CBC · California Building Code

How are earthquake loads determined and the seismic design category assigned?

The CBC requires buildings to be designed for earthquake motions and to be assigned a Seismic Design Category either by the CBC figure or by ASCE 7; if the site has poor soils (Site Class DE, E or F) you must use ASCE 7. The plans must list specific earthquake design data (risk category, site class, Ss/S1, SDS/SD1, SDC, base shear, etc.) so the assigned SDC and resultant detailing and inspection requirements are clear.

Ask a question free See coverage

Last reviewed: July 5, 2026

What the code requires — 2–4 sentences

The California Building Code requires every structure (and permanently attached nonstructural components) to be designed to resist earthquake motions in accordance with ASCE 7 and the CBC seismic provisions; the seismic design category (SDC) may be determined using Section 1613 of the CBC or by ASCE 7 (§ 1613.1) . Section 1613.2 sets the permitted methods for assigning the SDC and requires that where Site Class DE, E or F soils exist the SDC be determined in accordance with ASCE 7 (§ 1613.2) . Construction documents must show specific earthquake design data (risk category, Ie, Ss and S1, site class, SDS/SD1, SDC, design base shear, Cs, R, analysis procedure, and irregularities) per § 1603.1.5 (§ 1603.1.5) .

Requirements in detail

1) Scope and who it applies to

  • All structures and permanently attached nonstructural components must be designed for earthquake effects per § 1613.1; several narrow exceptions are listed (e.g., detached one- and two‑family dwellings are assigned to SDC A, B or C by the CBC) (§ 1613.1) . The CBC also notes certain categories (OSHPD, state-owned) have additional constraints stated in § 1613 and related notes .

2) How the Seismic Design Category (SDC) is assigned

There are two permitted paths in the CBC:

  • Use the risk‑category-based procedure that references Figure 1613.2(1) (the CBC default site‑condition SDC table) (§ 1613.2) .
  • Determine the SDC in accordance with ASCE 7 (i.e., use the ASCE 7 procedure/tables and maps) (§ 1613.2) .

Important constraint: if authoritative geotechnical information or the authority having jurisdiction indicates Site Class DE, E or F at the site, the CBC requires the SDC be determined in accordance with ASCE 7 (not the CBC default figure) (§ 1613.2) .

3) What must appear on the drawings (construction documents)

The CBC requires specific earthquake design data be shown on construction documents regardless of whether seismic governs the design. The list in § 1603.1.5 includes (non‑exhaustive): risk category, seismic importance factor Ie, Ss and S1, site class, SDS and SD1, seismic design category, basic seismic force‑resisting system(s), design base shear(s), Cs, R, analysis procedure, applicable irregularities, and base location (§ 1603.1.5) .

Decision‑relevant dimensions/values (abbreviated) — CODE REFERENCE table

Decision item Typical inputs / choices Code Reference
Method to assign SDC (a) CBC Figure 1613.2(1) for default sites, or (b) ASCE 7 procedure/tables § 1613.2 — see CBC Section on determination of SDC
Site soil class A, B, C, D, DE, E, F — if DE/E/F → must use ASCE 7 § 1613.2 — Site Class DE/E/F require ASCE 7 determination
Required plan data Risk category, Ie, Ss, S1, site class, SDS, SD1, SDC, base shear, Cs, R, analysis method, irregularities, base location § 1603.1.5 — list of earthquake design data to be shown on construction documents
Exceptions (who’s excluded or preassigned) Detached 1–2 family dwellings (assigned A,B,C), certain wood‑frame per § 2308, agricultural storage, special facilities § 1613.1 — scope exceptions and notes

(If you need the full Figure 1613.2(1) values or the ASCE 7 tables, those are contained in the CBC figures or in ASCE 7; the CBC text points you to those sources — § 1613.2) .

