CBC · California Building Code

How are buildings assigned Risk Category and Seismic Design Category?

Risk Category is set from the building’s occupancy/nature using Table 1604A.5; Seismic Design Category is then determined either from that Risk Category via the CBC figure or by using ASCE 7 procedures (required when certain poor site soils are present). The Risk Category controls consequence-based requirements; the SDC controls the level of seismic detailing and inspections. file

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Last reviewed: July 5, 2026

What the code requires — 2-4 sentences

The California Building Code requires each building to be assigned a Risk Category (a measure of the consequences of failure) using Table 1604A.5 and related provisions in § 1604.5. The Seismic Design Category (SDC) for that building is then determined either from the structure’s Risk Category using Figure 1613.2(1) or by following ASCE 7 procedures; if site soils are Site Class DE, E or F the SDC must be determined in accordance with ASCE 7. § 1613.2.

Note: I was not able to locate the text of § 1601 in the uploaded files, so I cannot quote or cite § 1601 here. If you can provide § 1601 or permit me to search additional files I will incorporate it.

Requirements in detail

1) Assigning Risk Category (what to use and where)

  • The building official assigns a Risk Category using the code’s Risk Category table (Table 1604A.5) and the occupancy/usage definitions in the table. § 1604.5 and Table 1604A.5.
  • Where a building contains multiple occupancies, the portion(s) are assigned the highest applicable Risk Category; separated portions are classified separately unless they provide required access/egress or share life-safety or essential systems, in which case both portions take the higher category. § 1604.5.1.
  • Special equipment/structures (for example photovoltaic systems) have specific Risk Category assignments in § 1604.5.2.

Decision table — risk-category assignment (decision-relevant dimensions)

Decision factor Typical values / outcomes Code reference
Low‑hazard occupancies (e.g., agricultural, minor storage) Risk Category I § 1604.5 / Table 1604A.5
General buildings (default) Risk Category II § 1604.5 / Table 1604A.5
Substantial‑hazard occupancies (large assembly, certain education, some utilities) Risk Category III § 1604.5 / Table 1604A.5
Essential facilities (hospitals, some emergency facilities) and buildings whose loss is critical Risk Category IV § 1604.5 / Table 1604A.5
Multiple occupancies Assign highest Risk Category that applies (per portion rules) § 1604.5.1
PV systems / elevated supports See § 1604.5.2 (assignments vary: rooftop = same RC as building; some ground-mounted = RC I or II; ESS-paired systems for RC IV = RC IV) § 1604.5.2

2) Determining Seismic Design Category (how to get SDC)

Code prescribes two permitted methods (unless soils force ASCE 7):

  • Method A — Use the code’s Figure 1613.2(1) to assign SDC from Risk Category and seismic parameters for default site conditions. § 1613.2(1).
  • Method B — Determine the SDC in accordance with ASCE 7 (calculate MCE, S_DS, site class, etc.) and then follow ASCE 7 mapping. § 1613.2.
  • Mandatory ASCE 7 route when Site Class DE, E or F soils are present — the SDC must be determined in accordance with ASCE 7. § 1613.2.

Decision table — seismic design category decision variables

Decision factor Where it matters / value Code reference
Selected procedure Figure 1613.2(1) (CBC figure) OR ASCE 7 procedures § 1613.2
Site class = DE, E or F Must use ASCE 7 (Figure method not permitted) § 1613.2
Structure Risk Category Used by Figure 1613.2(1) method to locate SDC § 1613.2

(If you need numeric SDS → SDC breakpoints, those are established in ASCE 7; the Residential Code includes the same mapping as a practical table — see Table R301.2.2.1.1 for typical SDS ranges and corresponding SDCs. )

3) Implications of Risk Category and SDC

  • Risk Category drives required functional expectations, e.g., Risk Category IV buildings (essential facilities) get more stringent SDC-related detailing and performance expectations per § 1613 and the referenced standards. § 1613.1 and § 1613.2.
  • Seismic Design Category determines the level of seismic detailing, special inspections, and testing requirements (many special inspection rules apply for SDC C and higher, and are stricter for D/E/F). See special inspection provisions tied to SDC (example: nondestructive testing / inspection thresholds are tied to SDC).

Exceptions & special cases

  • Multiple occupancies: each portion gets the highest applicable Risk Category; structurally-separated portions that share life-safety or essential systems must be assigned the higher category. § 1604.5.1.
  • Photovoltaic systems: ground‑mounted and elevated PV systems have their own assignments (some ground-mounted are RC I or II; rooftop-mounted PV take the building’s Risk Category; PV + energy storage paired with RC IV buildings are RC IV). § 1604.5.2.
  • Soil/site limitations: when Site Class DE/E/F is present, the CBC requires using ASCE 7 to determine SDC (Figure method in the CBC is not permitted). § 1613.2.
  • Agency-specific limitations: certain state agencies or OSHPD have addenda or further restrictions (for example OSHPD notes in § 1613 that SDC shall be D or higher for some facilities). § 1613.2 (OSHPD notes).

