CRC · California Residential Code

What are the basic design duties for foundations and soil/fill?

Q: When can I use the CRC presumptive bearing values instead of a geotechnical report?

You may use the code’s presumptive values (Table R401.4.1(1)) when no site conditions trigger required soil testing; however, if expansive, compressible, shifting soils, groundwater issues, or seismic category C+ conditions exist, the code requires a geotechnical investigation and site‑specific recommendations. § R401.4 / § R401.4.1 .

Q: Who is responsible for inspecting engineered fill that supports a foundation?

The project’s geotechnical engineer or their qualified representative is responsible to inspect and verify fills used to support foundations; continuous inspection and a verified report are required where applicable. See special inspection provisions and § R401.2 / special inspections tables.

Q: What minimum grading slopes should I provide to protect the foundation?

Grade should fall not fewer than 6 inches within the first 10 feet away from foundation walls; if physical barriers prevent that, provide drains or swales. Impervious surfaces within 10 feet must slope not less than 2% away from the building. § R401.3 .

In plain terms: the CRC requires foundations to be designed to carry building loads to the ground and says that any fill used under footings must be engineered, placed and tested by a geotechnical professional. Follow drainage rules (6 in in 10 ft), use the CRC presumptive bearing values only when appropriate, and get a geotechnical report when site conditions, seismic category, or fill depth require one.

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

Foundation construction must be able to carry all building loads and transmit those loads safely to the supporting soil. Fill soils that support footings and foundations must be designed, installed and tested in accordance with accepted engineering practice. These duties are stated directly in § R401.2.

The single most important duty: foundations must safely carry the building loads to the soil, and any fill used to support those foundations must be engineered, placed and tested so it actually will perform. § R401.2.

Requirements in detail

1) Primary design duty — loads to soil

The designer must ensure foundations are capable of accommodating the loads required by Chapter 3 (see Section R301) and that those loads are transmitted to the supporting soil. This is the core requirement in § R401.2.
If the designer relies on engineered fill rather than undisturbed soil, that fill must be treated as a design element (i.e., engineered, placed and tested). § R401.2.

2) Drainage and surface grading (affects soils)

Surface drainage must move water away from foundation walls; grade shall fall not fewer than 6 inches within the first 10 feet, and impervious surfaces within 10 feet must slope not less than 2 percent away from the building. See § R401.3.

3) When soil testing / geotechnical evaluation is required

The building official may require soil tests where expansive, compressible, shifting or other questionable soils are likely; when tests are made, geotechnical reports must include site class and SDS when seismic category is C or greater. See § R401.4.
The code also provides a prescriptive (in‑lieu) option — where a full geotechnical evaluation is not performed, the code supplies presumptive allowable bearing values and soil classifications that may be assumed. See § R401.4.1 (Table R401.4.1(1)).

4) Presumptive bearing values (decision table)

Use these only when you are relying on the code’s in‑lieu provisions and no site-specific geotechnical report is required.

Decision item	Value / threshold	Code reference
Presumptive allowable bearing — Crystalline bedrock	12,000 psf	§ R401.4.1 (Table R401.4.1(1))
Presumptive allowable bearing — Sedimentary & foliated rock	4,000 psf	§ R401.4.1
Presumptive allowable bearing — Sandy gravel / gravel (GW, GP)	3,000 psf	§ R401.4.1
Presumptive allowable bearing — Sand, silty sand, clayey sand, silty gravel, clayey gravel (SW, SP, SM, SC, GM, GC)	2,000 psf	§ R401.4.1
Presumptive allowable bearing — Clay, silt, silty clay (CL, ML, MH, CH)	1,500 psf	§ R401.4.1
Minimum surface drainage fall	6 in in 10 ft (minimum)	§ R401.3
Minimum slope for impervious surfaces within 10 ft of foundation	2% away from building	§ R401.3

5) Fill used to support foundations (duties and inspection)

Fill soils that support footings and foundations are specifically required to be designed, installed and tested per accepted engineering practice — that places a duty on the project geotechnical engineer and the designer to provide specs, compaction criteria and acceptance testing. See § R401.2 and the geotechnical provisions in § R401.4.
For projects where deeper or engineered fills are used (or when agency rules require it), special inspection and continuous inspection of fill placement by the geotechnical engineer is required (see special‑inspection rules in the CBC; e.g., continuous inspection of fills used to support foundations). See Table and text in the special inspections section.

