CBC · California Building Code

What does the CBC require for footings in light‑frame construction?

The CBC allows 6‑inch plain concrete footings for Group R‑3 and other light‑frame buildings under two stories as long as the footing thickness is 6 inches and it does not extend more than 4 inches beyond either side of the supported wall; otherwise use the prescriptive sizes in Table 1809.7 and comply with minimum depth, frost protection and any seismic/engineered requirements in Chapters 18 and 19.

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Last reviewed: July 5, 2026

What the code requires — 2–4 sentences

The California Building Code permits plain concrete footings for light‑frame walls of Group R‑3 and for buildings of other occupancies that are less than two stories above grade plane to be 6 inches thick, provided the footing does not extend more than 4 inches on either side of the supported wall (see §1906.1). For prescriptive footing widths, and minimum footing depth and other shallow‑foundation rules applicable to light‑frame construction, use the prescriptive Table 1809.7 and the shallow‑foundation provisions in Chapter 18 (for example §1809.4 and §1809.5).

Requirements in detail

Governing plain‑footing rule (thickness & projection)

Plain concrete footings for Group R‑3 occupancies and for other occupancies of light‑frame construction that are less than two stories above grade plane are permitted to be 6 inches (152 mm) thick. The footing must not extend more than 4 inches (102 mm) on either side of the supported wall. See §1906.1.

Prescriptive footing sizes (width & thickness)

Where a specific engineered design is not provided, footings supporting light‑frame walls may be sized per the prescriptive Table 1809.7 (prescriptive footing table for light‑frame construction). The table provides decision‑relevant footing widths and thicknesses based on number of floors supported:

Condition / decision point	Prescriptive dimension (US units)	Code Reference
Plain footing thickness allowed for Group R‑3 and other light‑frame (<2 stories)	6 in (152 mm); max projection 4 in each side	§1906.1
Prescriptive footing — supports 1 floor (light‑frame)	12 in wide × 6 in thick (Table 1809.7)	§1809.7 / Table 1809.7
Prescriptive footing — supports 2 floors (light‑frame)	15 in wide × 6 in thick (Table 1809.7)	§1809.7 / Table 1809.7
Prescriptive footing — supports 3 floors (light‑frame)	18 in wide × 8 in thick (Table 1809.7)	§1809.7 / Table 1809.7
Minimum footing width and depth where otherwise required	Minimum width 12 in; minimum depth below undisturbed ground 12 in	§1809.4

Notes:

The prescriptive table is explicit that footings for light‑frame walls may be sized per Table 1809.7 when no specific design is provided; depth of footings (top elevation) and other notes in table footnotes refer back to §1809.4.

Depth, bearing and frost protection

The minimum depth of footings below undisturbed ground is 12 inches (305 mm) (§1809.4).
Foundations and permanent supports must be protected from frost where required (extend below frost line, ASCE 32, or other allowed methods) — see §1809.5.

Concrete strength, reinforcement and special design triggers

Concrete strength and other durability/design requirements for foundations are covered elsewhere in Chapter 18 and Chapter 19 (see Table and § references in those chapters). Where a specific engineered foundation is required (seismic design categories, special soils, structural slabs transmitting loads, etc.), use the engineered design provisions rather than the prescriptive table. See §1907 and cross‑references in Chapter 19.

Exceptions & special cases

OSHPD limitations: Plain concrete footings as permitted above are not allowed for OSHPD 1R, 2 and 5 projects — the code explicitly notes that the plain‑footing allowance is not permitted by OSHPD. See §1906.1 note.
Where a specific engineered design is provided (for example, required by seismic design category, soil conditions, or ACI 318 triggers), the prescriptive Table 1809.7 and the simple §1906.1 allowance do not replace engineered requirements — see the cross references and Chapter 19 seismic/design provisions.
For walls or conditions other than light‑frame construction, plain concrete footings may require an 8‑inch minimum edge thickness (§1809.8) unless an exception applies (Group R‑3 exception that mirrors §1906.1).