Common mistakes

  • Assigning Risk Category by occupancy name only, without checking the occupancies’ quantitative thresholds in Table 1604A.5 (for example, assembly or education spaces have occupant-load thresholds that change the Risk Category). Always check Table 1604A.5. § 1604.5.
  • Treating separated portions as automatically the lower category — if a separated portion provides required egress, life‑safety systems or essential support to a higher‑category portion, it must be assigned the higher category. § 1604.5.1.
  • Using the CBC figure-based SDC method without verifying site class; Site Class DE/E/F forces ASCE 7. § 1613.2.
  • Forgetting PV rules: rooftop PV take the building’s Risk Category, but many ground-mounted or elevated systems have separate assignments in § 1604.5.2.
  • Thinking SDC alone determines special inspection — both Risk Category and SDC feed inspection and testing obligations (special inspection thresholds vary with SDC). See special inspection provisions tied to SDC.

Worked example — concrete scenario with numbers

Scenario: A general acute-care hospital building (continuous operation, essential services) located on a site with Site Class D soils. The short‑period design spectral acceleration (SDS) at the site is calculated to be 0.65g.

Step 1 — Risk Category:

  • A general acute‑care hospital is explicitly listed as an essential facility and therefore is Risk Category IV per Table 1604A.5. § 1604.5 / Table 1604A.5.

Step 2 — Choose SDC determination method:

  • Because Site Class = D (not DE/E/F), the CBC allows either: (a) use Figure 1613.2(1) (CBC figure method) or (b) determine SDC per ASCE 7. § 1613.2.

Step 3 — Using ASCE 7 mapping (practical numeric method):

  • Using the site SDS = 0.65g and the common SDS → SDC ranges shown in CBC/Residential guidance, SDS = 0.65g falls in the range 0.50 < SDS ≤ 0.67, which corresponds to Seismic Design Category D (specifically D0 in the Residential Code table). (See Table R301.2.2.1.1 for the SDS ranges used to map to SDC.)
  • Therefore the hospital (Risk Category IV) with SDS = 0.65g is assigned Seismic Design Category D (D0 per the numeric range example). Combined with the Risk Category IV designation, design and detailing follow the CBC’s § 1613/ASCE 7 requirements for an essential facility in SDC D. § 1613.2.

Notes:

  • If the site soils had been DE, E or F, the code would have required determining the SDC using ASCE 7 (no figure shortcut). § 1613.2.
  • The example used the Residential Code table for SDS → SDC ranges as a practical numerical illustration; final SDC determinations for non‑residential essential facilities should be made using ASCE 7 procedures or CBC figure as allowed by § 1613.2. file

Related provisions

  • § 1604.5 — Risk category assignment; multiple‑occupancy rules; PV system assignments (Table 1604A.5).
  • § 1604.5.1 — Multiple occupancies and structurally separated portions rules.
  • § 1604.5.2 — Photovoltaic (PV) panel systems and elevated support structure risk‑category assignments.
  • § 1613.1 — Scope for earthquake loads and applicability of ASCE 7.
  • § 1613.2 — Determination of Seismic Design Category (Figure method or ASCE 7; Site Class DE/E/F rule).
  • Table R301.2.2.1.1 (California Residential Code) — numeric SDS → SDC mapping used commonly for examples/thresholds.
  • Special inspection and testing provisions tied to Seismic Design Category (examples: § 1705.* special‑inspection thresholds).

Code references

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

  • CBC § 506.5.1 High relevance — show source text

    [BS] 506.5.1 Live loads. Structural elements carrying tributary live loads from an area with a change of occupancy shall satisfy the requirements of Section 1607 of the California Building Code . Design live loads for areas of new occupancy shall be based on Section 1607 of the California Building Code . Design live loads for other areas shall be permitted to use previously approved design live loads.

    Exception: Structural elements whose demand-capacity ratio considering the change of occupancy is not more than 5 percent greater than the demand-capacity ratio based on previously approved live loads need not comply with this section.

    [BS] 506.5.2 Snow and wind loads. Where a change of occupancy results in a structure being assigned to a higher risk category, the structure shall satisfy the requirements of Sections 1608 and 1609 of the California Building Code for the new risk category.

    Exception: Where the area of the new occupancy is less than 10 percent of the building area, compliance with this section is not required. The cumulative effect of occupancy changes over time shall be considered.

    [BS] 506.5.3 Seismic loads (seismic force-resisting system). Where a change of occupancy results in a building being assigned to a higher risk category, or where the change is from a Group S or Group U occupancy to any occupancy other than Group S or

    2025 CALIFORNIA EXISTING BUILDING CODE 5-9

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    PRESCRIPTIVE COMPLIANCE METHOD

    Group U, the lateral force-resisting system of the building shall comply with Section 304.3.1 for the new risk category. Where a change of occupancy results in a building being assigned to Risk Category IV and Seismic Design Category D or F, nonstructural components serving any portion of the building changed to Risk Category IV shall comply with the requirements of Section 1613 of the California Building Code or shall comply with ASCE 41 using an objective of Operational nonstructural performance with the BSE-1N earthquake hazard level.