6) Limits and complementary design duties (expansive soils, seismic, deep foundations)

Where expansive, shifting, liquefiable or other problematic soils are present, the code requires more detailed geotechnical work and foundation design measures (see § R401.4 and the referenced seismic/site provisions).
If you assume prescriptive values but project conditions (slopes, groundwater, seismic category C+) exist, a site geotechnical investigation is required; the geotechnical report must include bearing recommendations, settlement estimates and mitigation measures. § R401.4 and associated reporting requirements.

Exceptions & special cases

The code allows use of the chapter provisions for certain wood foundations only in limited buildings (see § R401.1 exceptions).
The building official may waive a geotechnical report where quantifiable data show problematic soils are unlikely; conversely, the official may require tests where expansive or shifting soils are suspected — this is discretionary in § R401.4.
The CRC provides presumptive bearing values for convenience, but those are not substitutes for a geotechnical report where site conditions (expansive soils, groundwater, seismic category C+) warrant testing. § R401.4.1 and § R401.4.
Coastal high‑hazard or flood areas impose additional foundation types and documentation (see § R306.3 related provisions).

Common mistakes

Relying on the presumptive bearing table when obvious site problems exist (expansive soils, high groundwater, steep slopes). The code requires testing or a geotechnical report in those situations — see § R401.4.
Omitting proper drainage grading (6 in per 10 ft) and thereby allowing moisture to change soil conditions near the foundation — required by § R401.3.
Using fill under footings without engineered specifications and tests (the CRC requires fill supporting footings to be designed/installed/tested — § R401.2).
Forgetting special inspection/testing obligations (continuous inspection for fills supporting foundations) or not obtaining the verified geotechnical report. Special inspection requirements are described in the building‑code special inspection tables (see related provisions).

Worked example — applying the presumptive bearing table

Scenario: A designer is working on a small residence with footings to bear on a site where the soil classification from test pits is typical clean sand (classification group SW / SP).

The CRC presumptive allowable bearing for sandy gravel / sand (SW, SP, etc.) is 3,000 psf for GW/GP and 2,000 psf for sand/silty sand group depending on precise classification. Use the appropriate line in § R401.4.1 (Table R401.4.1(1)).
If the footing supports a column with a net load (dead + live) of 40,000 pounds (40 kips) and the designer is using the 2,000 psf presumption (e.g., classified as SM/SC group), required footing area = 40,000 lb ÷ 2,000 psf = 20 ft².
For a rectangular footing 2 ft wide that gives an area of 20 ft², the required length along the footing under the column reaction would be 10 ft (2 ft × 10 ft = 20 ft²). The designer can choose an alternate geometry (e.g., 4 ft × 5 ft) as long as area and code clearances are met.
Caveat: if the site has expansive soils, groundwater close to the footing elevation, or the project is in Seismic Design Category C or greater, the presumption is insufficient — a geotechnical report is required per § R401.4 and likely additional design provisions will apply.

(This worked example shows how to use the CRC presumptive bearing values in a sizing calculation; it does not substitute for project‑specific geotechnical analysis when the code requires one.)

Related provisions (selected)

§ R401.2 — Foundation requirements (primary controlling section).
§ R401.3 — Drainage and grading near foundations (6 in in 10 ft; 2% slope).
§ R401.4 — Soil tests and requirements for geotechnical reports; seismic information requirements.
§ R401.4.1 — Presumptive load‑bearing values (Table R401.4.1(1)).
§ R404.x / R405.1 — Foundation wall details, drainage around concrete/masonry foundations (foundation drainage).
CBC § 1803.5.8 — Compacted fill deeper than 12 in: geotechnical investigation requirements (applies as referenced for engineered fill).
CBC Table 1705.6 / 1705A.6 — Special inspections and tests for soils and fills (continuous inspection of fills supporting foundations).

