Fire-rated glass is one of the most technically complex and most frequently misunderstood product categories in commercial construction. It's required in specific locations by the International Building Code and the Florida Building Code — and substituting a non-rated product, or the wrong rated product, is a serious code violation that can result in failed inspections, project delays, and life safety liability. This guide explains where fire-rated glass is required, what the ratings actually mean, which glass types perform at which rating levels, and what to expect from a cost and installation standpoint.
Where Fire-Rated Glass Is Required in Commercial Buildings
The International Building Code (IBC), adopted by Florida as the basis for the Florida Building Code, establishes fire-resistance requirements for building elements based on occupancy type, building height, construction type, and the specific element's role in the egress and compartmentalization strategy. Fire-rated glazing is typically required in the following locations:
Stairwell Enclosures
Exit stair enclosures in most commercial buildings must be enclosed in fire-rated construction — typically 1-hour or 2-hour fire-resistance-rated walls depending on the building's construction type and the number of stories the stair serves. Any glazing in those enclosure walls — including sidelites, borrowed lights, and vision panels in stair doors — must be fire-rated to match or be compatible with the wall assembly rating.
The IBC limits the total glazed area in fire-rated stair enclosures based on the required rating: in a 1-hour enclosure, glazing using fire-protective assemblies is limited in area per the IBC Section 716 provisions. Fire-resistance-rated glazing (not just fire-protective) has more flexibility in terms of allowed area.
Exit Access Corridors
Corridors serving as exit access in most commercial occupancies require fire-resistance-rated construction — typically 1-hour — under IBC Section 1020. Glazing in corridor walls, including office sidelites and borrowed lights, must comply with the applicable fire rating requirements. The specific requirements vary depending on whether the wall is a fire partition, fire barrier, or fire wall, and whether the glazing is in a door assembly or a fixed location.
Fire Barriers and Fire Partitions
Fire barriers and fire partitions are required throughout commercial buildings to create fire compartments, separate occupancies, protect exit enclosures, and limit fire spread between building areas. The required rating depends on the wall type and its function: fire partitions are typically 1-hour, fire barriers can be 1-hour to 3-hour depending on the application, and fire walls (the highest category) can be 2-hour to 4-hour.
Glazing in these assemblies must be listed and labeled as a component of a tested and listed fire-rated assembly, with the framing, glass, and anchorage all included in the listing.
Lobby Separations and Tenant Separations
In multi-tenant commercial buildings, the separations between tenant spaces and between tenant spaces and common areas may require fire-rated construction. This is increasingly common in speculative office buildings where architects want to use glass for the lobby-to-corridor transition. Fire-rated glass allows that visual transparency while meeting the code requirement for the separation.
Hazardous Areas
IBC Section 509 identifies occupancy areas that require separation from the remainder of the building due to hazard — mechanical rooms, storage rooms with flammable materials, laundry rooms, and similar spaces. The separation ratings for these areas generate fire-rated glazing requirements at doors and sidelites.
Understanding Fire Ratings: 20, 45, 60, and 90 Minutes
Fire ratings for glazing assemblies are expressed in minutes — the duration for which the assembly must resist fire in a standardized furnace test per ASTM E119 (for fire-resistance-rated assemblies) or NFPA 257 / ANSI/UL 9 (for fire windows and fire-protective glazing).
There is an important distinction between two categories of fire-rated glazing that is frequently confused in the industry:
Fire-protective glazing resists fire and hot gases but does not limit radiant heat transfer to the unexposed side. Products in this category can achieve ratings of 20 minutes (for door vision panels), 45 minutes (for door assemblies), and 60 or 90 minutes (for fire window assemblies), but because they do not limit radiant heat, their use is limited in area per the IBC where radiant heat could affect occupants or combustibles on the unexposed side.
Fire-resistance-rated glazing both resists fire and limits radiant heat transmission to the unexposed side. This is a much higher performance standard, achievable only with certain glass types (primarily intumescent laminated systems). Fire-resistance-rated glazing can be used without area limitations in fire-rated assemblies, which makes it far more versatile architecturally — and significantly more expensive.
| Rating | Typical Application | Notes |
|---|---|---|
| 20-minute | Vision panels in fire doors | Most common rating; area-limited under IBC |
| 45-minute | Door assemblies in 1-hour walls | Required for doors in 1-hour exit access corridors |
| 60-minute | Sidelites and windows in 1-hour fire barriers | Fire-protective products are area-limited; fire-resistance-rated are not |
| 90-minute | Stair enclosures, 2-hour fire barriers | Requires ceramic or intumescent glass in most applications |
Types of Fire-Rated Glass
Wired Glass
Wired glass — glass with an embedded wire mesh — was the traditional fire-rated glazing product in commercial construction for decades. The wire mesh holds the glass together during a fire, allowing the assembly to resist fire for the rated duration.
Wired glass has significant limitations: it is available only in a 25 SF maximum panel size for most rated applications, it has poor optical clarity compared to modern alternatives, and it is not impact-resistant, which created a significant safety hazard in locations where human impact was possible. The Consumer Product Safety Commission (CPSC) has progressively restricted wired glass use in safety-glazing locations, and most modern commercial projects avoid it.
Wired glass is still code-compliant in certain applications — specifically in fire doors where the vision panel is small (100 in² or less for some door types) — but it has been largely displaced by ceramic and intumescent alternatives in new commercial construction.