    Exceptions:

    1. Where the area of the new occupancy is less than 10 percent of the building area, the occupancy is not changing from a Group S or Group U occupancy, and the new occupancy is not assigned to Risk Category IV, compliance with this section is not required. The cumulative effect of occupancy changes over time shall be considered.
    2. Where a change of use results in a building being reclassified from Risk Category I or II to Risk Category III and the seismic coefficient, S DS, is less than 0.33, compliance with this section is not required.
    3. Unreinforced masonry bearing wall buildings assigned to Risk Category III and to Seismic Design Category A or B, shall be permitted to use Appendix Chapter A1 of this code.
    4. Where the change is from a Group S or Group U occupancy and there is no change of risk category, compliance with Section 304.3.2 shall be permitted.

    [BS] 506.5.4 Access to Risk Category IV. Any structure that provides operational access to an adjacent structure assigned to Risk Category IV as the result of a change of occupancy shall itself comply with Sections 1608 and 1609 of the California Building Code and Section 304.3.1 of this code. Where operational access to the Risk Category IV structure is less than 10 feet (3048 mm) from either an interior lot line or from another structure, access protection from potential falling debris shall be provided.

  • CBC § 1004.1 High relevance — show source text

    SECTION 1004—FIRE PROTECTION

    1004.1 General. Fire protection requirements in Section 1011 shall apply where either of the following occur:

    1. A building or portion thereof undergoes a change of occupancy.
    2. A building or portion thereof undergoes a change of occupancy and there is a different fire protection system threshold requirement in Chapter 9 of the current California Building Code than exists in the current building or portion thereof.

    SECTION 1005—MEANS OF EGRESS

    1005.1 General. Means of egress in portions of buildings undergoing a change of occupancy classification shall comply with Section 1011.

    SECTION 1006—STRUCTURAL

    [BS] 1006.1 Live loads. Structural elements carrying tributary live loads from an area with a change of occupancy shall satisfy the requirements of Section 1607 of the California Building Code . Design live loads for areas of new occupancy shall be based on Section 1607 of the California Building Code . Design live loads for other areas shall be permitted to use previously approved design live loads.

    Exception: Structural elements whose demand-capacity ratio considering the change of occupancy is not more than 5 percent greater than the demand-capacity ratio based on previously approved live loads.

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    CHANGE OF OCCUPANCY

    [BS] 1006.2 Snow and wind loads. Where a change of occupancy results in a structure being assigned to a higher risk category, the structure shall satisfy the requirements of Sections 1608 and 1609 of the California Building Code for the new risk category.

    Exception: Where the area of the new occupancy is less than 10 percent of the building area. The cumulative effect of occupancy changes over time shall be considered.

    [BS] 1006.3 Seismic loads. Where a change of occupancy results in a building being assigned to a higher risk category, or where the change is from a Group S or Group U occupancy to any occupancy other than Group S or Group U, the lateral force-resisting system of the building shall comply with Section 304.3.1 for the new risk category. Where a change of occupancy results in a building being assigned to Risk Category IV and Seismic Design Category D or F, nonstructural components serving any portion of the building changed to Risk Category IV shall comply with the requirements of Section 1613 of the California Building Code or shall comply with ASCE 41 using an objective of operational nonstructural performance with the BSE-1N earthquake hazard level.

    Exceptions:

    1. Where a change of use results in a building being reclassified from Risk Category I or II to Risk Category III and the seismic coefficient, S DS, is less than 0.33, compliance with this section is not required.

    2. Where the area of the new occupancy is less than 10 percent of the building area, the occupancy is not changing from a Group S or Group U occupancy, and the new occupancy is not assigned to Risk Category IV, compliance with this section is not required. The cumulative effect of occupancy changes over time shall be considered.

    3. Reserved.

    4. Where the change is from a Group S or Group U occupancy and there is no change of risk category, compliance with Section 304.3.2 shall be permitted.

  • CBC § 1.5.3 High relevance — show source text

    Where approved by the building official, the classification of buildings and other structures as Risk Category III or IV based on their quantities of toxic, highly toxic or explosive
    materials is permitted to be reduced to Risk Category II, provided that it can be demonstrated by a hazard assessment in accordance with Section 1.5.3 of ASCE 7 that a release
    of the toxic, highly toxic or explosive materials is not sufficient to pose a threat to the public.|a. For purposes of occupant load calculation, occupancies required by Table 1004.5 to use gross floor area calculations shall be permitted to use net floor areas to determine the
    total occupant load. The floor area for vehicular drive aisles shall be permitted to be excluded in the determination of net floor area in parking garages.
    b. Where approved by the building official, the classification of buildings and other structures as Risk Category III or IV based on their quantities of toxic, highly toxic or explosive
    materials is permitted to be reduced to Risk Category II, provided that it can be demonstrated by a hazard assessment in accordance with Section 1.5.3 of ASCE 7 that a release
    of the toxic, highly toxic or explosive materials is not sufficient to pose a threat to the public.|

    1604.5.1 Multiple occupancies. Where a building or structure is occupied by two or more occupancies not included in the same risk category, it shall be assigned the classification of the highest risk category corresponding to the various occupancies. Where buildings or structures have two or more portions that are structurally separated, each portion shall be separately classified.

