IBC Fire-Resistance-Rated Construction
Summary
Fire-resistance-rated construction divides a building into fire compartments using fire walls, fire barriers, fire partitions, smoke barriers, horizontal assemblies, and shaft enclosures, each rated in hours and built continuous from floor to floor or deck. Each element has its own rating table, continuity rule, and opening limit, so choose the element type first, then the hours.
Cols
Scope
- Cites the 2024 IBC, Chapter 7. Always verify the adopted code edition and local amendments for the project jurisdiction
- Covers the type of separation, the rating, continuity, and opening limits. Protection of openings and penetrations is in the openings and penetrations note, and exterior wall ratings are in the exterior walls note
- Rated assemblies are chosen from listed designs tested to ASTM E119 or UL 263
- Which separations are required comes from other provisions: occupancy, egress, shafts, fire area limits, and unit separation
Terminology
- Fire wall: rated wall that divides a building into separate buildings for code purposes (Section 706)
- Fire barrier: rated wall that separates occupancies, shafts, exits, and fire areas (Section 707)
- Fire partition: rated wall for corridors, dwelling unit separations, and tenant separations (Section 708)
- Smoke barrier: rated barrier that limits smoke movement between smoke compartments (Section 709)
- Horizontal assembly: rated floor or roof-ceiling assembly (Section 711)
- Shaft enclosure: rated enclosure of a vertical opening through floors, such as an elevator hoistway or duct shaft (Section 713)
- Fire area: floor area enclosed by rated walls and floors, or by exterior walls, used for sprinkler and alarm thresholds
- Fire-resistance rating: hours an assembly resists the standard fire test (ASTM E119 or UL 263)
- Continuity: the barrier extends from the floor or floor-ceiling below to the deck or slab above, through concealed spaces
- Fireblocking and draftstopping: concealed-space barriers in combustible construction
Requirements
Choosing the element
| Element | Typical use | Section |
|---|---|---|
| Fire wall | Divide one structure into separate buildings, for area or type limits | 706 |
| Fire barrier | Separate occupancies, enclose shafts and exits, divide fire areas, incidental uses | 707 |
| Fire partition | Corridor walls, dwelling and sleeping unit separations, tenant separations | 708 |
| Smoke barrier | Smoke compartments in healthcare and similar uses | 709 |
| Horizontal assembly | Floor and roof-ceiling assemblies that serve as separations | 711 |
| Shaft enclosure | Elevators, duct, pipe, and chase shafts through floors | 713 |
Fire walls
- IBC 2024, Table 706.4: fire wall rating by occupancy
| Group | Rating (hours) |
|---|---|
| H-1, H-2 | 4 |
| F-1, H-3, H-5, M, S-1 | 3 |
| A, B, E, H-4, I, R-1, R-2, U | 3, or 2 in Type II or V construction |
| F-2, S-2, R-3, R-4 | 2 |
- IBC 2024, Section 706.5: continuous from exterior wall to exterior wall, extending at least 18 in. beyond the exterior surface of exterior walls, with exceptions; also to the outer edge of projections within 4 ft
- IBC 2024, Section 706.6: extends from the foundation to at least 30 in. above both adjacent roofs, with exceptions for stepped buildings and sloped roofs
- IBC 2024, Section 706.8: each opening protected under Section 716, no single opening over 156 sq ft, and aggregate width at any floor no more than 25 percent of the wall length; the 156 sq ft limit is waived where both buildings are sprinklered throughout (Section 903.3.1.1); no openings in party walls on lot lines
Fire barriers
- IBC 2024, Table 707.3.10: fire barrier rating separating fire areas
| Group | Rating (hours) |
|---|---|
| H-1, H-2 | 4 |
| F-1, H-3, S-1 | 3 |
| A, B, E, F-2, H-4, H-5, I, L, M, R, S-2 | 2 |
| U | 1 |