4) How earthquake loads are determined (process overview)

  1. Determine the structure’s Risk Category (as required throughout Chapter 16 and referenced in § 1603 and § 1613) and identify whether any code exceptions apply (§ 1603.1, § 1613.1) file.
  2. Obtain the short‑period and 1‑second spectral site parameters (Ss and S1) from ASCE 7 ground motion maps or a site‑specific study (ASCE 7 is the technical standard called out by § 1613.1) .
  3. Determine site class (A–F) from geotechnical data. If site class is DE/E/F, the SDC must be assigned using ASCE 7 (§ 1613.2) .
  4. Compute the design spectral parameters SDS and SD1 (ASCE 7 procedure) and then assign the Seismic Design Category either via CBC Figure 1613.2(1) (for default site conditions) or per ASCE 7 (§ 1613.2) .
  5. Show required earthquake design data on the construction documents per § 1603.1.5 .
  6. Use the assigned SDC to select detailing, special inspection, foundation/geotech scope, and nonstructural anchorage requirements elsewhere in the CBC (for example, special inspection and geotechnical rules for SD C–F) — see § 1705 special inspection and § 1803 geotechnical investigation cross‑references in the CBC file.

Exceptions & special cases

  • Detached one‑ and two‑family dwellings are assigned to Seismic Design Category A, B, or C under § 1613.1 and are handled by the Residential Code exceptions noted there (§ 1613.1) .
  • Where site class is DE, E or F (very soft soils, partially saturated to saturated), the CBC requires the SDC determination follow ASCE 7 — you cannot use CBC’s default figure in that case (§ 1613.2) .
  • Some building types and situations are excluded from Chapter 1613/ASCE 7 application (vehicular bridges, transmission towers, nuclear reactors, etc.) — see § 1613.1 exceptions .
  • State agencies and OSHPD have additional or altered requirements in some CBC amendments (the code text notes OSHPD/DSA provisions in § 1613) — check the agency annotations in the CBC (§ 1613 and annotated subsections) .

Common mistakes

  • Failing to show the full earthquake design data required by § 1603.1.5 on the construction documents (risk category, Ss, S1, SDS/SD1, site class, SDC, Cs, R, base shear, analysis method, etc.) — the code explicitly requires these items (§ 1603.1.5) .
  • Using the CBC default SDC figure when geotechnical information shows Site Class DE/E/F — in that case ASCE 7 must be used (§ 1613.2) .
  • Assuming residential‑code SDC tables always apply for nonresidential work; the CBC permits either § 1613 procedures or ASCE 7 and references its own Figure 1613.2(1) for default conditions (§ 1613.2) .
  • Omitting the seismic importance factor Ie or the site class from calculations and plans — both are required data items on the documents (§ 1603.1.5) .
  • Forgetting that special inspection and geotechnical investigation scopes increase for buildings assigned to higher SDCs (see special inspection requirements and geotechnical investigation cross‑references in Chapters 17 and 18) file.

Worked example — concrete scenario with numbers (illustrative)

Note: the numerical hazard values (Ss, S1, SDS) below are example inputs for illustration only; Ss/S1 must be taken from ASCE 7 maps or a site‑specific study in actual design. The procedural references below are the applicable CBC sections.

Scenario: 3‑story office building (Risk Category II) on default site class D.

  1. Risk category: II (determine per Chapter 16 definitions). Show this on plans per § 1603.1.5 (§ 1603.1.5) .
  2. Assume ASCE 7 maps yield Ss = 1.00g and S1 = 0.40g at the site (example values; obtain actual values from ASCE 7) — these are the short‑period (Ss) and 1‑second (S1) spectral accelerations referenced by § 1603.1.5 .
  3. Using the standard ASCE 7 relations for converting to design spectral values (these formulas are part of ASCE 7, which the CBC references for seismic procedures), the example gives: SDS ≈ 0.67g and SD1 ≈ 0.27g (these are illustrative computed values based on the assumed Ss/S1 — consult ASCE 7 for exact calculation steps). The CBC requires you to record SDS/SD1 on the documents (§ 1603.1.5) .
  4. If you use the Residential Code SDS→SDC mapping as an illustrative guide (Table R301.2.2.1.1), that table assigns SDC by SDS ranges: e.g., SDS = 0.50–0.67 → D0; SDS = 0.67–0.83 → D1, etc. In our example SDS ≈ 0.67g sits at the top of the D0 range in that table, so the structure would be classed as approximately SDC D0 under that mapping (this mapping is from the Residential Code table allowed as an alternate determination; for nonresidential projects follow § 1613.2 using CBC Figure 1613.2(1) or ASCE 7) file.
  5. Record the assigned SDC and all required items from § 1603.1.5 on the construction documents and then apply the detailing/special inspection/geotechnical requirements that correspond to the assigned SDC in the CBC and referenced standards (special inspection and geotechnical rules are in Chapters 17 and 18) filefile.

