CHBC · California Historical Building Code
What are minimum room size, light and ventilation requirements for historic residences?
Under the CHBC, a sleeping room must be at least 50 sq ft with an average 7‑ft ceiling, habitable rooms must have windows equal to 6% of floor area or at least 6 sq ft, sleeping‑room windows must be openable and basements/sleeping rooms below the fourth floor require an emergency escape opening (3.3 sq ft clear, 18 in min dimension). These are found in §§ 8‑303.5, 8‑303.6 and 8‑503 .
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
The CHBC lets qualified historic dwelling units use relaxed, historically‑sensitive provisions for room size, lighting and ventilation while still protecting occupant safety. The core, controlling rules are: rooms used for sleeping purposes must be at least 50 square feet with an average ceiling height of 7 feet (§ 8-303.5) and windows in habitable rooms must provide at least 6% of the floor area or at least 6 square feet (whichever is greater); windows in sleeping rooms must be openable (§ 8-303.6) — and escape/openable windows have separate minimum clear opening requirements (§ 8-503) .
The single most important rule: sleeping rooms must meet a minimum floor area of 50 sq ft and have openable windows that satisfy both the glazing/ventilation rule and any required escape‑opening criteria (see §§ 8-303.5, 8-303.6, 8-503) .
Requirements in detail
Minimum room size (sleeping rooms)
- Minimum floor area for sleeping rooms: 50 square feet (4.6 m2).
- Minimum average ceiling height for those rooms: 7 feet (2134 mm).
- Other habitable rooms: need only be of adequate size to be functional for the purpose intended (not a numeric minimum) — see § 8-303.5 .
Light and ventilation (habitable rooms and sleeping rooms)
- Windows in habitable rooms: required area = 6% of the floor area OR 6 square feet (0.56 m2), whichever is greater.
- Windows in sleeping rooms: must be openable (see escape/ rescue rules in § 8-503).
- Electrical lighting: not required by the CHBC for residential occupancies (i.e., historic residences may remain without electrical lighting) — see § 8-303.6 .
Escape / rescue (sleeping rooms and basements)
- Basements in dwelling units and every sleeping room located below the fourth floor must have at least one openable window or door approved for emergency escape that opens directly to a public way, yard or exit court. (§ 8-503)
- Minimum clear opening for escape windows/doors: 3.3 square feet (0.31 m2).
- Minimum dimension (width or height): 18 inches (457 mm).
- Operability: Operable from the inside to provide a full, clear opening without use of special tools. See § 8-503 .
Quick reference table (decision‑relevant dimensions/values)
| Requirement | Value / threshold | Code Reference |
|---|---|---|
| Sleeping room minimum floor area | 50 sq ft (4.6 m2) | § 8-303.5 |
| Sleeping room minimum average ceiling height | 7 ft (2134 mm) | § 8-303.5 |
| Window area for habitable rooms | 6% of floor area OR 6 sq ft, whichever is greater | § 8-303.6 |
| Windows in sleeping rooms | Must be openable (and meet escape rules where applicable) | § 8-303.6 |
| Emergency escape clear opening | 3.3 sq ft (0.31 m2) minimum | § 8-503 |
| Escape opening min width OR height | 18 in (457 mm) minimum | § 8-503 |
| Escape opening operation | Operable from the inside w/o special tools | § 8-503 |
| Electrical lighting | Not required for residential occupancies under CHBC | § 8-303.6 |
Exceptions & special cases
- The CHBC intentionally allows greater flexibility for non‑sleeping habitable rooms — they only need to be “adequate” for their intended use rather than meet a numeric minimum (§ 8-303.5) .
- The openable window requirement for sleeping rooms references § 8-503’s escape/opening rules; for basements and all sleeping rooms below the fourth floor an approved escape opening is mandatory (§ 8-503) .
- Existing historic conditions for light and ventilation that do not, in the enforcing agency’s judgment, create a safety hazard may be permitted to remain (see cross‑reference on existing provisions) — see § 8-302.7 for the CHBC policy that existing light/ventilation may remain if not a safety hazard .