Common mistakes

Applying the 6‑inch plain‑footing allowance to multi‑story buildings: §1906.1 is limited to Group R‑3 and other occupancies less than two stories above grade plane — it does not authorize 6‑inch plain footings for taller/other structures.
Ignoring the 4‑inch maximum projection rule: the 6‑inch plain footing is allowed only when the footing does not extend more than 4 inches on either side of the supported wall. Exceeding that projection invalidates the §1906.1 allowance.
Using the prescriptive table when site‑specific conditions (poor soils, high seismic design category, unbalanced fills, sloping/aggraded sites) require engineered foundations — Table 1809.7 applies only where a specific design is not provided and where its footnotes/limitations are met.
Forgetting minimum depth and frost protection requirements (§1809.4 and §1809.5) when placing footings.

Worked example — one‑story Group R‑3 light‑frame house (practical check)

Scenario: A single‑story Group R‑3 wood‑framed house (one floor only) with continuous bearing wall. No engineered foundation design provided; the site has conventional soils, and the project is not OSHPD.

Apply the CBC prescriptive rules:

Use Table 1809.7 for a one‑story light‑frame wall: prescriptive footing = 12 in wide × 6 in thick. (§1809.7 / Table 1809.7).
The 6‑inch thickness also meets the §1906.1 allowance for Group R‑3 plain footings; confirm that the footing projection beyond the supported wall is not more than 4 in on either side. (§1906.1).
Place the top of footing at a depth not less than 12 in below undisturbed ground per §1809.4 (or deeper where frost or local code requires). (§1809.4).
Verify frost protection/other local requirements per §1809.5; if the locality has a frost line that requires deeper footing, the prescriptive 12‑in depth is the minimum, not a maximum. (§1809.5).

Result: For this simple one‑story R‑3 example, a 12" × 6" footing placed at least 12" below undisturbed ground and with no more than 4" projection beyond each side of the wall satisfies the CBC prescriptive allowances referenced above.

Related provisions

§1906.1 — Plain concrete footings for light‑frame construction (primary allowance discussed above).
§1809.4 — Minimum depth and minimum width of footings (12 in minimum).
§1809.5 — Frost protection for foundations and permanent supports.
§1809.7 / Table 1809.7 — Prescriptive footing widths and thicknesses for light‑frame construction.
§1809.8 — Plain concrete footings (edge thickness for other than light‑frame).
§1907.3 — Minimum slab‑on‑ground thickness where slabs are used (related slab provision).

Code references

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

CBC § 1.3. High relevance — show source text
The maximum anchor nominal diameter is [5] / 8 inch (16 mm). 1.3. Anchor bolts are embedded into concrete not less than 7 inches (178 mm). 1.4. Anchor bolts are located not less than 1¾ inches (45 mm) from the edge of the concrete parallel to the length of the wood sill plate. 1.5. Anchor bolts are located not less than 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate. 1.6. The sill plate is 2-inch (51 mm) or 3-inch (76 mm) nominal thickness. 2. For the calculation of the in-plane shear strength of anchor bolts attaching cold-formed steel track of bearing or nonbearing walls of light-frame construction to foundations or foundation stemwalls, the in-plane shear strength in accordance with Sections 17.7.2 and 17.7.3 of ACI 318 need not be computed and 17.10.6.3 shall be deemed to be satisfied provided that all of the following are met:

Allowable in-plane shear strength of exempt anchors, parallel to the edge of concrete, shall be permitted to be determined in accordance with AISI S100 Section J3.3.1.

2.1. The maximum anchor nominal diameter is [5] / 8 inch (16 mm). 2.2. Anchors are embedded into concrete a minimum of 7 inches (178 mm).

2025 CALIFORNIA BUILDING CODE 19-7

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CONCRETE

2.3. Anchors are located a minimum of 1 [3] / 4 inches (45 mm) from the edge of the concrete parallel to the length of the track.

2.4. Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track. 2.5. The track is 33 to 68 mil (0.84 mm to 1.73 mm) designation thickness. 3. In light-frame construction bearing or nonbearing walls, shear strength of concrete anchors less than or equal to 1 inch (25 mm) in diameter attaching sill plate or track to foundation or foundation stemwalls need not satisfy Sections 17.10.6.3(a) through (c) when the design strength of the anchors is determined in accordance with Section 17.7.2.1(c) of ACI 318.

