CBC · California Building Code

Combustible materials allowed in Types I & II

This hub explains the CBC’s limited, conditional allowances for combustible materials in otherwise noncombustible Type I and II construction and points to the controlling sections.

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Last reviewed: July 5, 2026

Overview

Types I and II are primarily noncombustible construction types, but the California Building Code permits specific combustible materials and assemblies in limited applications. The principal allowance is collected in §603.1, which authorizes items such as fire‑retardant‑treated wood (per §2303.2) for certain nonbearing partitions, some roof elements and limited exterior projections, plus restricted insulation, trim, millwork and similar components when installed in accordance with the code and its exceptions . The definition of Types I and II and the baseline noncombustible requirement appear at §602.2 and related provisions in Chapter 6 .

These allowances come with limits tied to fire‑resistance ratings, occupancy (for example Group I‑2 exceptions), building height and fire separation distance. Exterior combustible coverings and projections are further constrained by Chapter 14 (notably §1405.1.1 for exterior wall coverings) and by the projection rules in §705.2.3, which require noncombustible materials, rated construction, heavy timber, or fire‑retardant‑treated wood under prescribed conditions . Concealed spaces in Types I and II generally prohibit combustible materials except as explicitly allowed by §603 or other limited provisions, and sprinkler or draftstopping requirements may apply where combustibles are present .

In this section

Code references

Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:

  • CBC § 603.1.1 High relevance — show source text

    ** 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 complying with Section 2303.2 shall be permitted in: 1.1. Nonbearing partitions where the required fire-resistance rating is 2 hours or less except in shaft enclosures within Group I-2 occupancies and ambulatory care facilities. 1.2. Nonbearing exterior walls where fire-resistance-rated construction is not required. 1.3. Roof construction, including girders, trusses, framing and decking. Exceptions:

    2. 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).

    3. Group I-2, roof construction containing fire-retardant-treated wood shall be covered by not less than a Class A roof covering or roof assembly, and the roof assembly shall have a fire-resistance rating where required by the construction type. 1.4. Balconies, porches, decks and exterior stairways not used as required exits on buildings three stories or less above grade plane.

    4. Thermal and acoustical insulation, other than foam plastics, having a flame spread index of not more than 25. Exceptions:

    5. 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.

    6. 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.

    7. Foam plastics in accordance with Chapter 26.

    8. Roof coverings that have an A, B or C classification.

    9. Interior floor finish and floor covering materials installed in accordance with Section 804.

    10. Millwork such as doors, door frames, window sashes and frames.

    11. Interior wall and ceiling finishes installed in accordance with Section 803.

    12. Trim installed in accordance with Section 806.6.

    13. 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.

    14. Finish flooring installed in accordance with Section 805.

    15. 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 complying with Section 2303.2, 1-hour fire-resistance-rated construction or of wood panels or similar light construction up to 6 feet (1829 mm) in height.

    16. Stages and platforms constructed in accordance with Sections 410.2 and 410.3, respectively.

    17. Combustible exterior wall coverings, balconies and similar projections and bay or oriel windows in accordance with Chapter 14 and Section 705.2.3.1.

    18. Blocking such as for handrails, millwork, cabinets and window and door frames.

    19. Light-transmitting plastics as permitted by Chapter 26.

    20. Mastics and caulking materials applied to provide flexible seals between components of exterior wall construction.

    21. Exterior plastic veneer installed in accordance with Section 2605.2.

    22. Nailing or furring strips as permitted by Section 803.15.

  • CBC § 602.4.4.3 High relevance — show source text
    1. A noncombustible material.

    602.4.4.3 Concealed spaces. Concealed spaces shall not contain combustible materials other than building elements and electrical, mechanical, fire protection, or plumbing materials and equipment permitted in plenums in accordance with the California Mechanical Code . Concealed spaces shall comply with applicable provisions of Section 718. Concealed spaces shall be protected in accordance with one or more of the following:

    1. The building shall be sprinklered throughout in accordance with Section 903.3.1.1 and automatic sprinklers shall also be provided in the concealed space.
    2. The concealed space shall be completely filled with noncombustible insulation.

    6-6 2025 CALIFORNIA BUILDING CODE

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    TYPES OF CONSTRUCTION

    1. Combustible surfaces within the concealed space shall be fully sheathed with not less than [5] / 8 -inch Type X gypsum board.

