Questions to Ask a Glass Contractor About Safety Glass Standards

Safety glazing requirements exist because glass failures in certain locations — showers, doors, railings — can cause catastrophic injuries. A person who falls into a non-safety glass shower door can be severely lacerated. A glass railing panel that fails under load can cause a fall from elevation. Safety glass — tempered, laminated, or tempered laminated — breaks in ways that significantly reduce injury risk. Understanding the requirements and verifying compliance before installation is complete is how homeowners protect themselves and their families.

“The certification mark is the only thing that actually tells you what’s in the glass. You can’t see the tempering process. You can’t see the laminate interlayer. You can’t distinguish safety glass from standard glass by looking at it. The SGCC mark etched into the corner of the glass is the proof — it tells you the manufacturer, the applicable standard, and that the glass was tested and certified. If there’s no mark, you don’t know what you have.”

— Alex from Alex Glass & Railings, glass and railing specialist with 15 years of experience providing custom shower glass, railings, mirrors, and glass installation services across Toronto, focused on precision craftsmanship, modern design, and quality workmanship

Understanding Safety Glass Types

What is tempered glass, and when is it required?

Tempered glass is manufactured through a thermal tempering process — the glass is heated to approximately 620°C and then rapidly cooled. This creates a compressive stress on the surface that makes the glass approximately four times stronger than standard (annealed) glass of the same thickness.

When tempered glass breaks: It shatters into small, relatively harmless granules (similar in size to aquarium gravel) rather than the large, sharp shards produced by standard glass failure. This characteristic makes it appropriate for hazardous locations where human impact is possible.

Applications where tempered glass is required or standard:
– Shower and tub enclosures (required by OBC)
– Glass within 900mm of door openings
– Sidelights and transoms adjacent to doors
– Glass at stair landings
– Glass that is part of a railing or balustrade system
– Sliding patio doors

Limitations of tempered glass:
– Cannot be cut after tempering — must be ordered to the correct dimensions before the tempering process
– A nick or chip at the edge can cause spontaneous breakage of the entire panel (called “spontaneous breakage” or “nickel sulphide inclusion failure” — rare but a known characteristic of tempered glass)
– When it breaks, all fragments fall immediately — not held in place

What is laminated glass, and when is it required?

Laminated glass consists of two or more glass layers bonded with an interlayer — typically polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) film. When laminated glass breaks, the interlayer holds the fragments together, keeping the glass in place rather than allowing it to fall.

Applications where laminated glass is required or preferred:
– Overhead glazing (glass skylights, glass canopies) — where falling glass would injure people below
– Walking surfaces (glass floors, glass-topped tables with access underneath)
– Glass railings in some applications — laminated or laminated tempered provides the security of keeping the panel in place even when broken
– Anywhere that broken glass must stay in place rather than fall away

What is tempered laminated glass?

Combines both: two layers of tempered glass bonded with an interlayer. Provides the strength advantage of tempering AND the fallout prevention of lamination. The highest-performance option for structural glass applications like glass railings and overhead glazing.

Questions About Certification

What is the SGCC certification, and how do I verify it?

The Safety Glazing Certification Council (SGCC) is the North American certification organization for safety glazing products. SGCC-certified products have been independently tested to the applicable ANSI standards.

ANSI Z97.1: The performance standard for safety glazing materials in buildings. Specifies the impact resistance requirements for safety glass in various hazardous locations.

ANSI Z97.1 Class A vs. Class B: Class A is a more stringent impact resistance standard, required in some applications. Class B is a less stringent standard. Ask which class the specified glass meets for your application.

The SGCC mark: Certified safety glass bears a permanent identification mark on the glass itself — not on a label, but etched, ceramic-fused, or sandblasted into the glass surface. The mark identifies the manufacturer and the applicable standard.

Ask the contractor to show you the SGCC mark location on the glass before installation is complete, or on the glass specification sheet for custom-ordered pieces.

Does the glass specification sheet confirm the safety glazing classification?

For custom-fabricated glass (custom-sized shower enclosures, custom mirror dimensions, custom railing panels), ask for a copy of the glass specification sheet from the fabricator confirming the glass type, thickness, and safety glazing classification.

Questions About the applicable building code Compliance

What section of the OBC applies to this application?

The applicable building code Part 9 (housing and small buildings) and the supplementary technical standards reference specific glazing requirements. Ask the contractor to confirm which OBC section governs the application and how the specified glass meets those requirements.

Common OBC hazardous glazing locations in residential construction:
– All glazing in shower and tub enclosures
– Glazing in doors and adjacent to doors within specified distances
– Glass railings and balustrades
– Glazing in areas adjacent to stairways

What a good answer looks like: The contractor can identify the applicable OBC requirement and confirm the specified glass meets it.

Will the glass installation be subject to inspection?

For glass railing systems and other structural glass applications that require a building permit, the glass installation will be subject to building inspection. Ask whether the installation will be inspected and how the inspector will verify safety glass compliance — typically by inspecting the certification mark on the installed glass.

Questions About Glass Quality Beyond Safety Classification

What is the glass clarity and quality grade?

Beyond safety classification, glass quality varies in clarity and optical distortion:

Float glass quality grades:
– Mirror/select quality: The clearest, lowest-distortion glass. Used for mirrors and applications where optical clarity matters.
– Standard quality: Slight distortion visible when looking through the glass at an oblique angle. Acceptable for most shower enclosures and railings.

Low-iron glass (extra-clear glass, Starphire, Optiwhite): Standard glass has a slight green tint visible at edges and in large panes. Low-iron glass removes most of this tint, producing a clearer, more neutral appearance. Often specified for large frameless shower enclosures and glass railings where the glass edge is visible.

Ask whether low-iron glass is appropriate or specified for your application.

Related Questions

• Questions to Ask a Glass Contractor Before You Hire One
• Questions to Ask a Glass Contractor About Shower Enclosures
• Questions to Ask a Glass Contractor About Glass Railings
• Red Flags When Hiring a Glass Contractor

Have a question we didn’t cover? Submit it below.