CBC · California Building Code

What are the minimum seismic evaluation and design requirements for alterations/repairs?

If an alteration, structurally attached addition, or repair meets the thresholds in CBC §317.3 (for example, state projects over 25% of replacement cost, changes raising seismic demand by more than 10%, or damage reducing lateral capacity by more than 10%), California’s Existing Building Code requires a seismic evaluation by a registered design professional and retrofit if the building fails the minimum performance levels in §317.2–§317.6; limited, narrowly written exceptions (e.g., small rooftop equipment or low‑dead‑load PV) exist but must be checked exactly in the code.

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Last reviewed: July 5, 2026

What the code requires — 2–4 sentences

All alterations, structurally connected additions, and repairs to existing buildings must, at a minimum, be designed and constructed to resist seismic ground motions and the structural system must be evaluated by a registered design professional; if the system does not meet the minimum seismic-design performance required in Section 317 it must be retrofitted to comply with those requirements (§ 317.2) . Section 317.3 then lists when that seismic assessment and (if needed) retrofit are required (triggers based on cost, change in risk category, increased seismic demand or loss of lateral capacity, and similar thresholds) (§ 317.3) .

Requirements in detail

Scope and controlling rule

  • Core requirement: every alteration, structurally connected addition, or repair must be evaluated for seismic performance by a registered design professional; if the building does not meet the minimum seismic performance levels in Section 317 it must be retrofitted to those requirements (§ 317.2) .

Applicability — decision triggers (what makes Section 317 apply)

Section 317.3 establishes specific triggers that require the Section 317 evaluation/retrofit. Key, decision-relevant thresholds include the following (these are the common, decision-driving dimensions you will use to determine applicability):

Trigger / decision factor Threshold / value Action required Code reference
Project cost (state‑owned buildings) Total construction cost for the building exceeds 25% of replacement cost (excluding FF&E and maintenance) Section 317 applies — evaluation and, if necessary, retrofit per § 317.2 § 317.3.1(1)
Change in Risk Category Any change in the building’s risk category (as defined in CBC Chapters) Section 317 applies § 317.3.1(2)
Increase in seismic force demand on any structural component Cumulative increase to seismic forces or strength requirements of any structural component > 10% (unless capacity can be shown per § 319) Evaluation required; retrofit if performance not met § 317.3.1(3)
Damage to lateral‑force system Damage that has reduced lateral‑load‑resisting capacity by more than 10% Evaluation required; repair/retrofit if performance not met § 317.3.1(4)
Change in gravity loads that affect lateral shear Change in live or dead load that increases story shear by more than 10% Evaluation required; retrofit if performance not met § 317.3.1(5)
Public schools / community colleges Separate applicability rules per DSA references; follow § 317.3.2 and § 317.3.3 Section 317 applies when required by the California Administrative Code references § 317.3.2, § 317.3.3
Specified small rooftop equipment exception Individual rooftop‑supported mechanical equipment < 400 lb and total added weight < 10% of roof dead load — may be excluded from increasing demand‑capacity See exception wording for when cumulative change is due only to such equipment (exception language shown in code)
Rooftop PV panels If added roof dead load ≤ 5 psf and ≤ 10% of existing roof dead load, the increase in lateral demand need not be evaluated Exemption for PV installation under these limits (exception language shown in code)

Notes:

  • The 10% thresholds described above are cumulative since original construction unless a component’s capacity can be demonstrated per § 319; use those tests when tallying past and proposed changes (§ 317.3.1(3)) .
  • The code explicitly treats state‑owned buildings, public schools and community colleges under the Section 317 framework and points to agency‑specific references where applicable (§ 317.3) .

Evaluation and performance criteria

  • When Section 317 applies the design professional must provide an evaluation of the building’s seismic performance (the evaluation procedures, performance levels and earthquake hazard levels are established elsewhere in Section 317 and referenced standards) (§ 317.4, § 317.5) .
  • Section 317.5 sets the minimum seismic performance levels (ASCE‑41 notations such as BSE‑1N/BSE‑2N, S‑levels for structural performance and N‑levels for nonstructural) and prescribes how to apply Tiered ASCE‑41 evaluations or the alternative of designing the altered/entire building to the new building code rules as allowed (§ 317.5) .

Methods of compliance and peer review

  • The code allows Method A (linear static/dynamic ASCE‑41 procedures) or Method B (detailed evaluation) per the methods sections; Method B evaluations require the proposed evaluation procedures to be accepted by the building official prior to work and typically require peer review when invoked for the building (§ 320, § 321, § 317.10) .