Code references

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

CRC § 1808.6. High relevance — show source text
** Foundations shall be so designed that the allowable bearing capacity of the soil is not exceeded, and that differential settlement is minimized. Foundations in areas with expansive soils shall be designed in accordance with the provisions of Section 1808.6. 1808.3 Design loads. Foundations shall be designed for the most unfavorable effects due to the combinations of loads specified in Section 2.3 or 2.4 of ASCE 7 or the alternative allowable stress design load combinations of Section 1605.2. The dead load is permitted to include the weight of foundations and overlying fill. Reduced live loads, as specified in Sections 1607.13 and 1607.14, shall be permitted to be used in the design of foundations. 1808.3.1 Seismic overturning. Where foundations are proportioned using the load combinations of Section 2.3 or 2.4 of ASCE 7 and the computation of seismic over-turning effects is by equivalent lateral force analysis or modal analysis, the proportioning shall be in accordance with Section 12.13.4 of ASCE 7.

1808.3.2 Surcharge. Fill or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by the fill or the surcharge. Existing footings or foundations that will be affected by any excavation shall be underpinned or otherwise protected against settlement and shall be protected against detrimental lateral or vertical movement or both.

Exception: Minor grading for landscaping purposes shall be permitted where done with walk-behind equipment, where the grade is not increased more than 1 foot (305 mm) from original design grade or where approved by the building official. 1808.4 Vibratory loads. Where machinery operations or other vibrations are transmitted through the foundation, consideration shall be given in the foundation design to prevent detrimental disturbances of the soil. 1808.5 Shifting or moving soils. Where it is known that the shallow subsoils are of a shifting or moving character, foundations shall be carried to a sufficient depth to ensure stability. 1808.6 Design for expansive soils. Foundations for buildings and structures founded on expansive soils shall be designed in accordance with Section 1808.6.1 or 1808.6.2.

Exceptions: Foundation design need not comply with Section 1808.6.1 or 1808.6.2 where one of the following conditions is satisfied:
1. The soil is removed in accordance with Section 1808.6.3.
2. The building official approves stabilization of the soil in accordance with Section 1808.6.4. 1808.6.1 Foundations. Foundations placed on or within the active zone of expansive soils shall be designed to resist differential volume changes and to prevent structural damage to the supported structure. Deflection and racking of the supported structure shall be limited to that which will not interfere with the usability and serviceability of the structure.
Foundations placed below where volume change occurs or below expansive soil shall comply with the following provisions:
1. Foundations extending into or penetrating expansive soils shall be designed to prevent uplift of the supported structure.
2. Foundations penetrating expansive soils shall be designed to resist forces exerted on the foundation due to soil volume changes or shall be isolated from the expansive soil.
1808.6.2 Slab-on-ground foundations. Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on expansive soils shall be determined in accordance with WRI/CRSI or PTI DC 10.5.

CRC § 1705A.6 High relevance — show source text

TABLE 1705A.6—REQUIRED SPECIAL INSPECTIONS AND TESTS OF SOILS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1. Verify materials below shallow foundations are adequate to achieve the design bearing capacity.	—	X
2. Verify excavations are extended to proper depth and have reached proper material.	—	X
3. Perform classification and testing of compacted fill materials.	—	X
4. During fill placement, verify use of proper materials and procedures in accordance with the provisions of the approved geotechnical report. Verify densities and lift thicknesses during placement and compaction of compacted fill.	X	—
5. Prior to placement of compacted fill, inspect subgrade and verify that site has been prepared properly.	—	X

1705A.6.1 Soil fill. All fills used to support the foundations of any building or structure shall be continuously inspected by the geotechnical engineer or his or her qualified representative. It shall be the responsibility of the geotechnical engineer to verify that fills meet the requirements of the approved construction documents and to coordinate all fill inspection and testing during construc- tion involving such fills.

The duties of the geotechnical engineer or his or her qualified representative shall include, but need not be limited to, the inspec- tion of cleared areas and benches prepared to receive fill; inspection of the removal of all unsuitable soils and other materials; the approval of soils to be used as fill material; the inspection of placement and compaction of fill materials; the testing of the completed fills; and the inspection or review of geotechnical drainage devices, buttress fills or other similar protective measures in accordance with the approved construction documents.

