CBC · California Building Code

What are the wind load requirements and how is basic wind speed determined?

For a homeowner: the CBC requires every building be designed for wind using standardized wind‑speed maps or the ASCE hazard tool, choosing the map that matches the building’s Risk Category, selecting the correct exposure (open/urban/water), and applying any local topographic adjustments; engineers then convert that basic wind speed to design pressures per ASCE 7 and document the wind speed and exposure on the plans (§ 1609, § 1609.3) .

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Last reviewed: July 5, 2026

What the code requires — 2-4 sentences

The California Building Code requires every building, structure and component to be designed for minimum wind loads determined in accordance with Chapters 26–30 of ASCE 7; the code permits using the CBC procedures in Section 1609 or ASCE 7 for determining opening protection, basic wind speed (V) and exposure category (§ 1609.1, § 1609.1.1) . The CBC provides wind‑speed maps/figures for basic wind speed by Risk Category (Figures 1609.3(1)–(4)) and requires conversion to allowable‑stress design wind speed where noted (§ 1609.3) .

Requirements in detail

1) Basic rule and authoritative procedures

  • Determine wind loads using ASCE 7 Chapters 26–30, or use the CBC provisions in Section 1609 where permitted; wind may be assumed from any horizontal direction and pressures act normal to surfaces (§ 1609.1.1) .
  • Basic wind speed (V) is taken from the CBC basic‑wind maps: Figures 1609.3(1)–(4). Which figure you use depends on the structure Risk Category (I–IV) (§ 1609.3) .
  • For locations or conditions not covered by the map (islands, coastal boundaries, special wind regions, mountainous/gorge areas), the ASCE Wind Design Geodatabase (ASCE 7 Hazard Tool) or local‑jurisdiction determinations (per ASCE 7, Chapter 26) are required (§ 1609.3) .

2) Units, reference conditions, interpolation and topography

  • CBC map values are 3‑second gust wind speeds in mph at 33 ft (10 m) above ground for Exposure C (note in § 1609.3 figures) — linear interpolation between contours is permitted; extrapolation beyond the last contour is not permitted (§ 1609.3 notes) .
  • Special topographic amplification (Kzt) must be considered per ASCE Chapter 26 — the CBC notes that tabulated values apply where Kzt = 1.0 or where Kzt has been incorporated into the basic wind speed (§ 1609 notes) .

3) Allowable‑stress design wind speed (Vasd)

  • When certain alternative standards/methods listed in §1609.1.1 Exceptions are used (e.g., ICC 600, AWC WFCM, AISI S230, NAAMM FP 1001, TIA‑222), the CBC requires converting the basic wind speed V to an allowable‑stress design wind speed Vasd using the conversion in Section 1609.3.1 (Table 1609A.3.1) (§ 1609.1.1, § 1609.3.1) .

Decision‑relevant quick reference table

Decision factor Typical values / rule Code reference
Which map/figure to use Use Figure 1609.3(1) for Risk Category I, 1609.3(2) for II, 1609.3(3) for III, 1609.3(4) for IV § 1609.3
Source for site‑specific speeds ASCE Wind Design Geodatabase (ASCE 7 Hazard Tool) for location‑specific values; required for some territories § 1609.3
Units / reference 3‑second gust, mph, at 33 ft (10 m) above ground for Exposure C; interpolate between contours allowed § 1609.3 notes
Interpolate / extrapolate Linear interpolation permitted; extrapolation beyond last contour is not permitted § 1609.3 notes
Convert to Vasd Use Table 1609A.3.1 (V → Vasd) when allowable‑stress methods in Exceptions of §1609.1.1 are used § 1609.3.1 / Table 1609A.3.1
Topography / Kzt Topographic factor per ASCE 7 Chapter 26; tabulated CBC values assume Kzt = 1.0 unless incorporated in V § 1609 notes; ASCE 7 reference in § 1609.1.1

4) Exposure category / surface roughness (how to choose exposure)

  • The CBC permits determining exposure category per Section 1609A.4 (surface roughness and exposure categories B, C, D) to reflect upwind terrain and obstructions; select the exposure that produces the greatest wind load for the direction considered (§ 1609A.4) .