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    STRUCTURAL DESIGN

    Where a separated portion of a building or structure provides required access to, required egress from or shares life safety systems, designated seismic systems, emergency power systems, or emergency and egress lighting systems with another portion having a higher risk category, or provides required electrical, communications, mechanical, plumbing or conveying support to another portion assigned to Risk Category IV, both portions shall be assigned to the higher risk category. Exception: Where a storm shelter designed and constructed in accordance with ICC 500 is provided in a building, structure or portion thereof normally occupied for other purposes, the risk category for the normal occupancy of the building shall apply unless the storm shelter is a designated emergency shelter in accordance with Table 1604.5. 1604.5.2 Photovoltaic (PV) panel systems. Photovoltaic (PV) panel systems and elevated PV support structures shall be assigned a risk category as follows:

    1. Ground-mounted PV panel systems serving only Group R-3 buildings shall be assigned to Risk Category I.
    2. Ground-mounted PV panel systems other than those described in Items 1 and 5 shall be assigned to Risk Category II.
    3. Elevated PV support structures other than those described in Items 4, 5 and 6 shall be assigned to Risk Category II.
    4. Rooftop-mounted PV panel systems and elevated PV support structures installed on top of buildings shall be assigned to the same risk category as the risk category of the building on which they are mounted.
    5. PV panel systems and elevated PV support structures paired with energy storage systems (ESS) and serving as a dedicated, stand-alone source of backup power for Risk Category IV buildings shall be assigned to Risk Category IV.
    6. Elevated PV support structures where the usable space underneath is used for parking of emergency vehicles shall be assigned to Risk Category IV. **1604.6 In-situ load tests.
  • CBC § 503.7 High relevance — show source text

    [BS] 503.7 Anchorage for concrete and reinforced masonry walls. Where the work area exceeds 50 percent of the building area, the building is assigned to Seismic Design Category C, D, E or F and the building’s structural system includes concrete or reinforced masonry walls with a flexible roof diaphragm, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of wall anchors at the roof line.

    [BS] 503.8 Anchorage for unreinforced masonry walls in major alterations. Where the work area exceeds 50 percent of the building area, the building is assigned to Seismic Design Category C, D, E or F and the building’s structural system includes unreinforced masonry bearing walls, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of wall anchors at the floor and roof lines.

    [BS] 503.9 Bracing for unreinforced masonry parapets in major alterations. Where the work area exceeds 50 percent of the building area, and where the building is assigned to Seismic Design Category C, D, E or F, and the building has parapets constructed of unreinforced masonry, the alteration shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of parapet bracing to resist out-of-plane seismic forces.

    [BS] 503.10 Anchorage of unreinforced masonry partitions in major alterations. Where the work area exceeds 50 percent of the building area, or where the building is assigned to Seismic Design Category C, D, E or F, and the building has unreinforced masonry partitions and nonstructural walls, the alteration work shall include evaluation of the existing condition or removal, anchoring or alteration of any such partitions or walls within the work area and adjacent to egress paths from the work area, to comply with Section 304.3.2.

    [BS] 503.11 Substantial structural alteration. Where the work area exceeds 50 percent of the building area and where work involves a substantial structural alteration, the lateral load-resisting system of the altered building shall satisfy the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Where the building is assigned to Seismic Design Category D or F, supports and attachments for nonstructural components required to serve any portion of the building with a use included in Risk Category IV shall comply with Section 1613 of the California Building Code or shall comply with ASCE 41 using an objective of Position Retention nonstructural performance with the BSE-1E earthquake hazard level.

    Exceptions:

    1. Buildings of Group R occupancy with not more than five dwelling or sleeping units used solely for residential purposes that are altered based on the conventional light-frame construction methods of the California Building Code or in compliance with the provisions of the California Residential Code .
    2. Where the intended alteration involves structural components of the lowest story of a building, only the lateral loadresisting system above that story need not comply with this section.

    [BS] 503.12 Roof diaphragms resisting wind loads in high-wind regions. Where the intended alteration requires a permit for reroofing and involves removal of roofing materials from more than 50 percent of the roof diaphragm of a building or section of a building located where the basic wind speed, V, is greater than 130 mph (58 m/s) in accordance with Figure 1609.3(2) of the California

  • CBC § 304.3.2 High relevance — show source text

    [BS] 304.3.2 Reduced seismic criteria. Where required, seismic evaluation or design shall comply with one of the following methodologies, which shall not be applied in combination with each other:

    1. Section 1613 of the California Building Code using 75 percent of the prescribed forces. Values of R, Ω 0 and C d used for analysis shall be as specified in Section 304.3.1 of this code.