Takeaway: the example shows the workflow and how SDS ties to SDC; actual Ss/S1/SDS must be taken from ASCE 7 maps or a site‑specific geotechnical/ground‑motion study and the final SDC must be assigned per § 1613.2 (CBC figure or ASCE 7 when required) file.

Related provisions

  • § 1613.1 — Earthquake loads; scope and exceptions (CBC) .
  • § 1613.2 — Determination of Seismic Design Category (methods and Site Class DE/E/F rule) .
  • § 1603.1.5 — Earthquake design data required on construction documents (list of items) .
  • § 1803.5.11 / § 1803.5.12 — Geotechnical investigation requirements for SDC C–F and D–F (liquefaction, dynamic earth pressures, etc.) .
  • § 1705 (and related A‑tables) — Special inspection requirements that change with SDC (D, E, F trigger additional inspection) .
  • CBC Figure 1613.2(1) — default SDC figure for map/figure‑based assignment; see § 1613.2 statement for use of that figure .

Code references

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

  • 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.

    16-34 2025 CALIFORNIA BUILDING CODE

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

    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 § 1807.1.6.3.2 High relevance — show source text

    1807.1.6.3.2 Seismic requirements. Based on the seismic design category assigned to the structure in accordance with Section 1613, masonry foundation walls designed using Tables 1807.2.5.

    1. Seismic Design Categories A and B. No additional seismic requirements.
    2. Seismic Design Category C. A design using Tables 1807.1.6.3(1) through 1807.1.6.3(4) is subject to the seismic requirements of Section 7.4.3 of TMS 402.
    3. Seismic Design Category D. A design using Tables 1807.1.6.3(2) through 1807.1.6.3(4) is subject to the seismic requirements of Section 7.4.4 of TMS 402.
    4. Seismic Design Categories E and F. A design using Tables 1807.1.6.3(2) through 1807.1.6.3(4) is subject to the seismic requirements of Section 7.4.5 of TMS 402.

    1807.2 Retaining walls. Retaining walls shall be designed in accordance with Sections 1807.2.1 through 1807.2.4.

    1807.2.1 General. Retaining walls shall be designed to ensure stability against overturning, sliding, excessive foundation pressure and water uplift.

    1807.2.2 Design lateral soil loads. Retaining walls shall be designed for the lateral soil loads set forth in Section 1610. [OSHPD 1R, 2 & 5] Retaining wall lateral soil loads determined by a geotechnical investigation report in accordance with Section 1803.5.12 and shall not be less than 80 percent of the lateral soil loads determined in accordance with Section 1610. For use with the load combina-

    18-14 2025 CALIFORNIA BUILDING CODE

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

    SOILS AND FOUNDATIONS

    tions, lateral soil loads due to gravity load surcharge shall be considered gravity loads and seismic earth pressure increases due to earthquake shall be considered as seismic loads. For structures assigned to Seismic Design Category D, E or F, the design of retaining walls supporting more than 6 feet (1829 mm) of backfill height shall incorporate the additional seismic lateral earth pressure in accordance with the geotechnical investigation where required in Section 1803.2.

    1807.2.3 Safety factor. Retaining walls shall be designed to resist the lateral action of soil to produce sliding and overturning with a minimum safety factor of 1.5 in each case. The load combinations of Section 1605 shall not apply to this requirement. Instead, design shall be based on 0.7 times nominal earthquake loads, 1.0 times other nominal loads, and investigation with one or more of the variable loads set to zero. The safety factor against lateral sliding shall be taken as the available soil resistance at the base of the retaining wall foundation divided by the net lateral force applied to the retaining wall.

    Exception: Where earthquake loads are included, the minimum safety factor for retaining wall sliding and overturning shall be 1.1.

    1807.2.4 Segmental retaining walls. Dry-cast concrete units used in the construction of segmental retaining walls shall comply with ASTM C1372.

  • CBC § 1803.5.9 High relevance — show source text

    1. Field test method for determining the in-place dry density of the compacted fill.

    2. Minimum acceptable in-place dry density expressed as a percentage of the maximum dry density determined in accordance with Item 3.

