Building codes treat tub and shower areas as hazardous glazing locations, so glass in a shower door or enclosure has to be safety glazing, which in practice means tempered. New Jersey follows the model codes on this point. Ordinary window or mirror glass is not a substitute, and no reputable shop will build a door from it.
Tempered glass carries a permanent mark, sandblasted or acid etched into one corner, naming the fabricator and the standard the glass was tested against. On a shower door it often hides near a hinge, low on a panel, or under a clamp, and on a very old door it may have worn faint. That small block of text is the proof an inspector wants, and reading it is the fastest way to know what is already hanging in your bathroom. When no mark turns up anywhere along the edges, treat the panel as unknown rather than as safe. Very old enclosures, and the occasional shop-made panel dropped into a tub surround, are precisely the ones worth replacing instead of reusing.
Tempering is a heat treatment. Cut glass rides through a furnace and then gets chilled fast, locking the outer surfaces into compression while the core stays in tension. The result is several times stronger than the same pane untreated, and a failure crumbles the panel into small dulled pieces rather than long shards. That is the entire safety argument.
The catch is that everything has to happen first. Once glass is tempered it cannot be cut, drilled, notched or ground, so every hinge hole, handle hole, hardware cutout and notch around a bench or curb must be located before it enters the oven. That is why measuring matters so much on a custom enclosure, and why a shop measures finished tile rather than framing. We cut, edge and prepare glass in our Lodi shop and verify openings ourselves before anything goes for tempering.
Requirements shift with what you are doing and where you are doing it. A straight swap of an existing enclosure gets treated differently from a new bathroom or a gut renovation, and the town where the property sits decides whether a permit and an inspection apply. Call them, get the answer in your own words, then build to it. Accurate Glass & Mirror supplies tempered safety glass for every shower door and enclosure we make, so the glass half of that conversation is settled already.
Laminated is also a safety glazing, and codes accept it in many hazardous locations, but shower doors and enclosures get built from tempered in nearly every case. Tempered stays rigid, holds a clean polished edge through constant wetting, and carries hinge and handle hardware. Laminated belongs where a panel must stay together after breaking, which describes a railing far more than a shower.
It is rare, and it nearly always traces to an edge. A nick or chip along the edge, a screw torqued directly onto glass, or a clamp closed without its gasket introduces a stress point in a panel that is under tension by design. Protect the edges, use hardware made for heavy glass, and let a shop set panels instead of wrestling them alone.
If no stamp turns up on an older door, that is worth settling before somebody leans against it. Send photos of the corners, or bring your measurements to the Lodi showroom, and we will tell you what you have.
