go look at the corners of the glass. The mark is usually a small etched stamp an inch or two in from a corner, and it will name a standard — the two you will see are “CPSC 16 CFR 1201” and “ANSI Z97.1.” On divided units there is an allowance worth knowing: Section R308.1.1 lets multipane assemblies whose individual panes do not exceed 1 square foot identify just one pane in the assembly, with the others labeled with one of those two standards. If you are comparing that against how your windows are divided, our window grid patterns guide explains why most modern divided looks are a single sealed pane rather than many small ones.

What This Means on a Replacement Quote

• Safety glazing is specified per opening, so it should appear per opening. Ask which units on your quote are being supplied as safety glazing and under which provision. “Code glass where required” is not an answer you can check.
• Changing an opening can change its status. Lowering a sill, enlarging a pane past 9 square feet, or adding flooring that raises the walking surface can move an opening into a hazardous location that it was not in before. The same is true in reverse. If your project changes opening geometry, our guide to full frame vs. insert replacement covers which method touches what.
• Tempered glass is made to size, not cut to size. It cannot be cut or drilled after tempering, which is why a measurement error on a tempered unit means a new unit and a new lead time. Our guide to measuring openings covers why the ordering measurement belongs to the installer.
• The code is a floor, not a ceiling. Nothing stops you from specifying safety glazing somewhere it is not required — a playroom window, a low window on a child’s route through the house. That is a reasonable request, and it should be priced as an option rather than presented as a requirement.

How Bradley James Windows & Doors Handles Safety Glazing

We are veteran-owned and owner-operated, and we do not use subcontractors, so the person who measures your openings is the person who writes the quote. We identify the openings that sit in hazardous locations during the free consultation rather than discovering them at installation, and we will tell you which provision applies and which openings are not affected.

What we will not do is interpret your city’s code for you, or use safety glazing to inflate a quote. Adopted editions, local amendments and final determinations belong to your municipality — the decorative-glazing exception in particular is a building official’s call rather than ours — and we serve 24 cities across the metroplex, each with its own permit desk. Browse the window styles we install, read the rest of our window and door guides, or request a free estimate and we will walk the house with you, opening by opening.