CHBC · California Historical Building Code
What are maximum floor area and height limits for qualified historical buildings?
For homeowners: a one‑story historic building is generally limited to 15,000 square feet unless you install a full automatic sprinkler system or (for small residential buildings) provide a complete fire alarm and compliant exits; multistory historic buildings and height are handled under the regular code but the CHBC won’t force you to reduce height below the building’s original historic design — see **§ 8‑302.4**, **§ 8‑302.5**, and **§ 8‑302.5.1** for the exact rules.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
The CHBC sets a hard cap on the size of a one‑story qualified historical building at 15,000 square feet unless another regular‑code allowance or a listed exception applies (§ 8‑302.4). Multistory qualified historical buildings (including basements and cellars) follow the regular code for area limits rather than the CHBC one‑story cap (§ 8‑302.4). The CHBC does not impose additional height or story limits based on construction type so long as the building’s height/number of stories does not exceed its historical design (§ 8‑302.5). For certain high‑rise occupancies the CHBC allows partial sprinklering above 75 feet if specific conditions are met (§ 8‑302.5.1) .
The single most important rule: a one‑story qualified historical building is limited to 15,000 ft² unless you use one of the CHBC exceptions (sprinklers or limited residential conditions) — § 8‑302.4.
Requirements in detail
One‑story floor‑area limit
- The CHBC caps the floor area of a one‑story qualified historical building at 15,000 square feet (1393.5 m²) unless an increase is allowed by the regular code (§ 8‑302.4).
- If the building is not one‑story (i.e., has more than one story, or includes basements/cellars counted as stories), area rules from the regular code apply instead (§ 8‑302.4).
Exceptions that remove the 15,000 ft² limit
- Unlimited area without fire‑resistive area separation walls is permitted when:
- an automatic sprinkler system is provided throughout the building, or
- the building is a residential occupancy of two stories or less, provided there is a complete fire alarm and annunciation system and the exiting conforms to the regular code (§ 8‑302.4).
Height and stories
- The CHBC does not limit maximum height or number of stories because of construction type, provided the height/stories do not exceed the building’s historical design. In short: you cannot be made to reduce height beyond the original historic configuration solely because of construction type under the CHBC (§ 8‑302.5) .
High‑rise special provision (stories over 75 ft)
- For occupancies B, F‑1, F‑2, or S in high‑rise buildings, the CHBC permits only the stories above 75 feet (measured from the lowest floor level with building access) to be sprinklered (instead of the entire building) if all three conditions below are met (§ 8‑302.5.1):
- Building construction type and exits conform to the regular code;
- A complete building fire alarm and annunciation system is installed; and
- A fire barrier separates the sprinklered and nonsprinklered floors.
Decision‑relevant summary (quick reference table)
| Decision factor | Limit / Requirement | When it applies | Code Reference |
|---|---|---|---|
| One‑story area cap | 15,000 ft² | One‑story qualified historical buildings | § 8‑302.4 |
| Multistory area | Follow regular code (including basements/cellars) | Multistory qualified historical buildings | § 8‑302.4 |
| Unlimited area (no separation walls) | Allowed if an automatic sprinkler is provided | Any historical building meeting sprinkler requirement | § 8‑302.4 (Exception 1) |
| Unlimited area (residential) | Allowed for residential occupancies ≤ 2 stories with complete fire alarm/annunciation and regular‑code exiting | Residential historic buildings of 1–2 stories | § 8‑302.4 (Exception 2) |
| Height / stories | Not limited by construction type; may not exceed historical design | All qualified historical buildings | § 8‑302.5 |
| High‑rise partial sprinklering | Stories > 75 ft may be sprinklered only (not whole building) if 3 conditions met | Occupancies B, F‑1, F‑2, S in high‑rise buildings | § 8‑302.5.1 |
Exceptions & special cases
- Automatic sprinklers remove the CHBC one‑story area cap; however, the CHBC cross‑references sprinkler and alarm requirements elsewhere (see related provisions below) — confirm the sprinkler standard and documentation required with the enforcing agency (§ 8‑302.4) .
- A historic property that is converted to a multistory use (or that already has multiple stories including basements) is evaluated under the regular code for allowable area — the CHBC one‑story cap does not apply (§ 8‑302.4) .
- For high‑rise situations, the CHBC allows a compromise (sprinklering only the floors above 75 ft) but only for the specific occupancies named and only if construction/exits comply with regular code, a full building alarm/annunciation is installed, and a fire barrier is provided between sprinklered and nonsprinklered areas (§ 8‑302.5.1) .
Common mistakes
- Assuming every historic building can be unlimited in area by default — the 15,000 ft² cap applies to one‑story historic buildings unless an exception is met (§ 8‑302.4) .
- Treating a building with a basement or cellar as “one‑story” for area limits — basements and cellars count for the multistory determination and that triggers regular‑code area rules (§ 8‑302.4) .
- Overlooking the requirement that height under the CHBC cannot exceed the building’s historical design; owners sometimes try to add stories beyond the historic configuration under CHBC protections — that is not permitted by § 8‑302.5 .