Exceptions & special cases

  • The CBC lists specific alternative standards permitted in place of ASCE 7 (ICC 600, AWC WFCM, AISI S230, NAAMM FP 1001, TIA‑222) and allows wind tunnel testing per ASCE 49; these have limitations and, when used, require Vasd conversion (§ 1609.1.1 Exceptions) .
  • Hawaii, US Virgin Islands and Puerto Rico: basic wind speeds shall be determined using the ASCE Wind Design Geodatabase (§ 1609.3) .
  • Mountainous terrain, gorges, ocean promontories and other special wind regions: site‑specific values or local‑jurisdiction determinations are required and must follow ASCE 7 Chapter 26 (§ 1609.3) .
  • Where CBC tables or notes assume Kzt = 1.0, special topographic amplification must be applied per ASCE 7 or by incorporating it into the basic wind speed (§ 1609 notes) .

Common mistakes

  • Treating the map value as design pressure without following ASCE 7 procedures: the maps give basic wind speed (V); wind pressures must be computed per ASCE 7 Chapters 26–30 (CBC § 1609.1.1) .
  • Failing to use the correct Risk Category figure: the CBC assigns different basic‑speed figures by Risk Category (I–IV) (§ 1609.3) .
  • Forgetting to convert to Vasd when using allowable‑stress design provisions called out in the Exceptions — Table 1609A.3.1 must be used for conversion (§ 1609.3.1, Table 1609A.3.1) .
  • Ignoring topography (Kzt) and special wind regions — local adjustments per ASCE Chapter 26 can change design speeds (§ 1609 notes) .
  • Extrapolating beyond contour limits on the map — interpolation is allowed but extrapolation is not (§ 1609.3 notes) .
  • Using seasonal or measured gusts instead of the mapped 3‑second gust, 33‑ft reference without properly adjusting per ASCE 7 (§ 1609.3 notes) .

Worked example — applying the rule step‑by‑step

Note: the CBC figures themselves (the geographic contours and their numeric values) are contained in Figures 1609.3(1)–(4) and are not reproduced here. The example below shows the method; any numeric basic wind speed used as an input must come directly from the applicable CBC figure or the ASCE geodatabase for your site.

Scenario: A typical single‑family residence (Risk Category II) on flat terrain.

  1. Determine Risk Category: single‑family = Risk Category II → use Figure 1609.3(2) to read basic wind speed V for the site (§ 1609.3) .
  2. Obtain V from the map (or ASCE geodatabase if location‑specific). (For this worked example we assume the applicable map/geodatabase value at the site is V = 140 mph — this is an illustrative choice, not pulled from the CBC figures in the supplied files.)
  3. If you are using one of the allowable‑stress methods referenced in § 1609.1.1 Exceptions, convert V to Vasd using Table 1609A.3.1. Table 1609A.3.1 shows V = 140 mph converts to Vasd = 108 mph (use table values/interpolate if needed) (§ 1609.3.1, Table 1609A.3.1) .
  4. Determine exposure category (B, C, or D) per Section 1609A.4 based on upwind terrain; assume Exposure C for this example (§ 1609A.4) .
  5. Apply topographic factor (Kzt) if applicable (per ASCE Chapter 26); if no special topography and Kzt = 1.0, proceed without modification (§ 1609 notes) .
  6. Finally, compute wind pressures and load combinations per ASCE 7 Chapters 26–30 as required by § 1609.1.1 and document V (and Vasd if used), exposure, and Risk Category on construction documents per § 1603.1/1603.1.4 (§ 1609.1.1, § 1603.1.4) .

Related provisions

  • § 1609.1 — Applications and general rules for wind loads (use ASCE 7 or Section 1609 procedures) .
  • § 1609.3 — Basic design wind speed, map usage, and special‑region rules (Figures 1609.3(1)–(4)) .
  • § 1609.3.1 / Table 1609A.3.1 — Wind speed conversions (V → Vasd) where required .
  • § 1609A.4 — Exposure categories / surface roughness (determination of Exposure B/C/D) .
  • § 1603.1 and § 1603.1.4 — Construction documents must show basic wind speed, allowable stress design speed, exposure, risk category and related wind/tornado data (§ 1603.1, § 1603.1.4) .
  • ASCE 7 Chapters 26–30 — procedures for converting V into pressures and load combinations (referenced in § 1609.1.1) .

Code references

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

  • CBC § 1609.3 High relevance — show source text

    1609.3 Basic design wind speed. The basic wind speed, V, in mph, for the determination of the wind loads shall be determined by Figures 1609.3(1) through 1609.3(4).

    The basic wind speed, V, for use in the design of Risk Category I buildings and structures shall be obtained from Figure 1609.3(1).

    The basic wind speed, V, for use in the design of Risk Category II buildings and structures shall be obtained from Figure 1609.3(2).