    3. Number and frequency of field tests required to determine compliance with Item 6.

    1803.5.9 Controlled low-strength material (CLSM). Where shallow foundations will bear on controlled low-strength material (CLSM), a geotechnical investigation shall be conducted and shall include all of the following:

    1. Specifications for the preparation of the site prior to placement of the CLSM.
    2. Specifications for the CLSM.
    3. Laboratory or field test method(s) to be used to determine the compressive strength or bearing capacity of the CLSM .
    4. Test methods for determining the acceptance of the CLSM in the field.
    5. Number and frequency of field tests required to determine compliance with Item 4.

    1803.5.10 Alternate setback and clearance. Where setbacks or clearances other than those required in Section 1808.7 are desired, the building official shall be permitted to require a geotechnical investigation by a registered design professional to demonstrate that the intent of Section 1808.7 would be satisfied. Such an investigation shall include consideration of material, height of slope, slope gradient, load intensity and erosion characteristics of slope material.

    1803.5.11 Seismic Design Categories C through F. For structures assigned to Seismic Design Category C, D, E or F, a geotechnical investigation shall be conducted, and shall include an evaluation of all of the following potential geologic and seismic hazards:

    1. Slope instability.

    2. Liquefaction.

    3. Total and differential settlement.

    4. Surface displacement due to faulting or seismically induced lateral spreading or lateral flow.

    1803.5.12 Seismic Design Categories D through F. For structures assigned to Seismic Design Category D, E or F, the geotechnical investigation required by Section 1803.5.11 shall include all of the following as applicable:

    1. The determination of dynamic seismic lateral earth pressures on foundation walls and retaining walls supporting more than 6 feet (1.83 m) of backfill height due to design earthquake ground motions.
    2. The potential for liquefaction and soil strength loss evaluated for site peak ground acceleration, earthquake magnitude and source characteristics consistent with the maximum considered earthquake ground motions. Peak ground acceleration shall be determined based on one of the following: 2.1. A site-specific study in accordance with Chapter 21 of ASCE 7.

    2.2. In accordance with Section 11.8.3 of ASCE 7.

    1. An assessment of potential consequences of liquefaction and soil strength loss including, but not limited to, the following:

    2025 CALIFORNIA BUILDING CODE 18-5

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

    SOILS AND FOUNDATIONS

    3.1. Estimation of total and differential settlement.

    3.2. Lateral soil movement.

    3.3. Lateral soil loads on foundations.

    3.4. Reduction in foundation soil-bearing capacity and lateral soil reaction. 3.5. Soil downdrag and reduction in axial and lateral soil reaction for pile foundations. 3.6. Increases in soil lateral pressures on retaining walls.

    3.7. Flotation of buried structures.

    1. Discussion of mitigation measures such as, but not limited to, the following: 4.1. Selection of appropriate foundation type and depths. 4.2. Selection of appropriate structural systems to accommodate anticipated displacements and forces.
  • CBC § 5.9 High relevance — show source text
    1. Number and frequency of field tests required to determine compliance with Item 6.

    1803 A .5.9 Controlled low-strength material (CLSM). Where shallow foundations will bear on controlled low-strength material (CLSM), a geotechnical investigation shall be conducted and shall include all of the following:

    1. Specifications for the preparation of the site prior to placement of the CLSM.
    2. Specifications for the CLSM.
    3. Laboratory or field test method(s) to be used to determine the compressive strength or bearing capacity of the CLSM.
    4. Test methods for determining the acceptance of the CLSM in the field.
    5. Number and frequency of field tests required to determine compliance with Item 4.

    1803 A .5.10 Alternate setback and clearance. Where setbacks or clearances other than those required in Section 1808 A .7 are desired, the building official shall be permitted to require a geotechnical investigation by a registered design professional to demonstrate that the intent of Section 1808 A .7 would be satisfied. Such an investigation shall include consideration of material, height of slope, slope gradient, load intensity and erosion characteristics of slope material.