    Exception: Concealed spaces within interior walls and partitions with a 1-hour or greater fire-resistance rating complying with Section 2304.11.2.2 shall not require additional protection.

    602.4.4.4 Exterior structural members. Where a fire separation distance 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.

    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 complying with Section 2303.2 shall be permitted in: 1.1. Nonbearing partitions where the required fire-resistance rating is 2 hours or less except in shaft enclosures within Group I-2 occupancies and ambulatory care facilities. 1.2. Nonbearing exterior walls where fire-resistance-rated construction is not required. 1.3. Roof construction, including girders, trusses, framing and decking. Exceptions:
    2. 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).
    3. Group I-2, roof construction containing fire-retardant-treated wood shall be covered by not less than a Class A roof covering or roof assembly, and the roof assembly shall have a fire-resistance rating where required by the construction type. 1.4. Balconies, porches, decks and exterior stairways not used as required exits on buildings three stories or less above grade plane.
    4. Thermal and acoustical insulation, other than foam plastics, having a flame spread index of not more than 25. Exceptions:
    5. 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.
    6. 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.
    7. Foam plastics in accordance with Chapter 26.
  • CBC § 705.1 High relevance — show source text

    SECTION 705—EXTERIOR WALLS

    705.1 General. Exterior walls shall comply with this section.

    705.2 Projections. Cornices, eave overhangs, exterior balconies and similar projections extending beyond the exterior wall shall conform to the requirements of this section and Section 1405. Exterior egress balconies and exterior exit stairways and ramps shall comply with Sections 1021 and 1027, respectively. Projections shall not extend any closer to the line used to determine the fire separation distance than shown in Table 705.2.

    Exception: Buildings on the same lot and considered as portions of one building in accordance with Section 705.3 are not required to comply with this section for projections between the buildings.

    TABLE 705.2—MINIMUM DISTANCE OF PROJECTION Col2
    FIRE SEPARATION DISTANCE (FSD) (feet) MINIMUM DISTANCE FROM LINE USED TO DETERMINE FSD
    0 to less than 2 Projections not permitted
    2 to less than 3 24 inches
    3 to less than 5 Two-thirds of FSD
    5 or greater 40 inches
    For SI: 1 foot = 304.8 mm; 1 inch = 25.4 mm. For SI: 1 foot = 304.8 mm; 1 inch = 25.4 mm.

    705.2.1 Types I and II construction. Projections from walls of Type I or II construction shall be of noncombustible materials or combustible materials as allowed by Sections 705.2.3.1 and 705.2.4.

    705.2.2 Type III, IV or V construction. Projections from walls of Type III, IV or V construction shall be of any approved material.

    705.2.3 Projection protection. Projections extending to 5 feet (1524 mm) or less from the line used to determine the fire separation distance shall be one of the following:

    1. Noncombustible materials.

    2. Combustible materials of not less than 1-hour fire-resistance-rated construction.

    3. Heavy timber construction complying with Section 2304.11.

    4. Fire-retardant-treated wood.

    5. As permitted by Section 705.2.3.1.

    Exception: Type VB construction shall be allowed for combustible projections in Group R-3 and U occupancies with a fire separation distance greater than or equal to 5 feet (1524 mm).

    7-6 2025 CALIFORNIA BUILDING CODE

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    FIRE AND SMOKE PROTECTION FEATURES

    705.2.3.1 Balconies and similar projections. Balconies and similar projections of combustible construction other than fireretardant-treated wood shall be fire-resistance rated where required by Table 601 for floor construction or shall be of heavy timber construction in accordance with Section 2304.11. The aggregate length of the projections shall not exceed 50 percent of the building’s perimeter on each floor.