- For high‑rise occupancies, assuming partial sprinklering is automatic — the three conditions in § 8‑302.5.1 must all be satisfied and verified by the enforcing agency .
Worked example — concrete scenario
Scenario A — One‑story historic mercantile building:
- Existing building: single story, historical footprint = 20,000 ft².
- CHBC baseline: one‑story cap = 15,000 ft², so the building exceeds the CHBC one‑story limit (§ 8‑302.4) .
Options:
- Install an automatic sprinkler system throughout the building: the CHBC exception allows unlimited floor area without fire‑resistive area separation walls once fully sprinklered (Exception 1 to § 8‑302.4) .
- If the building were a residential occupancy of two stories or less, adding a complete fire alarm and annunciation system and bringing exiting into conformity with the regular code could also remove the cap (Exception 2 to § 8‑302.4) .
- If neither exception is feasible, the enforcing agency will require the project to meet regular code area allowances for multistory or limit usable area to 15,000 ft².
Scenario B — Ten‑story historic office (Group B) with top floors above 75 ft:
- Occupancy: Group B, some floors above 75 ft. The CHBC allows those floors over 75 ft to be the only sprinklered floors (instead of sprinkling the whole building) provided: 1) construction type and exits conform to regular code, 2) a complete building fire alarm and annunciation system is installed, and 3) a fire barrier separates the sprinklered and nonsprinklered floors (§ 8‑302.5.1) .
- Practical step: verify compliance with regular‑code construction/egress requirements and design the fire barrier and building alarm system before relying on the partial‑sprinkler approach.
Related provisions
- § 8‑410.2 — Automatic sprinkler system requirements referenced by CHBC exceptions (see CHBC sprinkler chapter) .
- § 8‑410.3 — Limitations on using sprinklers as a substitute for required exits (see CHBC fire protection) .
- § 8‑302.6 — Fire‑resistive construction (see Chapter 8‑4) referenced by area/exception rules .
- § 8‑302.7 — Light and ventilation allowances for existing historic provisions .
- § 8‑412 — CHBC guidance where historic buildings have floors located more than 75 feet above access; coordination with regular code for existing high‑rise buildings .
- SECTION 8‑2 (Definitions) — Definitions such as addition, alteration, and terms used in Chapter 8 that affect scope and interpretation .
Code references
Grounded in the retrieved California Historical Building Code — click a citation to read the verbatim passage:
CHBC § 8-302.3 High relevance — show source text
8-302.3 Occupancy separations. Required occupancy separations of more than one hour may be reduced to one-hour fire-resistive construction with all openings protected by not less than three-fourths-hour fire-resistive assemblies of the self-closing or automatic-closing type when the building is provided with an automatic sprinkler system throughout the entire building in accordance with Section 8-410.2. Doors equipped with automatic-closing devices shall be of a type which will function upon activation of a device which responds to products of combustion other than heat.
Required occupancy separations of one hour may be omitted when the building is provided with an automatic sprinkler system throughout.
8-302.4 Maximum floor area. Regardless of the use or character of occupancy, the area of a one-story qualified historical building or property may have, but shall not exceed, a floor area of 15,000 square feet (1393.5 m [2] ) unless such an increase is otherwise permitted in regular code. Multistory qualified historical buildings (including basements and cellars) shall be in accordance with regular code requirements.
Exception: Historical buildings may be unlimited in floor area without fire-resistive area separation walls:
- When provided with an automatic sprinkler, or
- Residential occupancies of two stories or less when provided with a complete fire alarm and annunciation system and where the exiting system conforms to regular code.
8-302.5 Maximum height. The maximum height and number of stories of a qualified historical building or property shall not be limited because of construction type, provided such height or number of stories does not exceed that of its historical design.
8-302.5.1 High-rise buildings. Occupancies B, F-1, F-2 or S in high-rise buildings with floors located more than 75 feet above the lowest floor level having building access may be permitted with only the stories over 75 feet provided with an automatic fire sprinkler system if:
- The building construction type and the exits conform to regular code, and
- A complete building fire alarm and annunciation system is installed, and
- A fire barrier is provided between the sprinklered and nonsprinklered floors.
8-302.6 Fire-resistive construction. See Chapter 8-4.
8-302.7 Light and ventilation. Existing provisions for light and ventilation which do not, in the opinion of the enforcing agency, constitute a safety hazard may remain. See Section 8-303.6 for residential requirements. See Section 8-503 for Escape or Rescue Windows and Doors.
SECTION 8-303 — RESIDENTIAL OCCUPANCIES
8-303.1 Purpose. The purpose of this section is to provide regulations for those buildings designated as qualified historical buildings or properties and classified as residential occupancies. The CHBC requires enforcing agencies to accept any reasonably equivalent alternative to the regular code when dealing with qualified historical buildings and properties.
8-303.2 Intent. The intent of the CHBC is to preserve the integrity of qualified historical buildings and properties while maintaining a reasonable degree of protection of life, health and safety for the occupants.