Exceptions & special cases

  • Exception in § 317.2: If Section 317.3 determines that an assessment is not required for the project, or if Section 317.4 determines that retrofit is not needed, then only the requirements of § 317.11 (voluntary lateral‑force‑resisting system modifications) apply to the work (i.e., you do not have to do a full § 317 evaluation/retrofit) (§ 317.2 Exception) .
  • Small rooftop‑equipment and PV exceptions: the code contains narrowly written exemptions (examples: individual rooftop equipment under 400 lb and total rooftop additions under 10% of roof dead load; PV dead load additions ≤ 5 psf and ≤ 10% of roof dead load) — these are limited and must be checked carefully against the exact exception language before assuming an exemption applies .
  • Work can always be done to the new‑construction CBC requirements for the entire building (design the whole building as new) in lieu of complying with the existing‑building provisions; that path is permitted (§ 317.7) .
  • For projects proposing seismic isolation or passive energy dissipation, ASCE‑41 Chapters 14 and 15 apply and peer review is required (§ 317.8) .

Common mistakes

  • Treating “less than a permit threshold” as a free pass: even small projects can trigger the 10% cumulative thresholds — sum prior work since original construction when determining the % change (§ 317.3.1(3)) .
  • Ignoring nonstructural hazards: Section 317 and referenced ASCE‑41 performance levels cover both structural and nonstructural components; nonstructural performance objectives must be addressed where required (§ 317.5) .
  • Failing to use a registered design professional (RDP) for the required evaluation: Section 317.2 requires the structural system be evaluated by an RDP; documentation of the evaluation must be provided to the building official (§ 317.2) .
  • Not obtaining building official acceptance for Method B: when using Method B the evaluation/design procedures must be accepted by the building official before work begins (§ 317.10) .
  • Overlooking agency‑specific requirements for state‑owned buildings, schools and community colleges: these have mandatory adoption/administrative cross‑references in § 317.3 and related sections (§ 317.3.1–.3) .

Worked example — concrete scenario

Scenario: A state‑owned office building built in 1990 has a replacement cost of $2,000,000. The owner wants to do an alteration with total construction cost (excluding furniture, fixtures and equipment) of $600,000 and add rooftop mechanical equipment that weighs 300 lb each; total added rooftop weight equals 12% of the existing roof dead load.

Step 1 — cost trigger: 600,000 / 2,000,000 = 30% which exceeds the 25% threshold. Because the project exceeds 25% of replacement cost, Section 317 applies and a seismic evaluation is required (§ 317.3.1(1)) .

Step 2 — rooftop equipment exception check: each unit is under 400 lb (so an individual‑weight exemption criterion would be met), but the total rooftop added weight is 12% of roof dead load — that exceeds the 10% “total added weight” limit in the narrow rooftop equipment exception. Therefore you cannot rely on that exception to avoid evaluation; the increase in demand must be evaluated (§ 317.3 exception language and rooftop equipment exception) .

Step 3 — evaluation and outcome: a registered design professional must perform the seismic evaluation (per § 317.2 and § 317.4) using the applicable ASCE‑41 performance levels in § 317.5. If the evaluation shows the modified building does not meet the required performance objectives, the owner must retrofit the structure in accordance with § 317 (either during the alteration or via a code‑official‑accepted plan to complete retrofit timely) (§ 317.2, § 317.4, § 317.6) .

Practical result: because the project triggers § 317, expect to submit an evaluation report by an RDP, and be prepared to design and document retrofit work if the building fails the evaluation performance targets.

Related provisions (quick list)

  • § 317.2 — Scope and core requirement that alterations/additions/repairs be evaluated by an RDP and retrofitted if minimum performance not met
  • § 317.3 — Applicability: the numerical and situational triggers (cost, risk category, >10% increases, damage thresholds, school/college exceptions)
  • § 317.4 — Evaluation required when § 317.3 triggers apply; how evaluation is accepted and when retrofit is not required if performance is satisfactory
  • § 317.5 — Minimum seismic performance levels and reference to ASCE‑41 performance levels and seismic hazard levels
  • § 317.6 — Retrofit required when evaluation indicates performance objectives are not met; timing and options for retrofit
  • § 317.7 — Option to design the altered building to new‑construction CBC requirements (alternate compliance path)
  • § 317.8 — Requirements for seismic isolation / passive energy systems and peer review when used
  • § 317.10 — Acceptance requirements for Method B evaluations and design procedures prior to commencing work
  • § 317.11 — Voluntary lateral‑force‑resisting system modifications when the § 317.2 exception applies

Code references

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

  • CBC § 317.2 High relevance — show source text

    317.2 Scope. All alterations, structurally connected additions and/or repairs to existing structures or portions thereof shall, at a minimum, be designed and constructed to resist the effects of seismic ground motions as provided in this section. The structural system shall be evaluated by a registered design professional and, if not meeting or exceeding the minimum seismic design performance requirements of this section, shall be retrofitted in compliance with these requirements.