  • CBC § 5-8 High relevance — show source text

    505 Mezzanines and Equipment Platforms. . . . . . . . . . . . 5-8

    506 Building Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

    507 Unlimited Area Buildings. . . . . . . . . . . . . . . . . . . . . . . 5-13

    508 Mixed Use and Occupancy. . . . . . . . . . . . . . . . . . . . . . 5-15

    509 Incidental Uses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

    510 Special Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-19

    CHAPTER 6 TYPES OF CONSTRUCTION . . . . . . . . . . . . . . . 6-1

    601 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

    602 Construction Classification. . . . . . . . . . . . . . . . . . . . . . 6-3

    603 Combustible Material in Types I and II Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

    CHAPTER 7 FIRE AND SMOKE PROTECTION FEATURES. . 7-1

    701 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3

    702 Multiple-Use Fire Assemblies . . . . . . . . . . . . . . . . . . . . 7-3

    703 Fire-Resistance Ratings and Fire Tests . . . . . . . . . . . . 7-3

    704 Fire-Resistance Rating of Structural Members . . . . . 7-4

    705 Exterior Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

    706 Fire Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-12

    707 Fire Barriers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-14

    708 Fire Partitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16

    709 Smoke Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-17

    710 Smoke Partitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-18

    711 Floor and Roof Assemblies. . . . . . . . . . . . . . . . . . . . . . 7-19

  • CBC § 705.2.1 High relevance — show source text

    705.2.1 Types I and II construction. Projections from walls of Type I or II construction shall be of noncombustible materials or combustible materials as allowed by Sections 705.2.3.1 and 705.2.4.

    705.2.2 Type III, IV or V construction. Projections from walls of Type III, IV or V construction shall be of any approved material.

    705.2.3 Projection protection. Projections extending to 5 feet (1524 mm) or less from the line used to determine the fire separation distance shall be one of the following:

    1. Noncombustible materials.

    2. Combustible materials of not less than 1-hour fire-resistance-rated construction.

    3. Heavy timber construction complying with Section 2304.11.

    4. Fire-retardant-treated wood.

    5. As permitted by Section 705.2.3.1.

    Exception: Type VB construction shall be allowed for combustible projections in Group R-3 and U occupancies with a fire separation distance greater than or equal to 5 feet (1524 mm).

    7-6 2025 CALIFORNIA BUILDING CODE

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    FIRE AND SMOKE PROTECTION FEATURES

    705.2.3.1 Balconies and similar projections. Balconies and similar projections of combustible construction other than fireretardant-treated wood shall be fire-resistance rated where required by Table 601 for floor construction or shall be of heavy timber construction in accordance with Section 2304.11. The aggregate length of the projections shall not exceed 50 percent of the building’s perimeter on each floor.

    Exceptions:

    1. On buildings of Types I and II construction, three stories or less above grade plane, fire-retardant-treated wood shall be permitted for balconies, porches, decks and exterior stairways not used as required exits.

    2. Untreated wood and plastic composites that comply with ASTM D7032 and Section 2612 are permitted for pickets, rails and similar guard components that are limited to 42 inches (1067 mm) in height.

    3. Balconies and similar projections on buildings of Types III, IV-HT and V construction shall be permitted to be of Type V construction and shall not be required to have a fire-resistance rating where sprinkler protection is extended to these areas.

    4. Where sprinkler protection is extended to the balcony areas, the aggregate length of the balcony on each floor shall not be limited.

    705.2.3.2 Vents. [SFM] Vents required by Section 2304.12.2.5 in fire-rated exterior balconies or elevated walkway surfaces shall be designed where the voids created at the intersection of the exterior curtain wall and the balcony floor are sealed with an approved material or system to retard the interior spread of flame, hot gases and products of combustion. Rated assemblies shall comply with Section 715. Ventilation openings shall comply with the fire sprinkler protection as required by Section 903.3.1.1 or 903.3.1.2 and the reference standard.

    705.2.4 Bay and oriel windows. Bay and oriel windows constructed of combustible materials shall conform to the type of construction required for the building to which they are attached.

    Exception: Fire-retardant-treated wood shall be permitted on buildings three stories or less above grade plane of Type I, II, III or IV construction.

  • CBC § 718.4 High relevance — show source text

    718.4 Draftstops in attics. Draftstops shall be installed to subdivide attic spaces where required by Section 708.4.3. In other than Group R, draftstops shall be installed to subdivide combustible attic spaces and combustible concealed roof spaces such that any horizontal area does not exceed 3,000 square feet (279 m [2] ). Ventilation of concealed roof spaces shall be maintained in accordance with Section 1202.2.1.

    Exception: Buildings equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1.

    718.4.1 Draftstops material. Materials utilized for draftstops of attic spaces shall comply with Section 718.3.1.

    718.4.1.1 Openings. Openings in the partitions shall be protected by self-closing doors with automatic latches constructed as required for the partitions.

    718.5 Combustible materials in concealed spaces in Type I or II construction. Combustible materials shall not be permitted in concealed spaces of buildings of Type I or II construction.