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    PROVISIONS FOR ALL COMPLIANCE METHODS

    1. Applicable chapters of Appendix A of this code, for structures or portions of structures specified in Items 2.1 through 2.4 subject to the limitations of the respective chapter. 2.1. Chapter A1 for unreinforced masonry bearing wall buildings assigned to Risk Category I or II. 2.2. Chapter A2 for the wall anchorage system in reinforced concrete and reinforced masonry wall buildings with flexible diaphragms assigned to Risk Category I or II. 2.3. Chapter A3 for cripple walls and sill plate anchorage in residential buildings of light-frame wood construction assigned to Risk Category I or II. 2.4. Chapter A4 for soft, weak or open-front wall conditions in multiple-unit residential buildings of wood construction assigned to Risk Category I or II.
    2. ASCE 41, using the performance objective in Table 304.3.2 for the applicable risk category.
    [BS] TABLE 304.3.2—PERFORMANCE OBJECTIVES FOR USE IN ASCE 41 FOR COMPLIANCE WITH REDUCED CRITERIA FORCES Col2 Col3
    RISK CATEGORY
    (Based on IBC Table 1604.5)    		 STRUCTURAL PERFORMANCE LEVEL FOR USE
    WITH BSE-1E EARTHQUAKE HAZARD LEVEL    		 STRUCTURAL PERFORMANCE LEVEL FOR USE
    WITH BSE-2E EARTHQUAKE HAZARD LEVEL
    I Life Safety (S-3).
    See Note a    		 Collapse Prevention (S-5)
    II Life Safety (S-3).
    See Note a    		 Collapse Prevention (S-5)
    III Damage Control (S-2).
    See Note a    		 Limited Safety (S-4).
    See Note b
    IV Immediate Occupancy (S-1) Life Safety (S-3).
    See Note c
    a. For Risk Categories I, II and III, the Tier 1 and Tier 2 procedures need not be considered for the BSE-1E earthquake hazard level.
    b. For Risk Category III, the Tier 1 screening checklists shall be based on the Collapse Prevention, except that checklist statements using the Quick Check provisions shall be
    based on_MS_-factors that are the average of the values for Collapse Prevention and Life Safety.
    c. For Risk Category IV, the Tier 1 screening checklists shall be based on Collapse Prevention, except that checklist statements using the Quick Check provisions shall be based
    on_MS_-factors for Life Safety.    		 a. For Risk Categories I, II and III, the Tier 1 and Tier 2 procedures need not be considered for the BSE-1E earthquake hazard level.
    b.
  • CBC § 1613.1 High relevance — show source text

    SECTION 1613—EARTHQUAKE LOADS

    1613.1 Scope. Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthquake motions in accordance with Chapters 11, 12, 13, 15, 17 and 18 of ASCE 7, as applicable. The seismic design category for a structure is permitted to be determined in accordance with Section 1613 or ASCE 7.

    Exceptions:

    1. Detached one- and two-family dwellings, assigned to Seismic Design Category A, B or C.
    2. The seismic force-resisting system of wood-frame buildings that conform to the provisions of Section 2308 are not required to be analyzed as specified in this section. [OSHPD 1R, 2 & 5] Not permitted by OSHPD, see Section 2308.
    3. Agricultural storage structures intended only for incidental human occupancy.
    4. Structures that require special consideration of their response characteristics and environment that are not addressed by this code or ASCE 7 and for which other regulations provide seismic criteria, such as vehicular bridges, electrical transmission towers, hydraulic structures, buried utility lines and their appurtenances and nuclear reactors.
    5. References within ASCE 7 to Chapter 14 shall not apply, except as specifically required herein.
    6. Temporary structures complying with Section 3103.6.1.4.

    1613.1.1 Scope. [SL] For applications listed in Section 1.12 regulated by the State Librarian, only the provisions of ASCE 7 Tables 13.5- 1 and 1607.1, as amended, of this code shall apply.

    1613.1.2 State-owned buildings. [BSC] State-owned buildings, including those of the University of California, CSU and Judicial Council, shall not be constructed where any portion of the foundation would be within a mapped area of earthquake-induced lique- faction or landsliding or within 50 feet of a mapped fault rupture hazard as established by Section 1803.7.

    1613.1.3 Existing state buildings. [BSC] Additions, alterations, repairs or change of occupancy category of existing buildings shall be in accordance with the California Existing Building Code, Part 10.

