User note:
About this chapter: Chapter 6 establishes five types of construction in which each building must be categorized. This chapter looks at the materials used in the building (combustible or noncombustible) and the extent to which building elements such as building frame, roof, wall and floor can resist fire. Depending on the type of construction, the specific building element and its proximity to a lot line, fire resistance of 1 to 3 hours is specified.
| BUILDING ELEMENT | TYPE I | TYPE II | TYPE III |
TYPE IV | TYPE V | |||||||
| A | B | A | B | A | B |
A
|
B
|
C
|
HT | A | B | |
| Primary structural framef (see Section 202) | 3a,b | 2a,b | 1b | 0 | 1b | 0 |
3a
|
2a
|
2a
|
HT | 1b | 0 |
| Bearing walls | ||||||||||||
Exteriore,f |
3 | 2 | 1 | 0 | 2 | 2 |
3
|
2
|
2
|
2 | 1 | 0 |
Interior |
3a | 2a | 1 | 0 | 1 | 0 |
3
|
2
|
2
|
1/HT | 1 | 0 |
| Nonbearing walls and partitions Exterior | See Table 602 | |||||||||||
| Nonbearing walls and partitions Interiord | 0 | 0 | 0 | 0 | 0 | 0 |
0
|
0
|
0
|
See Section 2304.11.2 |
0 | 0 |
| Floor construction and associated secondary members (see Section 202) |
2 | 2 | 1 | 0 | 1 | 0 |
2
|
2
|
2
|
HT | 1 | 0 |
| Roof construction and associated secondary members (see Section 202) |
11/2b | 1b,c | 1b,c | 0c | 1b,c | 0 | 1 1/2 |
1
|
1
|
HT | 1b,c | 0 |
For SI: 1 foot = 304.8 mm.
- Roof supports: Fire-resistance ratings of primary structural frame and bearing walls are permitted to be reduced by 1 hour where supporting a roof only.
- Except in Group F-1, H, M and S-1 occupancies, fire protection of structural members in roof construction shall not be required, including protection of primary structural frame members, roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below. Fire-retardant-treated wood members shall be allowed to be used for such unprotected members.
- In all occupancies, heavy timber complying with Section 2304.11 shall be allowed where a 1-hour or less fire-resistance rating is required.
- Not less than the fire-resistance rating required by other sections of this code.
- Not less than the fire-resistance rating based on fire separation distance (see Table 602).
- Not less than the fire-resistance rating as referenced in Section 704.10.
Upcodes Diagrams
The provisions of this chapter shall control the classification of buildings as to type of construction.
|
FIRE SEPARATION DISTANCE =
X (feet) |
TYPE OF CONSTRUCTION
|
OCCUPANCY GROUP He
|
||
|
X < 5b
|
All
|
3
|
2
|
1
|
|
5 ≤ X < 10
|
IA, IV-A
|
3
|
2
|
1
|
|
Others
|
2
|
1
|
1
|
|
|
10 ≤ X < 30
|
IA, IB, IV-A, IV-B
|
2
|
1
|
1c
|
|
IIB, VB
|
1
|
0
|
0
|
|
|
Others
|
1
|
1
|
1c
|
|
|
X ≥ 30
|
All
|
0
|
0
|
0
|
- Load-bearing exterior walls shall also comply with the fire-resistance rating requirements of Table 601.
- See Section 706.1.1 for party walls.
- Open parking garages complying with Section 406 shall not be required to have a fire-resistance rating.
- The fire-resistance rating of an exterior wall is determined based upon the fire separation distance of the exterior wall and the story in which the wall is located.
- For special requirements for Group H occupancies, see Section 415.6.
- For special requirements for Group S aircraft hangers, see Section 412.3.1.
- Where Table 705.8 permits nonbearing exterior walls with unlimited area of unprotected openings, the required fire-resistance rating for the exterior walls is 0 hours.
- For a building containing only a Group U occupancy private garage or carport, the exterior wall shall not be required to have a fire-resistance rating where the fire separation distance is 5 feet (1523 mm) or greater.
- For a Group R-3 building of Type II-B or Type V-B construction, the exterior wall shall not be required to have a fire-resistance rating where the fire separation distance is 5 feet (1523 mm) or greater.
Upcodes Diagrams
Buildings and structures erected or to be erected, altered or extended in height or area shall be classified in one of the five construction types defined in Sections 602.2 through 602.5. The building elements shall have a fire-resistance rating not less than that specified in Table 601 and exterior walls shall have a fire-resistance rating not less than that specified in Table 602. Where required to have a fire-resistance rating by Table 601, building elements shall comply with the applicable provisions of Section 703.2. The protection of openings, ducts and air transfer openings in building elements shall not be required unless required by other provisions of this code.
