CBC · California Building Code

What are the CBC requirements for spread footings, grade beams and slab-on-grade?

The CBC requires shallow foundations (spread footings and slab-on-grade) to meet minimum sizing and stepping rules and, for certain seismic conditions (Site Class E/F in SDC D/E/F), requires ties between individual spread footings sized per § 1809.13; grade beams must follow ACI 318 unless the limited exception in § 1809.14 applies, and trenches/pipes near footings must meet clearance and sleeve rules in § 1809.15.

Ask a question free See coverage

Last reviewed: July 5, 2026

What the code requires — 2-4 sentences

The California Building Code (CBC) requires shallow foundations (spread footings and slab-on-grade) to be designed and constructed per the provisions of Section § 1809, with minimum dimensions, stepping and bearing requirements in that section (§ 1809.1–§ 1809.4) . In seismic Site Classes E or F and Seismic Design Categories D, E or F, individual spread footings must be interconnected by seismic ties sized by the formula in § 1809.13 unless equivalent restraint is provided by a reinforced slab or beams (§ 1809.13) . Grade beams are required to comply with ACI 318 unless the limited exception in § 1809.14 applies (§ 1809.14) . Trenches and pipes near footings have minimum slope and clearance limitations (§ 1809.15) .

Requirements in detail

Scope and general rules (§ 1809)

  • Shallow foundations must follow § 1809 (design and construction of spread footings, shallow foundations and related elements) and its subsections (supporting soils, stepping, minimum dimensions) .
  • Shallow foundations shall be built on undisturbed soil, compacted fill or CLSM per § 1809.2 .
  • Footings must be stepped where required by grade changes; steps and slopes are limited by § 1809.3 .
  • Minimum footing depth and width: footings must be at least 12 inches deep and 12 inches wide (minimums) per § 1809.4 .

Footing seismic ties (§ 1809.13)

  • When a structure is assigned Seismic Design Category D, E or F and a spread footing is founded on Site Class E or F (as defined in ASCE 7), individual spread footings must be interconnected by ties (§ 1809.13) .
  • Where a reinforced concrete slab-on-grade or reinforced concrete beams within a slab on grade provide demonstrated equivalent restraint, the ties may not be required; otherwise ties must be sized to carry the lesser of:
    • (larger footing design gravity load) × SDS ÷ 10, and
    • 25% of the smaller footing design gravity load (§ 1809.13) .
  • Ties must be capable of resisting tension or compression per the formula in § 1809.13 .

Grade beams (§ 1809.14)

  • Grade beams shall comply with the provisions of ACI 318 (referenced design and detailing standard) (§ 1809.14) .
  • Exception: Grade beams that are not subject to differential settlement exceeding one‑fourth of the thresholds in ASCE 7 Table 12.13‑3, and that are designed to resist seismic load effects (including overstrength) per ASCE 7 Section 2.3.6 or 2.4.5, need not comply with ACI 318 Section 18.13.3.1 (§ 1809.14) .

Pipes and trenches near footings (§ 1809.15)

  • Unless the soils report says otherwise, open or backfilled trenches parallel with a footing shall not be below a plane having a downward slope of 1 vertical to 2 horizontal from a line 9 inches above the bottom edge of the footing, and shall not be closer than 18 inches from the face of the footing (§ 1809.15) .
  • When pipes cross under footings, the footings shall be specially designed. Where pipes cross through footings or footing walls, pipe sleeves are required and sleeve clearances must allow for possible footing settlement but not less than 1 inch all around the pipe (§ 1809.15) .
  • An alternate trench or pipe clearance is permitted when approved by a registered design professional and the enforcement agency (§ 1809.15 exception) .

Decision-relevant dimensions & values (quick reference)

Item Typical value / rule Code reference
Minimum footing depth below undisturbed ground 12 in (305 mm) § 1809.4
Minimum footing width 12 in (305 mm) § 1809.4
Maximum single step height in continuous footing (where allowed) 18 in (457 mm) § 1809.3 (see stepped footing guidance)
Bottom slope allowed for footing bottom surface 1 vertical : 10 horizontal (10%) § 1809.3
Series-of-steps slope limit (continuous footings) 1 vertical : 2 horizontal (50%) § 1809.3
Seismic tie required when SDC = D/E/F and Site Class E or F Yes (ties connecting spread footings) § 1809.13
Seismic tie force sizing Lesser of (larger footing gravity load × SDS / 10) or (25% of smaller footing gravity load) § 1809.13
Minimum pipe sleeve clearance through footing 1 in (25 mm) all around pipe § 1809.15
Minimum trench offset from footing face 18 in (457 mm) § 1809.15
Grade beams design standard ACI 318 (unless limited exception applies) § 1809.14

Exceptions & special cases

  • Grade-beam exception: Grade beams that are not subject to significant differential settlement (less than one-fourth of ASCE 7 Table 12.13‑3 thresholds) and that are designed for seismic effects per ASCE 7 provisions need not meet ACI 318 Section 18.13.3.1 (§ 1809.14) .
  • Pipes and trenches: alternate trench locations and pipe clearances may be approved by a registered design professional and the enforcement agency (§ 1809.15) .
  • Equivalent restraint for seismic ties: where the designer demonstrates that reinforced concrete beams within slabs-on-grade or the slab-on-grade itself provide equivalent restraint, the seismic tie requirement of § 1809.13 can be avoided; otherwise ties sized per § 1809.13 are required .
  • Soils report controls: § 1809.2 lets the soils report modify allowable locations and construction (compacted fill, CLSM placement) — follow the geotechnical recommendations when provided (§ 1809.2) .