    Exceptions:

    1. Combustible materials in accordance with Section 603.

    2. Combustible materials exposed within plenums complying with the California Mechanical Code .

    3. Class A interior finish materials classified in accordance with Section 803.

    2025 CALIFORNIA BUILDING CODE 7-41

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    FIRE AND SMOKE PROTECTION FEATURES

    1. Combustible piping within partitions or shaft enclosures installed in accordance with the provisions of this code.
    2. Combustible piping within concealed ceiling spaces installed in accordance with the California Mechanical Code and the California Plumbing Code .
    3. Combustible insulation and covering on pipe and tubing, installed in concealed spaces other than plenums, complying with Section 720.7.

    SECTION 719—FIRE-RESISTANCE REQUIREMENTS FOR PLASTER

    719.1 Thickness of plaster. The minimum thickness of gypsum plaster or Portland cement plaster used in a fire-resistance-rated system shall be determined by the prescribed fire tests. The plaster thickness shall be measured from the face of the lath where applied to gypsum lath or metal lath. 719.2 Plaster equivalents. For fire-resistance purposes, [1] / 2 inch (12.7 mm) of unsanded gypsum plaster shall be deemed equivalent to [3] / 4 inch (19.1 mm) of one-to-three gypsum sand plaster or 1 inch (25 mm) of Portland cement sand plaster.

    719.3 Noncombustible furring. In buildings of Types I and II construction, plaster shall be applied directly on concrete or masonry or on approved noncombustible plastering base and furring.

    719.4 Double reinforcement. Plaster protection more than 1 inch (25 mm) in thickness shall be reinforced with an additional layer of approved lath embedded not less than [3] / 4 inch (19.1 mm) from the outer surface and fixed securely in place.

    Exception: Solid plaster partitions or where otherwise determined by fire tests.

  • CBC § 1404.19 High relevance — show source text

    [BS] 1404.19 Fiber-mat reinforced cementitious backer units. Fiber-mat reinforced cementitious backer units shall be permitted on exterior walls and shall meet the requirements of Section 1404.19.1.

    [BS] 1404.19.1 Installation. Installation of fiber-mat reinforced cementitious backer units used as an exterior substrate for the application of exterior finish materials shall be in accordance with backer unit manufacturer’s installation instructions. Panels shall be installed using corrosion-resistant fasteners. Finish materials shall be installed in accordance with approved finish material manufacturer’s instructions.

    SECTION 1405—COMBUSTIBLE MATERIALS ON THE EXTERIOR SIDE OF EXTERIOR WALLS

    1405.1 Combustible exterior wall coverings. Combustible exterior wall coverings shall comply with this section.

    Exception: Plastics complying with Chapter 26.

    1405.1.1 Types I, II, III and IV-HT construction. On buildings of Types I, II, III and IV-HT construction, exterior wall coverings shall be permitted to be constructed of combustible materials, complying with the following limitations:

    1. Combustible exterior wall coverings shall not exceed 10 percent of an exterior wall surface area where the fire separation distance is 5 feet (1524 mm) or less.
    2. Combustible exterior wall coverings shall be limited to 40 feet (12 192 mm) in height above grade plane. Exceptions:
    3. Metal composite material (MCM) systems complying with Section 1406.
    4. Exterior insulation and finish systems (EIFS) complying with Section 1407.
    5. High-pressure decorative exterior-grade compact laminate (HPL) systems complying with Section 1408.
    6. Exterior wall coverings containing foam plastic insulation complying with Section 2603.
    7. Combustible exterior wall coverings constructed of fire-retardant-treated wood complying with Section 2303.2 for exterior installation shall not be limited in wall surface area where the fire separation distance is 5 feet (1524 mm) or less and shall be permitted up to 60 feet (18 288 mm) in height above grade plane regardless of the fire separation distance.
    8. Wood veneers shall comply with Section 1404.6.

    1405.1.1.1 Ignition resistance. Where permitted by Section 1405.1.1, combustible exterior wall coverings shall be tested in accordance with NFPA 268.

    Exceptions:

    1. Wood or wood-based products.
    2. Other combustible materials covered with an exterior weather covering, other than vinyl sidings, included in and complying with the thickness requirements of Table 1404.2.
    3. Aluminum having a minimum thickness of 0.019 inch (0.48 mm).