    1613.2 Determination of seismic design category. Structures shall be assigned to a seismic design category based on one of the following methods unless the authority having jurisdiction or geotechnical data determines that Site Class DE, E or F soils are present at the site:

    1. Based on the structure risk category using Figure 1613.2(1).

    2. Determined in accordance with ASCE 7.

    Where Site Class DE, E or F soils are present, the seismic design category shall be determined in accordance with ASCE 7.

    [OSHPD 1R, 2 & 5] Seismic design category shall be D or higher.

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    STRUCTURAL DESIGN

    FIGURE 1613.2(1)—SEISMIC DESIGN CATEGORIES FOR DEFAULT SITE CONDITIONS FOR THE CONTERMINOUS UNITED STATES (WESTERN)

    2025 CALIFORNIA BUILDING CODE 16-35

  • CBC § 2.2. High relevance — show source text

    2.2. Construction documents shall include a statement that the building is designed in accordance with ASCE 24, including that the pile or column foundation and building or structure to be attached thereto is designed to be anchored to resist flotation, collapse and lateral movement due to the effects of wind and flood loads acting simultaneously on all building components, and other load requirements of Chapter 16. 2.3. For breakaway walls designed to have a resistance of more than 20 psf (0.96 kN/m [2] ) determined using allowable stress design or a resistance to an ultimate load of more than 33 pounds per square foot (1.58 kN/m [2] ), construction documents shall include a statement that the breakaway wall is designed in accordance with ASCE 24. 2.4 For breakaway walls where provisions to allow for the automatic entry and exit of floodwaters do not meet the minimum requirements in Section 2.7.2.1 of ASCE 24, construction documents shall include a statement that the design will provide for equalization of hydrostatic flood forces in accordance with Section 2.7.2.2 of ASCE 24.

    SECTION 1613 A —EARTHQUAKE LOADS

    1613 A .1 Scope. Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthquake motions in accordance with Chapters 11, 12, 13, 15, 17 and 18 of ASCE 7, as applicable. The seismic design category for a structure is permitted to be determined in accordance with Section 1613 A or ASCE 7.

    1613 A .2 Determination of seismic design category. Structures shall be assigned to a Seismic Design Category D or higher based on one of the following methods unless the authority having jurisdiction or geotechnical data determines that Site Class DE, E or F soils are present at the site:

    1. Based on the structure risk category using Figure 1613.2(1).

    2. Determined in accordance with ASCE 7.

    Where Site Class DE, E or F soils are present, the seismic design category shall be determined in accordance with ASCE 7.

    1613 A .3 Simplified design procedure. Not permitted by DSA-SS and OSHPD.

    1613 A .4 Ballasted photovoltaic panel systems. Ballasted, roof-mounted photovoltaic panel systems need not be rigidly attached to the roof or supporting structure.

    [DSA-SS] Ballasted, roof-mounted photovoltaic panel systems shall comply with ASCE 7, Section 13.6.12. [OSHPD 1 & 4] Ballasted photovoltaic panel systems shall be considered as an alternative system.

    1613 A .5 Elevators, escalators and other conveying systems. Elevators, escalators and other conveying systems and their components shall satisfy the seismic requirements of ASCE 7 and ASME A17.1/CSA B44 as applicable.

    1613 A .6 Automatic sprinkler systems. Where required, automatic sprinkler systems, including anchorage and bracing, shall comply with ASCE 7 and Section 903.3.1.1.

    SECTION 1614 A —ATMOSPHERIC ICE LOADS

  • CBC § 0.33 High relevance — show source text

    Exceptions:

    1. Where the area of the new occupancy is less than 10 percent of the building area, the occupancy is not changing from a Group S or Group U occupancy, and the new occupancy is not assigned to Risk Category IV, compliance with this section is not required. The cumulative effect of occupancy changes over time shall be considered.
    2. Where a change of use results in a building being reclassified from Risk Category I or II to Risk Category III and the seismic coefficient, S DS, is less than 0.33, compliance with this section is not required.
    3. Unreinforced masonry bearing wall buildings assigned to Risk Category III and to Seismic Design Category A or B, shall be permitted to use Appendix Chapter A1 of this code.
    4. Where the change is from a Group S or Group U occupancy and there is no change of risk category, compliance with Section 304.3.2 shall be permitted.

    [BS] 506.5.4 Access to Risk Category IV. Any structure that provides operational access to an adjacent structure assigned to Risk Category IV as the result of a change of occupancy shall itself comply with Sections 1608 and 1609 of the California Building Code and Section 304.3.1 of this code. Where operational access to the Risk Category IV structure is less than 10 feet (3048 mm) from either an interior lot line or from another structure, access protection from potential falling debris shall be provided.

    506.6 Enhanced classroom acoustics. In Group E occupancies, where the work area exceeds 50 percent of the building area, enhanced classroom acoustics shall be provided in all classrooms with a volume of 20,000 cubic feet (565 m [3] ) or less. Enhanced classroom acoustics shall comply with the reverberation time in Section 808 of ICC A117.1.