    The basic wind speed, V, for use in the design of Risk Category III buildings and structures shall be obtained from Figure 1609.3(3).

    The basic wind speed, V, for use in the design of Risk Category IV buildings and structures shall be obtained from Figure 1609.3(4).

    Basic wind speeds for Hawaii, the US Virgin Islands and Puerto Rico shall be determined by using the ASCE Wind Design Geodatabase. The ASCE Wind Design Geodatabase is available at https://asce7hazardtool.online, or an approved equivalent.

    The basic wind speed, V, for the special wind regions indicated near mountainous terrain and near gorges shall be in accordance with local jurisdiction requirements. The basic wind speeds, V, determined by the local jurisdiction shall be in accordance with Chapter 26 of ASCE 7.

    In nonhurricane-prone regions, when the basic wind speed, V, is estimated from regional climatic data, the basic wind speed, V, shall be determined in accordance with Chapter 26 of ASCE 7.

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    Notes:

    1. Values are 3-second gust wind speeds in miles per hour (m/s) at 33 feet (10 m) above ground for Exposure Category C.
    2. Linear interpolation is permitted between contours. Point values are provided to aid with interpolation.
    3. Islands, coastal areas and land boundaries outside the last contour shall use the last wind speed contour.
    4. Location-specific basic wind speeds shall be determined using the ASCE Wind Design Geodatabase.
    5. Wind speeds for Hawaii, the US Virgin Islands and Puerto Rico shall be determined from the ASCE Wind Design Geodatabase.
    6. Mountainous terrain, gorges, ocean promontories and special wind regions shall be examined for unusual wind conditions. Site-specific values for selected special wind regions shall be determined using the ASCE Wind Design Geodatabase.
    7. Wind speeds correspond to approximately a 15-percent probability of exceedance in 50 years (annual exceedance probability = 0.00333, MRI = 300 years). 8. The ASCE Wind Design Geodatabase can be accessed at the ASCE 7 Hazard Tool (https://asce7hazardtool.online ) or approved equivalent.

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    Notes:

    1. Values are 3-second gust wind speeds in miles per hour (m/s) at 33 feet (10 m) above ground for Exposure Category C.
    2. Linear interpolation is permitted between contours. Point values are provided to aid with interpolation.
  • CBC § 16-19 High relevance — show source text

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    SECTION 1609—WIND LOADS

    1609.1 Applications. Buildings, structures and parts thereof shall be designed to withstand the minimum wind loads prescribed herein. Decreases in wind loads shall not be made for the effect of shielding by other structures.

    1609.1.1 Determination of wind loads. Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7. The type of opening protection required, the basic wind speed, V, and the exposure category for a site is permitted to be determined in accordance with Section 1609 or ASCE 7. Wind shall be assumed to come from any horizontal direction and wind pressures shall be assumed to act normal to the surface considered.

    Exceptions:

    1. Subject to the limitations of Section 1609.1.1.1, the provisions of ICC 600 shall be permitted for applicable Group R-2 and R-3 buildings.

    2. Subject to the limitations of Section 1609.1.1.1, residential structures using the provisions of AWC WFCM.

    3. Subject to the limitations of Section 1609.1.1.1, residential structures using the provisions of AISI S230.

    4. Designs using NAAMM FP 1001.

    5. Designs using TIA-222 for antenna-supporting structures and antennas, provided that the horizontal extent of Topographic Category 2 escarpments in Section 2.6.6.2 of TIA-222 shall be 16 times the height of the escarpment.

    6. Wind tunnel tests in accordance with ASCE 49 and Sections 31.4 and 31.7 of ASCE 7.

    7. Temporary structures complying with Section 3103.6.1.2.

    The wind speeds in Figures 1609.3(1) through 1609.3(4) are basic wind speeds, V, and shall be converted in accordance with Section 1609.3.1 to allowable stress design wind speeds, V asd, when the provisions of the standards referenced in Exceptions 4 and 5 are used.

  • CBC § 1.1 High relevance — show source text

    1609 A .1.1 Determination of wind loads. Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7. The type of opening protection required, the basic wind speed, V, and the exposure category for a site is permitted to be determined in accordance with Section 1609 A or ASCE 7. Wind shall be assumed to come from any horizontal direction and wind pressures shall be assumed to act normal to the surface considered.

    Exceptions:

    1. Subject to the limitations of Section 1609 A .1.1.1, the provisions of ICC 600 shall be permitted for applicable Group R-2 and R-3 buildings.

