Fire-Resistance Ratings for Structural Steel

IBC Chapter 6, ASTM E119 and UL 263, and how coatings and assemblies demonstrate a rating

Last updated: June 20, 2026

Overview

Building codes require the structural frame of many commercial buildings to resist fire for a set period, known as the fire-resistance rating. Bare steel weakens quickly when heated, so the frame is protected to keep its strength for the rated time. This page covers where the IBC requires a rating, how ASTM E119 and UL 263 establish one, and how coatings and assemblies demonstrate compliance.

Specifying a coating? See the intumescent fireproofing guide for how thin-film coatings achieve a rating, how they compare to cementitious fireproofing, and how to request a quote.

When a Rating Is Required

IBC Chapter 6 assigns fire-resistance ratings to structural elements by construction type. For the steel frames most often fireproofed (noncombustible Type I and Type II construction), the primary structural frame ratings in Table 601 are:

Construction type	Primary structural frame
Type I-A	3 hours
Type I-B	2 hours
Type II-A	1 hour
Type II-B	0 hours

The minimum required rating is set by the adopted code and the authority having jurisdiction, based on the construction type and other applicable provisions. The architect or engineer documents it on the drawings, so always work from the project documents.

ASTM E119 and UL 263

A fire-resistance rating is established by a standard fire test, ASTM E119, and UL 263, which the IBC treats as equivalent. The test exposes the assembly to a defined time-temperature curve, and the rating is the length of time it continues to meet the acceptance criteria, including load-carrying ability for loadbearing members and staying within the steel-temperature limits the test specifies. The rating belongs to the tested assembly, not to a product in isolation.

How Products Demonstrate a Rating

A fire-resistive product is used as part of a tested design or assembly that carries the stated rating when it is installed as tested.
For coatings, the rating is tied to a dry film thickness for a given steel member, based on its weight-to-heated-perimeter (W/D) ratio. The published design or evaluation document, such as a UL design or an ICC-ES Evaluation Report, gives the required thickness per member.
You cannot extrapolate a thickness for a steel profile that is not covered by a tested design. The member has to fall within one.

Protection Methods

Several methods can deliver a rated steel frame. The choice depends on appearance, location, cost, and durability:

Intumescent thin-film coatings for exposed, architectural steel that needs a finished look.
Spray-applied fire-resistive material (SFRM), cementitious or mineral-fiber, for concealed steel above ceilings or in shafts, at lower cost.
Board enclosure of gypsum, mineral-fiber, or calcium-silicate board built around the member.
Concrete or masonry encasement of the steel.

For how the coating options compare and how to spec one, see the intumescent fireproofing guide.

Frequently Asked Questions

What fire-resistance rating does my building need?

It is set by IBC Chapter 6 and Table 601 based on construction type. For the primary structural frame, that runs from 3 hours (Type I-A) down to 0 hours (Type II-B). The project architect or engineer specifies the required rating on the drawings.

Are ASTM E119 and UL 263 the same test?

They are equivalent fire-test methods for fire-resistance ratings, and the IBC accepts either. UL 263 is widely used for the listings that cover structural steel assemblies.

How is a coating's required thickness determined?

From the product's UL design or ICC-ES Evaluation Report, tied to the steel member's weight-to-heated-perimeter (W/D) ratio. You cannot extrapolate to a profile that is not listed, so the member has to match a tested design.

What are the ways to fireproof structural steel?

Intumescent coatings, spray-applied fire-resistive material (SFRM, cementitious or mineral-fiber), board enclosure (gypsum, mineral-fiber, or calcium-silicate), and concrete or masonry encasement, depending on appearance, location, and cost.