    Exception: Those structures for which Section 317.3 determines that assessment is not required, or for which Section 317.4 determines that retrofit is not needed, then only the requirements of Section 317.11 apply.

    317.3 Applicability.

    317.3.1 Existing state-owned buildings. [BSC, DSA-SS] For existing state-owned structures including all buildings owned by the University of California and the California State University, the requirements of Section 317 apply whenever the structure is to be retrofitted, repaired or modified and any of the following apply: 1. Total construction cost, not including cost of furnishings, fixtures and equipment, or normal maintenance, for the building exceeds 25 percent of the construction cost for the replacement of the existing building. The changes are cumulative for past modifications to the building that occurred after adoption of the 1995 California Building Code and did not require seismic retrofit.

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    2. There are changes in risk category. 3. The modification to the structural components increases the seismic forces in or strength requirements of any structural component of the existing structure by more than 10 percent cumulative since the original construction, unless the component has the capacity to resist the increased forces determined in accordance with Section 319. If the building’s seismic base shear capacity has been increased since the original construction, the percent change in base shear may be calculated relative to the increased value.

    4. Structural elements need repair where the damage has reduced the lateral-load-resisting capacity of the structural system by more than 10 percent. 5. Changes in live or dead load increase story shear by more than 10 percent.

    317.3.2 Public school buildings. [DSA-SS] For public schools, the provisions of Section 317 apply when required in accordance with Sections 4-307 and 4-309(c) of the California Administrative Code.

    317.3.3 Community college buildings. [DSA-SS/CC] For community colleges, the provisions of Section 317 apply when required in accordance with Sections 4-307 and 4-309(c) of the California Administrative Code.

    317.4 Evaluation required. If the criteria in Section 317.3 apply to the project under consideration, the design professional of record shall provide an evaluation in accordance with Section 317 to determine the seismic performance of the building in its current configuration and condition. If the structure's seismic performance as required by Section 317.5 is evaluated as satisfactory and the peer reviewer(s), when Method B of Section 321 is used, concur, then no structural retrofit is required.

    _**317.5 Minimum seismic design performance levels for structural and nonstructural components.

  • CBC § 317.1.2.1 High relevance — show source text

    The provisions of Section 317 through 323 also establish minimum standards for earthquake evaluation and design for rehabilitation of existing public buildings currently under the jurisdiction of DSA-SS.

    317.1.2.1 Reference to other chapters. For public schools, where reference within this chapter is made to sections in Chapters 16, 17, 18, 19, 21 or 22 of the California Building Code, the provisions in Chapters 16A, 17A, 18A, 19A, 21A and 22A of the California Building Code, respectively, shall apply instead.

    317.1.3 Community college buildings. [DSA-SS/CC] The provisions of Sections 317 through 323 establish minimum standards for earthquake evaluation and design for the rehabilitation of existing buildings for use as community college buildings under the jurisdiction of the Division of the State Architect—Structural Safety/Community Colleges [DSA-SS/CC], refer to Section 1.9.2.2.

    The provisions of Section 317 through 323 also establish minimum standards for earthquake evaluation and design for rehabilitation of existing community college buildings currently under the jurisdiction of DSA-SS/CC.

    317.1.3.1 Reference to other chapters. For community colleges, where reference within this chapter is made to sections in Chapters 17 or 18 of the California Building Code, the provisions in Chapters 17A and 18A of the California Building Code, respectively, shall apply instead.

    317.2 Scope. All alterations, structurally connected additions and/or repairs to existing structures or portions thereof shall, at a minimum, be designed and constructed to resist the effects of seismic ground motions as provided in this section. The structural system shall be evaluated by a registered design professional and, if not meeting or exceeding the minimum seismic design performance requirements of this section, shall be retrofitted in compliance with these requirements.

    Exception: Those structures for which Section 317.3 determines that assessment is not required, or for which Section 317.4 determines that retrofit is not needed, then only the requirements of Section 317.11 apply.

    317.3 Applicability.

    317.3.1 Existing state-owned buildings. [BSC, DSA-SS] For existing state-owned structures including all buildings owned by the University of California and the California State University, the requirements of Section 317 apply whenever the structure is to be retrofitted, repaired or modified and any of the following apply: 1. Total construction cost, not including cost of furnishings, fixtures and equipment, or normal maintenance, for the building exceeds 25 percent of the construction cost for the replacement of the existing building. The changes are cumulative for past modifications to the building that occurred after adoption of the 1995 California Building Code and did not require seismic retrofit.

