Laminated and tempered glass
In brief: Windshields are laminated glass that cracks but holds together; most side and back windows are tempered glass that shatters into small pieces. All automotive glazing, including replacements, must meet Federal Standard 205 and carry DOT and AS marks[1].
What kinds of safety glass are in a car?
Federal Motor Vehicle Safety Standard No. 205 governs all glazing in passenger cars, trucks, buses and other vehicles. Its stated purposes are to reduce injuries from impact with glass, to keep windows transparent enough for driver visibility, and to minimize the chance of occupants being thrown through windows in collisions[1]. Glazing must conform to the ANSI/SAE Z26.1-1996 standard, and glazing made for aftermarket replacement must meet the same standard[1]. Two kinds dominate:
| Laminated | Tempered | |
|---|---|---|
| Construction | Two layers of glass bonded to a plastic interlayer | A single sheet heat-treated to be stronger |
| Where used | All windshields; some side windows and sunroofs | Most side, quarter and back windows |
| When broken | Cracks but stays in one piece, held by the interlayer | Shatters into small, blunt pieces |
| Repairable? | Chips and short cracks often can be (see ROLAGS) | No; it must be replaced |
Why are windshields laminated?
Laminated glass holds together when struck, so it resists penetration and keeps occupants inside. FMVSS 205 defines glass-plastic glazing as a laminate of glass and plastic layers[1], and the repair industry’s standard, ROLAGS, applies specifically to laminated glass because a break in the outer layer can be filled with resin[2]. Indiana’s own definition of safety glazing focuses on the same goal: glass that substantially reduces the likelihood of injury when struck or broken[3].
Why are side and back windows tempered?
Tempered glass is several times stronger than ordinary glass and, when it fails, breaks into small granules rather than sharp shards. That makes it suitable for door glass that must also be breakable as an emergency exit. The trade-off is that a tempered window cannot be repaired: one strike usually shatters it completely, which is why door glass replacement is a common job for shops like Low Price Auto Glass, whose power window page talks of windows “broken out”[4].
How can I tell what glass I have?
Every piece of certified automotive glazing carries a small mark, usually in a lower corner. Under FMVSS 205, a prime glazing manufacturer certifies its glass by adding to the ANSI/SAE Z26.1 marks the symbol “DOT” and a manufacturer code assigned by the National Highway Traffic Safety Administration[1]. The “AS” number in the mark describes where the glass may be used; AS1 is the clearest grade required for windshields. Words such as “laminated” or “tempered” often appear in the mark too. The auto glass glossary explains these and other terms.
Is OEM glass different from aftermarket glass?
Original equipment (OEM) glass is made by or for the vehicle maker and carries its logo; aftermarket or original-equipment-equivalent glass is made by other manufacturers. Both must meet FMVSS 205 to be sold for replacement[1]. Differences, if any, lie in fit, optical quality, shade bands and how brackets for cameras and sensors are placed. Low Price Auto Glass says it keeps vehicles “as close to it’s original OEM standards as possible” with a wide range of windshields[5]. Some insurers specify which type they pay for; ask before work begins.
What features can a windshield include?
- Acoustic interlayer to reduce wind noise
- Rain and light sensors behind the mirror
- Camera brackets for driver assistance; see calibration
- Heated wiper park area or heating wires
- Head-up display zones with a special interlayer
- Solar-control coatings and shade bands
Questions and answers
Is a windshield laminated or tempered?
Laminated: two glass layers bonded to a plastic interlayer.
Can tempered side glass be repaired?
No. Tempered glass shatters and must be replaced.
Does aftermarket windshield glass meet safety rules?
Glass sold for replacement must meet Federal Motor Vehicle Safety Standard 205.
Related articles
Notes
- ^ a b c d e f 49 CFR 571.205, Standard No. 205: Glazing materials. Electronic Code of Federal Regulations. Checked 9 November 2026.
- ^ The Right Repairs at the Right Time (ROLAGS repair limits). National Windshield Repair Division. Checked 9 November 2026.
- ^ Indiana Code § 9-19-19-1, safety glazing materials defined. Justia (Indiana Code). Checked 9 November 2026.
- ^ Power Window Repair. Low Price Auto Glass (autoglasshammond.com). Checked 9 November 2026.
- ^ Windshield Replacement in Hammond, Indiana. Low Price Auto Glass (autoglasshammond.com). Checked 9 November 2026.