Upcodes Diagrams
A building or portion thereof shall not be required to conform to the details of a type of construction higher than that type which meets the minimum requirements based on occupancy even though certain features of such a building actually conform to a higher type of construction.
As an alternative to the construction types defined in 602.2 through 602.5, buildings and structures erected or to be erected, altered or extended in height or area shall be permitted to be classified as construction Type IV-A, IV-B or IV-C in accordance with Appendix P. Buildings and structures classified as IV-A, IV-B, and IV-C shall comply with the provisions of Appendix P, as well as all other applicable provisions of this code, including provisions for buildings of Type IV construction.
(Effective January 1, 2022)
(Effective January 1, 2022)
Types I and II construction are those types of construction in which the building elements listed in Table 601 are of noncombustible materials, except as permitted in Section 603 and elsewhere in this code.
Upcodes Diagrams
Type III construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of any material permitted by this code. Fire-retardant-treated wood framing and sheathing complying with Section 2303.2 shall be permitted within exterior wall assemblies of a 2-hour rating or less.
Upcodes Diagrams
Type IV construction is that type of construction in which the building elements are mass timber or noncombustible materials and have fire resistance ratings in accordance with Table 601. Mass timber elements shall meet the fire resistance rating requirements of this section based on either the fire resistance rating of the noncombustible protection, the mass timber, or a combination of both and shall be determined in accordance with Section 703.2 or 703.3. The minimum dimensions and permitted materials for building elements shall comply with the provisions of this section and Section 2304.11. Mass timber elements of Type IV-A, IV-B and IV-C construction shall be protected with noncombustible protection applied directly to the mass timber in accordance with Sections 602.4.1 through 602.4.3. The time assigned to the noncombustible protection shall be determined in accordance with Section 703.8 and comply with Section 722.7.
Cross laminated timber shall be labeled as conforming to PRG 320-19 as reference in Section 2303.1.4.
Exterior load bearing walls and nonload-bearing walls shall be mass timber construction, or shall be of noncombustible construction.
Exception: Exterior load-bearing walls and nonload-bearing walls of Type IV-HT
Construction in accordance with Section 602.4.4.
The interior building elements, including nonload-bearing walls and partitions, shall be of mass timber construction or of noncombustible construction.
Exception: Interior building elements and nonload-bearing walls and partitions of Type IV-HT Construction in accordance with Section 602.4.4.
Combustible concealed spaces are not permitted except as otherwise indicated in Sections 602.4.1 through 602.4.4. Combustible stud spaces within light frame walls of Type IV-HT construction shall not be considered concealed spaces, but shall comply with Section 718.
In buildings of Type IV-A, IV-B and IV-C, construction with an occupied floor located more
than 75 feet (22 860 mm) above the lowest level of fire department access, up to and
including 12 stories or 180 feet (54 864 mm) above grade plane, mass timber interior exit and elevator hoistway enclosures shall be protected in accordance with Section 602.4.1.2. In buildings greater than 12 stories or 180 feet (54 864 mm) above grade plane, interior exit and elevator hoistway enclosures shall be constructed of non-combustible materials.
Exception: Exterior load-bearing walls and nonload-bearing walls of Type IV-HT
Construction in accordance with Section 602.4.4.
The interior building elements, including nonload-bearing walls and partitions, shall be of mass timber construction or of noncombustible construction.
Exception: Interior building elements and nonload-bearing walls and partitions of Type IV-HT Construction in accordance with Section 602.4.4.
Combustible concealed spaces are not permitted except as otherwise indicated in Sections 602.4.1 through 602.4.4. Combustible stud spaces within light frame walls of Type IV-HT construction shall not be considered concealed spaces, but shall comply with Section 718.
In buildings of Type IV-A, IV-B and IV-C, construction with an occupied floor located more
than 75 feet (22 860 mm) above the lowest level of fire department access, up to and
including 12 stories or 180 feet (54 864 mm) above grade plane, mass timber interior exit and elevator hoistway enclosures shall be protected in accordance with Section 602.4.1.2. In buildings greater than 12 stories or 180 feet (54 864 mm) above grade plane, interior exit and elevator hoistway enclosures shall be constructed of non-combustible materials.
Upcodes Diagrams
Building elements in Type IV-A construction shall be protected in
accordance with Sections 602.4.1.1 through 602.4.1.6. The required fire resistance rating of
noncombustible elements and protected mass timber elements shall be determined in accordance
with Section 703.2 or Section 703.3.
