Steel fireproofing

One-line orientation

Steel does not burn but softens in fire, so structural steel is insulated to hold a required hourly fire-resistance rating — the exam tests the methods and that “rating” comes from the IBC construction type, not a flat story count.

Key points

• Why protect steel: steel is non-combustible but loses strength and stiffness as temperature rises, eventually deforming/buckling under load. Fireproofing insulates the member so it stays below its critical temperature for the rated duration.
• Protection methods:
  • Spray-applied fire-resistive material (SFRM): cementitious/mineral-fiber spray applied directly; common, economical, usually concealed.
  • Intumescent paint: swells into an insulating char when heated; clean finish, good for exposed/architectural steel.
  • Gypsum board enclosure: boxing the member in fire-rated gypsum; lightweight, cost-effective.
  • Concrete encasement: durable, robust enclosure (also adds mass).
  • Older/other: plaster on lath, sheet metal with loose insulating fill.
• Rating is measured in hours: the required fire-resistance rating (hours) for columns, beams, and floors comes from the building’s occupancy and IBC construction type — pick the protection method/thickness that achieves it.
• Cross-bracing: bracing that is essential to vertical stability / gravity-load support is protected with the rated frame. Purely lateral bracing is not treated the same way as the primary gravity frame.

Confusions / comparison

Method	How it protects	Finish / where used
SFRM (cementitious spray)	Sprayed insulating layer slows heat	Concealed; economical, common
Intumescent paint	Swells to char foam when heated	Clean — exposed/architectural steel
Gypsum board enclosure	Boxed in fire-rated board	Lightweight, cost-effective
Concrete encasement	Mass/insulation around member	Durable, robust; heavier

Related

→ Steel types and production (this module): steel keeps full strength only until heated · Steel shapes and members (this module): the members being protected · Code (module): IBC construction types and required fire-resistance ratings.