Ceramic Fire-Rated Glass
Ceramic fire-rated glass (sometimes called pyroceramic or borosilicate glass) is a high-temperature glass product that does not crack or shatter under the thermal shock of a fire test. It maintains its integrity for the rated duration — typically up to 90 minutes — and provides good optical clarity. It is available in larger panel sizes than wired glass.
Ceramic glass is a fire-protective product, not fire-resistance-rated — it does not limit radiant heat transmission to the unexposed side. Its use in fixed sidelite applications is therefore limited by the IBC's area restrictions for fire-protective glazing. It performs well as a vision panel product in fire doors and in locations where the area limitations are not a constraint.
Manufacturers of ceramic fire-rated glass for commercial applications include TGP (Technical Glass Products), which produces the FireLite product line — one of the most widely specified ceramic fire-rated glass products in North America.
Intumescent Laminated Fire-Rated Glass
Intumescent laminated fire-rated glass uses a clear intumescent interlayer between glass plies that reacts to heat by expanding and opacifying, forming an insulating barrier that limits radiant heat transmission to the unexposed side. This is what makes it fire-resistance-rated rather than merely fire-protective.
Intumescent laminated glass can achieve ratings of 45 minutes to 120 minutes depending on the specific product and number of interlayer plies. When properly rated, it can be used without area limitations in fire-rated assemblies — which is a critical architectural advantage for applications like full-height sidelites in stair enclosures, large lobby separations, and any location where the fire-protective area restrictions would be prohibitive.
TGP's FireLite IGS and Pilkington Pyrostop are among the products in this category. These products are significantly more expensive than ceramic glass — but for applications requiring large glazed areas in rated assemblies, they are the only code-compliant solution.
The Listed Assembly Requirement: Why You Can't Mix and Match
One of the most important things to understand about fire-rated glazing is that the rating belongs to the complete listed assembly — not to the glass alone. A fire-rated glass product is listed and labeled as part of a specific assembly that includes the glass, the framing system, the anchorage method, and sometimes specific sealant and gasket requirements.
Substituting a different frame, a different anchor pattern, a different sealant product, or a different glass size than what is specified in the listing directory invalidates the listing. An inspector looking at a fire-rated assembly is looking for the label on the product and verifying that the installed condition matches the listing — and if it doesn't, the assembly fails.
This has practical implications for substitution during construction. If the specified fire-rated product is unavailable due to lead times, a substitution must be made with a product that carries its own listing for the same application and rating — not simply a product from the same manufacturer or with the same glass type.
See our existing post on fire-rated glass requirements in Florida for additional background on how these requirements apply in Florida construction.
TGP: The Industry Standard for Commercial Fire-Rated Glazing
Technical Glass Products (TGP) is the leading manufacturer of fire-rated glass and framing systems for commercial construction in North America. Their product lines include FireLite (ceramic fire-protective glass), FireLite IGS (fire-resistance-rated intumescent glass), Pilkington Pyrostop (fire-resistance-rated), and a full line of listed framing systems designed to work with their glass products.
TGP products are specified by architects on a wide range of commercial projects — from low-rise office and retail to high-rise mixed-use — because the product line covers every rating category and application type, the listing documentation is thorough and well-organized, and the technical support team is responsive to project-specific questions. For projects with complex fire-rated glazing scopes, working with a glazing contractor who has experience installing TGP systems and access to TGP technical support is a significant advantage.
ACG installs TGP fire-rated glass and framing systems as part of our commercial glazing scope. Our project history includes fire-rated glazing installations in stair enclosures, corridors, lobby separations, and specialty applications across Florida.
Cost Premiums for Fire-Rated Glazing
Fire-rated glass carries a significant cost premium over standard commercial glass. The premium reflects the specialized manufacturing processes, the testing and listing costs, the limited number of manufacturers, and the more complex installation requirements. As a general guide:
- Wired glass — modest premium over standard glass; limited applications in new construction
- Ceramic fire-rated glass (FireLite and similar) — typically 3–5× the cost of standard tempered glass for comparable panel sizes
- Intumescent fire-resistance-rated glass — typically 8–15× the cost of standard tempered glass, depending on the panel size and rating level
The installed cost premium is further amplified by the listed framing requirement — fire-rated framing systems cost more than standard commercial framing, and the installation labor is more intensive due to the need to maintain listing compliance at every connection, anchor, and joint condition.
These are wide ranges because the framing system, panel size, and rating level all significantly affect the final number.
Working with ACG on Fire-Rated Glazing Scopes
Fire-rated glazing scopes require a glazing contractor who understands listing requirements, can navigate the product approval documentation, and has experience coordinating with the building inspector on rated assembly verification. ACG has completed fire-rated glazing installations on multiple Florida commercial projects and maintains the manufacturer relationships and technical knowledge to execute these scopes correctly.
Browse our project portfolio to see examples of our fire-rated glazing work. Review our services page for a full overview of fire-rated glass systems we install. Use our Scope Engine for a preliminary estimate, or send your plans through our contact page for a complete scope within 48 hours.
For projects with a significant fire-rated scope, early engagement with your glazing sub during the design phase — before the specs are finalized — can prevent costly specification errors and lead time surprises. Fire-rated glass products, particularly intumescent assemblies, can have longer lead times than standard commercial glass. Plan ahead.
See also our related guide on glass partition walls for offices, which covers fire-rated partition options in the context of interior office design.