The outside face of exterior walls of mass timber construction shall be protected with noncombustible protection with a minimum assigned time of 40 minutes as determined in Table 722.7.1(1). Components of the exterior wall covering shall be of noncombustible material except water resistive barriers having a peak heat release rate of less than 150 kW/m2, a total heat release of less than 20 MJ/m2 and an effective heat of combustion of less than 18 MJ/kg as determined in accordance with ASTM E1354 and having a flame spread index of 25 or less and a smoke-developed index of 450 of less as determined in accordance with ASTM E84 or UL 723. The ASTM E1354 test shall be conducted on specimens at the thickness intended for use, in the horizontal orientation and at an incident radiant heat flux of 50 kW/m2.
Interior faces of all mass timber elements, including the inside faces of exterior mass timber walls and mass timber roofs, shall be protected with material complying with Section 703.5.
Noncombustible protection shall contribute a time equal to
or greater than times assigned in Table 722.7.1(1), but not less than 80 minutes. The use
of materials and their respective protection contributions listed in Table 722.7.1(2) shall
be permitted to be used for compliance with Section 722.7.1.
The floor assembly shall contain a noncombustible material not less than 1
inch (25 mm) in thickness above the mass timber. Floor finishes in accordance with Section 804 shall be permitted on top of the noncombustible material. The underside of floor
assemblies shall be protected in accordance with 602.4.1.2.
The interior surfaces of roof assemblies shall be protected in accordance
with Section 602.4.1.2. Roof coverings in accordance with Chapter 15 shall be permitted on
the outside surface of the roof assembly.
Concealed spaces shall not contain combustibles other than electrical, mechanical, fire protection, or plumbing materials and equipment permitted in plenums in accordance with Section 602 of the International Mechanical Code, and shall comply with all applicable provisions of Section 718. Combustible construction forming concealed spaces shall be protected in accordance with Sections 602.4.1.2.
Shafts shall be permitted in accordance with Section 713 and Section 718.
Both the shaft side and room side of mass timber elements shall be protected in accordance
with Section 602.4.1.2.
Building elements in Type IV-B construction shall be protected in
accordance with Sections 602.4.2.1 through 602.4.2.6. The required fire resistance rating of
noncombustible elements or mass timber elements shall be determined in accordance with
Section 703.2 or Section 703.3.
The outside face of exterior walls of mass timber construction shall be protected with non-combustible protection with a minimum assigned time of 40 minutes as determined in Table 722.7.1(1). Components of the exterior wall covering shall be of noncombustible material except water resistive barriers having a peak heat release rate of less than 150 kW/m2, a total heat release of less than 20 MJ/m2 and an effective heat of combustion of less than 18 MJ/kg as determined in accordance with ASTM E1354, and having a flame spread index of 25 or less and a smoke-developed index of 450 or less as determined in accordance with ASTM E84 or UL 723. The ASTM E1354 test shall be conducted on specimens at the thickness intended for use, in the horizontal orientation and at an incident radiant heat flux of 50 kW/m2.
Interior faces of all mass timber elements, including the inside
face of exterior mass timber walls and mass timber roofs, shall be protected, as required by
this section, with materials complying with Section 703.5.
Noncombustible protection shall contribute a time equal to
or greater than times assigned in Table 722.7.1(1), but not less than 80 minutes. The use
of materials and their respective protection contributions listed in Table 722.7.1(2) shall
be permitted to be used for compliance with Section 722.7.1.
Interior faces of all mass timber elements, including the inside face of exterior mass timber walls and mass timber roofs, shall be protected in accordance with Section 602.4.2.2.1.
Exceptions: Unprotected portions of mass timber ceilings and walls complying with Section 602.4.2.2.4 and the following:
- Unprotected portions of mass timber ceilings and walls complying with one of the following:
- Unprotected portions of mass timber ceilings, including attached beams, shall be permitted and shall be limited to an area equal to 20 percent of the floor area in any dwelling unit or fire area.
- Unprotected portions of mass timber walls, including attached columns, shall be permitted and shall be limited to an area equal to 40 percent of the floor area in any dwelling unit or fire area.
- Unprotected portions of both walls and ceilings of mass timbers, including attached columns and beams, in any dwelling unit or fire area shall be permitted in accordance with Section 602.4.2.2.3.
- Mass timber columns and beams that are not an integral portion of walls or ceilings, respectively, shall be permitted to be unprotected without restriction of either aggregate area or separation from one another.