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  • CBC § 181.4 High relevance — show source text
    1. Buildings in which the increase in the demand-capacity ratio is due entirely to the addition of rooftop-supported mechanical equipment individually having an operating weight less than 400 pounds (181.4 kg) and where the total additional weight of all rooftop equipment placed after initial construction of the building is less than 10 percent of the roof dead load. For purposes of this exception, “roof” shall mean the roof level above a particular story.
    2. Increases in the demand-capacity ratio due to lateral loads from seismic forces need not be evaluated for the installation of rooftop photovoltaic panel systems where the additional roof dead load due to the system, including ballast where applicable, does not exceed 5 pounds per square foot (psf) (0.2394 kN/m [2] ) and does not exceed 10 percent of the dead load of the existing roof.

    [BS] 503.5 Seismic Design Category F. Where the work area exceeds 50 percent of the building area, and where the building is assigned to Seismic Design Category F, the lateral force-resisting system of the altered building shall meet the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Supports and attachments for nonstructural components serving 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.

    [BS] 503.6 Bracing for unreinforced masonry parapets on reroofing. Where the intended alteration requires a permit for reroofing and involves removal of roofing materials from more than 25 percent of the roof area of a building assigned to Seismic Design Category D, E or F that has parapets constructed of unreinforced masonry, the work 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] 503.7 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.

  • CBC § 317.3.2 High relevance — show source text

    2. There are changes in risk category. 3. The modification to the structural components increases the seismic forces in or strength requirements of any structural component of the existing structure by more than 10 percent cumulative since the original construction, unless the component has the capacity to resist the increased forces determined in accordance with Section 319. If the building’s seismic base shear capacity has been increased since the original construction, the percent change in base shear may be calculated relative to the increased value.

    4. Structural elements need repair where the damage has reduced the lateral-load-resisting capacity of the structural system by more than 10 percent. 5. Changes in live or dead load increase story shear by more than 10 percent.

    317.3.2 Public school buildings. [DSA-SS] For public schools, the provisions of Section 317 apply when required in accordance with Sections 4-307 and 4-309(c) of the California Administrative Code.

    317.3.3 Community college buildings. [DSA-SS/CC] For community colleges, the provisions of Section 317 apply when required in accordance with Sections 4-307 and 4-309(c) of the California Administrative Code.

    317.4 Evaluation required. If the criteria in Section 317.3 apply to the project under consideration, the design professional of record shall provide an evaluation in accordance with Section 317 to determine the seismic performance of the building in its current configuration and condition. If the structure's seismic performance as required by Section 317.5 is evaluated as satisfactory and the peer reviewer(s), when Method B of Section 321 is used, concur, then no structural retrofit is required.

    317.5 Minimum seismic design performance levels for structural and nonstructural components. Following the notations of ASCE 41, the seismic requirements for design and assessment are based upon a prescribed Seismic Hazard Level (BSE-1N, BSE-2N, BSE-1E, BSE-R or BSE-C), a specified structural performance level (S-1 through S-5) and a nonstructural performance level (N-A through N-E). The minimum seismic performance criteria are given in Table 317.5 according to the Building Regulatory Authority and the Risk Category as determined in Chapter 16 of the California Building Code or by the regulatory authority. The building shall be evaluated in accordance with a Tier 3 Systematic Evaluation and Retrofit per ASCE 41 Chapter 6 for both the Level 1 and Level 2 performance levels, and the more restrictive requirements shall apply.

    Exception: If the floor area of an addition is greater than the larger of 50 percent of the floor area of the original building or 1,000 square feet (93 m [2] ), then the Table 317.5 entries for BSE-R (or BSE-1E) and BSE-C are replaced by BSE-1N and BSE-2N, respectively.

    |TABLE 317.5—SEISMIC PERFORMANCE REQUIREMENTS2,

  • CBC § 301.1 High relevance — show source text

    SECTION 301—ADMINISTRATION

    301.1 Applicability. The repair, alteration, change of occupancy, addition or relocation of all existing buildings shall comply with Section 301.2, 301.3 or 301.4. The provisions of Sections 302 through 309 shall apply to all alterations, repairs, additions, relocation of structures and changes of occupancy regardless of compliance method. [OSHPD 1R, 2, 4 and 5] Section 301.4 not permitted by OSHPD.