SECTION 1906—FOOTINGS FOR LIGHT-FRAME CONSTRUCTION

[OSHPD 1R, 2 & 5] Plain concrete footings not permitted by OSHPD.

1906.1 Plain concrete footings. For Group R-3 occupancies and buildings of other occupancies less than two stories above grade plane of light-frame construction, the required thickness of plain concrete footings is permitted to be 6 inches (152 mm), provided that the footing does not extend more than 4 inches (102 mm) on either side of the supported wall.

SECTION 1907—SLABS-ON-GROUND

1907.1 Structural slabs-on-ground. Structural concrete slabs-on-ground shall comply with all applicable provisions of this chapter. Slabs-on-ground shall be considered structural concrete where required by ACI 318 or where designed to transmit either of the following:
1. Vertical loads or lateral forces from other parts of the structure to the soil.
2. Vertical loads or lateral forces from other parts of the structure to foundations.
CBC § 1807.1.6. High relevance — show source text
Interior stud-bearing walls shall be permitted to be supported by isolated footings. The footing width and length shall be twice the width shown in this table, and footings
shall be spaced not more than 6 feet on center.
d. See Section 1905 for additional requirements for concrete footings of structures assigned to Seismic Design Category C, D, E or F.
e. For thickness of foundation walls, see Section 1807.1.6.
f. Footings shall be permitted to support a roof in addition to the stipulated number of floors. Footings supporting roof only shall be as required for supporting one floor.
g. Plain concrete footings for Group R-3 occupancies shall be permitted to be 6 inches thick.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Depth of footings shall be in accordance with Section 1809.4.
b. The ground under the floor shall be permitted to be excavated to the elevation of the top of the footing.
c. Interior stud-bearing walls shall be permitted to be supported by isolated footings. The footing width and length shall be twice the width shown in this table, and footings
shall be spaced not more than 6 feet on center.
d. See Section 1905 for additional requirements for concrete footings of structures assigned to Seismic Design Category C, D, E or F.
e. For thickness of foundation walls, see Section 1807.1.6.
f. Footings shall be permitted to support a roof in addition to the stipulated number of floors. Footings supporting roof only shall be as required for supporting one floor.
g. Plain concrete footings for Group R-3 occupancies shall be permitted to be 6 inches thick.|

1809.8 Plain concrete footings. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. The edge thickness of plain concrete footings supporting walls of other than light-frame construction shall be not less than 8 inches (203 mm) where placed on soil or rock.

Exception: For plain concrete footings supporting Group R-3 occupancies, the edge thickness is permitted to be 6 inches (152 mm), provided that the footing does not extend beyond a distance greater than the thickness of the footing on either side of the supported wall.

1809.9 Masonry-unit footings. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. The design, materials and construction of masonry-unit footings shall comply with Sections 1809.9.1 and 1809.9.2, and the provisions of Chapter 21.

Exception: Where a specific design is not provided, masonry-unit footings supporting walls of light-frame construction shall be permitted to be designed in accordance with Table 1809.7.

1809.9.1 Dimensions. Masonry-unit footings shall be laid in Type M or S mortar complying with Section 2103.2.1 and the depth shall be not less than twice the projection beyond the wall, pier or column. The width shall be not less than 8 inches (203 mm) wider than the wall supported thereon. 1809.9.2 Offsets. The maximum offset of each course in brick foundation walls stepped up from the footings shall be 1 [1] / 2 inches (38 mm) where laid in single courses, and 3 inches (76 mm) where laid in double courses.
CBC § 18-19 High relevance — show source text
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SOILS AND FOUNDATIONS