If you need to apply the grade-beam exception, be prepared to document differential-settlement assessment per ASCE 7 and seismic design per the referenced ASCE 7 sections; the code text cites those specific ASCE 7 provisions in the exception (§ 1809.14) .

Common mistakes

  • Omitting seismic ties where required: designers sometimes omit ties when Site Class/SDC conditions trigger § 1809.13; unless equivalent restraint is demonstrated, ties sized by the code formula are required .
  • Incorrect footing minimums: using depths or widths less than the § 1809 minimums (12 in) without explicit justification or soil report support (§ 1809.4) .
  • Placing trenches too close or too deep beside footings: failing to maintain the 18 in horizontal clearance or keeping trench bottoms below the protective plane defined in § 1809.15 can undermine footings (§ 1809.15) .
  • Assuming grade beams are "light" elements and ignoring ACI 318: grade beams must meet ACI 318 detailing unless they qualify for the specific exception in § 1809.14 .
  • Not designing footings that bear on fill or CLSM per the supporting soils rules of § 1809.2 and related geotechnical recommendations .

Worked example — seismic tie sizing (apply § 1809.13)

Scenario: Two adjacent spread footings on Site Class E, Seismic Design Category D.

  • Larger footing design gravity load (DL+LL) = 120 kips.
  • Smaller footing design gravity load = 30 kips.
  • SDS (site short‑period design spectral response) = 0.75 (example value supplied by the structural/geo engineer).

Per § 1809.13 the required tie force is the lesser of:

  1. larger footing load × SDS ÷ 10 = 120 kips × 0.75 ÷ 10 = 9.0 kips, and
  2. 25% of the smaller footing load = 0.25 × 30 kips = 7.5 kips.
    So the tie must be capable of carrying 7.5 kips (tension or compression) because that is the lesser value. Document this calculation on the structural drawings and reference § 1809.13 when specifying tie size and reinforcement .

Notes: If the slab-on-grade or tied reinforced beams are shown to provide equivalent restraint, document the analysis and why the ties can be omitted per § 1809.13 .

Related provisions

  • § 1809 (Shallow foundations: general, stepping, minimum dimensions)
  • § 1809.13 (Footing seismic ties)
  • § 1809.14 (Grade beams — ACI 318 requirement and exception)
  • § 1809.15 (Pipes and trenches near footings)
  • § 1808.6.2 (Slab-on-ground provisions referenced elsewhere in the CBC) — see index entries and slab-on-ground references in the code
  • § 1803 (Geotechnical investigation requirements that inform shallow‑foundation design) — referenced elsewhere in the CBC and necessary for foundation design

If you want, I can produce a checklist for plan reviewers or a worksheet you can drop into your structural drawings that records SDS, footing loads, and the resulting tie forces per § 1809.13.

Code references

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

  • CBC § 1809.13 High relevance — show source text

    1809.13 Footing seismic ties. Where a structure is assigned to Seismic Design Category D, E or F, individual spread footings founded on soil defined in Chapter 20 of ASCE 7 as Site Class E or F shall be interconnected by ties. Unless it is demonstrated that equivalent restraint is provided by reinforced concrete beams within slabs on grade or reinforced concrete slabs on grade, ties shall be capable of carrying, in tension or compression, a force equal to the lesser of the product of the larger footing design gravity load times the seismic coefficient, S DS, divided by 10 and 25 percent of the smaller footing design gravity load.

    1809.14 Grade beams. Grade beams shall comply with the provisions of ACI 318.

    Exception: Grade beams not subject to differential settlement exceeding one-fourth of the thresholds specified in ASCE 7 Table 12.13-3 and designed to resist the seismic load effects including overstrength factor in accordance with Section 2.3.6 or 2.4.5 of ASCE 7 need not comply with ACI 318 Section 18.13.3.1.

    1809.15 Pipes and Trenches. [OSHPD 1R, 2 & 5] Unless otherwise recommended by the soils report, open or backfilled trenches parallel with a footing shall not be below a plane having a downward slope of 1 unit vertical to 2 units horizontal (50-percent slope) from a line 9 inches (229 mm) above the bottom edge of the footing, and not closer than 18 inches (457 mm) from the face of such footing.

    Where pipes cross under footings, the footings shall be specially designed. Pipe sleeves shall be provided where pipes cross through footings or footing walls and sleeve clearances shall provide for possible footing settlement, but not less than 1 inch (25 mm) all around pipe.

    Exception: Alternate trench locations and pipe clearances shall be permitted when approved by registered design professional and the enforcement agent.