- IBC 2024, Section 707.3: other ratings come from the provision that requires the barrier: shafts (Section 713.4), interior exit stairways (Section 1023.1), exit passageways (Section 1024.3), horizontal exits (Section 1026.1), atriums (Section 404.6), incidental uses (Table 509.1), control areas (Section 414.2.4), separated occupancies (Table 508.4)
- IBC 2024, Section 707.5: continuous from the top of the foundation or floor-ceiling assembly below to the underside of the floor or roof sheathing, slab, or deck above, through concealed spaces such as above a suspended ceiling
- IBC 2024, Section 707.6: openings protected under Section 716; aggregate width no more than 25 percent of the wall length; no single opening over 156 sq ft; exceptions include sprinklered adjoining floor areas, fire doors serving exit access and interior exit stairway enclosures, and elevator car entrances
Fire partitions
- IBC 2024, Section 708.3: 1 hour minimum
- IBC 2024, Section 708.3, exceptions: corridor walls may be 1/2 hour where Table 1020.2 allows; dwelling and sleeping unit separations in Type II-B, III-B, or V-B buildings sprinklered throughout (Section 903.3.1.1) may be 1/2 hour
- IBC 2024, Section 708.4: extend from the top of the foundation or floor-ceiling assembly below to the underside of the floor or roof sheathing, deck, or slab above, or to a rated floor-ceiling or roof-ceiling assembly at least as high as the partition
- IBC 2024, Section 708.4, exceptions: corridor walls need not extend above the corridor ceiling under specified conditions, such as sprinklers in the space above
- IBC 2024, Section 708.4.3: in combustible construction where partitions stop below the deck, fireblocking or draftstops are required above
Smoke barriers
- IBC 2024, Section 709.3: 1-hour fire-resistance rating
Horizontal assemblies
- IBC 2024, Section 711.2.4: rating not less than that required by the type of construction, and also not less than the separation it serves: mixed occupancies per Section 508.4, fire areas per Section 707.3.10, incidental uses per Section 509
- IBC 2024, Section 711.2.4.3: dwelling and sleeping unit separations at least 1 hour; 1/2 hour allowed in Type II-B, III-B, and V-B sprinklered throughout (Section 903.3.1.1)
- IBC 2024, Section 711.2.3: supporting construction is protected to the rating of the assembly it supports, with exceptions for Types II-B, III-B, and V-B (incidental use separations up to 1 hour, dwelling and sleeping unit separations, smoke barriers)
- IBC 2024, Section 711.2.5: lay-in ceiling panels in rated assemblies that cannot resist 1 psf upward force need wire or other devices to stay in place
- IBC 2024, Section 711.2.6: in 1-hour floor-ceiling assemblies the ceiling membrane is not required over unusable crawl spaces; in 1-hour roof assemblies the floor membrane is not required below unusable attic space
Shaft enclosures
- IBC 2024, Section 713.4: shafts connecting four stories or more are rated 2 hours; fewer than four stories, 1 hour; the rating need not exceed 2 hours but is at least that of the floor assembly penetrated; basements count toward the story total, mezzanines do not
- IBC 2024, Section 713.5: built as fire barriers (Section 707) or horizontal assemblies (Section 711), or both
- IBC 2024, Section 713.7: openings protected under Section 716; doors are self-closing or close on smoke detection
- IBC 2024, Section 713.8: penetrations protected under Section 714; penetrations not needed for the shaft's purpose are prohibited
- IBC 2024, Section 713.11: shafts that do not extend to the bottom of the building enclose the lowest level, end in a related-use room, or use fire dampers at the lowest floor, with exceptions
Worked examples
Splitting a building with a fire wall
Group B, Type II-B, two stories, sprinklered throughout. Program is 120,000 sq ft total, 60,000 sq ft per story, 300 ft long.