    2. Subject to the limitations of Section 1609 A .1.1.1, residential structures using the provisions of AWC WFCM.

    3. Subject to the limitations of Section 1609 A .1.1.1, residential structures using the provisions of AISI S230.

    4. Designs using NAAMM FP 1001.

    5. Designs using TIA-222 for antenna-supporting structures and antennas, provided that the horizontal extent of Topographic Category 2 escarpments in Section 2.6.6.2 of TIA-222 shall be 16 times the height of the escarpment.

    6. Wind tunnel tests in accordance with ASCE 49 and Sections 31.4 and 31.7 of ASCE 7.

    7. Temporary structures complying with Section 3103.6.1.2.

    The wind speeds in Figures 1609 A .3(1) through 1609 A .3(4) are basic wind speeds, V, and shall be converted in accordance with Section 1609.3.1 to allowable stress design wind speeds, V asd, when the provisions of the standards referenced in Exceptions 4 and 5 are used.

    1609 A .1.1.1 Applicability. The provisions of ICC 600 are applicable only to buildings located within Exposure B or C as defined in Section 1609 A .4. The provisions of ICC 600, AWC WFCM and AISI S230 shall not apply to buildings sited on the upper half of an isolated hill, ridge or escarpment meeting all of the following conditions:

    1. The hill, ridge or escarpment is 60 feet (18 288 mm) or higher if located in Exposure B or 30 feet (9144 mm) or higher if located in Exposure C.
    2. The maximum average slope of the hill exceeds 10 percent.
    3. The hill, ridge or escarpment is unobstructed upwind by other such topographic features for a distance from the high point of 50 times the height of the hill or 2 miles (3.22 km), whichever is greater.

    1609A.1.2 Story drift for wind loads. The calculated story drift due to wind pressures with ultimate design wind speed, V ult , shall not exceed 0.008 times the story height for buildings less than 65 feet (19812 mm) in height or 0.007 times the story height for buildings 65 feet (19812 mm) or greater in height.

    Exception: [DSA-SS] This story drift limit need not be applied for single-story open structures in Risk Categories I and II.

    Exception: [OSHPD 1 & 4] This story drift limit need not be applied for single-story open structures.

  • CBC § 12.4 High 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.

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    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.

  • CBC § 2.2 High relevance — show source text

    1609 A .2.2 Garage doors. Garage door glazed opening protection for windborne debris shall meet the requirements of an approved impact-resisting standard or ANSI/DASMA 115.

    1609 A .3 Basic design wind speed. The basic wind speed, V, in mph, for the determination of the wind loads shall be determined by Figures 1609 A .3(1) through 1609 A .3(4).

    The basic wind speed, V, for use in the design of Risk Category I buildings and structures shall be obtained from Figure 1609 A .3(1).

    The basic wind speed, V, for use in the design of Risk Category II buildings and structures shall be obtained from Figure 1609 A .3(2).

    The basic wind speed, V, for use in the design of Risk Category III buildings and structures shall be obtained from Figure 1609 A .3(3).

    The basic wind speed, V, for use in the design of Risk Category IV buildings and structures shall be obtained from Figure 1609 A .3(4).

    Basic wind speeds for Hawaii, the US Virgin Islands and Puerto Rico shall be determined by using the ASCE Wind Design Geodatabase. The ASCE Wind Design Geodatabase is available at https://asce7hazardtool.online, or an approved equivalent.

    The basic wind speed, V, for the special wind regions indicated near mountainous terrain and near gorges shall be in accordance with local jurisdiction requirements. The basic wind speeds, V, determined by the local jurisdiction shall be in accordance with Chapter 26 of ASCE 7.

    In nonhurricane-prone regions, when the basic wind speed, V, is estimated from regional climatic data, the basic wind speed, V, shall be determined in accordance with Chapter 26 of ASCE 7.

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    Notes:

    1. Values are 3-second gust wind speeds in miles per hour (m/s) at 33 feet (10 m) above ground for Exposure Category C.
    2. Linear interpolation is permitted between contours. Point values are provided to aid with interpolation.
    3. Islands, coastal areas and land boundaries outside the last contour shall use the last wind speed contour.
    4. Location-specific basic wind speeds shall be determined using the ASCE Wind Design Geodatabase.
    5. Wind speeds for Hawaii, the US Virgin Islands and Puerto Rico shall be determined from the ASCE Wind Design Geodatabase.
    6. Mountainous terrain, gorges, ocean promontories and special wind regions shall be examined for unusual wind conditions. Site-specific values for selected special wind regions shall be determined using the ASCE Wind Design Geodatabase.
    7. Wind speeds correspond to approximately a 15-percent probability of exceedance in 50 years (annual exceedance probability = 0.00333, MRI = 300 years).
    8. The ASCE Wind Design Geodatabase can be accessed at the ASCE 7 Hazard Tool (https://asce7hazardtool.online ) or approved equivalent.