    Exceptions: 1. Existing state-owned structures. [BSC] The repair, alteration, change of occupancy, addition or relocation of all existing buildings shall comply with the provisions of Sections 317 through 322 as the minimum standards for earthquake evaluation and design for retrofit of existing state-owned structures, including buildings owned by the University of California, the California State University or the Judicial Council. The provisions of Sections 317 through 322 may be adopted by a local jurisdiction for earthquake evaluation and design for retrofit of existing buildings. 2. Public school buildings [DSA-SS] The provisions of Sections 317 through 323 establish minimum standards for earthquake evaluation and design for the rehabilitation of existing buildings for use as public school buildings under the jurisdiction of the Division of the State Architect—Structural Safety (DSA-SS, refer to Section 1.9.2.1) where required by Sections 4-307 and 4-309(c) of the California Administrative Code. The provisions of Sections 317 through 323 also establish minimum standards for earthquake evaluation and design for rehabilitation of existing public school buildings currently under the jurisdiction of DSA-SS. 3. Community college buildings. [DSA-SS/CC] The provisions of Sections 317 through 323 establish minimum standards for earthquake evaluation and design for the rehabilitation of existing buildings for use as community college buildings under the jurisdiction of the Division of the State Architect—Structural Safety/Community Colleges (DSA-SS/CC, refer to Section 1.9.2.2) where required by Sections 4-307 and 4-309(c) of the California Administrative Code. The provisions of Sections 317 through 323 also establish minimum standards for earthquake evaluation and design for rehabilitation of existing community college buildings currently under the jurisdiction of DSA-SS/CC. 4. [HCD 1] In addition to the requirements in this chapter, maintenance, alteration, repair, addition or change of occupancy to existing buildings and accessory structures under the authority of the Department of Housing and Community Development, as provided in Section 1.8.2.1.1, shall comply with California Code of Regulations, Title 25, Division 1, Chapter 1, Subchapter 1.

    Exceptions: 1. [HCD 2] For moved buildings and maintenance, alteration, repair, addition or change of occupancy to existing buildings and accessory structures in mobilehome parks or special occupancy parks as provided in Section 1.8.2.1.3, see California Code of Regulations, Title 25, Division 1, Chapters 2 and 2.2. 2. [HCD 1] Limited-density owner-built rural dwellings, as defined in Chapter 2 of the California Residential Code. _**5.

  • 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 § 906.2 High relevance — show source text

    [BS] 906.2 Existing structural elements resisting lateral loads. Where work involves a substantial structural alteration,the lateral load-resisting system of the altered building shall be shown to 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 only the lowest story of a building, structural components of the lateral load resisting system above that story need not comply with this section.

    [BS] 906.3 Seismic Design Category F. Where the building is assigned to Seismic Design Category F, the lateral force-resisting system of the altered building shall meet the requirements of Section 1609 of the California Building Code and Section 304.3.2 of this code. Supports and attachments for nonstructural components serving any portion of the building with a use included in Risk Cate- gory 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.

    [BS] 906.4 Anchorage for concrete and masonry buildings. For any building assigned to Seismic Design Category D, E or F with a structural system that 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 of all subject buildings and at the floor lines of unreinforced masonry.

    [BS] 906.5 Anchorage for unreinforced masonry walls. For any building assigned to Seismic Design Category C, D, E or F with a structural system that 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 roof line.

    [BS] 906.6 Bracing for unreinforced masonry parapets. Parapets constructed of unreinforced masonry in buildings assigned to Seismic Design Category C, D, E or F shall comply with Section 304.3.2 by evaluation of the existing condition or by installation of parapet bracing.

    [BS] 906.7 Anchorage of unreinforced masonry partitions. Where the building is assigned to Seismic Design Category C, D, E or F, unreinforced masonry partitions and nonstructural walls within the work area and adjacent to egress paths from the work area shall have their existing conditions evaluated or shall be anchored, removed or altered to resist out-of-plane seismic forces to comply with Section 304.3.2.

    SECTION 907—ENERGY CONSERVATION

    907.1 Minimum requirements. Level 3 alterations to existing buildings or structures shall comply with applicable provisions of the California Energy Code (Part 6, Title 24, C.C.R).

  • CBC § 309.2.1 High relevance — show source text

    2||||X|X|||||||||||||||||||| |309.2.1|||X|||||||||||||||||||||| |310 – 311|||||||||||X|X|||X|||||||||| |312|||||||||||X|||||||||||||| |313 – 316|||X|||||||||||||||||||||| |317 – 322|X|||||||X|X|||||||||||||||| |323||||||||X|X||||||||||||||||

    The state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.

    2025 CALIFORNIA EXISTING BUILDING CODE 3-1

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    User notes:

    About this chapter: Chapter 3 explains the three compliance options for alterations and additions available in the code. In addition, this chapter also lays out the methods to be used for seismic design and evaluation throughout this code. Finally, this chapter clarifies that provisions in other I-Codes related to repairs, alterations, additions, relocation and changes of occupancy must also be addressed unless they conflict with this code. In that case, this code takes precedence.

    SECTION 301—ADMINISTRATION

    301.1 Applicability. The repair, alteration, change of occupancy, addition or relocation of all existing buildings shall comply with Section 301.2, 301.3 or 301.4. The provisions of Sections 302 through 309 shall apply to all alterations, repairs, additions, relocation of structures and changes of occupancy regardless of compliance method. [OSHPD 1R, 2, 4 and 5] Section 301.4 not permitted by OSHPD.