8-303.3 Application and scope. The provisions of this section shall apply to all qualified historical buildings used for human habitation. Those dwelling units intended only for display, or public use with no residential use involved, need not comply with the requirements of this section.
8-303.4 Fire escapes. See Chapter 8-5.
2025 CALIFORNIA HISTORICAL BUILDING CODE 5
CHBC § 8-3 High relevance — show source text
TREATMENT. An act of work to carry out preservation, restoration, stabilization, rehabilitation or reconstruction.
4 2025 CALIFORNIA HISTORICAL BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
8-3 USE AND OCCUPANCY
SECTION 8-301 — PURPOSE AND SCOPE
8-301.1 Purpose. The purpose of the CHBC is to provide regulations for the determination of occupancy classifications and conditions of use for qualified historical buildings or properties.
8-301.2 Scope. Every qualified historical building or property for which a permit or approval has been requested shall be classified prior to permit issuance according to its use or the character of its occupancy in accordance with the regular code and applicable provisions of this chapter.
SECTION 8-302 — GENERAL
8-302.1 Existing use. The use or character of occupancy of a qualified historical building or property, or portion thereof, shall be permitted to continue in use regardless of any period of time in which it may have remained unoccupied or in other uses, provided such building or property otherwise conforms to all applicable requirements of the CHBC.
8-302.2 Change in occupancy. The use or character of the occupancy of a qualified historical building or property may be changed from or returned to its historical use or character, provided the qualified historical building or property conforms to the requirements applicable to the new use or character of occupancy as set forth in the CHBC. Such change in occupancy shall not mandate conformance with new construction requirements as set forth in regular code.
8-302.3 Occupancy separations. Required occupancy separations of more than one hour may be reduced to one-hour fire-resistive construction with all openings protected by not less than three-fourths-hour fire-resistive assemblies of the self-closing or automatic-closing type when the building is provided with an automatic sprinkler system throughout the entire building in accordance with Section 8-410.2. Doors equipped with automatic-closing devices shall be of a type which will function upon activation of a device which responds to products of combustion other than heat.
Required occupancy separations of one hour may be omitted when the building is provided with an automatic sprinkler system throughout.
8-302.4 Maximum floor area. Regardless of the use or character of occupancy, the area of a one-story qualified historical building or property may have, but shall not exceed, a floor area of 15,000 square feet (1393.5 m [2] ) unless such an increase is otherwise permitted in regular code. Multistory qualified historical buildings (including basements and cellars) shall be in accordance with regular code requirements.
Exception: Historical buildings may be unlimited in floor area without fire-resistive area separation walls:
- When provided with an automatic sprinkler, or
- Residential occupancies of two stories or less when provided with a complete fire alarm and annunciation system and where the exiting system conforms to regular code.
8-302.5 Maximum height. The maximum height and number of stories of a qualified historical building or property shall not be limited because of construction type, provided such height or number of stories does not exceed that of its historical design.
CHBC § 406.5.4.1 Medium relevance — show source text
0929 m2.|
406.5.4.1 Single use. Where the open parking garage is used exclusively for the parking or storage of private motor vehicles, and the building is without other uses, the area and height shall be permitted to comply with Table 406.5.4, along with increases allowed by Section 406.5.5.
Exception: The grade-level tier is permitted to contain an office, waiting and toilet rooms having a total combined area of not more than 1,000 square feet (93 m [2] ). Such area need not be separated from the open parking garage.
In open parking garages having a spiral or sloping floor, the horizontal projection of the structure at any cross section shall not exceed the allowable area per parking tier. In the case of an open parking garage having a continuous spiral floor, each 9 feet 6 inches (2896 mm) of height, or portion thereof, shall be considered under these provisions to be a tier.
406.5.5 Area and height increases. The allowable area and height of open parking garages shall be increased in accordance with the provisions of this section. Garages with sides open on three-fourths of the building’s perimeter are permitted to be increased by 25 percent in area and one tier in height. Garages with sides open around the entire building’s perimeter are permitted to be increased by 50 percent in area and one tier in height. For a side to be considered open under these provisions, the total area of openings along the side shall be not less than 50 percent of the interior area of the side at each tier and such openings shall be equally distributed along the length of the tier. For purposes of calculating the interior area of the side, the height shall not exceed 7 feet (2134 mm).
Allowable tier areas in Table 406.5.4 shall be increased for open parking garages constructed to heights less than the table maximum. The gross tier area of the garage shall not exceed that permitted for the higher structure. Not fewer than three sides of each such larger tier shall have continuous horizontal openings not less than 30 inches (762 mm) in clear height extending for not less than 80 percent of the length of the sides. All parts of such larger tier shall be not more than 200 feet (60 960 mm) horizontally from such an opening. In addition, each such opening shall face a street or yard with access to a street with a width of not less than 30 feet (9144 mm) for the full length of the opening, and standpipes shall be provided in each such tier.