1809.10 Pier and curtain wall foundations. Except in Seismic Design Categories D, E and F, pier and curtain wall foundations shall be permitted to be used to support light-frame construction not more than two stories above grade plane, provided that the following requirements are met:
1. All load-bearing walls shall be placed on continuous concrete footings bonded integrally with the exterior wall footings.
2. The minimum actual thickness of a load-bearing masonry wall shall be not less than 4 inches (102 mm) nominal or 3 [5] / 8 inches (92 mm) actual thickness, and shall be bonded integrally with piers spaced 6 feet (1829 mm) on center (o.c.).
3. Piers shall be constructed in accordance with Chapter 21 and the following: 3.1. The unsupported height of the masonry piers shall not exceed 10 times their least dimension. 3.2. Where structural clay tile or hollow concrete masonry units are used for piers supporting beams and girders, the cellular spaces shall be filled solidly with concrete or Type M or S mortar. Exception: Unfilled hollow piers shall be permitted where the unsupported height of the pier is not more than four times its least dimension.
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.
CBC § 2.4. High relevance — show source text
2.4. Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track. 2.5. The track is 33 to 68 mil (0.84 mm to 1.73 mm) designation thickness. 3. In light-frame construction bearing or nonbearing walls, shear strength of concrete anchors less than or equal to 1 inch (25 mm) in diameter attaching sill plate or track to foundation or foundation stemwalls need not satisfy Sections 17.10.6.3(a) through (c) when the design strength of the anchors is determined in accordance with Section 17.7.2.1(c) of ACI 318.

SECTION 1906—FOOTINGS FOR LIGHT-FRAME CONSTRUCTION

[OSHPD 1R, 2 & 5] Plain concrete footings not permitted by OSHPD.

1906.1 Plain concrete footings. For Group R-3 occupancies and buildings of other occupancies less than two stories above grade plane of light-frame construction, the required thickness of plain concrete footings is permitted to be 6 inches (152 mm), provided that the footing does not extend more than 4 inches (102 mm) on either side of the supported wall.

SECTION 1907—SLABS-ON-GROUND

1907.1 Structural slabs-on-ground. Structural concrete slabs-on-ground shall comply with all applicable provisions of this chapter. Slabs-on-ground shall be considered structural concrete where required by ACI 318 or where designed to transmit either of the following:
1. Vertical loads or lateral forces from other parts of the structure to the soil.
2. Vertical loads or lateral forces from other parts of the structure to foundations.
1907.2 Nonstructural slabs-on-ground. Nonstructural slabs-on-ground shall be required to comply with Sections 1904.2, 1907.3 and 1907.4. Portions of the nonstructural slabs-on-ground used to resist uplift forces or overturning shall be designed in accordance with accepted engineering practice throughout the entire portion designated as dead load to resist uplift forces or overturning. 1907.3 Thickness. The thickness of concrete floor slabs supported directly on the ground shall be not less than 3 [1] / 2 inches (89 mm).

1907.4 Vapor retarder. A 6-mil (0.006 inch; 0.15 mm) polyethylene vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the base course or subgrade and the concrete floor slab, or other approved equivalent methods or materials shall be used to retard vapor transmission through the floor slab.

Exception: A vapor retarder is not required:
1. For detached structures accessory to occupancies in Group R-3, such as garages, utility buildings or other unheated facilities.
2. For unheated storage rooms having an area of less than 70 square feet (6.5 m [2] ) and carports attached to occupancies in Group R-3.
3. For buildings of other occupancies where migration of moisture through the slab from below will not be detrimental to the intended occupancy of the building.
4. For driveways, walks, patios and other flatwork that will not be enclosed at a later date.
5. Where approved based on local site conditions.
CBC § 1809.8 High relevance — show source text
1809.8 Plain concrete footings. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. The edge thickness of plain concrete footings supporting walls of other than light-frame construction shall be not less than 8 inches (203 mm) where placed on soil or rock.

Exception: For plain concrete footings supporting Group R-3 occupancies, the edge thickness is permitted to be 6 inches (152 mm), provided that the footing does not extend beyond a distance greater than the thickness of the footing on either side of the supported wall.

1809.9 Masonry-unit footings. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. The design, materials and construction of masonry-unit footings shall comply with Sections 1809.9.1 and 1809.9.2, and the provisions of Chapter 21.