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  • CBC § 25.4 High relevance — show source text

    Fasteners shall be installed at opposing ends of the wood structural panel. Fasteners shall be located not less than 1 inch from the edge of the panel.
    c. Anchors shall penetrate through the exterior wall covering with an embedment length of 2 inches minimum into the building frame. Fasteners shall be located not less than
    21/2 inches from the edge of concrete block or concrete.
    d. Where panels are attached to masonry or masonry/stucco, they shall be attached using vibration-resistant anchors having a minimum ultimate withdrawal capacity of 1,500
    pounds.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 4.448 N, 1 mile per hour = 0.447 m/s.
    a. This table is based a on 140 mph basic wind speed,V, and a 45-foot mean roof height.
    b. Fasteners shall be installed at opposing ends of the wood structural panel. Fasteners shall be located not less than 1 inch from the edge of the panel.
    c. Anchors shall penetrate through the exterior wall covering with an embedment length of 2 inches minimum into the building frame. Fasteners shall be located not less than
    21/2 inches from the edge of concrete block or concrete.
    d. Where panels are attached to masonry or masonry/stucco, they shall be attached using vibration-resistant anchors having a minimum ultimate withdrawal capacity of 1,500
    pounds.|

    1609 A .2.1 Louvers. Louvers protecting intake and exhaust ventilation ducts not assumed to be open that are located within 30 feet (9144 mm) of grade shall meet the requirements of AMCA 540.

    1609 A .2.2 Garage doors. Garage door glazed opening protection for windborne debris shall meet the requirements of an approved impact-resisting standard or ANSI/DASMA 115.

    1609 A .3 Basic design wind speed. The basic wind speed, V, in mph, for the determination of the wind loads shall be determined by Figures 1609 A .3(1) through 1609 A .3(4).

    The basic wind speed, V, for use in the design of Risk Category I buildings and structures shall be obtained from Figure 1609 A .3(1).

    The basic wind speed, V, for use in the design of Risk Category II buildings and structures shall be obtained from Figure 1609 A .3(2).

    The basic wind speed, V, for use in the design of Risk Category III buildings and structures shall be obtained from Figure 1609 A .3(3).

    The basic wind speed, V, for use in the design of Risk Category IV buildings and structures shall be obtained from Figure 1609 A .3(4).

    Basic wind speeds for Hawaii, the US Virgin Islands and Puerto Rico shall be determined by using the ASCE Wind Design Geodatabase. The ASCE Wind Design Geodatabase is available at https://asce7hazardtool.online, or an approved equivalent.

    The basic wind speed, V, for the special wind regions indicated near mountainous terrain and near gorges shall be in accordance with local jurisdiction requirements. The basic wind speeds, V, determined by the local jurisdiction shall be in accordance with Chapter 26 of ASCE 7.

  • CBC § 16A-23 High relevance — show source text

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    1608 A .2.1 Ground snow conversion. Where required, the ground snow loads, p g, of Figures 1608 A .2(1) through 1608 A .2(4) and Table 1608 A .2 shall be converted to allowable stress design ground snow loads, p g(asd), using Equation 16 A -17. Equation 16 A -17 p g(asd) = 0.7 p g

    where:

    p g(asd) = Allowable stress design ground snow load. p g = Ground snow load determined from Figures 1608 A .2(1) through 1608 A .2(4) and Table 1608 A .2. 1608 A .3 Ponding instability. Ponding instability on roofs shall be evaluated in accordance with ASCE 7.

    1608A.4 Determination of snow loads. [DSA-SS] The ground snow load or the design snow load for roofs shall conform with the adopted ordinance of the city, county, or city and county in which the project site is located, and shall be approved by DSA. See Section 106.1.2 for snow load posting requirements.

    SECTION 1609 A —WIND LOADS

    1609 A .1 Applications. Buildings, structures and parts thereof shall be designed to withstand the minimum wind loads prescribed herein. Decreases in wind loads shall not be made for the effect of shielding by other structures.