    1405.1.1.1.1 Fire separation 5 feet or less. Where installed on exterior walls having a fire separation distance of 5 feet (1524 mm) or less, combustible exterior wall coverings shall not exhibit sustained flaming as defined in NFPA 268.

  • CBC § 2404.1 High relevance — show source text

    Vertical 2404.1 Walkways 2409.1 Grade (Adjacent Ground Elevation) 202 Grading Appendix J Grain Elevators 426.1.5

    Historic buildings G106.3 Interior finishes 802.4

    Manufactured homes G109

    Modifications 104.2.4.1

    Recreation vehicles G110

    Site improvements G108 Site plan 107.2.6 Subdivisions G107

    Tank G111

    Temporary G113 Utility G114 Floodway Appendix G, 1612.3 Floor Construction (see Floor Construction, Wood) Draftstopping 718.3 Finishes 804, 805, 1003.4, 1209.1 Fire resistance Table 601, 711 Loads (see Floor Loads) Materials Chapter 6 Penetration of fire-resistant

    assemblies 711, 714.5, 717.2, 717.6 Pipes and trenches 1809.15 Floor Construction, Wood Beams and girders 2304.12.1.1, 2308.8.1 Bridging/blocking 2308.8.6, 2308.11.7 Diaphragms 2305.1 Fastening schedule 2304.10.2 Framing 2304.4, 2304.11.1.2, 2304.11.3, Table 2304.11, 2308.8 Joists 2308.8.2 Sheathing 2304.8 Floor Level 1003.5, 1010.1.4 Floor Loads

    Construction documents 107.2

    Live 1603.1.1, 1607 Posting 106.1 Floor Opening Protection (see Vertical Opening Protection) Floor/Ceiling (see Floor Construction) Foam Plastics

    Attics 720.1, 2603.4.1.6 Cladding attachment 1404.5.1, 1404.5.2, 1404.5.3 Cold storage 2603.3, 2603.4.1.2, 2603.5

    Concealed 603 Covered mall and open mall buildings 402.6.2, 402.6.4.5 Crawl space 2603.4.1.6 Doors 2603.4.1.7, 2603.4.1.9 Exterior wall covering 806.6.1, Chapter 14 Exterior walls of multistory buildings 1403.12, 2603.5 Interior finish 2603.9, 2604 Label/identification 2603.2 Metal composite material (MCM) 1406.12

    Plenums 2603.7, 2604.1.1 Roofing 2603.4.1.5 Siding backer board 2603.4.1.10 Stages and platform scenery 410.2.6 Surface burning characteristics 2603.3 Termites, protection from 2603.8 Thermal barrier requirements 2603.5.2

    Trim 806.6.1, 2604.2 Type I and II construction 603.1

    Walk-in coolers 2603.4.1.3

  • CBC § 602.1 High relevance — show source text

    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 705.5. Where required to have a fire-resistance rating by Table 601, building elements shall comply with the applicable provisions of Section 703.2.

    2025 CALIFORNIA BUILDING CODE 6-3

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    TYPES OF CONSTRUCTION

    The protection of openings, ducts and air transfer openings in building elements shall not be required unless required by other provisions of this code.

    Exception: Noncombustible structural members supporting solar photovoltaic panels are not required to meet the fire resistance rating for the following: 1. Photovoltaic panel supported by a structure and having no use underneath. Signs may be provided, as determined by the enforcing agency prohibiting any use underneath including storage. 2. Solar photovoltaic (PV) panels supported by noncombustible framing that have sufficient uniformly distributed and unob- structed openings throughout the top of the array (horizontal plane) to allow heat and gases to escape, as determined by the enforcing agency. 3. Solar photovoltaic panels supported by a structure over parking stalls where the panels constitute the roof and all the following conditions are met (see Figure 5-1): 3.1. The area within the perimeter of the solar photovoltaic array has maximum rectangular dimension of 40 feet by 150 feet.

    3.2. The distance between solar photovoltaic array structures is a minimum of 10 feet clear. 3.3. The driveway aisle separating solar photovoltaic array structures has a minimum width of 25 feet clear. 3.4. Solar photovoltaic array structure is used only for parking purposes with no storage. 3.5. Completely open on all sides (other than necessary structural supports) with no interior partitions.

    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 specified in Table 601 are of noncombustible materials, except as permitted in Section 603 and elsewhere in this code.