Exception: Where a specific design is not provided, masonry-unit footings supporting walls of light-frame construction shall be permitted to be designed in accordance with Table 1809.7.

1809.9.1 Dimensions. Masonry-unit footings shall be laid in Type M or S mortar complying with Section 2103.2.1 and the depth shall be not less than twice the projection beyond the wall, pier or column. The width shall be not less than 8 inches (203 mm) wider than the wall supported thereon. 1809.9.2 Offsets. The maximum offset of each course in brick foundation walls stepped up from the footings shall be 1 [1] / 2 inches (38 mm) where laid in single courses, and 3 inches (76 mm) where laid in double courses.

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SOILS AND FOUNDATIONS

1809.10 Pier and curtain wall foundations. Except in Seismic Design Categories D, E and F, pier and curtain wall foundations shall be permitted to be used to support light-frame construction not more than two stories above grade plane, provided that the following requirements are met:
1. All load-bearing walls shall be placed on continuous concrete footings bonded integrally with the exterior wall footings.
2. The minimum actual thickness of a load-bearing masonry wall shall be not less than 4 inches (102 mm) nominal or 3 [5] / 8 inches (92 mm) actual thickness, and shall be bonded integrally with piers spaced 6 feet (1829 mm) on center (o.c.).
3. Piers shall be constructed in accordance with Chapter 21 and the following: 3.1. The unsupported height of the masonry piers shall not exceed 10 times their least dimension. 3.2. Where structural clay tile or hollow concrete masonry units are used for piers supporting beams and girders, the cellular spaces shall be filled solidly with concrete or Type M or S mortar. Exception: Unfilled hollow piers shall be permitted where the unsupported height of the pier is not more than four times its least dimension.

CBC § 1809.5 High relevance — show source text

1809.5 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:

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

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

Assigned to Risk Category I.
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.
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.

1809.5.1 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.

1809.6 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.

1809.7 Prescriptive footings for light-frame construction. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. Where a specific design is not provided, concrete or masonry-unit footings supporting walls of light-frame construction shall be permitted to be designed in accordance with Table 1809.7.

TABLE 1809.7—PRESCRIPTIVE FOOTINGS SUPPORTING WALLS OF LIGHT-FRAME CONSTRUCTIONa, b, c, d, e	Col2	Col3
NUMBER OF FLOORS SUPPORTED BY THE FOOTINGf	WIDTH OF FOOTING (inches)	THICKNESS OF FOOTING (inches)
1	12	6
2	15	6
3	18	8g
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm. a. Depth of footings shall be in accordance with Section 1809.4. b. The ground under the floor shall be permitted to be excavated to the elevation of the top of the footing. c. Interior stud-bearing walls shall be permitted to be supported by isolated footings. The footing width and length shall be twice the width shown in this table, and footings shall be spaced not more than 6 feet on center. d. See Section 1905 for additional requirements for concrete footings of structures assigned to Seismic Design Category C, D, E or F. e. For thickness of foundation walls, see Section 1807.1.6. f. Footings shall be permitted to support a roof in addition to the stipulated number of floors. Footings supporting roof only shall be as required for supporting one floor. g. Plain concrete footings for Group R-3 occupancies shall be permitted to be 6 inches thick.	For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm. a.

CBC § 19-5 High relevance — show source text
1903 Specifications for Tests and Materials . . . . . . . . . . . 19-5

1904 Durability Requirements . . . . . . . . . . . . . . . . . . . . . . . 19-6

1905 Seismic Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 19-6

1906 Footings for Light-Frame Construction . . . . . . . . . . 19-8

1907 Slabs-on-Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-8

1908 Shotcrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-8

1909 Additional Requirements for Community Colleges

[DSA-SS/CC]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-8

1910 Additional Requirements for Skilled Nursing Facilities, Intermediate Care Facilities, Acute Psychiatric and Non-GAC Buildings