Open parking garages of Type II construction, with all sides open, shall be unlimited in allowable area where the building height does not exceed 75 feet (22 860 mm). For a side to be considered open, the total area of openings along the side shall be not less than 50 percent of the interior area of the side at each tier and such openings shall be equally distributed along the length of the tier. For purposes of calculating the interior area of the side, the height shall not exceed 7 feet (2134 mm). All portions of tiers shall be within 200 feet (60 960 mm) horizontally from such openings or other natural ventilation openings as defined in Section 406.5.2. These openings shall be permitted to be provided in courts with a minimum dimension of 20 feet (6096 mm) for the full width of the openings.
CHBC § 803.11 Medium relevance — show source text
Occupancy classification also plays a key part in the appropriate protection measures. As such, threshold requirements for fire protection and means of egress systems are based on occupancy classification (see Chapters 9 and 10). Other sections of the code also contain requirements respective to the classification of building groups. For example, Section 706 specifies requirements for fire wall fire-resistance ratings that are tied to the occupancy classification of a building and Section 803.11 contains interior finish requirements that are dependent upon the occupancy classification. The use of the space, rather than the occupancy of the building, is utilized for determining occupant loading (Section 1004) and live loading (Section 1607).
Chapter 4 Special Detailed Requirements Based on Occupancy and Use.
Chapter 4 contains the requirements for protecting special uses and occupancies which are supplemental to the remainder of the code. For example, the height and area limitations established in Chapter 5 apply to all special occupancies unless Chapter 4 contains height and area limitations. In this case, the limitations in Chapter 4 supersede those in other sections. An example of this is the height and area limitations for open parking garages given in Section 406.5.4, which supersede the limitations given in Sections 504 and 506.
In some instances, it may not be necessary to apply the provisions of Chapter 4. For example, if a covered mall building complies with the provisions of the code for Group M, Section 402 does not apply; however, other sections that address a use, process or operation must be applied to that specific occupancy, such as stages and platforms, special amusement buildings and hazardous materials (Sections 410, 411 and 414).
The chapter includes requirements for buildings and conditions that apply to one or more groups, such as high-rise buildings, underground buildings or atriums. Special uses may also imply specific occupancies and operations, such as for Group H, hazardous materials, and uses with associated combustibility hazards, which are coordinated with the CFC. Unique consideration is taken for special use areas, such as covered mall buildings, motor-vehicle-related occupancies, special amusement buildings and aircraftrelated occupancies. Special facilities within other occupancies are considered, such as stages and platforms, motion picture projection rooms, children’s play structures and storm shelters. Finally, in order that the overall package of protection features can be easily understood, unique considerations for specific occupancies are also addressed.
Chapter 5 General Building Heights and Areas.
Chapter 5 contains the provisions that regulate the minimum type of construction for area limits and height limits based on the occupancy of the building. Height and area increases are permitted based on open frontage for fire department access, separation and the type of sprinkler protection provided (Sections 503 through 506, 510). Provisions include the protection and/or separation of incidental uses (Table 509.1), accessory occupancies (Section 508.2) and mixed uses in the same building (Sections 506.2.2, 508.3, 508.4 and 510). Unlimited area buildings are permitted in certain occupancies when they meet special provisions (Section 507). Live/work units are provided for in Section 508.5.
Tables 504.3, 504.4 and 506.2 are the keystones in setting thresholds for building size based on the building’s use and the materials with which it is constructed. Respective to each group classification, the greater the fire-resistance rating of structural elements, as represented by the type of construction, the greater the floor area and height allowances. The greater the potential fire hazards indicated as a function of the group, the lesser the height and area allowances for a particular construction type.
CHBC § 33.3 Medium relevance — show source text
Stairway openings in such balconies shall not be less than 22 inches by 44 inches (559 by 1118 mm). The balustrade of each balcony shall not be less than 36 inches (914 mm) high with not more than 9 inches (287 mm) between balusters. 6. Fire escapes shall extend to the roof or provide an approved gooseneck ladder between the top floor landing and the roof when serving buildings four or more stories in height having roofs with less than 4 units vertical in 12 units horizontal (33.3 percent slope). Fire escape ladders shall be designed and connected to the building to withstand a horizontal force of 100 pounds (445 N) placed anywhere on the rung. All ladders shall be at least 15 inches (381 mm) wide, located within 12 inches (305 mm) of the building. Ladder rungs shall be [3] / 4 inch (19.1 mm) in diameter and shall be located 12 inches (305 mm) on center. Openings for roof access ladders through cornices and similar projections shall have minimum dimensions of 30 inches by 33 inches (762 by 838 mm). The length of fire escapes and exit ladder devices shall be limited to that approved by the building official based on products listed by a recognized testing laboratory. 7. The lowest balcony shall not be more than 18 feet (5486 mm) from the ground. Fire escapes shall extend to the ground or be provided with counterbalanced stairs reaching to the ground. 8. Fire escapes shall not take the place of stairways required by the codes under which the building was constructed. 9. Fire escapes shall be kept clear and unobstructed at all times and maintained in good working order.