    Exceptions: 1. Existing state-owned structures. [BSC] The repair, alteration, change of occupancy, addition or relocation of all existing buildings shall comply with the provisions of Sections 317 through 322 as the minimum standards for earthquake evaluation and design for retrofit of existing state-owned structures, including buildings owned by the University of California, the California State University or the Judicial Council. The provisions of Sections 317 through 322 may be adopted by a local jurisdiction for earthquake evaluation and design for retrofit of existing buildings. 2. Public school buildings [DSA-SS] The provisions of Sections 317 through 323 establish minimum standards for earthquake evaluation and design for the rehabilitation of existing buildings for use as public school buildings under the jurisdiction of the Division of the State Architect—Structural Safety (DSA-SS, refer to Section 1.9.2.1) where required by Sections 4-307 and 4-309(c) of the California Administrative Code. The provisions of Sections 317 through 323 also establish minimum standards for earthquake evaluation and design for rehabilitation of existing public school buildings currently under the jurisdiction of DSA-SS. 3. _**Community college buildings.

  • CBC § 1.9.2.1. High relevance — show source text

    State-owned and state-leased essential services buildings are subject to the regulatory authority of DSA-SS per Section 1.9.2.1._|1. ASCE 41 provides acceptance criteria (e.g., m-factor, rotation) for Immediate Occupancy (S1), Life Safety (S3) and Collapse Prevention (S5), and specifies in Table 2-1 the method
    to interpolate values for S-2 and S-4. When evaluating for the Hazards Reduced Nonstructural Performance Level, the requirements need not be greater than what would be
    required by ASCE 7 nonstructural provisions for new construction.
    2. Buildings evaluated and retrofitted to meet the structural and nonstructural requirements for a new building as given in the California Building Code as adopted by DSA or BSC, as
    applicable, are deemed to meet the seismic performance requirements of this section.
    3. Buildings complying with the requirements of the exception in Section 319.1 are deemed to meet the seismic performance requirements of this section.
    4. State-owned and state-leased essential services buildings are subject to the regulatory authority of DSA-SS per Section 1.9.2.1.|1. ASCE 41 provides acceptance criteria (e.g., m-factor, rotation) for Immediate Occupancy (S1), Life Safety (S3) and Collapse Prevention (S5), and specifies in Table 2-1 the method
    to interpolate values for S-2 and S-4. When evaluating for the Hazards Reduced Nonstructural Performance Level, the requirements need not be greater than what would be
    required by ASCE 7 nonstructural provisions for new construction.
    2. Buildings evaluated and retrofitted to meet the structural and nonstructural requirements for a new building as given in the California Building Code as adopted by DSA or BSC, as
    applicable, are deemed to meet the seismic performance requirements of this section.
    3. Buildings complying with the requirements of the exception in Section 319.1 are deemed to meet the seismic performance requirements of this section.
    4. State-owned and state-leased essential services buildings are subject to the regulatory authority of DSA-SS per Section 1.9.2.1.|

    317.6 Retrofit required. Where the evaluation indicates the building does not meet the required performance objectives of this section, the owner shall take appropriate steps to ensure that the building’s structural system is retrofitted in accordance with the provisions of Section 317. Appropriate steps are either: 1) undertake the seismic retrofit as part of the additions, alterations and/or repairs of the structure; or 2) provide a plan, acceptable to the building official, to complete the seismic retrofit in a timely manner. The relocation or moving of an existing building is considered to be an alteration requiring filing of the plans and specifications approved by the building official.

    317.7 The additions, alteration or repair to any existing building are permitted to be prepared in accordance with the structural and nonstructural requirements for a new building as given in the California Building Code, applied to the entire building.

    317.8 The requirements of ASCE 41 Chapters 14 and 15 are to apply to the use of seismic isolation and passive energy systems, respectively, for the repair, voluntary lateral-force-resisting system modification or retrofit of an existing structure. When seismic isolation or passive energy dissipation is used, the project must have project peer review as prescribed in Section 322.

  • CBC § 319.8. High relevance — show source text

    unless it can be demonstrated that_ reduced capacity meets the requirements of Section 319.8. 2. The lateral loading to or strength requirement of existing structural components is not increased beyond their capacity. 3. New structural components are detailed and connected to the existing structural components as required by the California Building Code. 4. New or relocated nonstructural components are detailed and connected to existing or new structural components as required by the California Building Code. 5. A dangerous condition is not created.

    Use of ASCE 41 Tier 1 and Tier 2 deficiency only retrofit procedures are pre-approved for use where Section 317.3 does not require an

    assessment.