    1803 A .5.11 Seismic Design Categories C through F. For structures assigned to Seismic Design Category C, D, E or F, a geotechnical investigation shall be conducted, and shall include an evaluation of all of the following potential geologic and seismic hazards:

    1. Slope instability.

    2. Liquefaction.

    3. Total and differential settlement.

    4. Surface displacement due to faulting or seismically induced lateral spreading or lateral flow.

    1803 A .5.12 Seismic Design Categories D through F. For structures assigned to Seismic Design Category D, E or F, the geotechnical investigation required by Section 1803 A .5.11 shall include all of the following as applicable:

    1. The determination of dynamic seismic lateral earth pressures on foundation walls and retaining walls supporting more than 6 feet (1.83 m) of backfill height due to design earthquake ground motions.
    2. The potential for liquefaction and soil strength loss evaluated for site peak ground acceleration, earthquake magnitude and source characteristics consistent with the maximum considered earthquake ground motions. Peak ground acceleration shall be determined based on one of the following: 2.1. A site-specific study in accordance with Chapter 21 of ASCE 7.

    2.2. In accordance with Section 11.8.3 of ASCE 7.

    1. An assessment of potential consequences of liquefaction and soil strength loss including, but not limited to, the following:

    3.1. Estimation of total and differential settlement.

    3.2. Lateral soil movement.

    3.3. Lateral soil loads on foundations.

    3.4. Reduction in foundation soil-bearing capacity and lateral soil reaction. 3.5. Soil downdrag and reduction in axial and lateral soil reaction for pile foundations. 3.6. Increases in soil lateral pressures on retaining walls.

    3.7. Flotation of buried structures.

    1. Discussion of mitigation measures such as, but not limited to, the following: 4.1. Selection of appropriate foundation type and depths. 4.2. Selection of appropriate structural systems to accommodate anticipated displacements and forces.

    4.3. Ground stabilization.

    4.4. Any combination of these measures and how they shall be considered in the design of the structure.

    2025 CALIFORNIA BUILDING CODE 18A-5

  • CBC § 1.4. High relevance — show source text

    1.4. For dry floodproofed nonresidential buildings, the elevation to which the building is dry floodproofed as required for the final inspection in Section 110.3.12.1. 2. For construction in coastal high hazard areas and coastal A zones: 2.1. The elevation of the bottom of the lowest horizontal structural member as required by the lowest floor elevation inspection in Section 110.3.3 and for the final inspection in Section 110.3.12.1. 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—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.

  • 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

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

    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 § 2.1.4. High relevance — show source text

    Where weathering requires a higher strength concrete or grade of masonry than necessary to satisfy the structural requirements of this code, the frost line depth strength required
    for weathering shall govern. The weathering column shall be filled in with the weathering index, “negligible,” “moderate” or “severe” for concrete as determined from Figure
    R301.2(1). The grade of masonry units shall be determined from ASTM C34, ASTM C55, ASTM C62, ASTM C73, ASTM C90, ASTM C129, ASTM C145, ASTM C216 or ASTM C652.
    b. Where the frost line depth requires deeper footings than indicated in Figure R403.1(1), the frost line depth strength required for weathering shall govern. The jurisdiction shall
    fill in the frost line depth column with the minimum depth of footing below finish grade.
    c. The jurisdiction shall fill in this part of the table to indicate the need for protection depending on whether there has been a history of local subterranean termite damage.
    d. The jurisdiction shall fill in this part of the table with the wind speed from the ultimate design wind speeds map [Figure R301.2(2)]. Wind exposure category shall be determined
    on a site-specific basis in accordance with Section R301.2.1.4.
    e. The jurisdiction shall fill in this section of the table to establish the design criteria using Table 10A from ACCA Manual J or established criteria determined by the jurisdiction.
    f. The jurisdiction shall fill in this part of the table with the seismic design category determined from Section R301.2.2.1.
    g. The jurisdiction shall fill in this part of the table with: the date of the jurisdiction’s entry into the National Flood Insurance Program (date of adoption of the first code or ordi-
    nance for management of flood hazard areas); and the title and date of the currently effective Flood Insurance Study or other flood hazard study and maps adopted by the
    authority having jurisdiction, as amended.
    h. In accordance with Sections R905.1.2, R905.4.3.1, R905.5.3.1, R905.6.3.1, R905.7.3.1 and R905.8.3.1, where there has been a history of local damage from the effects of ice
    damming, the jurisdiction shall fill in this part of the table with “YES.” Otherwise, the jurisdiction shall fill in this part of the table with “NO.”
    i. The jurisdiction shall fill in this part of the table with the 100-year return period air freezing index (BF-days) from Figure R403.3(2) or from the 100-year (99 percent) value on the
    National Climatic Data Center data table “Air Freezing Index-USA Method (Base 32°F).”
    j. The jurisdiction shall fill in this part of the table with the mean annual temperature from the National Climatic Data Center data table “Air Freezing Index-USA Method (Base 32°F).”
    k. In accordance with Section R301.2.1.5, where there is local historical data documenting structural damage to buildings due to topographic wind speed-up effects, the jurisdic-
    tion shall fill in this part of the table with “YES.” Otherwise, the jurisdiction shall indicate “NO” in this part of the table.
    l. In accordance with Figure R301.2(2), where there is local historical data documenting unusual wind conditions, the jurisdiction shall fill in this part of the table with “YES” and
    identify any specific requirements.