    1609 A .1.1 Determination of wind loads. Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7. The type of opening protection required, the basic wind speed, V, and the exposure category for a site is permitted to be determined in accordance with Section 1609 A or ASCE 7. Wind shall be assumed to come from any horizontal direction and wind pressures shall be assumed to act normal to the surface considered.

    Exceptions:

    1. Subject to the limitations of Section 1609 A .1.1.1, the provisions of ICC 600 shall be permitted for applicable Group R-2 and R-3 buildings.

    2. Subject to the limitations of Section 1609 A .1.1.1, residential structures using the provisions of AWC WFCM.

    3. Subject to the limitations of Section 1609 A .1.1.1, residential structures using the provisions of AISI S230.

    4. Designs using NAAMM FP 1001.

    5. Designs using TIA-222 for antenna-supporting structures and antennas, provided that the horizontal extent of Topographic Category 2 escarpments in Section 2.6.6.2 of TIA-222 shall be 16 times the height of the escarpment.

    6. Wind tunnel tests in accordance with ASCE 49 and Sections 31.4 and 31.7 of ASCE 7.

    7. Temporary structures complying with Section 3103.6.1.2.

  • CBC § 2404.3 High relevance — show source text

    2404.3 Wired, patterned and sandblasted glass.

    2404.3.1 Vertical wired glass. Wired glass sloped 15 degrees (0.26 rad) or less from vertical in windows, curtain and window walls, doors and other exterior applications shall be designed to resist the wind loads in Section 1609 for components and cladding according to the following equation: Equation 24-6 0.6 F gw < 0.5 F ge

    where:

    F gw = Wind load on the glass due to basic wind speed, V, computed in accordance with Section 1609. F ge = Nonfactored load from ASTM E1300 using a thickness designation for monolithic glass that is not greater than the thickness of wired glass.

    2404.3.2 Sloped wired glass. Wired glass sloped more than 15 degrees (0.26 rad) from vertical in skylights, sun-spaces, sloped roofs and other exterior applications shall be designed to resist the most critical of the combinations of loads from Section 2404.2.

    For Equations 24-2 and 24-3:

    Equation 24-7 F g < 0.5 F ge For Equation 24-4: Equation 24-8 F g < 0.3 F ge

    where:

    F g = Total load on the glass as determined by Equations 24-2, 24-3 and Equation 24-4. F = Nonfactored load in accordance with ASTM E1300. ge 2404.3.3 Vertical patterned glass. Patterned glass sloped 15 degrees (0.26 rad) or less from vertical in windows, curtain and window walls, doors and other exterior applications shall be designed to resist the wind loads in Section 1609 for components and cladding according to Equation 24-9. Equation 24-9 F gw < 1.0 F ge

    where:

    F gw = Wind load on the glass due to basic wind speed, V, computed in accordance with Section 1609. F ge = Nonfactored load in accordance with ASTM E1300. The value for patterned glass shall be based on the thinnest part of the glass. Interpolation between nonfactored load charts in ASTM E1300 shall be permitted.

    2404.3.4 Sloped patterned glass. Patterned glass sloped more than 15 degrees (0.26 rad) from vertical in skylights, sunspaces, sloped roofs and other exterior applications shall be designed to resist the most critical of the combinations of loads from Section 2404.2.

    For Equations 24-2 and 24-3:

    Equation 24-10 F g < 1.0 F ge

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    GLASS AND GLAZING

    For Equation 24-4:

    Equation 24-11 F g < 0.6 F ge

    where:

  • CBC § 2404.1 High relevance — show source text

    SECTION 2404—WIND, SNOW, SEISMIC AND DEAD LOADS ON GLASS

    2404.1 Vertical glass. Glass sloped 15 degrees (0.26 rad) or less from vertical in windows, curtain and window walls, doors and other exterior applications shall be designed to resist the wind loads due to basic wind speed, V, in Section 1609 for components and cladding. Glass in glazed curtain walls, glazed storefronts and glazed partitions shall meet the seismic requirements of ASCE 7, Section 13.5.9. The load resistance of glass under uniform load shall be determined in accordance with ASTM E1300.