    SECTION 507—HISTORIC BUILDINGS

    507.1 Historic buildings. The provisions of the California Historical Building Code (Part 8, Title 24, C.C.R), shall apply to qualified historical buildings or properties.

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    5-10 2025 CALIFORNIA EXISTING BUILDING CODE

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

    CALIFORNIA EXISTING BUILDING CODE – MATRIX ADOPTION TABLE

    CHAPTER 5A – PRESCRIPTIVE COMPLIANCE METHOD [OSHPD 1]

    (Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

  • CBC § 16A-7 High relevance — show source text

    Members that tend to accumulate residual deformations under repeated service loads shall have included in their analysis the effects of added deformations expected to occur during their service life.

    Any system or method of construction to be used shall be based on a rational analysis in accordance with well-established principles of mechanics. Such analysis shall result in a system that provides a complete load path capable of transferring loads from their point of origin to the load-resisting elements.

    The total lateral force shall be distributed to the various vertical elements of the lateral force-resisting system in proportion to their rigidities, considering the rigidity of the horizontal bracing system or diaphragm. Rigid elements assumed not to be a part of the lateral force-resisting system are permitted to be incorporated into buildings provided that their effect on the action of the system is considered and provided for in the design. Where a diaphragm is not permitted to be idealized as either flexible or rigid in accordance with ASCE 7 or for wood diaphragms in accordance with AWC SDPWS, the structure shall be analyzed and designed utilizing one of the following procedures:

    1. An envelope analysis of the structure using a flexible and rigid diaphragm analysis separately and designing each component for the more severe load condition.

    2. A semirigid diaphragm analysis and design.

    Where required by ASCE 7, provisions shall be made for the increased forces induced on resisting elements of the structural system resulting from torsion due to eccentricity between the center of application of the lateral forces and the center of rigidity of the lateral force-resisting system.

    2025 CALIFORNIA BUILDING CODE 16A-7

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

    STRUCTURAL DESIGN

    Every structure shall be designed to resist the effects caused by the forces specified in this chapter, including overturning, uplift and sliding. Where sliding is used to isolate the elements, the effects of friction between sliding elements shall be included as a force.

    1604 A .5 Risk category. Each building and structure shall be assigned a risk category in accordance with Table 1604 A .5. Where a referenced standard specifies an occupancy category, the risk category shall not be taken as lower than the occupancy category specified therein. Where a referenced standard specifies that the assignment of a risk category be in accordance with ASCE 7, Table 1.5-1, Table 1604 A .5 shall be used in lieu of ASCE 7, Table 1.5-1.

    Exceptions:

    1. The assignment of buildings and structures to Tsunami Risk Categories III and IV is permitted to be in accordance with Section 6.4 of ASCE 7.

    2. Freestanding parking garages not used for the storage of emergency services vehicles or not providing means of egress for buildings or structures assigned to a higher risk category shall be assigned to Risk Category II.

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    TABLE 1604A.5—RISK CATEGORY OF BUILDINGS AND OTHER STRUCTURES Col2
    RISK
    CATEGORY    		 NATURE OF OCCUPANCY
    I Buildings and other structures that represent a low hazard to human life in the event of failure, including but not limited to:
    • Agricultural facilities.
    • Certain temporary facilities.
    • Minor storage facilities.
    II Buildings and other structures except those listed in Risk Categories I, III and IV.
    III Buildings and other structures that represent a substantial hazard to human life in the event of failure,
  • CBC § 1705.14.1.2 High relevance — show source text

    1705.14.1.2 Structural steel elements. Nondestructive testing of structural steel elements in the seismic force-resisting systems of buildings and structures assigned to Seismic Design Category B, C, D, E or F other than those covered in Section 1705.14.1.1, including struts, collectors, chords and foundation elements, shall be performed in accordance with the quality assurance requirements of AISC 341. [OSHPD 1R, 2 & 5] and this code.

    Exceptions: [OSHPD 1R, 2 & 5] Not permitted by OSHPD.

    1. In buildings and structures assigned to Seismic Design Category B or C, nondestructive testing of structural steel elements is not required for seismic force-resisting systems with a response modification coefficient, R, of 3 or less.
    2. In structures assigned to Seismic Design Category D, E or F, nondestructive testing of structural steel elements is not required for seismic force-resisting systems where design and detailing other than AISC 341 is permitted by ASCE 7, Table 15.4-1. Nondestructive testing of structural steel elements shall be in accordance with the applicable referenced standard listed in ASCE 7, Table 15.4-1.

    17-16 2025 CALIFORNIA BUILDING CODE

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

    SPECIAL INSPECTIONS AND TESTS

    1705.14.2 Nonstructural components. For structures assigned to Seismic Design Category B, C, D, E or F, where the requirements of Section 13.2.1 of ASCE 7 for nonstructural components, supports or attachments are met by seismic qualification as specified in Item 2 therein, the registered design professional shall specify on the approved construction documents the requirements for seismic qualification by analysis, testing or experience data. Certificates of compliance for the seismic qualification shall be submitted to the building official as specified in Section 1704.5.