  • CBC § 3-17 High relevance — show source text

    2025 CALIFORNIA RESIDENTIAL CODE 3-17

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

    BUILDING PLANNING

    FIGURE R301.2.2.1(1)—SEISMIC DESIGN CATEGORIES FOR DEFAULT SITE CONDITIONS FOR THE CONTERMINOUS UNITED STATES (WESTERN) [a]

    � a. The seismic design categories and corresponding short-period design spectral response accelerations, S DS, shown in Figure R301.2.2.1(1) are based on the default site class as defined in Chapter 11 of ASCE 7.

    3-18 2025 CALIFORNIA RESIDENTIAL CODE

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

    BUILDING PLANNING

    R301.2.2.1.1 Alternate determination of seismic design category. The seismic design category and short-period design spectral response accelerations, S DS, for a site shall be allowed to be determined in accordance with Section 1613 of the Cali- fornia Building Code . The value of S DS determined in accordance with the California Building Code is permitted to be used to set the seismic design category in accordance with Table R301.2.2.1.1, and to interpolate between values in Tables R602.10.3(3) and R603.9.2(1) and other seismic design requirements of this code.

    TABLE R301.2.2.1.1—SEISMIC DESIGN CATEGORY DETERMINATION Col2
    ** CALCULATED****SDS** ** SEISMIC DESIGN CATEGORY**
    SDS ≤ 0.17g A
    0.17g <SDS ≤ 0.33g B
    0.33g <SDS ≤ 0.50g C
    0.50g <SDS ≤ 0.67g D0
    0.67g <SDS ≤ 0.83g D1
    0.83g <SDS ≤ 1.25g D2
    1.25g <SDS E

    R301.2.2.1.2 Alternative determination of Seismic Design Category E. Buildings located in Seismic Design Category E in accordance with Figure R301.2.2.1(1) are permitted to be reclassified as being in Seismic Design Category D 2 provided that one of the following is done:

    1. A more detailed evaluation of the seismic design category is made in accordance with the provisions and maps of the California Building Code . Buildings located in Seismic Design Category E in accordance with Table R301.2.2.1.1, but located in Seismic Design Category D in accordance with the California Building Code, shall be permitted to be designed using the Seismic Design Category D 2 requirements of this code.
    2. Buildings located in Seismic Design Category E that conform to all of the following additional restrictions are permitted to be constructed in accordance with the provisions for Seismic Design Category D 2 of this code: 2.1. All exterior shear wall lines or braced wall panels are in one plane vertically from the foundation to the uppermost story. 2.2. Floors shall not cantilever past the exterior walls. 2.3.
  • CBC § 1.1. High relevance — show source text

    1612 A .4 Flood hazard documentation. The following documentation shall be prepared and sealed by a registered design professional and submitted to the building official:

    1. For construction in flood hazard areas other than coastal high hazard areas or coastal A zones: 1.1. The elevation of the lowest floor, including the basement, as required by the lowest floor elevation inspection in Section 110.3.3 and for the final inspection in Section 110.3.12.1. 1.2. For fully enclosed areas below the design flood elevation 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.

    1.3. For dry floodproofed nonresidential buildings, construction documents shall include a statement that the dry floodproofing is designed in accordance with ASCE 24 and shall include the flood emergency plan specified in Chapter 6 of ASCE 24. 1.4. For dry floodproofed nonresidential buildings, the elevation to which the building is dry floodproofed as required for the final inspection in Section 110.3.12.1.