- The CHBC allows the enforcing agency to accept “reasonably equivalent alternatives” where strict application would threaten historic character; therefore local enforcement and case‑by‑case alternatives are possible (general CHBC approach across Chapter 8) .
Common mistakes
- Assuming the 50 sq ft rule applies to every habitable room — it applies specifically to rooms used for sleeping purposes; other habitable rooms are judged by adequacy for use (§ 8-303.5) .
- Treating the escape clear opening (3.3 sq ft) as the only window sizing requirement — the room still must meet the 6% or 6 sq ft glazing requirement for light/ventilation in habitable rooms (§ 8-303.6), so the window must satisfy both rules where they apply .
- Counting only the operable portion of a multi‑lite window toward the 6% unless clarified — the CHBC language specifies “windows … shall have an area” but does not detail measurement methodology here; confirm measurement conventions with the enforcing agency (measurement practice can vary) (§ 8-303.6) .
- Overlooking the CHBC statement that electrical lighting is not required for residential occupancies — some permit reviewers still expect minimum electrical fixtures per local practice; verify with the enforcing agency (§ 8-303.6) .
Worked example — concrete scenario
Scenario: converting a historic attic room into a sleeping room with finished floor area = 80 sq ft and average ceiling height = 7 ft.
- Minimum floor area: the room is 80 sq ft, which is ≥ 50 sq ft, so the size requirement of § 8-303.5 is satisfied (average ceiling height is 7 ft) .
- Window area for light/ventilation: required glazing = 6% of 80 sq ft = 4.8 sq ft, but CHBC requires 6 sq ft OR 6% — take the greater value. Therefore glazing must be at least 6 sq ft (0.56 m2) per § 8-303.6 .
- Escape window requirement: because this is a sleeping room (and it is below the fourth floor) you must provide at least one emergency escape window/door meeting § 8-503: minimum clear opening 3.3 sq ft, and width OR height ≥ 18 in, and operable from inside without tools .
- Conclusion: install at least one window that provides at least 6 sq ft of glazing area and, when opened, provides a clear opening ≥ 3.3 sq ft with a minimum width or height of 18 in and is operable from the inside without tools. That satisfies both § 8-303.6 and § 8-503 .
Related provisions (CHBC)
- § 8-303.5 — Room dimensions (sleeping room minimums)
- § 8-303.6 — Light and ventilation (habitable rooms, sleeping room openable requirement, and electrical lighting note)
- § 8-503 — Escape or rescue windows and doors (clear opening, dimensions, operability)
- § 8-302.7 — Existing provisions for light and ventilation may remain if not a safety hazard (policy for existing historic fabric)
- § 8-303.7 — Alteration and repair (sets context for how historic materials/methods are treated when altering historic residences)
Code references
Grounded in the retrieved California Historical Building Code — click a citation to read the verbatim passage:
CHBC § 8-302.6 High relevance — show source text
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.
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USE AND OCCUPANCY
8-303.5 Room dimensions. Rooms used for sleeping purposes may contain a minimum of 50 square feet (4.6 m [2] ) floor area, provided there is maintained an average ceiling height of 7 feet (2134 mm). Other habitable rooms need only be of adequate size to be functional for the purpose intended.
8-303.6 Light and ventilation. Windows in habitable rooms shall have an area of 6 percent of the floor area, or 6 square feet (0.56 m [2] ), whichever is greater. Windows in sleeping rooms shall be openable (see Section 8-503). Residential occupancies need not be provided with electrical lighting.
8-303.7 Alteration and repair. The alteration and repair of qualified historical buildings or properties may permit the replacement, retention and extension of original materials and the continued use of original methods of construction, provided a life safety hazard is not created or continued. Alterations and repairs shall be consistent with the CHBC.
The amount of alterations and repairs is not limited, provided there is no nonhistorical increase in floor area, volume or size of the building or property.
8-303.8 Exiting. See Chapter 8-5.
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8-4 FIRE PROTECTION
SECTION 8-401 — PURPOSE, INTENT AND SCOPE
8-401.1 Purpose. The purpose of this chapter is to provide regulations for fire protection of qualified historical buildings or properties. The CHBC requires enforcing agencies to accept any reasonably equivalent alternatives to the regular code when dealing with qualified historical buildings or properties.