    SECTION 1810—DEEP FOUNDATIONS

    1810.1 General. Deep foundations shall be analyzed, designed, detailed and installed in accordance with Sections 1810.1 through 1810.4.

    1810.1.1 Geotechnical investigation. Deep foundations shall be designed and installed on the basis of a geotechnical investigation as set forth in Section 1803.

    1810.1.2 Use of existing deep foundation elements. Deep foundation elements left in place where a structure has been demolished shall not be used for the support of new construction unless satisfactory evidence is submitted to the building official, which indicates that the elements are sound and meet the requirements of this code. Such elements shall be load tested or redriven to verify their capacities. The design load applied to such elements shall be the lowest allowable load as determined by tests or redriving data.

    18-20 2025 CALIFORNIA BUILDING CODE

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

    SOILS AND FOUNDATIONS

    1810.1.3 Deep foundation elements classified as columns. Deep foundation elements standing unbraced in air, water or fluid soils shall be classified as columns and designed as such in accordance with the provisions of this code from their top down to the point where adequate lateral support is provided in accordance with Section 1810.2.1.

  • CBC § 3.3. High relevance — show source text

    3.3. Hollow piers shall be capped with 4 inches (102 mm) of solid masonry or concrete or the cavities of the top course shall be filled with concrete or grout. 4. The maximum height of a 4-inch (102 mm) load-bearing masonry foundation wall supporting wood frame walls and floors shall not be more than 4 feet (1219 mm) in height. 5. The unbalanced fill for 4-inch (102 mm) foundation walls shall not exceed 24 inches (610 mm) for solid masonry, nor 12 inches (305 mm) for hollow masonry.

    1809.11 Steel grillage footings. Grillage footings of structural steel elements shall be separated with approved steel spacers and be entirely encased in concrete with not less than 6 inches (152 mm) on the bottom and not less than 4 inches (102 mm) at all other points. The spaces between the shapes shall be completely filled with concrete or cement grout.

    1809.12 Timber footings. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. Timber footings shall be permitted for buildings of Type V construction and as otherwise approved by the building official. Such footings shall be treated in accordance with AWPA U1 (Commodity Specification A, Use Category 4B). Treated timbers are not required where placed entirely below permanent water level, or where used as capping for wood piles that project above the water level over submerged or marsh lands. The compressive stresses perpendicular to grain in untreated timber footings supported on treated piles shall not exceed 70 percent of the allowable stresses for the species and grade of timber as specified in the ANSI/AWC NDS.

    1809.13 Footing seismic ties. Where a structure is assigned to Seismic Design Category D, E or F, individual spread footings founded on soil defined in Chapter 20 of ASCE 7 as Site Class E or F shall be interconnected by ties. Unless it is demonstrated that equivalent restraint is provided by reinforced concrete beams within slabs on grade or reinforced concrete slabs on grade, ties shall be capable of carrying, in tension or compression, a force equal to the lesser of the product of the larger footing design gravity load times the seismic coefficient, S DS, divided by 10 and 25 percent of the smaller footing design gravity load.

    1809.14 Grade beams. Grade beams shall comply with the provisions of ACI 318.

    Exception: Grade beams not subject to differential settlement exceeding one-fourth of the thresholds specified in ASCE 7 Table 12.13-3 and designed to resist the seismic load effects including overstrength factor in accordance with Section 2.3.6 or 2.4.5 of ASCE 7 need not comply with ACI 318 Section 18.13.3.1.

    1809.15 Pipes and Trenches. [OSHPD 1R, 2 & 5] Unless otherwise recommended by the soils report, open or backfilled trenches parallel with a footing shall not be below a plane having a downward slope of 1 unit vertical to 2 units horizontal (50-percent slope) from a line 9 inches (229 mm) above the bottom edge of the footing, and not closer than 18 inches (457 mm) from the face of such footing.

  • CBC § 5.1 High relevance — show source text
    1. Eave height of 10 feet (3048 mm) or less.

    Shallow foundations shall not bear on frozen soil unless such frozen condition is of a permanent character.

    1809 A .5.1 Frost protection at required exits. Frost protection shall be provided at exterior landings for all required exits with outward-swinging doors. Frost protection shall only be required to the extent necessary to ensure the unobstructed opening of the required exit doors.

    1809 A .6 Location of footings. Footings on granular soil shall be so located that the line drawn between the lower edges of adjacent footings shall not have a slope steeper than 30 degrees (0.52 rad) with the horizontal, unless the material supporting the higher footing is braced or retained or otherwise laterally supported in an approved manner or a greater slope has been properly established by engineering analysis.

    1809 A .7 Prescriptive footings for light-frame construction. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .8 Plain concrete footings. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .9 Masonry-unit footings. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .10 Pier and curtain wall foundations. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .11 Steel grillage footings. Grillage footings of structural steel elements shall be separated with approved steel spacers and be entirely encased in concrete with not less than 6 inches (152 mm) on the bottom and not less than 4 inches (102 mm) at all other points. The spaces between the shapes shall be completely filled with concrete or cement grout.