[OSHPD 1R, 2 & 5]. . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-12

1911 Existing Concrete Structures [OSHPD 1R, 2 & 5]. . . . . . .19-13

CHAPTER 19A CONCRETE . . . . . . . . . . . . . . . . . . . . . . . . . . 19A-1

1901A General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-3

1902A Coordination of Terminology . . . . . . . . . . . . . . . . . . . .19A-4

1903A Specifications for Tests and Materials . . . . . . . . . . . .19A-4

1904A Durability Requirements . . . . . . . . . . . . . . . . . . . . . . . .19A-4

1905A Seismic Requirements . . . . . . . . . . . . . . . . . . . . . . . . . .19A-4

1906A Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-5

1907A Slabs-on-Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-5

1908A Shotcrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19A-6

1909A Modifications to ACI 318. . . . . . . . . . . . . . . . . . . . . . . . .19A-6

CBC § 1808.7.2 High relevance — show source text

1808.7.2 Foundation setback from descending slope surface. Foundations on or adjacent to slope surfaces shall be founded in firm material with an embedment and set back from the slope surface sufficient to provide vertical and lateral support for the foundation without detrimental settlement. Except as provided for in Section 1808.7.5 and Figure 1808.7.1, the following setback is deemed adequate to meet the criteria. Where the slope is steeper than 1 unit vertical in 1 unit horizontal (100-percent slope), the required setback shall be measured from an imaginary plane 45 degrees (0.79 rad) to the horizontal, projected upward from the toe of the slope.

1808.7.3 Pools. The setback between pools regulated by this code and slopes shall be equal to one-half the building footing setback distance required by this section. That portion of the pool wall within a horizontal distance of 7 feet (2134 mm) from the top of the slope shall be capable of supporting the water in the pool without soil support.

1808.7.4 Foundation elevation. On graded sites, the top of any exterior foundation shall extend above the elevation of the street gutter at point of discharge or the inlet of an approved drainage device not less than 12 inches (305 mm) plus 2 percent. Alternate elevations are permitted subject to the approval of the building official, provided that it can be demonstrated that required drainage to the point of discharge and away from the structure is provided at all locations on the site.

1808.7.5 Alternate setback and clearance. Alternate setbacks and clearances are permitted, subject to the approval of the building official. The building official shall be permitted to require a geotechnical investigation as set forth in Section 1803.5.10.

1808.8 Concrete foundations. The design, materials and construction of concrete foundations shall comply with Sections 1808.8.1 through 1808.8.6 and the provisions of Chapter 19.

Exception: [OSHPD 1R, 2 & 5] Not permitted by OSHPD. Where concrete footings supporting walls of light-frame construction are designed in accordance with Table 1809.7, a specific design in accordance with Chapter 19 is not required.

1808.8.1 Concrete or grout strength and mix proportioning. Concrete or grout in foundations shall have a specified compressive strength ( f ′ c ) not less than the largest applicable value indicated in Table 1808.8.1.

Where concrete or grout is to be pumped, the mix design including slump shall be adjusted to produce a pumpable mixture.

TABLE 1808.8.1—MINIMUM SPECIFIED COMPRESSIVE STRENGTH f ′ OF CONCRETE OR GROUT c	Col2
FOUNDATION ELEMENT OR CONDITION	SPECIFIED COMPRESSIVE STRENGTH,f ′c
1. Foundations for structures assigned to Seismic Design Category A, B or C *[OSHPD 1R, 2 & 5]*Not permitted by OSHPD.	2,500 psi
2a. Foundations for Group R or U occupancies of light-frame construction, two stories or less in height, assigned to Seismic Design Category D, E or F_ [OSHPD 1R, 2 & 5]_Not permitted by OSHPD.	2,500 psi
2b.