8-401.2 Intent. The intent of the CHBC is to preserve the integrity of qualified historical buildings or properties while maintaining a reasonable degree of fire protection based primarily on the life safety of the occupants and firefighting personnel.
CHBC § 1.1.2 Medium relevance — show source text
1.1.2 Purpose. The purpose of this code is to establish the minimum requirements to safeguard the public health, safety and general welfare through structural strength, means of egress facilities, stability, access to persons with disabilities, sanitation, adequate lighting and ventilation and energy conservation; safety to life and property from fire and other hazards attributed to the built environment; and to provide safety to firefighters and emergency responders during emergency operations.
1.1.3 Scope. The provisions of this code shall apply to the construction, alteration, movement, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures throughout the State of California. [HCD 1 & 2] The provisions of this code shall apply to repair, alteration, change of occupancy, addition to and relocation of every existing building or structure or any appurtenances connected or attached to such buildings or structures throughout the State of California.
1.1.3.1 Nonstate-regulated buildings, structures and applications. Except as modified by local ordinance pursuant to Section 1.1.8, the following standards in the California Code of Regulations, Title 24, Parts 2, 2.5, 3, 4, 5, 6, 7, 9, 10 and 11 shall apply to all occupancies and applications not regulated by a state agency.
1.1.3.2 State-regulated buildings, structures and applications. The model code, state amendments to the model code and/or state amendments where there are no relevant model code provisions shall apply to the following buildings, structures and applications regulated by state agencies as specified in Sections 1.2 through 1.14, except where modified by local ordinance pursuant to Section 1.1.8. When adopted by a state agency, the provisions of this code shall be enforced by the appropriate enforcing agency, but only to the extent of authority granted to such agency by the state legislature.
Note: See “How to Distinguish Between Model Code Language and California Amendments” in the front of the code. 1. State-owned buildings, including buildings constructed by the Trustees of the California State University, and to the extent permitted by California laws, buildings designed and constructed by the Regents of the University of California, and regulated by the Building Standards Commission. See Section 1.2 for additional scope provisions. 2. Section 1.3 is reserved for the Board of State Community Corrections. 3. Section 1.4 is reserved for the Department of Consumer Affairs. 4. Section 1.5 is reserved for the California Energy Commission. 5. Section 1.6 is reserved for the Department of Food and Agriculture. 6. Section 1.7 is reserved for the Department of Public Health. 7. Hotels, motels, lodging houses, apartments, dwellings, dormitories, condominiums, shelters for homeless persons, congregate residences, employee housing, factory-built housing and other types of dwellings containing sleeping _accommodations with or without common toilets or cooking facilities.
CHBC § 8-303.6 Medium relevance — show source text
8-303.6 Light and ventilation. Windows in habitable rooms shall have an area of 6 percent of the floor area, or 6 square feet (0.56 m [2] ), whichever is greater. Windows in sleeping rooms shall be openable (see Section 8-503). Residential occupancies need not be provided with electrical lighting.
8-303.7 Alteration and repair. The alteration and repair of qualified historical buildings or properties may permit the replacement, retention and extension of original materials and the continued use of original methods of construction, provided a life safety hazard is not created or continued. Alterations and repairs shall be consistent with the CHBC.
The amount of alterations and repairs is not limited, provided there is no nonhistorical increase in floor area, volume or size of the building or property.
8-303.8 Exiting. See Chapter 8-5.
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8-4 FIRE PROTECTION
SECTION 8-401 — PURPOSE, INTENT AND SCOPE
8-401.1 Purpose. The purpose of this chapter is to provide regulations for fire protection of qualified historical buildings or properties. The CHBC requires enforcing agencies to accept any reasonably equivalent alternatives to the regular code when dealing with qualified historical buildings or properties.
8-401.2 Intent. The intent of the CHBC is to preserve the integrity of qualified historical buildings or properties while maintaining a reasonable degree of fire protection based primarily on the life safety of the occupants and firefighting personnel.
8-401.3 Scope. This chapter shall apply when required by the provisions of Section 8-102.