2025 CALIFORNIA HISTORICAL BUILDING CODE 9
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MEANS OF EGRESS
SECTION 8-503 — ESCAPE OR RESCUE WINDOWS AND DOORS
Basements in dwelling units and every sleeping room below the fourth floor shall have at least one openable window or door approved for emergency escape which shall open directly into a public street, public way, yard or exit court. Escape or rescue windows or doors shall have a minimum clear area of 3.3 square feet (0.31 m [2] ) and a minimum width or height dimension of 18 inches (457 mm) and be operable from the inside to provide a full, clear opening without the use of special tools.
SECTION 8-504 — RAILINGS AND GUARDRAILS
The height of railings and guard railings and the spacing of balusters may continue in their historical height and spacing unless a distinct hazard has been identified or created by a change in use or occupancy.
10 2025 CALIFORNIA HISTORICAL BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
8-6 ACCESSIBILITY
SECTION 8-601 — PURPOSE, INTENT AND SCOPE
8-601.1 Purpose. The purpose of the CHBC is to provide alternative regulations to facilitate access and use by persons with disabilities to and throughout facilities designated as qualified historical buildings or properties. These regulations require enforcing agencies to accept alternatives to regular code when dealing with qualified historical buildings or properties.
CHBC § 25.4 Medium relevance — show source text
7 or No.
67)|30|2|2|2|13|15|17|21|25|30|14|17|19|22|24|27|32|37|42| |ASTM D1863
(No. 7 or No.
67)|50|12|12|14|16|18|21|25|30|35|17|19|22|25|28|30|36|41|47| |ASTM D1863
(No. 7 or No.
67)|100|14|16|19|21|24|27|32|37|42|21|24|26|29|32|35|41|47|53| |ASTM D1863
(No. 7 or No.
67)|150|17|19|22|25|27|30|36|41|46|23|26|29|32|35|38|44|50|56| |ASTM D1863
(No. 6)|15|2|2|2|2|12|12|12|15|18|2|2|2|13|15|17|22|26|30| |ASTM D1863
(No. 6)|20|2|2|2|2|12|12|13|17|21|2|2|12|15|17|19|23|28|32| |ASTM D1863
(No. 6)|30|2|2|2|2|12|12|16|20|24|2|12|14|17|19|21|26|31|35| |ASTM D1863
(No. 6)|50|12|12|12|12|14|16|20|24|28|12|15|17|19|22|24|29|34|39| |ASTM D1863
(No. 6)|100|12|12|14|16|19|21|26|30|35|16|18|21|24|26|29|34|39|45| |ASTM D1863
(No. 6)|150|12|14|17|19|22|24|29|34|39|18|21|23|26|29|32|37|43|48| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.
a. Parapet height is measured vertically from the top surface of the coping down to the surface of the roof covering in the field of the roof adjacent to the parapet and outbound
of any cant strip.
b. Interpolation shall be permitted for wind speed, mean roof height and parapet height. Extrapolation is not permitted.
c. Basic wind speed,V, and wind exposure shall be determined in accordance with Section 1609.
d. Where the minimum required parapet height is indicated to be 2 inches (51 mm), a gravel stop shall be permitted and shall extend not less than 2 inches (51 mm) from the roof
surface and not less than the height of the aggregate.
e. The tabulated values apply only to conditions where the topographic factor (Kzt) determined in accordance with Chapter 26 of ASCE 7 is 1.0 or where_Kzt_ is incorporated in the
basic wind speed in Section 1609.
f.CHBC § 403.2 Medium relevance — show source text
For existing high-rise buildings and for existing Group R occupancies, see California Fire Code Chapter 11 and California Existing Building Code.
For the purpose of this section, in determining the level from which the highest occupied floor is to be measured, the enforcing agency should exercise reasonable judgment, including consideration of overall accessibility to the building by fire department personnel and vehicular equipment. When a building is located on sloping terrain and there is building access on more than one level, the enforcing agency may select the level that provides the most logical and adequate fire department access.
403.2 Construction. The construction of high-rise buildings shall comply with the provisions of Sections 403.2.1 through 403.2.3.
403.2.1 Reduction in fire-resistance rating. The fire-resistance rating reductions specified in Sections 403.2.1.1 and 403.2.1.2 shall be allowed in buildings that have sprinkler control valves equipped with supervisory initiating devices and water-flow initiating devices for each floor.
Exception: Buildings, or portions of buildings, classified as a Group H-1, H-2 or H-3 occupancy.
403.2.1.1 Type of construction. The following reductions in the minimum fire-resistance rating of the building elements in Table 601 shall be permitted as follows:
- For buildings not greater than 420 feet (128 m) in building height, the fire-resistance rating of the building elements in Type IA construction shall be permitted to be reduced to the minimum fire-resistance ratings for the building elements in Type IB. Exception: The required fire-resistance rating of the primary structural frame shall not be reduced.
- In other than Group F-1, H-2, H-3, H-5, M and S-1 occupancies, the fire-resistance rating of the building elements in Type IB construction shall be permitted to be reduced to the fire-resistance ratings in Type IIA. Exception: The required fire-resistance rating of the primary structural frame shall not be permitted to be reduced.
