CAN CGSB 12.8-2017: Requirements for Flat, Clear Sheet Glass

CAN CGSB 12.8-2017 is a Canadian national standard published by the Canadian General Standards Board (CGSB). It sets forth the minimum requirements for flat, clear sheet glass intended for use in building glazing, mirrors, display cases, and other general applications. This standard covers both nominal dimensions and permissible variations in thickness, flatness, optical quality, and surface defects. It serves as the primary reference for manufacturers, importers, specifiers, and regulatory authorities when assessing the acceptability of flat, clear glass products in Canada.

Scope

The standard applies to flat, clear sheet glass produced by the float process, in thicknesses from 2.5 mm to 19 mm (nominal). It covers glass that is transparent, essentially colorless, and with parallel surfaces. The scope explicitly excludes patterned, wired, laminated, tempered, insulating glass units, and other specialty glass products. It also does not cover glass with applied coatings or films unless specified by contract.

Applicable Products

• Clear float glass for windows, doors, storefronts
• Glass for mirrors and furniture
• Annealed flat glass for subsequent processing (e.g., tempering, laminating)
• Stock sheets for cut-to-size applications

Exclusions

• Safety glass (covered by CAN/CGSB 12.1)
• Insulating glass units (CAN/CGSB 12.8 does not apply; refer to CAN/CGSB 12.2)
• Patterned or obscure glass (CAN/CGSB 12.9)
• Coated, reflective, or low-emissivity glass

Technical Requirements

Thickness Tolerances

Glass must conform to the nominal thickness within the tolerances stated in Table 1. Thickness measurements are taken at least 15 mm from the edge using a micrometer or equivalent device. The standard also imposes a maximum allowable deviation from flatness (warp) expressed as a percentage of the diagonal length.

Optical Quality and Surface Defects

The standard defines acceptance criteria for visible defects such as bubbles, stones, scratches, and tin pick-up. Glass is inspected under controlled illumination (diffuse light at 600 lux minimum) at a distance of 600 mm with the unaided eye (or corrected vision). The following defects are considered unacceptable if they are visible within the central viewing area (defined as 75% of the sheet, centrally located):

• Bubbles or seeds larger than 1.0 mm in diameter
• Stones (inclusions) of any size
• Scratches exceeding 0.1 mm in depth or 25 mm in length
• Visible tin pick-up on the tin side (iridescence or haze)
• Edge damage (chips, cracks) extending more than 5 mm from the edge

Flatness (Warp)

Maximum allowable deviation from a flat reference plane is 0.3% of the diagonal length for sheets up to 6.0 mm nominal thickness, and 0.2% for thicker glass. For example, a 2000 mm × 3000 mm sheet (diagonal ≈ 3606 mm) with thickness 6 mm must not deviate more than 10.8 mm from flatness.

Implementation Highlights

To demonstrate compliance with CAN CGSB 12.8-2017, manufacturers and suppliers should adopt the following practices:

• Incoming inspection: Verify glass dimensions and defects on each shipment using calibrated tools and standardized lighting conditions.
• Traceability: Maintain records of production parameters (pull rate, temperature profile) that influence flatness and thickness consistency.
• Cutting optimization: Use computer-numerically controlled (CNC) cutting equipment with appropriate edge quality control to avoid chips.
• Handling: Ensure proper edge protection and clean vacuum cups to minimize surface scratches.

Marking and Certification

While CGSB standards often require marking, CAN CGSB 12.8-2017 does not mandate a permanent stamp on the glass surface. However, the standard recommends that each unit of sale (crate, stillage) carry a label stating:

• Supplier name and location
• Standard reference: CAN CGSB 12.8-2017
• Nominal thickness and dimensions
• Date of production

Compliance Notes

Conformity Assessment

Suppliers should provide a declaration of conformity, supported by type testing from an accredited laboratory. Third-party certification (e.g., by CSA Group or ISO 17025 accredited labs) is not strictly required but is strongly recommended for procurement contracts and building code submissions.

Relationship with Other Standards

CAN CGSB 12.8-2017 is often invoked together with other CGSB glass standards. The table below summarizes key related standards:

Regulatory Acceptance

CAN CGSB 12.8-2017 is recognized by the National Building Code of Canada (NBC) through referenced standards. Some provinces and territories have adopted it directly. It is also used by federal procurement agencies under the Government of Canada’s Green Procurement Policy. For projects outside Canada, this standard may be specified as an equivalent to ASTM C1036 (Standard Specification for Flat Glass) or EN 572-2 (Float Glass).