Red Seal Glazier cheat sheet

Glass thickness selection follows span, load and edge support: ASTM E1300 charts give allowable lateral load for a given nominal thickness, plate size and support condition (4-side, 3-side, 2-side, 1-side).

Annealed glass design uses a 4-second-duration load basis in ASTM E1300; sustained loads (snow, dead load on sloped glazing) must be checked against a separate long-duration limit, typically 1/3 to 1/2 of the short-duration capacity.

Heat-strength glass is roughly twice annealed strength; fully tempered glass is roughly four times annealed strength and, when broken, fractures into dice-like particles. Tempered glass cannot be cut, drilled or edge-worked after tempering.

Safety glazing (16 CFR 1201 / CPSC) is required in doors, glazing within 24 in of a door edge, glazing under 18 in above the floor, and large panes in hazardous locations; Category I applies to small panes, Category II to larger ones.

Laminated glass with a PVB or ionoplast interlayer retains fragments after breakage; ionoplast (SGP) interlayers provide much higher post-break stiffness and are used for overhead and blast applications.

Edge clearance and bite: minimum edge clearance to frame is typically 1/8 in for annealed and 3/16 in for tempered/heat-strengthened; glass must not bear on setting blocks at corners - blocks are placed at quarter points.

Glass substitutes: acrylic (PMMA) is roughly half the weight of glass and more impact resistant but scratches easily; polycarbonate is far tougher but yellows under UV unless coated; both have much higher thermal expansion than glass.

Wire glass in fire-rated assemblies is limited; ceramic glazing (e.g., fire-rated transparent ceramic) is used where hose-stream and radiant-heat ratings are required.

Mirror and spandrel glass use opaque backings; spandrel glass must be heat-treated when the opaque coating creates thermal stress, and ceramic frit applied before tempering is the durable option.

Curtain wall vs storefront: storefront is typically limited to about 12–14 ft in height and relies on the building structure for lateral support; curtain wall spans floor-to-floor and is designed to move with the structure.

SSG (two-sided structural silicone) requires the silicone bite calculation: bite = (shortest dimension of glass × design wind pressure) / (2 × allowable silicone stress). Typical allowable stress for structural silicone is about 20 psi (0.14 MPa) under wind load, reduced for long-duration loads.

SSG systems must have a mechanical retention system (edge block, toggle, or channel) capable of holding the glass if the structural silicone fails.

Curtain wall must accommodate inter-story drift - typically L/100 to L/200 plus 0.5 in - and the system's joints and gaskets must be designed for that movement.

Thermal movement: aluminum expands about 13 × 10⁻⁶ per °F (23 × 10⁻⁶ per °C); a 10 ft aluminum mullion with a 100°F swing moves roughly 0.16 in, so slip joints and slotted connections are required.

Curtain wall mock-up testing per AAMA 501 covers air infiltration (ASTM E283), water penetration (ASTM E331 static, AAMA 501.1 dynamic), and structural performance (ASTM E330).

Rain screen and pressure-equalized design: the key to water control is a drained, vented, pressure-equalized cavity behind the outer seal, with weeps and baffles - not simply more sealant.

Storefront framing typically uses 1¾ in × 4½ in or similar tube sections; glass bite in storefront glazing is commonly ½ in minimum with 1/8 in edge clearance.

SSG silicone adhesion must be verified with a field adhesion test (peel test) on the actual substrates, and compatibility with glazing tapes, setting blocks and spacers must be confirmed before installation.

Skylights and sloped glazing must use laminated glass, tempered glass, or a combination - many codes require laminated glass for sloped glazing above a certain size and height, and screens or guards below.

Sloped glazing drainage: minimum slope is typically 3 in 12 (about 14°) for shingle-type systems; lower slopes require special gasketed or sealed systems.

Skylight condensation control: a thermal break in the frame, warm-edge spacers and a weep/drainage path are required; the interior gutter must drain to the exterior.

Door hardware: standard door leaf thickness is 1¾ in; typical commercial door height is 7 ft 0 in; hinge reinforcement and closer reinforcement must be specified.

Tempered glass is required in door leaves and sidelights within 24 in of the door; glass in doors must have a visible label (safety glazing mark).

Window performance ratings: U-factor (thermal transmittance), SHGC (solar heat gain coefficient), VT (visible transmittance), air leakage (ASTM E283), water (ASTM E547/E331) and structural (ASTM E330).

NFRC labels report U-factor, SHGC and VT for the whole assembly; low-e coatings: soft-coat (sputtered) has lower emissivity and better U-value but must be on a protected (usually #2 or #3) surface; hard-coat (pyrolytic) is durable and can be exposed.

Skylight fall protection: many codes require impact-rated glazing or a guard/screen under skylights in roof areas, and glass must resist a 200 lb impact or be protected.

Sloped glazing thermal movement and glass-to-frame clearance: minimum 1/8 in edge clearance and setting blocks at quarter points; glass must not be pinched by the frame.

Shower doors and tub enclosures require safety glazing (tempered or laminated); typical thickness is 3/16 in to 3/8 in for framed and 3/8 in to 1/2 in for frameless.

Frameless shower doors: hinge and clamp locations must be drilled before tempering; hole diameter is typically 1/2 in, and holes must be at least 1½ times the hole diameter from any edge.

Mirror installation: mirrors must not be adhered directly to a wall with mastic that prevents the back from breathing; a cleat or continuous adhesive with air circulation is used, and mirror edges should be sealed to prevent black-edge corrosion.

Mirror safety: mirrors in gyms, doors and other hazardous locations must be safety-backed or laminated; mirror on doors must be tempered or backed.

Tempered glass for shower doors must carry a permanent label; frameless doors require a water-tight seal and a sweep at the bottom.

Glass railing and guard infill must resist a 200 lb concentrated load in any direction and a 50 plf uniform load at the top rail; glass panels are typically laminated (not monolithic tempered) for guard use.

Residential glass: single-pane annealed glass is used only where safety glazing is not required; low-e argon-filled IGUs are the common energy upgrade.

Stained and leaded glass: lead came and copper foil are the two common assembly methods; leaded panels need saddle bars or rebar for support over about 2–3 ft spans.

Patterned and textured glass: obscure glass reduces visibility but does not provide privacy at night when the lit side is opposite; consider the light direction.