- The building height and building area limitations of a building containing building elements with reduced fire-resistance ratings shall be permitted to be the same as the building without such reductions.
403.2.1.2 Shaft enclosures. For buildings not greater than 420 feet (128 m) in building height, the required fire-resistance rating of the fire barriers enclosing vertical shafts, other than interior exit stairway and elevator hoistway enclosures, is permitted to be reduced to 1 hour where automatic sprinklers are installed within the shafts at the top and at alternate floor levels.
[BS] 403.2.2 Structural integrity of interior exit stairways and elevator hoistway enclosures. For high-rise buildings of Risk Category III or IV in accordance with Section 1604.5, and for all buildings that are more than 420 feet (128 m) in building height, enclosures for interior exit stairways and elevator hoistway enclosures shall comply with Sections 403.2.2.1 through 403.2.2.4.
CHBC § 1.11 Medium relevance — show source text
In other than Group A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, the S increases_
for height and stories in Tables 504.3 and 504.4 are permitted in addition to the S area increase in accordance with Table 506.2.
o. For Group R-2 buildings of Type VA construction equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1, S area increase is permit-
ted in addition to the height and story increase provided the height shall not exceed 60 feet and 4 stories.
p. See Section 436.1 for additional regulations for child-care centers and adult day care.|2025 CALIFORNIA BUILDING CODE 5-7
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
GENERAL BUILDING HEIGHTS AND AREAS
SECTION 505—MEZZANINES AND EQUIPMENT PLATFORMS
505.1 General. Mezzanines shall comply with Section 505.2. Equipment platforms shall comply with Section 505.3.
505.2 Mezzanines. A mezzanine or mezzanines in compliance with Section 505.2 shall be considered a portion of the story below. Such mezzanines shall not contribute to either the building area or number of stories as regulated by Section 503.1. The area of the mezzanine shall be included in determining the fire area. The clear height above and below the mezzanine floor construction shall be not less than 7 feet (2134 mm).
505.2.1 Area limitation. The aggregate area of a mezzanine or mezzanines within a room shall be not greater than one-third of the floor area of that room or space in which they are located. The enclosed portion of a room shall not be included in a determination of the floor area of the room in which the mezzanine is located. In determining the allowable mezzanine area, the area of the mezzanine shall not be included in the floor area of the room.
Exceptions:
- The aggregate area of mezzanines in buildings and structures of Type I or II construction for special industrial occupancies in accordance with Section 503.1.1 shall be not greater than two-thirds of the floor area of the room.
- The aggregate area of mezzanines in buildings and structures of Type I or II construction shall be not greater than one-half of the floor area of the room in buildings and structures equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1 and an approved emergency voice/alarm communication system in accordance with Section 907.5.2.2.
- The aggregate area of a mezzanine within a dwelling unit that is located in a building equipped throughout with an approved automatic sprinkler system in accordance with Section 903.3.1.1 or 903.3.1.2 shall not be greater than onehalf of the floor area of the room, provided that: 3.1. Except for enclosed closets and bathrooms, the mezzanine shall be open to the room in which such mezzanine is located; 3.2. The opening to the room shall be unobstructed except for walls not more than 42 inches (1067 mm) in height, columns and posts; and 3.3. Exceptions to Section 505.2.3 shall not be permitted.
CHBC § 5-1. Medium relevance — show source text
The actual area of any individual floor shall not exceed the allowable area per Equation 5-1.
506.2.2 Mixed-occupancy buildings. The allowable area of each story of a mixed-occupancy building shall be determined in accordance with the applicable provisions of Section 508.3.2 for nonseparated occupancies and Section 508.4.2 for separated occupancies.
For buildings with more than two stories above grade plane, the total building area shall be such that the aggregate sum of the ratios of the actual area of each story divided by the allowable area of such stories, determined in accordance with Equation 5-3 based on the applicable provisions of Section 508.1, shall not exceed three, provided the aggregate sum of the ratios for portions of mixed-occupancy, multistory buildings containing A, E, H, I, L and R occupancies, high-rise buildings, and other applications listed in Section 1.11 regulated by the Office of the State Fire Marshal, including any other associated non-separated occupancies, shall not exceed two.
Equation 5-3 A a = [ A t + ( NS × I f )]
where:
A a = Allowable area (square feet). A t = Tabular allowable area factor (NS, S13R, S13D or SM value, as applicable) in accordance with Table 506.2.
NS = Tabular allowable area factor in accordance with Table 506.2 for a nonsprinklered building, regardless of whether the building is sprinklered.
I f = Area factor increase due to frontage (percent) as calculated in accordance with Section 506.3.
506.2.2.1 Group H-2 or H-3 mixed occupancies. For a building containing Group H-2 or H-3 occupancies, the allowable area shall be determined in accordance with Section 508.4.2, with the automatic sprinkler system increase applicable only to the portions of the building not classified as Group H-2 or H-3.
506.3 Frontage increase. Every building shall adjoin or have access to a public way to receive an area factor increase based on frontage. Area factor increase shall be determined in accordance with Sections 506.3.1 through 506.3.3.