SECTION 8-402 — FIRE-RESISTIVE CONSTRUCTION
8-402.1 Exterior wall construction. The fire-resistance requirement for existing exterior walls and existing opening protection may be satisfied when an automatic sprinkler system designed for exposure protection is installed per the CHBC. The automatic sprinklers may be installed on the exterior with at least one sprinkler located over each opening required to be protected. Additional sprinklers shall also be distributed along combustible walls under the roof lines that do not meet the fire-resistive requirement due to relationship to property lines as required by regular code. Such sprinkler systems may be connected to the domestic water supply on the supply-main side of the building shut-off valve. A shut-off valve may be installed for the sprinkler system, provided it is locked in an open position.
8-402.2 One-hour construction. Upgrading an existing qualified historical building or property to one-hour fire-resistive construction and one-hour fire-resistive corridors shall not be required regardless of construction or occupancy when one of the following is provided:
- An automatic sprinkler system throughout. See Section 8-410 for automatic sprinkler systems.
- An approved life safety evaluation.
- Other alternative measures as approved by the enforcing agency.
8-402.3 Openings in fire-rated systems. Historical glazing materials and solid wood unrated doors in interior walls required to have one-hour fire rating may be approved when operable windows and doors are provided with appropriate smoke seals and when the area affected is provided with an automatic sprinkler system. See Section 8-410 for automatic sprinkler systems.
SECTION 8-403 — INTERIOR FINISH MATERIALS
CHBC § 403.2.1. Medium relevance — show source text
Pz = Zone population: see Section 403.2.1. Ra = Area outdoor air rate, CFM/ft [2] . See Section 403.2.1.
Rp = People outdoor air rate, CFM/person. See Section 403.2.1.
Vbz = Breathing zone outdoor airflow, CFM. See Section 403.2.1.
Vdz = Zone discharge airflow, CFM. The expected discharge (supply) airflow to the zone that includes primary airflow and secondary recirculated airflow, CFM.
Vot = Outdoor air intake flow, CFM. See Section 403.3, Section 403.4, and Section 403.5.2.
Vou = Uncorrected outdoor air intake, CFM. See Section 403.5.1.
Voz = Zone outdoor airflow, CFM. See Section 403.2.3. Vps = System primary airflow, CFM. The total primary airflow supplied to all zones served by the system from the air-handling unit at which the outdoor air intake is located.
Vpz = Zone primary airflow, CFM. The zone primary airflow to the ventilation zone, including outdoor air and recirculated air.
Xs = Average outdoor air fraction: At the primary air handler, the fraction of outdoor air intake flow in the system primary airflow. Zpz = Primary outdoor air fraction: The outdoor air fraction required in the primary air supplied to the ventilation zone prior to the introduction of any secondary recirculation air. [ASHRAE 62.1:A3]
For SI Units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute =
0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s, 1 cubic foot per
minute per square foot = 5.08 [(L/s)/m [2] ]
405.0 Ventilation for Residential Occupancies.
405.1 General. Rooms or occupied spaces within residential occupancies, where the occupants are nontransient, shall be designed to have mechanical ventilation and exhaust air in accordance with Section 405.2 through Section 405.5.
405.1.1 Natural Ventilation. Where approved by the Authority Having Jurisdiction, natural ventilation shall be permitted for Climate Zone 1, Climate Zone 2, or for thermally conditioned buildings for less than 876 hours
per year.
405.2 Ventilation Air Rate. The required mechanical ventilation outdoor air rate ( Qtot ) shall be as calculated in accordance with Equation 405.2.
Exception: For existing buildings and where permitted by the Authority Having Jurisdiction, the total mechanical ventilation ( Qtot ) is not required where Qtot is calculated to be less than 15 ft [3] /min (7.08 L/s).