    319.12.1 State-owned buildings. [BSC] Voluntary modifications to lateral force-resisting systems conducted in accordance with Appendix A of this code and the referenced standards of the California Building Code shall be permitted.

    319.12.1.1 Design documents. [BSC] When Section 319.12 is the basis for structural modifications, the approved design documents must clearly state the scope of the seismic modifications and the accepted criteria for the design. The approved design documents must clearly have the phrase “The seismic requirements of the California Existing Building Code have not been checked to determine if these structural modifications meet the full seismic evaluation and strengthening requirements of Sections 317-322: the modifications proposed are to a different seismic performance standard than would be required in Section 319 if they were not voluntary as allowed in Section 319.12.”

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    PROVISIONS FOR ALL COMPLIANCE METHODS

    319.12.2 Public schools and community colleges. [DSA-SS, DSA-SS/CC] When Section 319.12 is the basis for structural modifications, the approved design documents must clearly indicate the scope of modifications and the acceptance criteria for the design.

    SECTION 320 [BSC, DSA-SS & DSA-SS/CC]—METHOD A

    320.1 General. The retrofit design shall employ the Linear Static or Linear Dynamic Procedures of ASCE 41, Section 7.4.1 or 7.4.2, and comply with the applicable general requirements of ASCE 41, Chapters 6 and 7. The earthquake hazard level and performance level given specified in Section 317.5 for the building’s risk category shall be used. Structures shall be designed for seismic forces coming from any horizontal direction.

    SECTION 321 [BSC, DSA-SS & DSA-SS/CC]—METHOD B

    321.1 The existing or retrofitted structure shall be demonstrated to have the capability to sustain the deformation response due to the specified earthquake ground motions and meet the seismic performance requirements of Section 317. The registered design professional shall provide an evaluation of the response of the existing structure in its modified configuration and condition to the ground motions specified. If the building’s seismic performance is evaluated as satisfactory and the peer reviewer(s) and the enforcement agency concurs, then no further structural retrofit and/or repair of the lateral load-resisting system is required.

  • CBC § 319.1 High relevance — show source text

    Buildings complying with the requirements of the exception in Section 319.1 are deemed to meet the seismic performance requirements of this section._
    4. State-owned and state-leased essential services buildings are subject to the regulatory authority of DSA-SS per Section 1.9.2.1.|

    317.6 Retrofit required. Where the evaluation indicates the building does not meet the required performance objectives of this section, the owner shall take appropriate steps to ensure that the building’s structural system is retrofitted in accordance with the provisions of Section 317. Appropriate steps are either: 1) undertake the seismic retrofit as part of the additions, alterations and/or repairs of the structure; or 2) provide a plan, acceptable to the building official, to complete the seismic retrofit in a timely manner. The relocation or moving of an existing building is considered to be an alteration requiring filing of the plans and specifications approved by the building official.

    317.7 The additions, alteration or repair to any existing building are permitted to be prepared in accordance with the structural and nonstructural requirements for a new building as given in the California Building Code, applied to the entire building.

    317.8 The requirements of ASCE 41 Chapters 14 and 15 are to apply to the use of seismic isolation and passive energy systems, respectively, for the repair, voluntary lateral-force-resisting system modification or retrofit of an existing structure. When seismic isolation or passive energy dissipation is used, the project must have project peer review as prescribed in Section 322.

    317.9 Any construction required by this chapter shall include structural observation by the registered design professional who is responsible for the structural design in accordance with Section 319.10.

    2025 CALIFORNIA EXISTING BUILDING CODE 3-17

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    PROVISIONS FOR ALL COMPLIANCE METHODS

    317.10 Where Method B of Section 321 is used or is required by Section 319.7, the proposed method of building evaluation and design procedures must be accepted by the building official prior to the commencement of the work.

    317.11 Voluntary lateral-force-resisting system modifications. Where the exception of Section 317.2 applies, modifications of existing structural components and additions of new structural components that are initiated for the purpose of improving the seismic performance of an existing structure and that are not required by other portions of this chapter are permitted under the requirements of Section 319.12.

    SECTION 318 [BSC, DSA-SS & DSA-SS/CC]—DEFINITIONS

    318.1 In addition to the definitions given in Section 202, for the purposes of Sections 317 through 323, certain terms are defined as follows:

    [DSA-SS & DSA-SS/CC] For the purposes of Section 317 through 323, definitions of terms given in Section 4-207 or 4-314 of the California Administrative Code govern over those in Section 202.

    ADDITION [BSC] means any work that increases the floor or roof area or the volume of enclosed space of an existing building, and is structurally attached to the existing building by connections that are required for transmitting vertical or horizontal loads between the addition and the existing structure.