    1809 A .12 Timber footings. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .13 Footing seismic ties. Where a structure is assigned to Seismic Design Category D, E or F, individual spread footings founded on soil defined in Chapter 20 of ASCE 7 as Site Class E or F shall be interconnected by ties. Unless it is demonstrated that equivalent restraint is provided by reinforced concrete beams within slabs on grade or reinforced concrete slabs on grade, ties shall

    18A-14 2025 CALIFORNIA BUILDING CODE

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

    SOILS AND FOUNDATIONS

    be capable of carrying, in tension or compression, a force equal to the lesser of the product of the larger footing design gravity load times the seismic coefficient, S DS, divided by 10 and 25 percent of the smaller footing design gravity load.

    1809 A .14 Grade beams. Grade beams shall comply with the provisions of ACI 318.

  • CBC § 1.3.3 High relevance — show source text

    4 horizontal bar shall be installed within 12 inches (305 mm) of the top of the wall and one No. 4 horizontal bar shall be located 3 to 4 inches (76 mm to 102 mm) from the bottom of the footing. Masonry stem walls shall be solid grouted.

    R403.1.3.3 Slabs-on-ground with turned-down footings. In Seismic Design Categories D 0, D 1 and D 2, slabs-on-ground cast monolithically with turned-down footings shall have not fewer than one No. 4 bar at the top and the bottom of the footing or one No. 5 bar or two No. 4 bars in the middle third of the footing depth.

    Where the slab is not cast monolithically with the footing, No. 3 or larger vertical dowels with standard hooks on each end shall be installed at not more than 4 feet (1219 mm) on center in accordance with Figure R403.1.3, Detail 2. Standard hooks shall comply with Section R608.5.4.5.

    R403.1.3.4 Interior bearing and braced wall panel footings in Seismic Design Categories D 0 , D 1 and D 2 . In Seismic Design Categories D 0, D 1 and D 2, interior footings supporting bearing walls or braced wall panels, and cast monolithically with a slab on grade, shall extend to a depth of not less than 12 inches (305 mm) below the top of the slab.

    R403.1.3.5 Reinforcement. Footing and stem wall reinforcement shall comply with Sections R403.1.3.5.1 through R403.1.3.5.4.

    R403.1.3.5.1 Steel reinforcement. Steel reinforcement shall comply with the requirements of ASTM A615, A706M or A996M. ASTM A996M bars produced from rail steel shall be Type R. The minimum yield strength of reinforcing steel shall be 40,000 psi (Grade 40) (276 MPa).

    R403.1.3.5.2 Location of reinforcement in wall. The center of vertical reinforcement in stem walls shall be located at the centerline of the wall. Horizontal and vertical reinforcement shall be located in footings and stem walls to provide the minimum cover required by Section R403.1.3.5.3.

    R403.1.3.5.3 Support and cover. Reinforcement shall be secured in the proper location in the forms with tie wire or other bar support system to prevent displacement during the concrete placement operation. Steel reinforcement in concrete cast against the earth shall have a minimum cover of 3 inches (75 mm). Minimum cover for reinforcement in concrete cast in removable forms that will be exposed to the earth or weather shall be 1 [1] / 2 inches (38 mm) for No. 5 bars and smaller, and 2 inches (50 mm) for No. 6 bars and larger. For concrete cast in removable forms that will not be exposed to the earth or weather, and for concrete cast in stay-in-place forms, minimum cover shall be [3] / 4 inch (19 mm).

  • CBC § 18A-14 Medium relevance — show source text

    1809 A .10 Pier and curtain wall foundations. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .11 Steel grillage footings. Grillage footings of structural steel elements shall be separated with approved steel spacers and be entirely encased in concrete with not less than 6 inches (152 mm) on the bottom and not less than 4 inches (102 mm) at all other points. The spaces between the shapes shall be completely filled with concrete or cement grout.

    1809 A .12 Timber footings. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .13 Footing seismic ties. Where a structure is assigned to Seismic Design Category D, E or F, individual spread footings founded on soil defined in Chapter 20 of ASCE 7 as Site Class E or F shall be interconnected by ties. Unless it is demonstrated that equivalent restraint is provided by reinforced concrete beams within slabs on grade or reinforced concrete slabs on grade, ties shall

    18A-14 2025 CALIFORNIA BUILDING CODE

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

    SOILS AND FOUNDATIONS

    be capable of carrying, in tension or compression, a force equal to the lesser of the product of the larger footing design gravity load times the seismic coefficient, S DS, divided by 10 and 25 percent of the smaller footing design gravity load.

    1809 A .14 Grade beams. Grade beams shall comply with the provisions of ACI 318.

    Exception: Grade beams not subject to differential settlement exceeding one-fourth of the thresholds specified in ASCE 7 Table 12.13-3 and designed to resist the seismic load effects including overstrength factor in accordance with Section 2.3.6 or 2.4.5 of ASCE 7 need not comply with ACI 318 Section 18.13.3.1.