Qtot = 0.03 Afloor + 7.5 ( Nbr + 1) (Equation 405.2)
Where:
Qtot = Total required ventilation outdoor air rate, CFM (L/s) Afloor = Floor area, ft [2] (m [2] ) Nbr = Number of bedrooms more than 1
For SI Units: 1 square foot = 0.0929 m [2], 1 cubic foot per minute = 0.0283 m [3] /min, 1 cubic foot per minute = 0.4719 L/s
CHBC § 1.859 Medium relevance — show source text
78|–|1.859|0.463| |35.31|–|2.247|0.559| |38.84|–|2.667|0.663| |42.37|–|3.121|0.775| |45.90|–|3.607|0.895| |49.43|–|4.125|1.022| |52.97|–|–|1.157| |56.50|–|–|1.299| |60.03|–|–|1.449| |63.56|–|–|1.607| |67.09|–|–|1.772| |70.62|–|–|1.944| |81.21|–|–|2.503| |91.81|–|–|3.127| |102.40|–|–|3.813|
For SI units: 1 standard cubic foot per minute = 28.32 SLPM, 1 inch = 25 mm, 1 foot = 304.8 mm, 1 pound-force per square inch = 6.8947 kPa
Notes: 1 Based on pressure of 14.7 psig (101 kPa) at 68°F (20°C). 2 Based on pressure of 55 psig (379 kPa) at 68°F (20 °C).
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HEALTH CARE FACILITIES AND MEDICAL GAS AND MEDICAL VACUUM SYSTEMS
TABLE 1323.1.4(5) PRESSURE LOSS FOR VACUUM (continued)
FLOW
RATE
(SCFM)1VACUUM LOSS (inch of mercury)
PER 100 FEET FOR COPPER TUBE2Col3 Col4 Col5 Col6 FLOW
RATE
(SCFM)13⁄4 INCH
TUBE1 INCH
TUBE11⁄4 INCH
TUBE11⁄2 INCH
TUBE2 INCH
TUBE49.43 – – – 3.645 0.956 52.97 – – – 4.122 1.081 56.50 – – – 4.626 1.212 63.56 – – – – 1.495 70.62 – – – – 1.803 77.68 – – – – 2.138 84.74 – – – – 2.497 91.81 – – – – 2.882 98.87 – – – – 3.291 105.93 – – – – 3.724 112.99 – – – – 4.181 CHBC § 8-302.3 Medium 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.
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CHBC § 8-9 Medium relevance — show source text
Bolt spacing shall not
exceed 6 feet (1830 mm) on center and shall not be less than 12 inches (305 mm) on center.
6. Other masonry based on tests or other substantiated data.
7. Embedded bolts to be tested as specified in regular code standards.
8. Stresses given may be increased for combinations of loads as specified in the regular code.
9. Adhesives shall be approved by the enforcing agency and installed in accordance with the manufacturer’s recommendations. All drilling dust shall be removed from drilled
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8-9 MECHANICAL, PLUMBING AND ELECTRICAL REQUIREMENTS
SECTION 8-901 — PURPOSE, INTENT AND SCOPE
8-901.1 Purpose. The purpose of the CHBC is to provide regulations for the mechanical, plumbing and electrical systems of buildings designated as qualified historical buildings or properties. The CHBC requires enforcing agencies to accept any reasonable equivalent solutions to the regular code when dealing with qualified historical buildings or properties.
8-901.2 Intent. The intent of the CHBC is to preserve the integrity of qualified historical buildings or properties while providing a reasonable level of protection from fire, health and life safety hazards (hereinafter referred to as safety hazards) for the building occupants.
8-901.3 Scope. The CHBC shall be applied in conjunction with the regular code whenever compliance with the regular code is required for qualified historical buildings or properties.
8-901.4 Safety hazard. No person shall permit any safety hazard to exist on premises under their control, or fail to take immediate action to abate such hazard. Existing systems which constitute a safety hazard when operational may remain in place, provided they are completely and permanently rendered inoperative. Safety hazards created by inoperative systems shall not be permitted to exist. Requirements of the regular code concerning general regulations shall be complied with, except that the enforcing agency shall accept solutions which do not cause a safety hazard.
8-901.5 Energy conservation. Qualified historical buildings or properties covered by this part are exempted from compliance with energy conservation standards. When new nonhistorical lighting and space conditioning system components, devices, appliances and equipment are installed, they shall comply with the requirements of Title 24, Part 6, The California Energy Code, except where the historical significance or character-defining features are threatened.
SECTION 8-902 — MECHANICAL
8-902.1 General. Mechanical systems shall comply with the regular code unless otherwise modified by this chapter.