In each dwelling unit or fire area, where both portions of ceilings and portions of walls are unprotected, the total allowable unprotected area shall be determined in accordance with Equations 6-1.
|
(Utc/Uac) + (Utw/Uaw) ≤ 1
|
(Equation 6-1)
|
| where: | |
| Utc = Total unprotected mass timber ceiling areas | |
|
Uac = Allowable unprotected mass timber ceiling area conforming to Exception 1.1 of Section 602.4.2.2.2.
|
|
| Utw = Total unprotected mass timber wall areas | |
|
Uaw = Allowable unprotected mass timber wall area conforming to Exception 1.2 of Section 602.4.2.2.2.
|
|
In each
dwelling unit or fire area, unprotected portions of mass timber walls and ceilings shall be
not less than 15 feet (4572 mm) from unprotected portions of other walls and ceilings,
measured horizontally along the ceiling and from other unprotected portions of walls
measure horizontally along the floor.
The floor assembly shall contain a noncombustible material not less than 1
inch (25 mm) in thickness above the mass timber. Floor finishes in accordance with Section
804 shall be permitted on top of the noncombustible material. The underside of floor
assemblies shall be protected in accordance with Section 602.4.1.2.
The interior surfaces of roof assemblies shall be protected in accordance
with Section 602.4.2.2 except, in nonoccupiable spaces, they shall be treated as a concealed
space with no portion left unprotected. Roof coverings in accordance with Chapter 15 shall
be permitted on the outside surface of the roof assembly.
Concealed spaces shall not contain combustibles other than
electrical, mechanical, fire protection, or plumbing materials and equipment permitted in plenums in accordance with Section 602 of the International Mechanical Code, and shall
comply with all applicable provisions of Section 718. Combustible construction forming
concealed spaces shall be protected in accordance with Section 602.4.1.2.
Shafts shall be permitted in accordance with Section 713 and Section 718.
Both the shaft side and room side of mass timber elements shall be protected in accordance
with Section 602.4.1.2.
Building elements in Type IV-C construction shall be protected in
accordance with Sections 602.4.3.1 through 602.4.3.6. The required fire resistance rating of
building elements shall be determined in accordance with Section 703.2 or Section 703.3.
The exterior side of walls of combustible construction shall be protected with noncombustible protection with a minimum assigned time of 40 minutes as determined in Table 722.7.1(1). Components of the exterior wall covering shall be of noncombustible material except water resistive barriers having a peak heat release rate of less than 150 kW/m2, a total heat release of less than 20 MJ/m2 and an effective heat of combustion of less than 18 MJ/kg as determined in accordance with ASTM E1354 and having a flame spread index of 25 or less and a smoke-developed index of 450 or less as determined in accordance with ASTM E84 or UL 723. The ASTM E1354 test shall be conducted on specimens at the thickness intended for use, in the horizontal orientation and at an incident radiant heat flux of 50 kW/m2.
Mass timber elements are permitted to be unprotected.
Floor finishes in accordance with Section 804 shall be permitted on top of
the floor construction.
Roof coverings in accordance with Chapter 15 shall be permitted on the
outside surface of the roof assembly.
Concealed spaces shall not contain combustibles other than
electrical, mechanical, fire protection, or plumbing materials and equipment permitted in
plenums in accordance with Section 602 of the International Mechanical Code, and shall
comply with all applicable provisions of Section 718. Combustible construction forming
concealed spaces shall be protected with noncombustible protection with a minimum
assigned time of 40 minutes as specified in Table 722.7.1(1).
Shafts shall be permitted in accordance with Section 713 and 718. Shafts
and elevator hoistway and interior exit stairway enclosures shall be protected with
noncombustible protection with a minimum assigned time of 40 minutes as specified in
Table 722.7.1(1), on both the inside of the shaft and the outside of the shaft.
Type IV-HT (Heavy Timber) construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of solid wood, laminated heavy timber or structural composite lumber (SCL), without concealed spaces. The minimum dimensions for permitted materials including solid timber, glued-laminated timber, structural composite lumber (SCL) and cross laminated timber (CLT) and details of Type IV construction shall comply with the provisions of this section and Section 2304.11. Exterior walls complying with Section 602.4.4.1 or 602.4.4.2 shall be permitted. Interior walls and partitions not less than 1-hour fire resistance rating or heavy timber conforming with Section 2304.11.2.2 shall be permitted.
Fire-retardant-treated wood framing and sheathing complying with Section 2303.2 shall be permitted within exterior wall assemblies not less than 6 inches (152 mm) in thickness with a 2-hour rating or less.