    The design of vertical glazing shall be based on Equation 24-1. Equation 24-1 0.6 F gw ≤ F ga

    where:

    F gw = Wind load on the glass due to basic wind speed, V, computed in accordance with Section 1609. F ga = Short duration load on the glass as determined in accordance with ASTM E1300. 2404.2 Sloped glass. Glass sloped more than 15 degrees (0.26 rad) from vertical in skylights, sunrooms, sloped roofs and other exterior applications shall be designed to resist the most critical combinations of loads determined by Equations 24-2, 24-3 and 24-4. Equation 24-2 F g = 0.6 W o – D

    24-4 2025 CALIFORNIA BUILDING CODE

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

    GLASS AND GLAZING

    Equation 24-3 F g = 0.6 W i + D + 0.35 S Equation 24-4 F g = 0.3 W i + D + 0.7 S

    where:

    D = Glass dead load psf (kN/m [2] ). For glass sloped 30 degrees (0.52 rad) or less from horizontal, = 13 t g (For SI: 0.0245 t g ). For glass sloped more than 30 degrees (0.52 rad) from horizontal, = 13 t g cos θ (For SI: 0.0245 t g cos θ ). F g = Total load, psf (kN/m [2] ) on glass. S = Snow load, psf (kN/m [2] ) as determined in Section 1608 from the reliability-targeted (strength-based) maps in Figures 1608.2(1) through 1608.2(4). t g = Total glass thickness, inches (mm) of glass panes and plies. W i = Inward wind force, psf (kN/m [2] ) due to basic wind speed, V, as calculated in Section 1609. W o = Outward wind force, psf (kN/m [2] ) due to basic wind speed, V, as calculated in Section 1609.

    θ = Angle of slope from horizontal.

    Exception: The performance grade rating of unit skylights and tubular daylighting devices shall be determined in accordance with Section 2405.5.

  • CBC § 1609A.3.1 High relevance — show source text

    V = Basic wind speeds determined from Figures 1609 A .3(1) through 1609 A .3(4).

    TABLE 1609A.3.1—WIND SPEED CONVERSIONSa, b, c Col2
    V
    100
    110
    120
    130
    140
    150    		 160
    170
    180
    190
    200
    Vasd
    78
    85
    93
    101
    108
    116    		 124
    132
    139
    147
    155
    For SI: 1 mile per hour = 0.44 m/s.
    a. Linear interpolation is permitted.
    b._ Vasd_ = allowable stress design wind speed applicable to methods specified in Exceptions 1 through 5 of Section 1609.1.1.
    c._ V_ = basic wind speeds determined from Figures 1609.3(1) through 1609_A_.3(4).    		 For SI: 1 mile per hour = 0.44 m/s.
    a. Linear interpolation is permitted.
    b._ Vasd_ = allowable stress design wind speed applicable to methods specified in Exceptions 1 through 5 of Section 1609.1.1.
    c._ V_ = basic wind speeds determined from Figures 1609.3(1) through 1609_A_.3(4).

    1609 A .4 Exposure category. For each wind direction considered, an exposure category that adequately reflects the characteristics of ground surface irregularities shall be determined for the site at which the building or structure is to be constructed. Account shall be taken of variations in ground surface roughness that arise from natural topography and vegetation as well as from constructed features.

    1609 A .4.1 Wind directions and sectors. For each selected wind direction at which the wind loads are to be evaluated, the exposure of the building or structure shall be determined for the two upwind sectors extending 45 degrees (0.79 rad) either side of the

    2025 CALIFORNIA BUILDING CODE 16A-29

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

    STRUCTURAL DESIGN

    selected wind direction. The exposures in these two sectors shall be determined in accordance with Sections 1609 A .4.2 and 1609 A .4.3 and the exposure resulting in the highest wind loads shall be used to represent winds from that direction.

    1609 A .4.2 Surface roughness categories. A ground surface roughness within each 45-degree (0.79 rad) sector shall be determined for a distance upwind of the site as defined in Section 1609.4.3 from the following categories, for the purpose of assigning an exposure category as defined in Section 1609 A .4.3.

    Surface Roughness B. Urban and suburban areas, wooded areas or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger.

    Surface Roughness C. Open terrain with scattered obstructions having heights generally less than 30 feet (9144 mm). This category includes flat open country, and grasslands.

    Surface Roughness D. Flat, unobstructed areas and water surfaces. This category includes smooth mud flats, salt flats and unbroken ice.

    1609 A .4.3 Exposure categories. An exposure category shall be determined in accordance with the following:

  • CBC § 1603.1 High relevance — show source text

    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.