    1809A.15 Pipes and trenches. Unless otherwise recommended by the soils report, open or backfilled trenches parallel with a footing shall not be below a plane having a downward slope of 1 unit vertical to 2 units horizontal (50 percent slope) from a line 9 inches (229 mm) above the bottom edge of the footing, and not closer than 18 inches (457 mm) from the face of such footing.

    Where pipes cross under footings, the footings shall be specially designed. Pipe sleeves shall be provided where pipes cross through footings or footing walls and sleeve clearances shall provide for possible footing settlement, but not less than 1 inch (25 mm) all around pipe.

    Exception: Alternate trench locations and pipe clearances shall be permitted when approved by registered design professional and the enforcement agent.

    SECTION 1810 A —DEEP FOUNDATIONS

    1810 A .1 General. Deep foundations shall be analyzed, designed, detailed and installed in accordance with Sections 1810 A .1 through 1810 A .4.

    1810 A .1.1 Geotechnical investigation. Deep foundations shall be designed and installed on the basis of a geotechnical investigation as set forth in Section 1803 A .

  • CBC § 2216.2 Medium relevance — show source text

    The welding inspector shall make a systematic daily record of all welds. This record shall include:

    1. Identification marks of welders.

    2. List of defective welds.

    3. Manner of correction of defects.

    The welding inspector shall check the material, details of construction and procedure, as well as workmanship of the welds. The special inspector shall verify that the installation of end-welded stud shear connectors are in accordance with the requirements of Section 2216.2 and the approved construction documents. The approved agency shall furnish the architect, structural engineer and the enforcement agency with a verified report that the welding has been done in conformance with AWS D1.1, D1.3, D1.4, D1.6, D1.8, and the approved construction documents.

    1705.2.8 Special inspection and tests of high-strength fastener assemblies. [OSHPD 1R, 2 & 5] Special inspections and tests for high-strength fasteners shall be in accordance with this section and Section 2216.1.

    1705.3 Concrete construction. Special inspections and tests of concrete construction shall be performed in accordance with this section and Table 1705.3.

    Exceptions: Special inspections and tests shall not be required for: [OSHPD 1R, 2 & 5] Exceptions 1 through 4 are not permitted by OSHPD.

    1. Isolated spread concrete footings of buildings three stories or less above grade plane that are fully supported on earth or rock.

    2. Continuous concrete footings supporting walls of buildings three stories or less above grade plane that are fully supported on earth or rock where: 2.1. The footings support walls of light-frame construction. 2.2. The footings are designed in accordance with Table 1809.7. 2.3. The structural design of the footing is based on a specified compressive strength, f′ c, not more than 2,500 pounds per square inch (psi) (17.2 MPa), regardless of the compressive strength specified in the approved construction documents or used in the footing construction.

    3. Nonstructural concrete slabs supported directly on the ground, including prestressed slabs on grade, where the effective prestress in the concrete is less than 150 psi (1.03 MPa).

    4. Concrete foundation walls constructed in accordance with Table 1807.1.6.2.

    5. Concrete patios, driveways and sidewalks, on grade.

    17-8 2025 CALIFORNIA BUILDING CODE

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

    SPECIAL INSPECTIONS AND TESTS

    TABLE 1705.3—REQUIRED SPECIAL INSPECTIONS AND TESTS OF CONCRETE CONSTRUCTION Col2 Col3 Col4 Col5 Col6
    TYPE CONTINUOUS
    SPECIAL
    INSPECTION    		 PERIODIC
    SPECIAL
    INSPECTION    		 REFERENCED
    STANDARDa    		 **CBC **
    REFERENCE
    1. Inspect reinforcement, including prestressing tendons, and verify
    placement.    		 — X ACI 318: Ch.
  • CBC § 5.1 Medium relevance — show source text

    1809 A .3 Stepped footings. The top surface of footings shall be level. The bottom surface of footings shall be permitted to have a slope not exceeding 1 unit vertical in 10 units horizontal (10-percent slope). Footings shall be stepped where it is necessary to change the elevation of the top surface of the footing or where the surface of the ground slopes more than 1 unit vertical in 10 units horizontal (10-percent slope).

    Individual steps in continuous footings shall not exceed 18 inches (457 mm) in height and the slope of a series of such steps shall not exceed 1 unit vertical to 2 units horizontal (50 percent slope) unless otherwise recommended by a geotechnical report. The steps shall be detailed on the drawings. The local effects due to the discontinuity of the steps shall be considered in the design of the foundation.

    1809 A .4 Depth and width of footings. The minimum depth of footings below the undisturbed ground surface shall be 12 inches (305 mm). Where applicable, the requirements of Section 1809 A .5 shall be satisfied. The minimum width of footings shall be 12 inches (305 mm).

    1809 A .5 Frost protection. Except where otherwise protected from frost, foundations and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:

    1. Extending below the frost line of the locality.
    2. Constructing in accordance with ASCE 32.
    3. Erecting on solid rock.

    Exception: Free-standing buildings meeting all of the following conditions shall not be required to be protected:

    1. Assigned to Risk Category I.

    2. Area of 600 square feet (56 m [2] ) or less for light-frame construction or 400 square feet (37 m [2] ) or less for other than lightframe construction.