8-902.1.1 The provisions of the CHBC shall apply to the acceptance, location, installation, alteration, repair, relocation, replacement or addition of any heating, ventilating, air conditioning, domestic incinerators, kilns or miscellaneous heat-producing appliances or equipment within or attached to a historical building.
8-902.1.2 Existing systems which do not, in the opinion of the enforcing agency, constitute a safety hazard may remain in use.
8-902.1.3 The enforcing agency may approve any alternative to the CHBC which would achieve equivalent life safety.
8-902.2 Heating facilities. All dwelling-type occupancies covered under this chapter shall be provided with heating facilities. Woodburning or pellet stoves or fireplaces may be acceptable as heating facilities.
CHBC § 8-1001 Medium relevance — show source text
Section
8-1001 Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8-1002 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8-1003 Site Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
APPENDIX A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
HISTORY NOTE APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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8-1 ADMINISTRATION
Note: The California Historical Building Code, Part 8 of Title 24, governs for all qualified historical buildings or properties in the State of California.
SECTION 8-101 — TITLE, PURPOSE AND INTENT
8-101.1 Title. These regulations shall be known as the California Historical Building Code and will be referred to herein as “the CHBC.”
8-101.2 Purpose. The purpose of the CHBC is to provide regulations for the preservation, restoration, rehabilitation, relocation or reconstruction of buildings or properties designated as qualified historical buildings or properties (as defined in Chapter 8-2). The CHBC is intended to provide solutions for the preservation of qualified historical buildings or properties, to promote sustainability, to provide access for persons with disabilities, to provide a cost-effective approach to preservation, and to provide for the reasonable safety of the occupants or users. The CHBC requires enforcing agencies to accept solutions that are reasonably equivalent to the regular code (as defined in Chapter 8-2) when dealing with qualified historical buildings or properties.
8-101.3 Intent. The intent of the CHBC is to facilitate the preservation and continuing use of qualified historical buildings or properties while providing reasonable safety for the building occupants and access for persons with disabilities.
SECTION 8-102 — APPLICATION
8-102.1 Application. The CHBC is applicable to all issues regarding code compliance for qualified historical buildings or properties. The CHBC may be used in conjunction with the regular code to provide solutions to facilitate the preservation of qualified historical buildings or properties. The CHBC shall be used by any agency with jurisdiction and whenever compliance with the code is required for qualified historical buildings or properties.
- State or local enforcing agency. The state or local enforcing agency shall apply the provisions of the CHBC in permitting repairs, alterations and additions necessary for the preservation, restoration, reconstruction, rehabilitation, relocation or continued use of a qualified historical building or property when so elected by the private property owner.
- **State agencies.
CHBC § 101.1 Medium relevance — show source text
PART 1—SCOPE AND APPLICATION
SECTION 101—SCOPE AND GENERAL REQUIREMENTS
[A] 101.1 Title. These regulations shall be known as the Building Code of [ NAME OF JURISDICTION ], hereinafter referred to as “this code.”
[A] 101.2 Scope. The provisions of this code shall apply to the construction, alteration, relocation, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures.
Exception: Detached one- and two-family dwellings and townhouses not more than three stories above grade plane in height with a separate means of egress, and their accessory structures not more than three stories above grade plane in height, shall comply with this code or the California Residential Code .
[A] 101.2.1 Appendices. Provisions in the appendices shall not apply unless specifically adopted.
[A] 101.3 Purpose. The purpose of this code is to establish the minimum requirements to provide a reasonable level of safety, health and general welfare through structural strength, means of egress, stability, sanitation, light and ventilation, energy conservation, and for providing a reasonable level of life safety and property protection from the hazards of fire, explosion or dangerous conditions, and to provide a reasonable level of safety to firefighters and emergency responders during emergency operations.
[A] 101.4 Referenced codes. The other codes specified in Sections 101.4.1 through 101.4.7 and referenced elsewhere in this code shall be considered to be part of the requirements of this code to the prescribed extent of each such reference.