    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.

    602.4 Type IV. 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.

  • CBC § 806.4 High relevance — show source text

    [F] 806.4 Acceptance criteria and reports. Where required to exhibit improved fire performance, curtains, draperies, fabric hangings and similar combustible decorative materials suspended from walls or ceilings shall be tested by an approved agency and shall be flame resistant in accordance with the provisions set forth in CCR, Title 19, Division 1, Chapter 8 . Reports of test results shall be prepared in accordance with the test method used and furnished to the building official on request.

    2025 CALIFORNIA BUILDING CODE 8-7

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    INTERIOR FINISHES

    [F] 806.5 Pyroxylin plastic. Imitation leather or other material consisting of or coated with a pyroxylin or similarly hazardous base shall not be used in Group A occupancies.

    [F] 806.6 Interior trim. Material, other than foam plastic used as interior trim, shall have a minimum Class B flame spread and 450 smoke-developed index in Group I-3 and for all other occupancies Class C flame spread and smoke-developed index when tested in accordance with ASTM E84 or UL 723, as described in Section 803.1.2. Combustible trim, excluding handrails and guardrails, shall not exceed 10 percent of the specific wall or ceiling area to which it is attached.

    [F] 806.6.1 Foam plastic. Foam plastic used as interior trim in any occupancy shall comply with Section 2604.2.

    [F] 806.7 Interior floor-wall base. Interior floor-wall base that is 6 inches (152 mm) or less in height shall be tested in accordance with Section 804.2 and shall be not less than Class II. Where a Class I floor finish is required, the floor-wall base shall be Class I.

    Exception: Interior trim materials that comply with Section 806.6.

    [F] 806.8 Combustible lockers. Where lockers constructed of combustible materials are used, the lockers shall be considered to be interior finish and shall comply with Section 803.

    Exception: Lockers constructed entirely of wood and noncombustible materials shall be permitted to be used wherever interior finish materials are required to meet a Class C classification in accordance with Section 803.1.2.

    SECTION 807—INSULATION

    807.1 Insulation. Thermal and acoustical insulation shall comply with Section 720.

    SECTION 808—ACOUSTICAL CEILING SYSTEMS

    808.1 Acoustical ceiling systems. The quality, design, fabrication and erection of metal suspension systems for acoustical tile and lay-in panel ceilings in buildings or structures shall conform to generally accepted engineering practice, the provisions of this chapter and other applicable requirements of this code.

    808.1.1 Materials and installation. Acoustical materials complying with the interior finish requirements of Section 803 shall be installed in accordance with the manufacturer’s recommendations and applicable provisions for applying interior finish.

    808.1.1.1 Suspended acoustical ceilings. Suspended acoustical ceiling systems shall be installed in accordance with the provisions of ASTM C635 and ASTM C636.

    808.1.1.2 Fire-resistance-rated construction. Acoustical ceiling systems that are part of fire-resistance-rated construction shall be installed in the same manner used in the assembly tested and shall comply with the provisions of Chapter 7.

  • CBC § 803.1.1.1 High relevance — show source text

    Exception: Where the interior trim material has been tested as an interior finish in accordance with NFPA 286 and complies with the acceptance criteria in Section 803.1.1.1, it is not required to be tested for flame spread index in accordance with ASTM E84 or UL 723.

    804.3 New interior floor finish. New interior floor finish and floor covering materials in new and existing buildings shall comply with Sections 804.3.1 through 804.3.3.2.

    Exception: Floor finishes and coverings of a traditional type, such as wood, vinyl, linoleum or terrazzo, and resilient floor covering materials that are not composed of fibers.

    804.3.1 Classification. Interior floor finish and floor covering materials required by Section 804.3.3.2 to be of Class I or II materials shall be classified in accordance with ASTM E648 or NFPA 253. The classification referred to herein corresponds to the classifications determined by ASTM E648 or NFPA 253 as follows: Class I, 0.45 watts/cm [2] or greater; Class II, 0.22 watts/cm [2] or greater.

    804.3.2 Testing and identification. Interior floor finish and floor covering materials shall be tested by an approved agency in accordance with ASTM E648 or NFPA 253 and identified by a hang tag or other suitable method so as to identify the manufacturer or supplier and style, and shall indicate the interior floor finish or floor covering classification in accordance with Section 804.3.1. Carpet-type floor coverings shall be tested as proposed for use, including underlayment. Test reports confirming the information provided in the manufacturer’s product identification shall be furnished to the fire code official upon request.