    3. Eave height of 10 feet (3048 mm) or less.

    Shallow foundations shall not bear on frozen soil unless such frozen condition is of a permanent character.

    1809 A .5.1 Frost protection at required exits. Frost protection shall be provided at exterior landings for all required exits with outward-swinging doors. Frost protection shall only be required to the extent necessary to ensure the unobstructed opening of the required exit doors.

    1809 A .6 Location of footings. Footings on granular soil shall be so located that the line drawn between the lower edges of adjacent footings shall not have a slope steeper than 30 degrees (0.52 rad) with the horizontal, unless the material supporting the higher footing is braced or retained or otherwise laterally supported in an approved manner or a greater slope has been properly established by engineering analysis.

    1809 A .7 Prescriptive footings for light-frame construction. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .8 Plain concrete footings. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .9 Masonry-unit footings. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

    1809 A .10 Pier and curtain wall foundations. Not permitted by DSA-SS, DSA-SS/CC or OSHPD.

  • CBC § 1.15 Medium relevance — show source text

    Exception: The gap-to-side plate thickness ratio shall be permitted to be modified for moment connections with unequal beam sizes on opposite sides of the column or when orthogonal beams acting as drag connections frame into the side plate. 9. Demand Critical fillet welds {2}, {5}, {5a} and {8} shall have Magnetic Particle Testing (MT) in accordance with AWS D1.1 for procedure, technique and acceptance. Inspect the beginning and end of these welds for a 6-inch (152 mm) length, plus any location along the length of the weld where a start and restart is visually noted for a distance of 6 inches (152 mm) on either side of the start/stop location. 10. The connection specific factor to account for peak connection strength, C pr , shall be between 1.15 and 1.35. Calculations shall be submitted to OSHPD for review and approval. 11. For in-plane collectors transferring axial loads into the sideplate connection, coordination between sideplate and the regis- tered design professional in responsible charge will be required to confirm the collector connection is sufficient to transfer the load into the moment frame system. This requirement shall be satisfied by designing the sideplate connections in the first bay of a multi-bay sideplate moment frame or an end bay to have a minimum connection capacity, including combined shear (V u + V g ) and moment (M pr ) demands, of at least 1.2 times the M pr at the plastic hinge location when the axial load, as determined by ASCE 7, Section 12.10.2.1 without Ω o , exceeds 0.1 F y A g of the sideplate beam. 12. A complete frame analysis for gravity and design wind loading using LRFD load combinations in Section 1605A.1 shall be performed including Demand/Capacity Ratios. Frame beam member nominal moment strengths (M n ) used for gravity and design wind loading for the bolted sideplate connection using Class A or Class B faying surfaces shall be taken as 0.80 F y Z for frame beams up to 300 plf and 0.60 F y Z for frame beams greater than 300 plf. 13. For moment frame beams with maximum beam shear greater than 90 percent of the vertical bolt shear capacity, a second- ary check is to be provided to confirm the vertical bolt shear capacities are sufficient. 14. Bolted sideplate connections used on heavy-shallow frame beams for beams greater than 200 plf and shallower than 24 inches (610 mm) in depth shall be considered as an alternative system. 15. Skewed beams shall utilize the link-beam fabrication method with CJP welded splices for skew angles. The skew angle shall be less than 15 degrees. 16. For two-sided bolted sideplate connections sharing the same side plates at the same height and depth across the column, the vertical offset in the beams shall not exceed 10 inches (254 mm).

  • CBC § 19.1 Medium relevance — show source text

    1. Structural reinforcing steel shall meet the requirements of ASTM A615, A706M or A996M. The minimum yield strength of reinforcing steel shall be 40,000 psi (Grade 40) (276 MPa). Steel reinforcement for precast concrete foundation walls shall have a minimum concrete cover of [3] / 4 inch (19.1 mm).

    2. Panel-to-panel connections shall be made with Grade II steel fasteners.

    3. The use of nonstructural fibers shall conform to ASTM C1116.

    4. Grout used for bedding precast foundations placed on concrete footings shall meet ASTM C1107.

    R402.4 Masonry. Masonry systems shall be designed and installed in accordance with this chapter and shall have a minimum specified compressive strength of 1,500 psi (10.3 MPa).

    SECTION R403—FOOTINGS

    R403.1 General. All exterior walls shall be supported on continuous solid or fully grouted masonry or concrete footings, crushed stone footings, wood foundations, or other approved structural systems that shall be of sufficient design to accommodate all loads according to Section R301 and to transmit the resulting loads to the soil within the limitations as determined from the character of the soil. Footings shall be supported on undisturbed natural soils or engineered fill. Concrete footing shall be designed and constructed in accordance with the provisions of Section R403 or in accordance with ACI 332.

