In Massachusetts, tempered glass — or any other qualifying safety glazing — is required by code anywhere a person could reasonably walk into, fall against, or break through a glass surface. The state building code (780 CMR, 10th edition) adopts the 2021 International Residential Code, and Section R308 lists the specific “hazardous locations” that trigger the requirement: doors, glass next to doors, large low-mounted windows, bathrooms and pool areas, stairways and ramps, and glass used as a railing or guard.1Mass.gov. Tenth Edition of the MA State Building Code 780 Each location has its own height and distance thresholds. Knowing them tells you whether the pane you’re about to install, replace, or inspect needs a safety rating.
Every Pane in a Door
Glass in a door is always a hazardous location. IRC Section R308.4.1 applies to swinging doors, sliding doors, bifold doors, and storm doors, covering both the fixed and operable panels.2International Code Council. 2021 International Residential Code – R308.4.1 Glazing in Doors Doors get pushed, pulled, and walked into, so impact with the glass is foreseeable.
Two narrow exceptions exist. Decorative glazing such as leaded or stained glass is exempt, and so are openings small enough that a 3-inch sphere cannot pass through, since a hand or body cannot realistically strike them.2International Code Council. 2021 International Residential Code – R308.4.1 Glazing in Doors Outside those situations, every pane in a door needs to be safety rated.
Glass Within 24 Inches of a Door
The hazard zone extends past the door itself. Under IRC Section R308.4.2, any glass panel within 24 inches of either side of a closed door is a hazardous location when the bottom edge of the glass sits less than 60 inches above the floor.3International Code Council. 2021 International Residential Code – R308.4.2 Glazing Adjacent to Doors Sidelights flanking a front door are the common example. The concern is a person stumbling on entry and reaching out to brace against a nearby window.
A second condition catches glass that sits around a corner from an in-swinging door. Glazing on a wall angled less than 180 degrees from the door’s plane needs safety glass if it falls within 24 inches of the hinge side, accounting for the door’s swing path.3International Code Council. 2021 International Residential Code – R308.4.2 Glazing Adjacent to Doors
Four exceptions apply:
- Decorative glazing (leaded, etched, or similar) is exempt.
- If a permanent wall or barrier separates the door from the glass, safety glazing isn’t required.
- Glass next to a door opening into a closet or storage area 3 feet deep or less is evaluated under the large-window rules instead.
- Glass adjacent to the fixed (non-sliding) panel of a patio door is exempt.
Large Low-Mounted Windows
Picture windows and floor-to-ceiling panels become hazardous only when all four of the following are true, under IRC Section R308.4.3:
- Exposed pane area exceeds 9 square feet.
- Bottom edge is less than 18 inches above the floor.
- Top edge is more than 36 inches above the floor.
- A walking surface exists within 36 inches of the glass.
Every one of the four must be met at the same time.4International Code Council. 2021 International Residential Code – R308.4.3 Glazing in Windows A window with a 20-inch sill fails the second condition, so ordinary glass is permitted no matter how large the pane. This is the most commonly misread rule, because the 9-square-foot figure gets quoted on its own. The four dimensions together describe glass a person could realistically fall through.
Bathrooms, Showers, and Pools
Wet, slippery surfaces raise the risk of falling against glass, so wet areas get their own rule. IRC Section R308.4.5 requires safety glazing in walls, enclosures, and fences near hot tubs, whirlpools, saunas, steam rooms, bathtubs, showers, and swimming pools whenever the bottom edge of the glass is less than 60 inches above a standing or walking surface.5International Code Council. 2021 International Residential Code – R308.4.5 Glazing and Wet Surfaces The rule applies pane by pane, so divided-light assemblies don’t escape it.
Distance provides an off-ramp. Glass more than 60 inches horizontally from the water’s edge of a tub, pool, or hot tub, or from the edge of a shower or sauna, is not a hazardous location.6International Code Council. 2018 International Residential Code – R308.4.5 Glazing and Wet Surfaces In a larger bathroom, a low window across the room from the shower stall may not need safety glass.