    [OSHPD 1R, 2 & 5] Seismic sway bracing components satisfying requirements of ANSI/FM 1950, ANSI/ASHRAE 171, or using an alter- native testing protocol approved by the building official shall be deemed to satisfy the requirements of this section.

    Note: Deemed to comply provisions provide acceptable options to comply with the code but do not mandate their use. Alternative systems in accordance with Section 104.2.3 and the California Administrative Code Section 7-104 are always acceptable when approved by the building official.

    1705.14.3 Designated seismic systems. For structures assigned to Seismic Design Category C, D, E or F and with designated seismic systems that are subject to the requirements of Section 13.2.4 of ASCE 7 for certification, the registered design professional shall specify on the approved construction documents the requirements to be met by analysis, testing or experience data as specified therein. Certificates of compliance documenting that the requirements are met shall be submitted to the building official as specified in Section 1704.5.

  • CBC § 5.2 High relevance — show source text

    Where a separated portion of a building or structure provides required access to, required egress from or shares life safety systems, designated seismic systems, emergency power systems, or emergency and egress lighting systems with another portion having a higher risk category, or provides required electrical, communications, mechanical, plumbing or conveying support to another portion assigned to Risk Category IV, both portions shall be assigned to the higher risk category. Exception: Where a storm shelter designed and constructed in accordance with ICC 500 is provided in a building, structure or portion thereof normally occupied for other purposes, the risk category for the normal occupancy of the building shall apply unless the storm shelter is a designated emergency shelter in accordance with Table 1604 A .5. 1604 A .5.2 Photovoltaic (PV) panel systems. Photovoltaic (PV) panel systems and elevated PV support structures shall be assigned a risk category as follows:

    1. Ground-mounted PV panel systems serving only Group R-3 buildings shall be assigned to Risk Category I.
    2. Ground-mounted PV panel systems other than those described in Items 1 and 5 shall be assigned to Risk Category II.
    3. Elevated PV support structures other than those described in Items 4, 5 and 6 shall be assigned to Risk Category II.

    [DSA-SS] The risk category shall not be less than the risk category that corresponds to the usable space underneath in accordance with the risk category and nature of occupancy descriptions in Table 1604A.5. 4. Rooftop-mounted PV panel systems and elevated PV support structures installed on top of buildings shall be assigned to the same risk category as the risk category of the building on which they are mounted. 5. PV panel systems and elevated PV support structures paired with energy storage systems (ESS) and serving as a dedicated, stand-alone source of backup power for Risk Category IV buildings shall be assigned to Risk Category IV. 6. Elevated PV support structures where the usable space underneath is used for parking of emergency vehicles shall be assigned to Risk Category IV. 1604 A .6 In-situ load tests. The building official is authorized to require an engineering analysis or a load test, or both, of any construction whenever there is reason to question the safety of the construction for the intended occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 1708 A .

    1604 A .7 Preconstruction load tests. Materials and methods of construction that are not capable of being designed by approved engineering analysis or that do not comply with the applicable referenced standards, or alternative test procedures in accordance with Section 1707 A, shall be load tested in accordance with Section 1709 A .

    1604 A .8 Anchorage. Buildings and other structures, and portions thereof, shall be provided with anchorage in accordance with Sections 1604 A .8.1 through 1604 A .8.3, as applicable. 1604 A .8.1 General. Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces that result from the application of the prescribed loads. 1604 A .8.2 Structural walls. Walls that provide vertical load-bearing resistance or lateral shear resistance for a portion of the structure shall be anchored to the roof and to all floors and members that provide lateral support for the wall or that are supported by the wall.

Frequently asked questions

What if my building has mixed uses (e.g., retail on first floor, apartments above)?

Assign each portion the highest Risk Category that applies to its occupancy per § 1604.5; if separated portions share required egress, life‑safety or essential systems, both portions take the higher category per § 1604.5.1. file

Can I always use the CBC figure (Figure 1613.2(1)) to pick the SDC?

You may use the CBC figure unless the site has Site Class DE, E or F soils — in that case the code requires determining SDC using ASCE 7. § 1613.2.

Where do PV arrays fit into Risk Category?

PV systems have special assignments: rooftop PV take the building’s Risk Category; some ground‑mounted systems are RC I or II; PV paired with ESS serving RC IV buildings are RC IV. See § 1604.5.2 for the details.

Does Risk Category affect required inspections?

Yes — Risk Category combined with SDC influences design expectations and special inspection/testing requirements; many special inspection rules reference SDC thresholds. See the special inspection provisions tied to SDC.

If my site SDS is 0.65g, what SDC is that?

As an example mapping (used in the Residential Code), SDS = 0.65g falls in 0.50 < SDS ≤ 0.67 → Seismic Design Category D (D0). For non‑residential or final determinations use ASCE 7 or the CBC figure per § 1613.2. file

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