    TABLE R403.1(1)—MINIMUM WIDTH AND THICKNESS FOR
    CONCRETE FOOTINGS FOR LIGHT-FRAME CONSTRUCTION (inches)a, b, c, d    		 Col2 Col3 Col4 Col5 Col6 Col7 Col8
    ** GROUND SNOW LOAD**
    OR ROOF LIVE LOAD    		 ** STORY AND TYPE OF**
    STRUCTURE WITH LIGHT
    FRAME    		 ** LOAD-BEARING VALUE OF SOIL (psf)** ** LOAD-BEARING VALUE OF SOIL (psf)** ** LOAD-BEARING VALUE OF SOIL (psf)** ** LOAD-BEARING VALUE OF SOIL (psf)** ** LOAD-BEARING VALUE OF SOIL (psf)** ** LOAD-BEARING VALUE OF SOIL (psf)**
    ** GROUND SNOW LOAD**
    OR ROOF LIVE LOAD    		 ** STORY AND TYPE OF**
    STRUCTURE WITH LIGHT
    FRAME    		 ** 1,500** ** 2,000** ** 2,500** ** 3,000** ** 3,500** ** 4,000**
    20 psf roof live load or 25 psf
    ground snow load    		 1 story—slab-on-grade 12 × 6 12 × 6 12 × 6 12 × 6 12 × 6 12 × 6
    20 psf roof live load or 25 psf
    ground snow load    		 1 story—with crawl space 12 × 6 12 × 6 12 × 6 12 × 6 12 × 6 12 × 6
    20 psf roof live load or 25 psf
    ground snow load    		 1 story—plus basement 16 × 6 12 × 6 12 × 6 12 × 6 12 × 6 12 × 6
    20 psf roof live load or 25 psf
    ground snow load    		 2 story—slab-on-grade 13 × 6 12 ×
  • CBC § 2.3. Medium relevance — show source text

    1 to 2.3._ Exception: The gap-to-side plate thickness ratio shall be permitted to be modified for moment connections with unequal beam sizes on opposite sides of the column or when orthogonal beams acting as drag connections frame into the side plate. 8. Demand critical fillet welds {2}, {5}, {5a} and {7} shall have Magnetic Particle Testing (MT) in accordance with AWS D1.1 for procedure, technique and acceptance. Inspect the beginning and end of these welds for a 6-inch length, plus any location along the length of the weld where a start and restart is visually noted for a distance of 6 inches on either side of the start/stop location.

    2202.4.3 Modifications to AISC 358 Chapter 11 Bolted Moment Connection The bolted sideplate steel moment connection shall be permitted, provided: 1. The beams shall consist of either rolled or built-up wide flange sections. Columns shall consist of rolled or built-up wide flange sections or noncomposite built-up box or HSS with a minimum wall thickness of [3] / 4 inch (19 mm), or satisfy the requirements of width-to-thickness ratios of highly ductile members in AISC 341-16. 2. The biaxial dual-strong axis and column minor axis configurations of the moment connection shall be considered as an alternative system. 3. For SMF and IMF systems, on the sideplate standard or configuration A the U-shaped cover plates shall be used with the k dimension extension. The k dimension extension length is defined as beam depth d b /6, rounded to the nearest [1] / 2 inch (12.7 mm).

    4. The hinge-to-hinge span to beam depth, L h /d, shall be greater than or equal to 4.5. 5. The width-to-thickness ratios for beam flanges shall not be less than 3.5. Exception: For width-to-thickness ratios less than 3.5 the C pr shall be calculated in accordance with that for welded side- plate connections but in no case shall the width-to-thickness ratio be less than 3.0. 6. The minimum bolt-to-bolt spacing shall not be less than 3 bolt diameters. 7. The extension of the side plates beyond the face of the column shall be within the range of 0.65d to 1.5d. 8. The gap-to-side plate thickness ratio shall range from 2.1 to 2.3.

    Exception: The gap-to-side plate thickness ratio shall be permitted to be modified for moment connections with unequal beam sizes on opposite sides of the column or when orthogonal beams acting as drag connections frame into the side plate. 9. Demand Critical fillet welds {2}, {5}, {5a} and {8} shall have Magnetic Particle Testing (MT) in accordance with AWS D1.1 for procedure, technique and acceptance. Inspect the beginning and end of these welds for a 6-inch (152 mm) length, plus any location along the length of the weld where a start and restart is visually noted for a distance of 6 inches (152 mm) on either side of the start/stop location. 10. The connection specific factor to account for peak connection strength, C pr _, shall be between 1.15 and 1.35.

  • CBC § 2.5 Medium relevance — show source text

    R507.2.5 Alternate materials. Alternative materials, including glass and metals, shall be permitted.

    R507.3 Footings. Decks shall be supported on concrete footings or other approved structural systems designed to accommodate all loads in accordance with Section R301. Deck footings shall be sized to carry the imposed loads from the deck structure to the ground as shown in Figure R507.3.

    Exceptions:

    1. Footings shall not be required for free-standing decks consisting of joists directly supported on grade over their entire length.
    2. Footings shall not be required for free-standing decks that meet all of the following criteria: 2.1. The joists bear directly on precast concrete pier blocks at grade without support by beams or posts. 2.2. The area of the deck does not exceed 200 square feet (18.6 m [2] ). 2.3. The walking surface is not more than 20 inches (508 mm) above grade at any point within 36 inches (914 mm) measured horizontally from the edge.

