Summary

Fire-rated glazing allows natural light into protected escape routes, stairwells, and compartment walls without compromising fire compartmentation. It is a specialist product — ordinary glass shatters within minutes of fire exposure, and even toughened or laminated glass provides no meaningful fire resistance without specific fire-rating treatment.

The performance classification system uses letters and numbers: E (integrity only — stops flame and hot gases for the stated period), EW (integrity plus limits radiant heat), and EI (integrity plus insulation — limits temperature rise on the cold face). These map to the older UK designations of "integrity only" and "integrity/insulation" fire-resisting glazing. The test period (in minutes) follows the letter, so EI 60 means integrity plus insulation for 60 minutes.

Critically, the glazing product and the framing system are tested together. A fire-rated glass pane in an unsuitable frame, with the wrong bead specification, or without the correct intumescent seals will not perform as tested. The system — glass, frame, beads, fixings, and intumescent components — must be installed as a complete assembly matching the tested configuration.

Key Facts

  • Classification standard — BS EN 13501-2 (classification using test data from BS EN 1364 series)
  • E (integrity) — Prevents passage of flame and hot gases for the rated period; radiant heat transfer not controlled
  • EW (integrity + radiation) — As E, plus limits radiant heat flux to ≤15 kW/m² at 1m
  • EI (integrity + insulation) — As E, plus limits mean temperature rise on unexposed face to ≤140°C above ambient
  • Common ratings — E30, E60, E30/EW30, EI30, EI60, EI90, EI120
  • Georgian wired glass — Older product; provides approximately 30 minutes integrity (E30) only; no longer manufactured in the UK but still installed in older buildings
  • Borosilicate fire glass — Modern alternative; can achieve E30, EI30, or higher without wired appearance
  • Intumescent products — Fire-rated glazing assemblies typically incorporate intumescent glazing tape or seals within the rebate
  • Maximum sizes — Depend on the tested system; typically 0.5 m² to 1.5 m² per pane for integrity-only products; varies widely
  • Frame materials — Timber (fire-resisting timber), steel, aluminium (with thermal break and intumescent), or specialist composite
  • Glazing beads — Must be the correct profile for the tested assembly; wooden beads on steel frames may not be valid
  • Certification marks — CE marking to EN 14449 (structural glazing); third-party certification via CERTIFIRE or equivalent
  • Installation competency — Should be installed by trained operatives; some certification schemes require accredited installers
  • ADB reference — Approved Document B Tables 1, 3, and Appendix A specify fire resistance requirements by element and occupancy

Quick Reference Table

Spending too long on quotes? squote turns a 2-minute voice recording into a professional quote.

Try squote free →
Location / Application Minimum Performance Notes
Fire door side panel (FD30 door) E30 Must be part of tested doorset assembly
Fire door side panel (FD60 door) E60 System tested as a complete doorset
Compartment wall glazing (up to 1,200mm from floor, escape route) EI30 or EI60 Insulation required where people could be in close proximity
Compartment wall glazing (high level, not near people) E30 or E60 Integrity only acceptable at height where radiant heat not a hazard
Protected stairwell internal screen E30 minimum Check ADB for building height/purpose group
Protected corridor screen E30 Vision panels may have reduced area limits
External glazing (boundary condition) Depends on boundary distance ADB Table 1 gives unprotected area limits
Roof lights in compartment walls E30 — but rarely used Specialist product; structural loading must be considered
Vision panels in fire doors E30/EI30 depending on doorset rating Must be within doorset test evidence

Detailed Guidance

Understanding the Performance Classifications

Integrity (E): The glazing panel prevents the passage of flames and hot combustion gases on the unexposed side for the stated period. However, it does not prevent radiant heat transfer — on the unexposed side, the surface temperature can reach several hundred degrees Celsius even when the glass remains in place. Standing near E-rated glazing during a fire is hazardous.

Radiation-limiting (EW): In addition to E performance, the product limits the radiant heat flux on the unexposed side to no more than 15 kW/m² measured at 1 metre from the surface. This is particularly relevant for glazing used where people might be close to the glass — for example, in shopping centres or commercial lobbies.

Insulating (EI): The most demanding classification. In addition to integrity, the mean temperature rise on the unexposed face is limited to 140°C above ambient, and the maximum temperature rise at any single point to 180°C above ambient. EI-rated glazing prevents harmful radiant and conductive heat transfer and is required wherever fire resistance must closely approximate that of a solid wall — for example in protected stairwells in higher-risk buildings.

Georgian Wired Glass

Georgian wired glass (wire mesh embedded in the glass) was the standard fire-rated glazing product for most of the 20th century. It achieves approximately 30 minutes of integrity performance (E30) because the wire reinforcement holds the glass in place even after the glass itself cracks from thermal shock. However:

  • It does not achieve EI rating at any period
  • Maximum pane size is typically 1.2m × 0.9m (check the specific product and framing system)
  • The wire creates a visual obstruction
  • Georgian wired glass is no longer manufactured in the UK and new supplies are imported; quality varies
  • Where upgrading from wired glass to modern products, the framing and all seals must be replaced as part of the system upgrade — it is not sufficient to re-glaze into an old frame

Georgian wired glass installed before the modern classification system is commonly found in school corridors, hospital walls, and older commercial buildings. It remains technically compliant where the E30 classification is all that is required and the installation is in good condition, but any replacement must use a modern tested system.

Modern Fire-Rated Glazing Products

The main types of modern fire-rated glazing available in the UK:

Borosilicate fire glass (single pane, E30/E60): Uses a glass formulation with very low thermal expansion coefficient. Remains intact under fire exposure. Achieves E30 or E60 integrity ratings in appropriate frames. Visually clear, no wires. Cannot achieve EI ratings at standard thicknesses.