CBC § 18A-11 High relevance — show source text
1808A Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18A-11

1809A Shallow Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . 18A-14

1810A Deep Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18A-15

1811A Prestressed Rock and Soil Foundation

Anchors [OSHPD 1R, 2 & 5] . . . . . . . . . . . . . . . . . . . . 18A-25

1812A Earth Retaining Shoring . . . . . . . . . . . . . . . . . . . . . . . . 18A-26

1813A Vibro Stone Columns for Ground

Improvement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18A-29

CHAPTER 19 CONCRETE. . . . . . . . . . . . . . . . . . . . . . . . . . . 19-1

1901 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-3

1902 Coordination of Terminology . . . . . . . . . . . . . . . . . . . 19-5

1903 Specifications for Tests and Materials . . . . . . . . . . . 19-5

1904 Durability Requirements . . . . . . . . . . . . . . . . . . . . . . . 19-6

1905 Seismic Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 19-6

1906 Footings for Light-Frame Construction . . . . . . . . . . 19-8

1907 Slabs-on-Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-8

1908 Shotcrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-8

1909 Additional Requirements for Community Colleges

[DSA-SS/CC]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-8

1910 Additional Requirements for Skilled Nursing Facilities, Intermediate Care Facilities, Acute Psychiatric and Non-GAC Buildings

[OSHPD 1R, 2 & 5]. . . . . . . . . . . . . . . . . . . . . . . . . . . . .19-12

1911 Existing Concrete Structures [OSHPD 1R, 2 & 5]. . . . . . .19-13
CBC § 2.25 Medium relevance — show source text
00|2.25|0.70|DR|3.70|1.05|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|33 mil cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|16|3.85|1.45|DR|DR|3.40|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|33 mil cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|24|3.40|DR|DR|DR|2.70|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|12|3.00|1.80|DR|DR|3.00|0.65|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|16|3.00|1.00|DR|DR|2.85|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#8 Screw|Steel thick-
ness plus 3
threads|24|2.85|DR|DR|DR|2.20|DR|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|12|4.00|3.85|2.80|1.80|4.00|3.05|1.50|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|16|4.00|3.30|1.95|0.60|4.00|2.25|DR|DR| |Minimum 33
mil steel
furring or
minimum
1x wood
furringc|43 mil or
thicker cold-
formed steel
stud|#10 screw|Steel thick-
ness plus 3
threads|24|4.00|2.25|DR|DR|4.00|0.65|DR|DR| |For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
DR = Design Required, o.c. = on center.
a. Wood furring shall be spruce-pine-fir or any softwood species with a specific gravity of 0.42 or greater.
CBC § 3.1. Medium relevance — show source text
Allowable in-plane shear strength of exempt anchors, parallel to the edge of concrete, shall be permitted to be determined in accordance with AISI S100 Section J3.3.1.

2.1. The maximum anchor nominal diameter is [5] / 8 inch (16 mm). 2.2. Anchors are embedded into concrete a minimum of 7 inches (178 mm). 2.3. Anchors are located a minimum of 1 [3] / 4 inches (45 mm) from the edge of the concrete parallel to the length of the track.

2.4. Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track. 2.5. The track is 33 to 68 mil (0.84 mm to 1.73 mm) designation thickness. 3. In light-frame construction bearing or nonbearing walls, shear strength of concrete anchors less than or equal to 1 inch (25 mm) in diameter attaching sill plate or track to foundation or foundation stemwalls need not satisfy Sections 17.10.6.3(a) through (c) when the design strength of the anchors is determined in accordance with Section 17.7.2.1(c) of ACI 318.

SECTION 1906 A — RESERVED

SECTION 1907 A —SLABS-ON-GROUND

1907 A .1 Structural slabs-on-ground. Structural concrete slabs-on-ground shall comply with all applicable provisions of this chapter. Slabs-on-ground shall be considered structural concrete where required by ACI 318 or where designed to transmit either of the following:
1. Vertical loads or lateral forces from other parts of the structure to the soil.
2. Vertical loads or lateral forces from other parts of the structure to foundations.
2025 CALIFORNIA BUILDING CODE 19A-5

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

CONCRETE

1907 A .2 Nonstructural slabs-on-ground. Nonstructural slabs-on-ground shall be required to comply with Sections 1904 A .2, 1907 A .3 and 1907 A .4. Portions of the nonstructural slabs-on-ground used to resist uplift forces or overturning shall be designed in accordance with accepted engineering practice throughout the entire portion designated as dead load to resist uplift forces or overturning. 1907 A .3 Thickness. The thickness of concrete floor slabs supported directly on the ground shall be not less than 3 [1] / 2 inches (89 mm).