    2025 CALIFORNIA RESIDENTIAL CODE 5-27

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

    FLOORS

    FIGURE R507.3—DECK POSTS TO DECK FOOTING CONNECTION

    MANUFACTURED POST CONNECTOR

    4″ GRAVEL

    NOTE:

    POSTS MUST BE CENTERED ON OR IN FOOTING
    For SI: 1 inch = 25.4 mm.
    R507.3.1 Minimum size. The minimum size of deck footings shall be in accordance with Table R507.3.1, based on the tributary
    area and allowable soil-bearing pressure in accordance with Table R401.4.1(1).    		 Col2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11
    TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS TABLE R507.3.1—MINIMUM FOOTING SIZE FOR DECKS
    LIVE OR
    GROUND
    SNOW
    LOADb
    (psf)
    TRIBUTARY
    AREAe
    (ft2)    		 LOAD-BEARING VALUE OF SOILSa, c, d (psf) LOAD-BEARING VALUE OF SOILSa, c, d (psf) LOAD-BEARING VALUE OF SOILS**_a, c,
  • CBC § 3107F.2.5.4.1 Medium relevance — show source text

    ε_c
    _MRSTS = Maximum Reinforcing Steel Tension Strain,ε_s
    _MPSTS = Maximum Prestressing Steel Tension Strain,ε_p|

    3107F.2.5.4.1 Method A. For Method A, the yield curvature, φ y is the curvature at the intersection of the secant stiffness, EI c , through first yield and the nominal strength, ( ε c = 0.004).

    Equation 7-10

    φ y = ------EIM yc

    FIGURE 31F-7-4 — METHOD A - MOMENT CURVATURE ANALYSIS

    3107F.2.5.4.2 Method B. For Method B, the elastic portion of the idealized moment-curvature curve is the same as in Method A (see Section 3107F.2.5.4.1). However, the idealized plastic moment capacity, M p , and the yield curvature, φ y , is obtained by balancing the areas between the actual and the idealized moment-curvature curves beyond the first yield point (see Figure 31F- 7-5). Method B applies to moment-curvature curves that do not experience reduction in section moment capacity.

    2025 CALIFORNIA BUILDING CODE 31F-65

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

    MARINE OIL TERMINALS

    FIGURE 31F-7-5 — METHOD B – MOMENT CURVATURE ANALYSIS [7.6]

    3107F.2.5.5 Ultimate concrete and steel flexural strains. Strain values computed in the nonlinear pushover analysis shall be compared to the following limits.

    3107F.2.5.5.1 Unconfined concrete piles: An unconfined concrete pile is defined as a pile having no confinement steel or one in which the spacing of the confinement steel exceeds 12 inches.

    Ultimate concrete compressive strain:

    Equation 7-11 ε cu = 0.005

    3107F.2.5.5.2 Confined concrete piles: Ultimate concrete compressive strain [7.1]:

    Equation 7-12 ε cu = 0.004 + (1.4 ρ s f yh ε sm )/f ' cc ≥ 0.005 ε cu ≤ 0.025

    where:

    ρ s = effective volume ratio of confining steel f yh = yield stress of confining steel ε sm = strain at peak stress of confining reinforcement, 0.15 for grade 40, 0.10 for grade 60

    f ' cc = confined strength of concrete approximated by 1.5 f' cc

Frequently asked questions

When exactly are seismic ties between spread footings required?

When the structure is in Seismic Design Category D, E or F and the footings are founded on Site Class E or F as defined in ASCE 7 — § 1809.13 requires interconnection by ties unless equivalent restraint by reinforced slab/beams is demonstrated .

How do I size a seismic tie between two footings?

Size the tie for the lesser of (larger footing gravity load × SDS ÷ 10) or 25% of the smaller footing gravity load, per § 1809.13. Show the calculation on the drawings and the SDS value used .

Do grade beams always have to be designed to ACI 318?

Yes, grade beams shall comply with ACI 318, except for the specific exception in § 1809.14 for grade beams with limited differential settlement and that are designed for seismic effects per ASCE 7 .

What clearance is required for pipes passing through footings?

Pipe sleeves are required where pipes pass through footings or footing walls, and sleeve clearances must allow for possible settlement but not less than 1 inch all around the pipe (§ 1809.15) .

Can trenches be located right next to a footing?

Not without meeting the limits in § 1809.15: trenches parallel to a footing must not be below the plane defined from a point 9 inches above the bottom edge of the footing with a 1:2 downward slope, and must be at least 18 inches from the face of the footing unless an alternate is approved (§ 1809.15) .

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

How are deep foundations (piles, drilled shafts) analyzed, designed and detailed?

What are the rules for retaining walls, foundation walls and embedded posts/poles?

What ground improvement provisions (vibro stone columns, VSC) must be followed?

Shallow & Deep Foundations, Retaining Walls & Ground Improvement

California Building Code