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Chapter 6 Types of Construction

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.

Section 601 General

TABLE 601
FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (HOURS)
BUILDING ELEMENT TYPE I TYPE II TYPE III TYPE IV TYPE V
A B A B A B HT A B
Primary structural framef (see Section 202) 3a, b 2a, b 1b 0 1b 0 HT 1b 0
Bearing walls
Exteriore, f
 3 2 1 0 2 2 2 1 0
Interior
 3a 2a 1 0 1 0 1/HT 1 0
Nonbearing walls and partitions
Exterior
 See Table 602
Nonbearing walls and partitions
Interiord
 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 HT 1 0
Roof construction and associated secondary members
(see Section 202)		 11/2b 1b, c 1b, c 0c 1b, c 0 HT 1b, c 0

For SI: 1 foot = 304.8 mm.
  1. 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.
  2. 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.
  3. In all occupancies, heavy timber complying with Section 2304.11 shall be allowed where a 1-hour or less fire-resistance rating is required.
  4. Not less than the fire-resistance rating required by other sections of this code.
  5. Not less than the fire-resistance rating based on fire separation distance (see Table 602).
  6. Not less than the fire-resistance rating as referenced in Section 704.10.
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601.1 Scope

The provisions of this chapter shall control the classification of buildings as to type of construction.

Section 602 Construction Classification

TABLE 602
FIRE-RESISTANCE RATING REQUIREMENTS FOR EXTERIOR WALLS BASED ON FIRE SEPARATION DISTANCEa, d, g
FIRE SEPARATION DISTANCE =
X (feet)		 TYPE OF CONSTRUCTION OCCUPANCY GROUP He OCCUPANCY
GROUP F-1, M, S-1f		 OCCUPANCY
GROUP A, B, E, F-2, I, Ri, S-2, Uh
X < 5b All 3 2 1
5 ≤ X < 10 IA 3 2 1
Others 2 1 1
10 ≤ X < 30 IA, IB 2 1 1c
IIB, VB 1 0 0
Others 1 1 1c
X ≥ 30 All 0 0 0

For SI: 1 foot = 304.8 mm.
  1. Load-bearing exterior walls shall also comply with the fire-resistance rating requirements of Table 601.
  2. See Section 706.1.1 for party walls.
  3. Open parking garages complying with Section 406 shall not be required to have a fire-resistance rating.
  4. 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.
  5. For special requirements for Group H occupancies, see Section 415.6.
  6. For special requirements for Group S aircraft hangars, see Section 412.3.1.
  7. 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.
  8. 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.
  9. 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.
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602.1 General

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.
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602.1.1 Minimum Requirements

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.

602.2 Types I and II

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.
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602.3 Type III

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.
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602.4 Type IV

Type IV 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 wood, heavy timber (HT) 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 and details of Type IV construction shall comply with the provisions of this section and Section 2304.11. Exterior walls complying with Section 602.4.1 or 602.4.2 shall be permitted. Interior walls and partitions not less than 1-hour fire-resistance rating or heavy timber complying with Section 2304.11.2.2 shall be permitted.
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602.4.1 Fire-Retardant-Treated Wood in Exterior Walls

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.

602.4.2 Cross-Laminated Timber in Exterior Walls

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 the following:
  1. Fire-retardant-treated wood sheathing complying with Section 2303.2 and not less than 15/32 inch (12 mm) thick;
  2. Gypsum board not less than 1/2 inch (12.7 mm) thick; or
  3. A noncombustible material.

602.4.3 Exterior Structural Members

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.

602.5 Type V

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.
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Section 603 Combustible Material in Types I and II Construction

603.1 Allowable Materials

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:
  1. Fire-retardant-treated wood shall be permitted in:
    1. Nonbearing partitions where the required fire-resistance rating is 2 hours or less.
    2. Nonbearing exterior walls where fire-resistance-rated construction is not required.
    3. 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).
    4. Balconies, porches, decks and exterior stairways not used as required exits on buildings three stories or less above grade plane.
  2. Thermal and acoustical insulation, other than foam plastics, having a flame spread index of not more than 25.
    Exceptions:
    1. 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.
    2. 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.
  3. Foam plastics in accordance with Chapter 26.
  4. Roof coverings that have an A, B or C classification.
  5. Interior floor finish and floor covering materials installed in accordance with Section 804.
  6. Millwork such as doors, door frames, window sashes and frames.
  7. Interior wall and ceiling finishes installed in accordance with Section 803.
  8. Trim installed in accordance with Section 806.
  9. 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.
  10. Finish flooring installed in accordance with Section 805.
  11. 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.
  12. Stages and platforms constructed in accordance with Sections 410.2 and 410.3, respectively.
  13. Combustible exterior wall coverings, balconies and similar projections and bay or oriel windows in accordance with Chapter 14 and Section 705.2.3.1.
  14. Blocking such as for handrails, millwork, cabinets and window and door frames.
  15. Light-transmitting plastics as permitted by Chapter 26.
  16. Mastics and caulking materials applied to provide flexible seals between components of exterior wall construction.
  17. Exterior plastic veneer installed in accordance with Section 2605.2.
  18. Nailing or furring strips as permitted by Section 803.15.
  19. Heavy timber as permitted by Note c to Table 601 and Sections 602.4.3 and 705.2.3.1.
  20. Aggregates, component materials and admixtures as permitted by Section 703.2.2.
  21. 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.
  22. Materials used to protect penetrations in fire-resistance-rated assemblies in accordance with Section 714.
  23. Materials used to protect joints in fire-resistance-rated assemblies in accordance with Section 715.
  24. Materials allowed in the concealed spaces of buildings of Types I and II construction in accordance with Section 718.5.
  25. Materials exposed within plenums complying with Section 602 of the International Mechanical Code.
  26. 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.

603.1.1 Ducts

The use of nonmetallic ducts shall be permitted where installed in accordance with the limitations of the International Mechanical Code.

603.1.2 Piping

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.

603.1.3 Electrical

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.