    2025 CALIFORNIA BUILDING CODE 16A-33

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

    �

    �

    �

    STRUCTURAL DESIGN

    1. For construction in coastal high hazard areas and coastal A zones: 2.1. The elevation of the bottom of the lowest horizontal structural member as required by the lowest floor elevation inspection in Section 110.3.3 and for the final inspection in Section 110.3.12.1. 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.

  • CBC § 2.1. High relevance — show source text
    1. A replacement window where such window complies with both of the following: 2.1. The replacement window meets the size requirements in Item 1. 2.2. The replacement window is the manufacturer’s largest standard size window that will fit within the existing frame or existing rough opening. The replacement window shall be permitted to be of the same operating style as the existing window or a style that provides for an equal or greater window opening area than the existing window.

    506 A .5 Structural. Any building undergoing a change of occupancy shall satisfy the requirements of this section.

    506 A .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 A of the California Building Code . Design live loads for areas of new occupancy shall be based on Section 1607 A 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.

    506 A .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 A and 1609 A 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.

    506 A .5.3 Seismic loads (seismic force-resisting system). Where a change of occupancy results in a building being assigned to a higher risk category, the lateral force-resisting system of the building shall comply with the California Building Code Section 1613A or Section 304A.3.4 of this code 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 A of the California Building Code or shall comply with ASCE 41 -23 using an objective of Operational nonstructural performance with the BSE-1N earthquake hazard level.

    2025 CALIFORNIA EXISTING BUILDING CODE 5A-7

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

    5A-8 2025 CALIFORNIA EXISTING BUILDING CODE

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

    CALIFORNIA EXISTING BUILDING CODE – MATRIX ADOPTION TABLE

    CHAPTER 6 – CLASSIFICATION OF WORK

    (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 § 2.1 Medium relevance — show source text

    Exceptions:

    1. Isolated cast-in-place deep foundation elements without lateral bracing shall be permitted where the least horizontal dimension is not less than 2 feet (610 mm), adequate lateral support in accordance with Section 1810 A .2.1 is provided for the entire height and analysis demonstrates that the element can support the required loads, including mislocations required by Section 1810 A .3.1.3, with neither harmful distortion nor instability in the structure.
    2. A single row of deep foundation elements without lateral bracing is permitted for one- and two-family dwellings and lightweight construction not exceeding two stories above grade plane or 35 feet (10 668 mm) in building height, provided that the centers of the elements are located within the width of the supported wall.

    2025 CALIFORNIA BUILDING CODE 18A-15

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

    SOILS AND FOUNDATIONS

    1810 A .2.3 Settlement. The settlement of a single deep foundation element or group thereof shall be estimated based on approved methods of analysis. The predicted settlement shall cause neither harmful distortion of, nor instability in, the structure, nor cause any element to be loaded beyond its capacity.

    1810 A .2.4 Lateral loads. The moments, shears and lateral deflections used for design of deep foundation elements shall be established considering the nonlinear interaction of the shaft and soil, as determined by a registered design professional. Where the ratio of the depth of embedment of the element to its least horizontal dimension is less than or equal to six, it shall be permitted to assume the element is rigid.

    1810 A .2.4.1 Seismic Design Categories D through F. For structures assigned to Seismic Design Category D, E or F, deep foundation elements on Site Class E or F sites, as determined in Section 1613 A .2.2, shall be designed and constructed to withstand maximum imposed curvatures from earthquake ground motions and structure response. Curvatures shall include free-field soil strains modified for soil-foundation-structure interaction coupled with foundation element deformations associated with earthquake loads imparted to the foundation by the structure.

    Exception: Deep foundation elements that satisfy the following additional detailing requirements shall be deemed to comply with the curvature capacity requirements of this section:

    1. Precast prestressed concrete piles detailed in accordance with Section 1810 A .3.8.
    2. Cast-in-place deep foundation elements with a minimum longitudinal reinforcement ratio of 0.005 extending the full length of the element and detailed in accordance with Sections 18.7.5.2, 18.7.5.3 and 18.7.5.4 of ACI 318 as required by Section 1810 A .3.9.4.2.2.
  • 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 § 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 § 12.4 Medium relevance — show source text

    D = Dead load.