Intumescent gel-filled units (EI30, EI60, EI90, EI120): Two or more panes of glass with an intumescent gel or layers between them. On exposure to fire, the gel foams and turns opaque, absorbing heat and providing insulation. Achieves full EI ratings. Heavier than single pane; more expensive. Requires compatible deep-rebate framing.

Pyroceramics (EI ratings): Ceramic glass (e.g., Pyroceram type) withstands extremely high temperatures without shattering. Used in high-specification applications.

Fire-rated glass blocks: Solid glass block construction can achieve E60 or higher in specialist configurations. Used architecturally.

Framing Requirements

The framing system is as important as the glazing product. Fire-rated glazing products are tested within a specific framing system, and the test evidence is only valid for that combination. Installers must use framing that matches the tested configuration in:

  • Profile depth and rebate dimensions — the depth of the glass seat affects performance
  • Material specification — steel, timber, or aluminium (aluminium requires thermal break and intumescent)
  • Intumescent glazing tape or seals — must be the specified product for the tested system
  • Glazing bead specification — correct section, material, and fixing method
  • Fixings and subframe — the way the framed assembly is fixed to the surrounding structure must also match the tested method

For door side panels and screens, the complete assembly (frame, glass, seals, and connection to the door frame or wall) must be within a tested configuration. This is typically demonstrated through the manufacturer's installation instructions and system test evidence.

Vision Panels in Fire Doors

Vision panels in fire doors are a specific sub-category. The glass and its installation must be within the door manufacturer's test evidence for the complete doorset:

  • The maximum panel area permitted within FD30 and FD60 doorsets varies by manufacturer and test evidence — commonly 0.065 m² or 0.1 m², but check the specific doorset certification
  • Vision panels must be glazed into the door leaf with the specified beads, sealants, and intumescent strips
  • Cutting and fitting glazing on site by unqualified operatives using non-specified products is a common cause of certification failure
  • Any vision panel modification that is outside the doorset's test evidence invalidates the fire rating of the door

Certification and Marking

Fire-rated glazing products should carry:

  • CE marking under EN 14449 (glass as a construction product) or the UKCA marking equivalent post-Brexit
  • Performance classification visible on the label (e.g., E 60, EI 30)
  • Third-party certification — CERTIFIRE, LPCB, or manufacturer's BBA certificate provides additional assurance

Where products lack clear certification, particularly for remediation or replacement work on older buildings, the responsible person should seek manufacturer documentation that confirms the tested performance classification and the compatible framing system.

Frequently Asked Questions

Can I replace wired glass with clear fire-rated glass without changing the frame?

Generally no. The performance of a fire-rated glazing system depends on the combination of glass and frame. Modern borosilicate or gel-filled units have different dimensions, weights, and rebate requirements from Georgian wired glass. In most cases, replacement requires changing the complete framing system as well as the glass. Attempting to re-glaze with a modern product into an old frame risks creating an installation that looks compliant but is not within any tested configuration.

What size can fire-rated glazing panels be?

Maximum panel sizes depend entirely on the specific product and framing system as tested. Integrity-only products in steel frames can often achieve larger panes (some up to 3 m²) while products requiring EI ratings in timber frames may be limited to 0.5 m² or less. There is no single universal maximum — always consult the manufacturer's product data and test evidence. Where panels need to be large (e.g., full-height screens), specialist framing systems tested to the required size are available but must be designed as a system, not assembled from components.

Is toughened or laminated glass fire-rated?

Standard toughened and laminated glass provides no meaningful fire resistance. Toughened glass will typically fail within a few minutes of intense fire exposure. Laminated glass may stay together briefly but does not achieve the rated performance needed for compartmentation purposes. Fire-rated glass is a distinct product class and must be specified and certified as such.

Does fire-rated glazing need to be maintained?

Yes. The RRO requires fire precautions to be maintained in effective working order. For glazed screens and fire door panels, maintenance means:

  • Checking that glass is intact and not cracked
  • Ensuring intumescent seals and strips remain in place and undamaged
  • Verifying that glazing beads are secure
  • Confirming that any repairs have used compatible, tested products Cracked or damaged fire-rated glazing must be replaced — even a hairline crack in a fire door vision panel can mean the panel fails almost immediately under fire conditions.

Regulations & Standards

  • Approved Document B (ADB) Volume 1 and 2 (2019) — Sets fire resistance requirements by location, occupancy, and building height; Appendix A defines performance specifications

  • BS EN 13501-2 — Fire classification of construction products and building elements; Part 2 covers doors, shutters, and opening protective devices

  • BS EN 1364-1 and BS EN 1364-2 — Fire resistance tests for non-loadbearing elements; covers walls and ceilings including glazed assemblies

  • BS EN 1634-1 — Fire resistance and smoke control tests for door and shutter assemblies

  • BS 476 Part 22 — Older UK test method for fire resistance of non-loadbearing elements (still referenced for historical installations)

  • EN 14449 — Glass in building — laminated glass and laminated safety glass; CE marking standard

  • BS 9999:2017 — Code of practice for fire safety; includes specification for fire-resisting elements

  • Approved Document B — Fire Safety — DLUHC official guidance with performance tables

  • Glass and Glazing Federation (GGF) Fire-Rated Glazing Guide — Industry guidance on fire-rated glazing selection and installation

  • CERTIFIRE scheme — Third-party certification for fire-rated products including glazing

  • BSI Standards publication BS EN 13501-2 — Classification standard for fire performance

  • fire door installation — Fire door standards, ratings, and installation requirements

  • compartmentation — How fire compartmentation works and maintenance requirements

  • passive fire protection — Overview of passive fire protection products

  • fire risk assessment — Identifying glazing deficiencies in fire risk assessments