Stairways, Landings, and Ramps
Stairs raise the fall risk, and the code reflects that in two provisions. IRC Section R308.4.6 treats glass as hazardous when its bottom edge sits less than 36 inches above the adjacent walking surface of a stairway, landing, or ramp.7International Code Council. 2021 International Residential Code – R308.4.6 Glazing Adjacent to Stairs and Ramps Glass higher than 36 inches above the walking surface, or more than 36 inches away horizontally, falls outside this rule.
A protective railing is an alternative. A rail installed on the accessible side of the glass between 34 and 38 inches above the walking surface, able to withstand a 50-pound-per-linear-foot horizontal load without touching the glass, satisfies the requirement without safety glazing.
Section R308.4.7 adds a zone at the bottom of indoor stairways, since a person losing footing on the stairs can travel forward past the last tread. Glass within 60 inches of the bottom tread is generally subject to safety glazing under this provision.7International Code Council. 2021 International Residential Code – R308.4.6 Glazing Adjacent to Stairs and Ramps
Glass Railings and Guards
Glass used as a structural guard on a balcony, loft, or staircase must meet the safety glazing standard and additional structural requirements. Under IRC Section R308.4.4, glass baluster panels in guards need an attached top rail or handrail supported by at least three glass panels, or the rail must be designed to stay in place if one panel fails.8International Code Council. 2018 International Residential Code – R308.4.4.1 Structural Glass Baluster Panels Laminated glass with two or more plies of equal thickness is the exception: it can serve as a guard without a top rail, because laminated panels hold together when broken.
Does It Have to Be Tempered Glass Specifically?
No. The code requires “safety glazing,” and that includes both tempered glass and laminated glass as long as they pass the impact tests under CPSC 16 CFR 1201 or ANSI Z97.1. Tempered glass shatters into small granules on impact. Laminated glass cracks but stays held together by an inner plastic layer, the same way an auto windshield behaves.
The two have different strengths in practice. Laminated glass is often preferred for overhead installations and glass railings because it doesn’t fall out of the frame when it breaks. Tempered is usually cheaper for standard windows and doors. For most residential hazardous locations in Massachusetts either type will pass inspection, but confirm with your glazier or inspector before choosing laminated for a specific spot, because some locations call for Category II testing under 16 CFR 1201, which narrows the options.9eCFR. 16 CFR Part 1201 – Safety Standard for Architectural Glazing Materials
How to Tell if Existing Glass Qualifies
Every piece of safety glazing carries a small permanent etching in one corner, sometimes called the “bug.” Inspectors look for it, and its absence means the glass fails inspection whether or not it’s actually tempered. The mark usually shows the manufacturer, the standard the glass was tested to (ANSI Z97.1 or 16 CFR 1201), and the word “Tempered” or a similar designation.
If you’re buying an older home or planning to reuse an existing opening, check the corner of each pane in a hazardous location. A missing bug doesn’t prove the glass is unsafe, since the etching can wear off or hide behind trim, but it leaves the inspector with no way to verify compliance. In that case the pane typically has to be replaced or independently tested.
When the Requirements Get Triggered
780 CMR covers new construction, reconstruction, alteration, and repair of buildings.10Massachusetts State Board of Building Regulations and Standards. 780 CMR Tenth Edition Massachusetts Amendments In practice, safety glazing rules apply any time a building permit involves glazing in one of the hazardous locations above — a new build, an addition, a bathroom remodel, or a window swap during a kitchen renovation. Replacement glass has to meet the current standard, not just match what was there before.
Minor repairs that don’t require a permit generally leave existing glass alone. But unpermitted work in a hazardous location carries its own risk. If someone is injured by non-compliant glass and the homeowner knew or should have known the spot was hazardous, that’s a difficult position to defend. Specifying safety glazing during any renovation that touches the locations above is the safer call, both for the inspection and for what happens afterward.