  • CBC § 9.2.2 High relevance — show source text

    _ Community college buildings. [DSA-SS/CC] The provisions of Sections 317 through 323 establish minimum standards for earthquake evaluation and design for the rehabilitation of existing buildings for use as community college buildings under the jurisdiction of the Division of the State Architect—Structural Safety/Community Colleges (DSA-SS/CC, refer to Section 1.9.2.2) where required by Sections 4-307 and 4-309(c) of the California Administrative Code. The provisions of Sections 317 through 323 also establish minimum standards for earthquake evaluation and design for rehabilitation of existing community college buildings currently under the jurisdiction of DSA-SS/CC. 4. _[HCD 1]**_ In addition to the requirements in this chapter, maintenance, alteration, repair, addition or change of occupancy to existing buildings and accessory structures under the authority of the Department of Housing and Community Development, as provided in Section 1.8.2.1.1, shall comply with California Code of Regulations, Title 25, Division 1, Chapter 1, Subchapter 1.

    Exceptions: 1. [HCD 2] For moved buildings and maintenance, alteration, repair, addition or change of occupancy to existing buildings and accessory structures in mobilehome parks or special occupancy parks as provided in Section 1.8.2.1.3, see California Code of Regulations, Title 25, Division 1, Chapters 2 and 2.2. 2. [HCD 1] Limited-density owner-built rural dwellings, as defined in Chapter 2 of the California Residential Code. 5. Hospital buildings removed from acute care service, skilled nursing facilities, intermediate-care facilities, correctional treatment centers and acute-psychiatric hospitals [OSHPD 1R, 2, 4 and 5]. The provisions of adopted sections in Chapters 3 through 5 shall control the alteration, repair and change of occupancy or function of existing structures for applications listed in Section 1.10.1, 1.10.2, 1.10.4 and 1.10.5 regulated by the Department of Health Care Access and Information/Office of Statewide Hospital Planning and Development (OSHPD). Functional service spaces shall comply with the requirements in the California Building Code, Sections 1224, 1225, 1226, 1227 and 1228.

    301.1.1 Bleachers, folding and telescopic seating and grandstands. Existing bleachers, folding and telescopic seating and grandstands shall comply with ICC 300.

    301.2 Repairs. Repairs shall comply with the requirements of Chapter 4.

    301.3 Alteration, addition or change of occupancy. The alteration, addition or change of occupancy of all existing buildings shall comply with one of the methods listed in Section 301.3.1, 301.3.2 or 301.3.3 as selected by the applicant. Sections 301.3.1 through 301.3.3 shall not be applied in combination with each other. [OSHPD 1R, 2, 4 and 5] Sections 301.3.2 and 301.3.3, not adopted by OSHPD.

    Exception: Subject to the approval of the code official, alterations complying with the laws in existence at the time the building or the affected portion of the building was built shall be considered in compliance with the provisions of this code. New structural

Frequently asked questions

Do all alterations automatically require a seismic evaluation under Section 317?

No — only those projects that meet the applicability triggers in § 317.3 (for example, the >25% cost threshold for state‑owned buildings, changes in risk category, >10% increases in seismic demand on a component, >10% reduction in lateral capacity from damage, etc.) require the § 317 evaluation; otherwise the § 317.2 exception or other code paths may apply (§ 317.3) .

Who must perform the seismic evaluation?

A registered design professional (architect or engineer) must evaluate the structural system and prepare the required evaluation documentation required by § 317.2 and § 317.4 (§ 317.2) .

If my project increases roof dead load by a small amount for PV panels, do I still need an evaluation?

There is a narrow PV exception: if the PV system increases roof dead load by no more than 5 psf and does not exceed 10% of the existing roof dead load, the increase in lateral demand need not be evaluated per the exception language — confirm exact limits and local enforcement interpretation before assuming exemption (§ 317.3 exceptions) .

Can I just design the altered building to current new‑building code instead of using Section 317?

Yes. Section 317.7 permits designing the addition/alteration/repair in accordance with the structural and nonstructural requirements for a new building under the CBC applied to the entire building; doing so is an accepted alternate compliance path (§ 317.7) .

What if my Method B evaluation shows compliance but the peer reviewer disagrees?

When Method B is used, peer review and building official concurrence are part of the acceptance process; if peer review and the enforcement agency concur with the evaluation, then no further retrofit is required; otherwise the building owner must address identified deficiencies (§ 317.4, § 321) .

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When is seismic evaluation/retrofit required for state-owned (and certain public) buildings?

What exceptions, thresholds or limited-scope options exist (assessment vs retrofit)?

Are peer review or earthquake monitoring requirements applicable for existing building projects?

Seismic Evaluation & Retrofit for Existing Buildings

California Building Code