    D i = Weight of ice in accordance with Chapter 10 of ASCE 7.

    E = Combined effect of horizontal and vertical earthquake induced forces as defined in Section 12.4 of ASCE 7.

    F = Load due to fluids with well-defined pressures and maximum heights.

    F a = Flood load in accordance with Chapter 5 of ASCE 7.

    H = Load due to lateral earth pressures, ground water pressure or pressure of bulk materials.

    L = Live load.

    L r = Roof live load. p g(asd) = Allowable stress design ground snow load. p g = Ground snow load determined from Figures 1608.2(1) through 1608.2(4) and Table 1608.2.

    2025 CALIFORNIA BUILDING CODE 16-3

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

    STRUCTURAL DESIGN

    R = Rain load.

    S = Snow load.

    T = Cumulative effects of self-straining load forces and effects.

    V asd = Allowable stress design wind speed, mph (m/s) where applicable.

    V = Basic wind speed, V, mph (m/s) determined from Figures 1609.3(1) through 1609.3(4) or ASCE 7.

    V T = Tornado speed, mph (m/s) determined from Chapter 32 of ASCE 7.

    W = Load due to wind pressure.

    W i = Wind-on-ice in accordance with Chapter 10 of ASCE 7.

    SECTION 1603—CONSTRUCTION DOCUMENTS

    1603.1 General. Construction documents shall show the material, size, section and relative locations of structural members with floor levels, column centers and offsets dimensioned. The design loads and other information pertinent to the structural design required by Sections 1603.1.1 through 1603.1.9 shall be indicated on the construction documents.

    Exception: Construction documents for buildings constructed in accordance with the conventional light-frame construction provisions of Section 2308 shall indicate the following structural design information:

    1. Floor and roof dead and live loads.

    2. Ground snow load, p g, and allowable stress design ground snow load, p g(asd) .

    3. Basic wind speed, V, mph (m/s), and allowable stress design wind speed, V asd , as determined in accordance with Section 1609.3.1 and wind exposure.

    4. Seismic design category and site class.

    5. Flood design data, if located in flood hazard areas established in Section 1612.3.

    6. Design load-bearing values of soils.

    7. Rain load data.

    [OSHPD 1R, 2 & 5] Additional requirements are included in Sections 7-115 and 7-125 of the California Administrative Code (Part 1, Title 24, C.C.R).

    1603.1.1 Floor live load. The uniformly distributed, concentrated and impact floor live load used in the design shall be indicated for floor areas. Use of live load reduction in accordance with Section 1607.13 shall be indicated for each type of live load used in the design.

Frequently asked questions

Who decides whether I must use ASCE 7 instead of the CBC figure for SDC?

If geotechnical data or the authority having jurisdiction shows Site Class DE, E or F, the CBC requires SDC to be determined using ASCE 7 (§ 1613.2) .

What items must my structural drawings include for earthquake design?

The CBC lists required earthquake design data in § 1603.1.5: risk category, Ie, Ss and S1, site class, SDS and SD1, SDC, base shear, Cs, R, analysis procedure, and applicable irregularities and base location, among others .

Can I use the Residential Code SDS→SDC table for a commercial building?

The Residential Code table is an alternate determination for buildings within its scope; for nonresidential buildings the CBC permits either Figure 1613.2(1) or ASCE 7 as the method for SDC assignment — follow § 1613.2 and your jurisdiction’s accepted method file.

If my project is Risk Category IV, does that change SDC assignment?

Risk category affects seismic detailing and may affect SDC mapping procedures per CBC/ASCE 7 interactions — always determine risk category first, then follow § 1613.2 for the SDC method and apply the higher detailing/special‑inspection requirements that correspond to Risk Category and SDC file.

Where do I get Ss and S1 for my site?

Ss and S1 come from ASCE 7 ground‑motion maps or a site‑specific seismic hazard analysis (ASCE 7 procedures are the referenced technical source; the CBC directs use of ASCE 7 in § 1613.1) .

More in California Building Code

Ask about the CBC

Get cited, plain-English answers on the California Building Code for your project — any code section, any scenario.

Start Free Trial

Related in the CBC

What seismic detailing and lateral force-resisting system requirements apply?

What anchorage and out-of-plane wall requirements apply for seismic forces?

Seismic Design & Structural Integrity

California Building Code