    804.3.3 Interior floor finish requirements. New interior floor covering materials shall comply with Sections 804.3.3.1 and 804.3.3.2, and interior floor finish materials shall comply with Section 804.3.1.

    804.3.3.1 Test requirement. In all occupancies, interior floor finish and interior floor covering materials shall comply with the requirements of ASTM Standard E648, and having a specific optical density smoke rating not to exceed 450 per ASTM E662. For Group I-3 occupancies and Group I-2 areas where patients are restrained, see Section 804.3.3.3.

    804.3.3.2 Minimum critical radiant flux. In all occupancies, new interior floor finish and floor covering materials in enclosures for stairways and ramps, exit passageways, corridors and rooms or spaces not separated from corridors by full-height partitions extending from the floor to the underside of the ceiling shall withstand a minimum critical radiant flux. The minimum critical radiant flux shall be not less than Class I in Groups I-2 and I-3 areas where restraint is not used and R-2.1 and not less than Class II in Groups A, B, E, H, I-4, M, R-1, R-2, R-2.2 and S.

    Exception: Where a building is equipped throughout with an automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2, Class II materials shall be permitted in any area where Class I materials are required and materials complying with ASTM Standard E648, and having a specific optical density smoke rating not to exceed 450 per ASTM E662 are permitted in any area where Class II materials are required.

  • CBC § 25-3 High relevance — show source text

    2503 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-3

    2504 Vertical and Horizontal Assemblies . . . . . . . . . . . . . . 25-4

    2505 Shear Wall Construction. . . . . . . . . . . . . . . . . . . . . . . . 25-4

    2506 Gypsum Panel Product Materials . . . . . . . . . . . . . . . . 25-4

    2507 Lathing and Plastering . . . . . . . . . . . . . . . . . . . . . . . . . 25-5

    xxviii 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    2508 Gypsum Construction . . . . . . . . . . . . . . . . . . . . . . . . . 25-6

    2509 Showers and Water Closets . . . . . . . . . . . . . . . . . . . . 25-7

    2510 Lathing and Furring for Cement Plaster (Stucco). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-7

    2511 Interior Plaster. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-8

    2512 Exterior Plaster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25-9

    2513 Exposed Aggregate Plaster. . . . . . . . . . . . . . . . . . . . 25-10

    2514 Reinforced Gypsum Concrete . . . . . . . . . . . . . . . . . 25-10

    CHAPTER 26 PLASTIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-1

    2601 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-3

    2602 Finish and Trim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-3

    2603 Foam Plastic Insulation. . . . . . . . . . . . . . . . . . . . . . . . 26-3

    2604 Interior Finish and Trim. . . . . . . . . . . . . . . . . . . . . . . . 26-7

    2605 Plastic Veneer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26-8

    2606 Light-Transmitting Plastics. . . . . . . . . . . . . . . . . . . . . 26-8

    2607 Light-Transmitting Plastic Wall Panels . . . . . . . . . . 26-9

Frequently asked questions

What combustible materials are specifically permitted in Type I and II construction?

The CBC lists specific permitted combustible items in §603.1—most notably fire‑retardant‑treated wood in defined locations (e.g., certain nonbearing partitions, some roof and balcony elements), limited thermal/acoustical insulation, trim, millwork, blocking and certain finish materials—each subject to the restrictions and exceptions in that section and related chapters .

Are combustibles allowed in concealed spaces of Type I/II buildings?

Combustible materials are generally not permitted in concealed spaces of Type I and II construction, except where expressly allowed by §603 or other limited provisions (and then usually only with conditions such as sprinklers, noncombustible sheathing or specific insulation criteria) .

Do exterior coverings and balconies have special limits?

Yes—combustible exterior wall coverings and projections are limited by area, height and fire separation distance (see §1405.1.1) and by the projection provisions in §705.2.3; fire‑retardant‑treated wood and other limited materials are permitted only where the code’s dimensional, rating and occupancy conditions are met .

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Related in the CBC

Classification & overview of Types of Construction

Fire‑resistance ratings and Type‑specific protections

Projections, balconies, bay windows and concealed spaces by construction type

Types of Construction

California Building Code