| Step | Calculation | Result |
|---|---|---|
| Area limit | Table 506.2, B, II-B, sprinklered multi-story | 69,000 sq ft per story allowed |
| Whole building | 60,000 sq ft per story in one building | Within the 69,000 sq ft limit; no fire wall needed for area |
| Larger program, 100,000 sq ft per story | Exceeds 69,000 | Divide with a fire wall into two buildings of 50,000 sq ft each |
| Fire wall rating | Table 706.4, Group B, Type II | 2 hours |
| Fire wall height | Section 706.6 | 30 in. above both adjacent roofs |
| Openings | Aggregate width 25 percent of a 300 ft wall; each opening 156 sq ft maximum | 75 ft aggregate width; both buildings are sprinklered, so the 156 sq ft single-opening limit is waived |
Elevator hoistway rating
| Building | Stories connected | Shaft rating |
|---|---|---|
| Three-story office | 3 | 1 hour |
| Five-story apartment building | 5 | 2 hours |
| Three-story with a basement served by the same shaft | 4 (basement counts) | 2 hours |
Coordination
- Structural: supports under rated assemblies carry the same rating; coordinate beams, columns, and bearing walls
- MEP: penetrations, dampers, and recessed fixtures in rated assemblies need listed protection
- Ceilings: a rated floor-ceiling assembly includes its ceiling; lay-in ceilings need hold-down and the tested membrane
- Drawings: show rated walls with their rating, extent, and the listed design number on a fire and life safety plan
- Door and glazing: doors, frames, and glass in rated walls are rated assemblies, limited by Section 716
- Field changes: moves of walls, shafts, or openings after permit change the rating path
Common issues
- Walls stop at the ceiling: a rated wall that ends at a suspended ceiling breaks continuity; carry it to the deck
- Shaft with unneeded openings: access doors and pass-throughs not needed for the shaft's purpose are prohibited
- Unprotected supports: a rated floor on unprotected beams fails the supporting-construction rule
- Wrong barrier type: corridor walls are fire partitions, shafts are fire barriers or horizontal assemblies, and occupancy separations are fire barriers
- Fire wall confused with a party wall: a fire wall makes two buildings; a party wall on a lot line has no openings
- Rating reduction assumed: sprinklers allow specific reductions only where the code says so (for example, dwelling unit separations in Type II-B, III-B, and V-B)
Standards
- ASTM E119 and UL 263: fire tests for building construction and materials, the basis for listed assembly ratings
- UL Fire Resistance Directory: listed wall, floor, and roof-ceiling designs by number
- NFPA 221: fire walls and fire barrier walls; fire walls built to it are deemed to comply with Section 706 (Section 706.1.2)
Sources
- UpCodes: 2024 IBC Chapter 7, Section 703 (Department of Defense adoption), https://up.codes/viewer/department-of-defense/ibc-2024/chapter/7/fire-and-smoke-protection-features
- GoCodebook: 2025 California Building Code, Section 706 fire walls (based on the 2024 IBC), https://gocodebook.com/library/us/ca/ca-building-code/chapter-7-fire-and-smoke-protection-features/section-706-fire-walls
- GoCodebook: 2025 California Building Code, Section 707 fire barriers (based on the 2024 IBC), https://gocodebook.com/library/us/ca/ca-building-code/chapter-7-fire-and-smoke-protection-features/section-707-fire-barriers
- GoCodebook: 2025 California Building Code, Section 708 fire partitions, https://gocodebook.com/library/us/ca/ca-building-code/chapter-7-fire-and-smoke-protection-features/section-708-fire-partitions
- GoCodebook: 2025 California Building Code, Section 711 floor and roof assemblies, https://gocodebook.com/library/us/ca/ca-building-code/chapter-7-fire-and-smoke-protection-features/section-711-floor-and-roof-assemblies
- GoCodebook: 2025 California Building Code, Section 713 shaft enclosures, https://gocodebook.com/library/us/ca/ca-building-code/chapter-7-fire-and-smoke-protection-features/section-713-shaft-enclosures