506.3.1 Minimum percentage of perimeter. To qualify for an area factor increase based on frontage, a building shall have not less than 25 percent of its perimeter on a public way or open space. Such open space shall be either on the same lot or dedicated for public use and shall be accessed from a street or approved fire lane.
506.3.2 Minimum frontage distance. To qualify for an area factor increase based on frontage, the public way or open space adjacent to the building perimeter shall have a minimum distance of 20 feet (6096 mm) measured at right angles from the building face to any of the following:
The closest interior lot line.
The entire width of a street, alley or public way.
The exterior face of an adjacent building on the same property.
The frontage increase shall be based on the smallest public way or open space that is 20 feet (6096 mm) or greater, and the percentage of building perimeter having a minimum 20 feet (6096 mm) public way or open space.
CHBC § 3.1 Medium relevance — show source text
Exception: Construction documents for buildings constructed in accordance with the conventional light-frame construction provisions of Section 2308 shall indicate the following structural design information:
Floor and roof dead and live loads.
Ground snow load, p g, and allowable stress design ground snow load, p g(asd) .
Basic wind speed, V, mph (m/s), and allowable stress design wind speed, V asd , as determined in accordance with Section 1609 A .3.1 and wind exposure.
Seismic design category and site class.
Flood design data, if located in flood hazard areas established in Section 1612 A .3.
Design load-bearing values of soils.
Rain load data.
[DSA-SS] Additional requirements are included in Section 4-210 and 4-317 of the California Administrative Code (Part 1, Title 24, C.C.R).
[OSHPD 1] Additional requirements are included in Section 7-115 and 7-125 of the California Administrative Code.
1603 A .1.1 Floor live load. The uniformly distributed, concentrated and impact floor live load used in the design shall be indicated for floor areas. Use of live load reduction in accordance with Section 1607 A .13 shall be indicated for each type of live load used in the design.
1603 A .1.2 Roof live load. The roof live load used in the design shall be indicated for roof areas. 1603 A .1.3 Roof snow load data. The ground snow load, p g, shall be indicated. In areas where the ground snow load, p g , exceeds 15 pounds per square foot (psf) (0.72 kN/m [2] ), the following additional information shall also be provided, regardless of whether snow loads govern the design of the roof:
- Flat-roof snow load, p f .
- Snow exposure factor, C e .
- Risk category.
- Thermal factor, C t .
- Slope factor(s), C s .
- Drift surcharge load(s), p d , where the sum of p d and p f exceeds 30 psf (1.44 kN/m [2] ) .
- Width of snow drift(s), w .
- Winter wind parameter for snow drift, W 2 .
1603 A .1.4 Wind and tornado design data. The following information related to wind loads and, where required by Section 1609 A .5, tornado loads shall be shown, regardless of whether wind or tornado loads govern the design of the lateral force-resisting system of the structure:
- Basic wind speed, V, mph (m/s), tornado speed, V T, mph (m/s), and allowable stress design wind speed, V asd, mph (m/s), as determined in accordance with Section 1609 A .3.1.
CHBC § 19-1.1 Medium relevance — show source text
Floor and beam
construction consisting of
3"-deep cellular steel floor
unit mounted on steel
members with 1:4 (propor-
tion of Portland cement to
perlite aggregate) perlite-
concrete floor slab on top.|19-1.1|Suspended envelope ceiling of perlite
gypsum plaster on metal lath attached
to3/4" cold-rolled channels, secured to
11/2" cold-rolled channels spaced 42"
on center supported by 0.203 inch (No.
6 B.W. gage) wire 36" on center. Beams
in envelope with 3" minimum airspace
between beam soffit and lath have a 4-
hour rating.|2p|—|—|—|1 l|—|—|—| |20. Perlite concrete propor-
tioned 1:6 (Portland cement
to perlite aggregate) poured
to1/8" thickness above top of
corrugations of 15/16"-deep
galvanized steel deck maxi-
mum span 8′-0" for 0.024"
(No. 24 galvanized sheet
gage) or 6′-0" for 0.019" (No.
26 galvanized sheet gage)
with deck supported by indi-
vidually protected steel
framing. Approved polysty-
rene foam plastic insulation
board having a flame spread
not exceeding 75 (1" to 4"
thickness) with vent holes
that approximate 3 percent of
the board surface area placed
on top of perlite slurry. A 2′ by
4′ insulation board contains
six 23/4" diameter holes.