    1603.1.2 Roof live load. The roof live load used in the design shall be indicated for roof areas. 1603.1.3 Roof snow load data. The ground snow load, p g, shall be indicated. In areas where the ground snow load, p g , exceeds 15 pounds per square foot (psf) (0.72 kN/m [2] ), the following additional information shall also be provided, regardless of whether snow loads govern the design of the roof:

    1. Flat-roof snow load, p f .
    2. Snow exposure factor, C e .
    3. Risk category.
    4. Thermal factor, C t .
    5. Slope factor(s), C s .
    6. Drift surcharge load(s), p d , where the sum of p d and p f exceeds 30 psf (1.44 kN/m [2] ) .
    7. Width of snow drift(s), w .
    8. Winter wind parameter for snow drift, W 2 .

    1603.1.4 Wind and tornado design data. The following information related to wind loads and, where required by Section 1609.5, tornado loads shall be shown, regardless of whether wind or tornado loads govern the design of the lateral force-resisting system of the structure:

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

    2. Risk category.

  • CBC § 0.52 High relevance — show source text

    where:

    D = Glass dead load psf (kN/m [2] ). For glass sloped 30 degrees (0.52 rad) or less from horizontal, = 13 t g (For SI: 0.0245 t g ). For glass sloped more than 30 degrees (0.52 rad) from horizontal, = 13 t g cos θ (For SI: 0.0245 t g cos θ ). F g = Total load, psf (kN/m [2] ) on glass. S = Snow load, psf (kN/m [2] ) as determined in Section 1608 from the reliability-targeted (strength-based) maps in Figures 1608.2(1) through 1608.2(4). t g = Total glass thickness, inches (mm) of glass panes and plies. W i = Inward wind force, psf (kN/m [2] ) due to basic wind speed, V, as calculated in Section 1609. W o = Outward wind force, psf (kN/m [2] ) due to basic wind speed, V, as calculated in Section 1609.

    θ = Angle of slope from horizontal.

    Exception: The performance grade rating of unit skylights and tubular daylighting devices shall be determined in accordance with Section 2405.5.

    The design of sloped glazing shall be based on Equation 24-5. Equation 24-5 F g ≤ F ga

    where:

    F g = Total load on the glass as determined by Equations 24-2, 24-3 and 24-4. F ga = Short duration load resistance of the glass as determined in accordance with ASTM E1300 for Equations 24-2 and 24-3; or the long duration load resistance of the glass as determined in accordance with ASTM E1300 for Equation 24-4.

    2404.3 Wired, patterned and sandblasted glass.

    2404.3.1 Vertical wired glass. Wired glass sloped 15 degrees (0.26 rad) or less from vertical in windows, curtain and window walls, doors and other exterior applications shall be designed to resist the wind loads in Section 1609 for components and cladding according to the following equation: Equation 24-6 0.6 F gw < 0.5 F ge

    where:

    F gw = Wind load on the glass due to basic wind speed, V, computed in accordance with Section 1609. F ge = Nonfactored load from ASTM E1300 using a thickness designation for monolithic glass that is not greater than the thickness of wired glass.

    2404.3.2 Sloped wired glass. Wired glass sloped more than 15 degrees (0.26 rad) from vertical in skylights, sun-spaces, sloped roofs and other exterior applications shall be designed to resist the most critical of the combinations of loads from Section 2404.2.

    For Equations 24-2 and 24-3:

    Equation 24-7 F g < 0.5 F ge For Equation 24-4: Equation 24-8 F g < 0.3 F ge

    where:

Frequently asked questions

Who decides which figure (1609.3(1)–(4)) I should use?

Use the figure that corresponds to the building’s Risk Category: Figure 1609.3(1) for Risk Category I, 1609.3(2) for II, 1609.3(3) for III, and 1609.3(4) for IV, per § 1609.3 .

When must I use the ASCE Wind Design Geodatabase instead of the CBC figures?

The CBC requires the ASCE Wind Design Geodatabase for location‑specific basic wind speeds in certain areas (islands, coastal boundaries, territories such as Hawaii/USVI/PR) and for selected site‑specific special wind regions; the code directs use of the Geodatabase or an approved equivalent (§ 1609.3) .

Do I always have to convert V to Vasd?

No — convert V to Vasd only when you use one of the allowable‑stress design methods listed in the Exceptions to § 1609.1.1. Conversion values are provided in Table 1609A.3.1 (Section 1609.3.1) .

How should exposure be determined?

Determine exposure from the upwind surface roughness and obstructions as described in Section 1609A.4 (Exposure B, C, D) and use the exposure that produces the largest wind loads for the wind direction considered (§ 1609A.4) .

Can I interpolate between wind‑speed contours on the CBC maps?

Yes — linear interpolation between contours is permitted; do not extrapolate beyond the last contour (§ 1609.3 notes) .

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