[A] 101.4.1 Gas. The provisions of the California Plumbing Code and/or the California Mechanical Code shall apply to the installation of gas piping from the point of delivery, gas appliances and related accessories as covered in this code. These requirements apply to gas piping systems extending from the point of delivery to the inlet connections of appliances and the installation and operation of residential and commercial gas appliances and related accessories.
[A] 101.4.2 Mechanical. The provisions of the California Mechanical Code shall apply to the installation, alterations, repairs and replacement of mechanical systems, including equipment, appliances, fixtures, fittings and appurtenances, including ventilating, heating, cooling, air-conditioning and refrigeration systems, incinerators and other energy-related systems.
[A] 101.4.3 Plumbing. The provisions of the California Plumbing Code shall apply to the installation, alteration, repair and replacement of plumbing systems, including equipment, appliances, fixtures, fittings and appurtenances, and where connected to a water or sewage system and all aspects of a medical gas system. The provisions of the California Plumbing Code shall apply to private sewage disposal systems.
[A] 101.4.4 Property maintenance. The provisions of the California Existing Building Code shall apply to existing structures and premises; equipment and facilities; light, ventilation, space heating, sanitation, life and fire safety hazards; responsibilities of owners, operators and occupants; and occupancy of existing premises and structures.
CHBC § 0.080 Medium relevance — show source text
1/4″|4d casing (11/2″ × 0.080″); or
4d finish (11/2″ × 0.072″)|6|12| |41.3/8″|6d casing (2″ × 0.099″); or
6d finish (2″ × 0.092″)
(Panel supports at 24 inches)|6|12| |For SI: 1 inch = 25.4 mm.
a. Nails spaced at 6 inches at intermediate supports where spans are 48 inches or more. For nailing of wood structural panel and particleboard diaphragms and shear walls, refer
to Section 2305. Nails for wall sheathing are permitted to be common, box or casing.
b. Spacing shall be 6 inches on center on the edges and 12 inches on center at intermediate supports for nonstructural applications. Panel supports at 16 inches (20 inches if
strength axis in the long direction of the panel, unless otherwise marked).
c. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule and the ceiling joist is fastened to the top plate in accordance with this schedule,
the number of toenails in the rafter shall be permitted to be reduced by one nail.
d. RSRS is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
e. Tabulated fastener requirements apply where the basic wind speed,V, is less than 140 mph. For wood structural panel roof sheathing attached to gable-end roof framing and
to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4 inches on center where the basic wind speed,V, is greater than 130 mph in Expo-
sure B or greater than 110 mph in Exposure C. Spacing exceeding 6 inches on center at intermediate supports shall be permitted where the fastening is designed per the AWC
NDS. Where the specific gravity of the wood species used for roof framing is greater than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, fastening of roof
sheathing shall be with RSRS-03 (21/2″ × 0.131″ × 0.281″ head) nails unless alternative fastening is designed in accordance with AWC NDS. Where the specific gravity of the wood
species used for roof framing is less than 0.35, fastening of the roof sheathing shall be designed in accordance with AWC NDS.
f. Fastening is only permitted where the basic wind speed,V, is less than or equal to 110 mph and where fastening is to wood framing of a species with specific gravity greater
than or equal to 0.42 in accordance with AWC NDS.
g. Nails and staples are carbon steel meeting the specifications of ASTM F1667. Connections using nails and staples of other materials, such as stainless steel, shall be designed
by acceptable engineering practice or approved under Section 104.2.3.|For SI: 1 inch = 25.4 mm.
a. Nails spaced at 6 inches at intermediate supports where spans are 48 inches or more. For nailing of wood structural panel and particleboard diaphragms and shear walls, refer
to Section 2305. Nails for wall sheathing are permitted to be common, box or casing.
b. Spacing shall be 6 inches on center on the edges and 12 inches on center at intermediate supports for nonstructural applications.CHBC § 1609.3.1. Medium relevance — show source text
Horizontal battens are required for slopes over 7:12.
e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound per square foot = 4.882 kg/m2.
a. Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s, 1 pound per square foot = 4.882 kg/m2.
a. Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
e.CHBC § 170.2 Medium relevance — show source text
244 2025 CALIFORNIA ENERGY CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
MULTIFAMILY BUILDINGS—PERFORMANCE AND PRESCRIPTIVE COMPLIANCE APPROACHES
F. Lighting. Lighting heating and cooling loads shall be based on actual design lighting levels or power densities as specified in Section 170.2(e)1. G. People. Occupant density shall be based on the expected occupancy of the building and shall be the same as determined under Section 160.2(c)3A, if used. Sensible and latent heat gains shall be as listed in the 2017 ASHRAE Handbook—Fundamentals, Chapter 18. H. Process loads. Loads caused by a process shall be based upon actual information on the intended use of the building. I. Miscellaneous equipment. Equipment loads other than process loads shall be calculated using design data compiled from one or more of the following sources: i. Actual information based on the intended use of the building; or ii. Published data from manufacturers’ technical publications or from technical societies, such as the ASHRAE Handbook, Applications Volume; or iii. Other data based on the designer's experience of expected loads and occupancy patterns. J. Internal heat gains. Internal heat gains may be ignored for heating load calculations. K. Safety factor. Calculated design loads based on Sections 170.2(c)2A through K may be increased by up to 10 percent to account for unexpected loads or changes in space usage. L. Other loads. Loads such as warm-up or cool-down shall be calculated from principles based on the thermal capacity of the building and its contents, the degree of setback, and desired recovery time; or may be assumed to be no more than 30 percent for heating and 10 percent for cooling of the steady-state design loads. In addition, the steady-state load may include a safety factor in accordance with Section 170.2(c)2K. 3. Dwelling unit space-conditioning systems. A. Heating system type. Space-conditioning systems serving dwelling units shall meet i or ii. Systems that cannot meet the requirements of i or ii, including multi-zone systems and systems using central boilers or chillers, shall comply with the performance requirements of Section 170.1. i. Multifamily buildings three habitable stories or fewer. For Climate Zones 1 through 15, the space-conditioning system shall be a heat pump. For Climate Zone 16, the space-conditioning system shall be an air conditioner with furnace. Additionally, balanced ventilation systems serving these dwelling units shall meet the applicable requirements of Section 170.2(c)3Bivc. ii. Multifamily buildings four habitable stories or greater. For Climate Zones 2 through 15, the space-conditioning system shall be a heat pump. For Climate Zones 1 and 16, the space-conditioning system shall be a dual-fuel heat pump. Exception to Section 170.2(c)3A: A supplemental heating unit may be installed in a space served directly or indirectly by a primary heating system, provided that the unit thermal capacity does not exceed 2 kW or 7,000 Btu/hr and is controlled by a time-limiting device not exceeding 30 minutes. B. Space-conditioning and ventilation systems.
Frequently asked questions
Do the CHBC room‑size and window rules apply to every historic dwelling?
Yes — the residential occupancy section (Section 8-303) applies to qualified historical buildings used for human habitation; sleeping‑room and habitable‑room rules therein apply to those dwelling units § 8-303.3 and § 8-303.5–8-303.6 .
If my sleeping room already has an old small window, do I have to enlarge it to meet escape opening sizes?
If the sleeping room is below the fourth floor or a basement, § 8-503 requires at least one approved escape opening (clear area 3.3 sq ft, min dimension 18 in, operable from inside). Existing historic windows may be modified or alternatives accepted by the enforcing agency, but you must meet the escape requirement or obtain an approved alternative .
How do I calculate the 6% window area?
The CHBC states the requirement as 6% of the floor area or 6 sq ft, whichever is greater (§ 8-303.6) but does not prescribe a specific measurement procedure in that clause. Confirm with the enforcing agency whether they measure gross opening, glazed area, or net operable area in practice .
Are historic bedrooms exempt from electrical lighting requirements?
Yes — the CHBC explicitly notes that residential occupancies need not be provided with electrical lighting under § 8-303.6, though local permitting or alterations may introduce modern lighting later .
Can the enforcing agency accept a different solution to preserve historic character?
Yes — the CHBC permits enforcing agencies to accept reasonably equivalent alternatives and to apply exceptions on a case‑by‑case basis where strict compliance would threaten historic features. Always document the rationale with the enforcing agency per CHBC guidance .
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