Board covered with 21/4"
minimum perlite concrete
slab. Slab reinforced with
mesh consisting of 0.042"
(No.19 B.W. gage) galvanized
steel wire twisted together to
form 2" hexagons with
straight 0.065" (No. 16 B.W.
gage) galvanized steel wire
woven into mesh and spaced
3". Alternate slab reinforce-
ment shall be permitted to
consist of 4" × 8",
0.109/0.238" (No. 12/4 B.W.
gage), or 2" × 2", 0.083/0.083"
(No. 14/14 B.W. gage) welded
wire fabric. Class A or B roof
covering on top.|20-1.1|None|—|—|Varies|—|—|—|—|—| |21. Wood joists, wood I-
joists, floor trusses and flat
or pitched roof trusses
spaced a maximum 24" o.c.
with1/2" wood structural
panels with exterior glue
applied at right angles to
top of joist or top chord of
trusses with 8 d nails.CHBC § 8-2 Medium relevance — show source text
2 2025 CALIFORNIA HISTORICAL BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
8-2 DEFINITIONS
SECTION 8-201 — DEFINITIONS
For the purpose of the CHBC, certain terms and phrases, words and their derivatives shall be construed as specified in this chapter. Additional definitions and/or terms may appear in the various other chapters relative to terms or phrases primarily applicable thereto. Any reference to “authority having jurisdiction” does not necessarily preclude the appellate process of Section 8-104.3.
ADDITION. A nonhistorical extension or increase in floor area or height of a building or property.
ALTERATION. A modification to a qualified historical building or property that affects the usability of the building or property, or part thereof. Alterations include, but are not limited to, remodeling, renovation, rehabilitation, reconstruction, historical restoration, changes or rearrangement of the structural parts or elements, and changes or rearrangements in the plan configuration of walls and full-height partitions.
BUILDING STANDARD. Any guideline, regulation or code that may be applied to a qualified historical building or property.
CHARACTER-DEFINING FEATURE. Those visual aspects and physical elements that comprise the appearance of a historical building or property, and that are significant to its historical, architectural and cultural values, including the overall shape of the historical building or property, its materials, craftsmanship, decorative details, interior spaces and features, as well as the various aspects of its site and environment.
CULTURAL RESOURCE. Building, site, property, object or district evaluated as having significance in prehistory or history.
DISTINCT HAZARD. Any clear and evident condition that exists as an immediate danger to the safety of the occupants or public right of way. Conditions that do not meet the requirements of current regular codes and ordinances do not, of themselves, constitute a distinct hazard. Section 8-104.3, SHBC appeals, remains applicable.
ENFORCING AGENCY, Authority Having Jurisdiction, Local Agency with Jurisdiction. An entity with the responsibility for regulating, enforcing, reviewing or otherwise that exerts control of or administration over the process of granting permits, approvals, decisions, variances, appeals for qualified historical buildings or properties.
EXIT LADDER DEVICE. An exit ladder device is a permanently installed, fixed, folding, retractable or hinged ladder intended for use as a means of emergency egress from areas of the second or third stories. Unless approved specifically for a longer length, the ladder shall be limited to 25 feet (7620 mm) in length. Exit ladders are permitted where the area served by the ladder has an occupant load less than 10 persons.
FIRE HAZARD. Any condition which increases or may contribute to an increase in the hazard or menace of fire to a greater degree than customarily recognized by the authority having jurisdiction, or any condition or act which could obstruct, delay, hinder or interfere with the operations of firefighting personnel or the egress of occupants in the event of fire. Section 8-104.3, SHBC appeals, remains applicable.
HISTORICAL FABRIC OR MATERIALS. Original and later-added historically significant construction materials, architectural finishes or elements in a particular pattern or configuration which form a qualified historical property, as determined by the authority having jurisdiction.
HISTORICAL SIGNIFICANCE. Importance for which a property has been evaluated and found to be historical, as determined by the authority having jurisdiction.
Frequently asked questions
Can I exceed 15,000 ft² by splitting the building into tenant spaces?
Not under the CHBC one‑story rule. The 15,000 ft² cap applies to the overall one‑story qualified historical building unless you meet a listed exception (sprinkler or the two‑story residential alarm/exiting exception) — § 8‑302.4 .
If I add a basement, does that make my one‑story building “multistory” for area limits?
Basements and cellars are counted in the CHBC multistory determination; if the building becomes multistory (including basements/cellars), area is governed by the regular code, not the CHBC one‑story cap (§ 8‑302.4) .
Does the CHBC allow me to add stories beyond the historic height?
No. The CHBC will not limit height because of construction type, but the building’s height and number of stories under CHBC may not exceed its historical design — you cannot expand height beyond the historic configuration under § 8‑302.5 .
If I install sprinklers, do I still need to meet fire‑resistance separations?
Installing an automatic sprinkler removes the CHBC one‑story area cap and allows unlimited area without fire‑resistive area separation walls per the exception in § 8‑302.4, but you must still meet other applicable CHBC requirements and applicable sprinkler standards referenced elsewhere in Chapter 8 .
For high‑rise historic office buildings, can I sprinkler only the top floors?
Yes—under § 8‑302.5.1 the CHBC permits only the stories above 75 ft to be sprinklered (instead of the entire building) for occupancies B, F‑1, F‑2, or S, but only if the three listed conditions (regular‑code construction/exits, full building alarm/annunciation, and a fire barrier) are satisfied .
More in California Historical Building Code
Ask about the CHBC
Get cited, plain-English answers on the California Historical Building Code for your project — any code section, any scenario.
Start Free Trial