1907 A .4 Vapor retarder. A 6-mil (0.006 inch; 0.15 mm) polyethylene vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the base course or subgrade and the concrete floor slab, or other approved equivalent methods or materials shall be used to retard vapor transmission through the floor slab.

Exception: A vapor retarder is not required:
1. For detached structures accessory to occupancies in Group R-3, such as garages, utility buildings or other unheated facilities.
CBC § 1.3.5.4 Medium relevance — show source text
R403.1.3.5.4 Lap splices. Vertical and horizontal reinforcement shall be the longest lengths practical. Where splices are necessary in reinforcement, the length of lap splice shall be in accordance with Table R608.5.4(1) and Figure R608.5.4(1). The maximum gap between noncontact parallel bars at a lap splice shall not exceed the smaller of one-fifth the required lap length and 6 inches (152 mm) [see Figure R608.5.4(1)].

R403.1.3.6 Isolated concrete footings. In detached one- and two-family dwellings that are three stories or less in height and constructed with stud bearing walls, isolated plain concrete footings supporting columns or pedestals are permitted.

R403.1.4 Minimum depth. Exterior footings shall be placed not less than 12 inches (305 mm) below the undisturbed ground surface. Where applicable, the depth of footings shall also conform to Section R403.1.4.1. Deck footings shall be in accordance with Section R507.3.

R403.1.4.1 Frost protection. Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:
1. Extended below the frost line specified in Table R301.2.
2. Constructed in accordance with Section R403.3.
3. Constructed in accordance with ASCE 32.
4. Erected on solid rock.
Footings shall not bear on frozen soil unless the frozen condition is permanent.

Exceptions:
1. Protection of free-standing accessory structures with an area of 600 square feet (56 m [2] ) or less, of light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
2. Protection of free-standing accessory structures with an area of 400 square feet (37 m [2] ) or less, of other than lightframe construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
4-14 2025 CALIFORNIA RESIDENTIAL CODE

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

FOUNDATIONS

R403.1.5 Slope. The top surface of footings shall be level. The bottom surface of footings shall not have a slope 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 footings or where the slope of the bottom surface of the footings will exceed 1 unit vertical in 10 units horizontal (10percent slope).

R403.1.6 Foundation anchorage. Wood sill plates and wood walls supported directly on continuous foundations shall be anchored to the foundation in accordance with this section.

Cold-formed steel framing shall be anchored directly to the foundation or fastened to wood sill plates in accordance with Section R505.3.1 or R603.3.1, as applicable. Wood sill plates supporting cold-formed steel framing shall be anchored to the foundation in accordance with this section.

Frequently asked questions

Can I always use a 6‑inch plain concrete footing for a wood‑framed house?

Only when the building is Group R‑3 or another occupancy that is less than two stories above grade plane and the footing does not extend more than 4 inches on either side of the supported wall; OSHPD projects are excluded. See §1906.1.

What if my project is two stories or in a high seismic zone?

If the project is two stories or higher, or seismic/soil conditions require an engineered foundation, you must use a specific engineered design rather than the §1906.1 prescriptive allowance — consult the seismic/design provisions in Chapter 19 and the applicable sections of Chapter 18.

Where do I find the prescriptive footing widths for 1, 2 or 3‑story light‑frame walls?

Use Table 1809.7 (prescriptive footings). It lists 12 × 6 in for one floor, 15 × 6 in for two floors, and 18 × 8 in for three floors (see table and footnotes). §1809.7 / Table 1809.7.

Is the 12‑inch minimum depth always sufficient in cold climates?

No — §1809.4 sets the minimum depth at 12 inches, but §1809.5 requires frost protection where applicable (extend below frost line, ASCE 32 method, etc.). Always comply with local frost requirements.

Are anchor bolt embedment and spacing covered by §1906?

No — anchor bolt embedment and spacing and other anchorage exceptions appear in the Chapter 19 modifications and seismic/anchorage provisions; check the applicable sections in Chapter 19 (see the code text for anchor requirements and exceptions). If you need the anchor details, consult those Chapter 19 provisions.

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