Cross-laminated timber complying with Section 2303.1.4 shall be permitted within exterior wall assemblies not less than 6 inches (152 mm) in thickness with a 2-hour rating or less, provided the exterior surface of the cross-laminated timber is protected by one of the following:
- Fire-retardant-treated wood sheathing complying with Section 2303.2 and not less than 15/32 inch (12 mm) thick; or
- Gypsum board not less than 1/2 inch (12.7 mm) thick; or
- A noncombustible material.
Where a horizontal separation of 20 feet
(6096 mm) or more is provided, wood columns and arches conforming to heavy timber sizes
complying with Section 2304.11 shall be permitted to be used externally.
Type V construction is that type of construction in which the structural elements, exterior walls and interior walls are of any materials permitted by this code.
Upcodes Diagrams
Combustible materials shall be permitted in buildings of Type I or II construction in the following applications and in accordance with Sections 603.1.1 through 603.1.3:
- Fire-retardant-treated wood shall be permitted in:
- Nonbearing partitions where the required fire-resistance rating is 2 hours or less.
- Nonbearing exterior walls where fire-resistance-rated construction is not required.
- Roof construction, including girders, trusses, framing and decking.
Exception: In buildings of Type IA construction exceeding two stories above grade plane, fire-retardant-treated wood is not permitted in roof construction where the vertical distance from the upper floor to the roof is less than 20 feet (6096 mm).
- Balconies, porches, decks and exterior stairways not used as required exits on buildings three stories or less above grade plane.
- Thermal and acoustical insulation, other than foam plastics, having a flame spread index of not more than 25.
Exceptions:
- Insulation placed between two layers of noncombustible materials without an intervening airspace shall be allowed to have a flame spread index of not more than 100.
- Insulation installed between a finished floor and solid decking without intervening airspace shall be allowed to have a flame spread index of not more than 200.
- Foam plastics in accordance with Chapter 26.
- Roof coverings that have an A, B or C classification.
- Interior floor finish and floor covering materials installed in accordance with Section 804.
- Millwork such as doors, door frames, window sashes and frames.
- Interior wall and ceiling finishes installed in accordance with Section 803.
- Trim installed in accordance with Section 806.
- Where not installed greater than 15 feet (4572 mm) above grade, show windows, nailing or furring strips and wooden bulkheads below show windows, including their frames, aprons and show cases.
- Finish flooring installed in accordance with Section 805.
- Partitions dividing portions of stores, offices or similar places occupied by one tenant only and that do not establish a corridor serving an occupant load of 30 or more shall be permitted to be constructed of fire-retardant-treated wood, 1-hour fire-resistance-rated construction or of wood panels or similar light construction up to 6 feet (1829 mm) in height.
- Stages and platforms constructed in accordance with Sections 410.2 and 410.3, respectively.
- Combustible exterior wall coverings, balconies and similar projections and bay or oriel windows in accordance with Chapter 14 and Section 705.2.3.1.
- Blocking such as for handrails, millwork, cabinets and window and door frames.
- Light-transmitting plastics as permitted by Chapter 26.
- Mastics and caulking materials applied to provide flexible seals between components of exterior wall construction.
- Exterior plastic veneer installed in accordance with Section 2605.2.
- Nailing or furring strips as permitted by Section 803.15.
- Heavy timber as permitted by Note c to Table 601 and Sections 602.4.3 and 705.2.3.1.
- Aggregates, component materials and admixtures as permitted by Section 703.2.2.
- Sprayed fire-resistant materials and intumescent and mastic fire-resistant coatings, determined on the basis of fire resistance tests in accordance with Section 703.2 and installed in accordance with Sections 1705.14 and 1705.15, respectively.
- Materials used to protect penetrations in fire-resistance-rated assemblies in accordance with Section 714.
- Materials used to protect joints in fire-resistance-rated assemblies in accordance with Section 715.
- Materials allowed in the concealed spaces of buildings of Types I and II construction in accordance with Section 718.5.
- Materials exposed within plenums complying with Section 602 of the International Mechanical Code.
- Wall construction of freezers and coolers of less than 1,000 square feet (92.9 m2), in size, lined on both sides with noncombustible materials and the building is protected throughout with an automatic sprinkler system in accordance with Section 903.3.1.1.
The use of nonmetallic ducts shall be permitted where installed in accordance with the limitations of the International Mechanical Code.
The use of combustible piping materials shall be permitted where installed in accordance with the limitations of the International Mechanical Code and the International Plumbing Code.
The use of electrical wiring methods with combustible insulation, tubing, raceways and related components shall be permitted where installed in accordance with the limitations of this code.