A verified report shall be submitted by the geotechnical engineer as required by the California Administrative Code. The report shall indicate that all tests and inspections required by the approved construction documents were completed and whether the tested materials and/or inspected work meet the requirements of the approved construction documents.

1705A.6.2 Earth-retaining shoring. Special inspections and tests of earth-retaining shoring shall be in accordance with applicable portions of Section 1812A.

1705A.6.3 Vibro stone columns. Special inspections and tests of vibro stone columns for ground improvement shall be in accordance with Section 1813A.5.

1705 A .7 Driven deep foundations. Special inspections and tests shall be performed during installation of driven deep foundation elements as specified in 1810A.3.3.1.2 and Table 1705 A .7. The approved geotechnical report and the construction documents prepared by the registered design professionals shall be used to determine compliance.

TABLE 1705A.7—REQUIRED SPECIAL INSPECTIONS AND TESTS OF DRIVEN DEEP FOUNDATION ELEMENTS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1. Verify element materials, sizes and lengths comply with the requirements.	X	—
2.

CRC § 1705.6 High relevance — show source text

Exception: Where Section 1803 does not require reporting of materials and procedures for fill placement, the special inspector shall verify that the in-place dry density of the compacted fill is not less than 90 percent of the maximum dry density at optimum moisture content determined in accordance with ASTM D1557.

TABLE 1705.6—REQUIRED SPECIAL INSPECTIONS AND TESTS OF SOILS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1. Verify materials below shallow foundations are adequate to achieve the design bearing capacity.	—	X
2. Verify excavations are extended to proper depth and have reached proper material.	—	X
3. Perform classification and testing of compacted fill materials.	—	X
4. During fill placement, verify use of proper materials and procedures in accordance with the provi- sions of the approved geotechnical report. Verify densities and lift thicknesses during placement and compaction of compacted fill.	X	—
5. Prior to placement of compacted fill, inspect subgrade and verify that site has been prepared properly.	—	X

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SPECIAL INSPECTIONS AND TESTS

1705.6.1 Soil fill. [OSHPD 1R, 2 & 5] All fills used to support the foundations of any building or structure shall be continuously inspected by the geotechnical engineer or his or her qualified representative. It shall be the responsibility of the geotechnical engi- neer to verify that fills meet the requirements of the approved construction documents and to coordinate all fill inspection and testing during construction involving such fills.

1705.7 Driven deep foundations. Special inspections and tests shall be performed during installation of driven deep foundation elements as specified in Table 1705.7. The approved geotechnical report and the construction documents prepared by the registered design professionals shall be used to determine compliance.

TABLE 1705.7—REQUIRED SPECIAL INSPECTIONS AND TESTS OF DRIVEN DEEP FOUNDATION ELEMENTS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1.

CRC § 4.1.1 High relevance — show source text
2||||X|||||||||||||||||||| |R401.4.1.1 through
R401.4.1.1.5||||X|||||||||||||||||||| |R404.5.1||||X|||||||||||||||||||| |R408.3||||X|||||||||||||||||||| |R408.4||||X|||||||||||||||||||| |R408.8||||||||||||||||||||X||||

The state agency does not adopt sections identified with the following symbol: †

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4 FOUNDATIONS

User notes:

About this chapter: Chapter 4 provides requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. In addition to a foundation’s ability to support the required design loads, this chapter addresses several other factors that can affect foundation performance. These include controlling surface water and subsurface drainage, requiring soil tests where conditions warrant and evaluating proximity to slopes and minimum depth requirements. This chapter also provides requirements to minimize adverse effects of moisture, decay and pests in basements and crawl spaces.

SECTION R401—GENERAL

R401.1 Application. The provisions of this chapter shall control the design and construction of the foundation and foundation spaces for buildings. In addition to the provisions of this chapter, the design and construction of foundations in flood hazard areas as established by Table R301.2 shall meet the provisions of Section R306. Wood foundations shall be designed and installed in accordance with AWC PWF.

Exception: The provisions of this chapter shall be permitted to be used for wood foundations only in the following situations:
1. In buildings that have not more than two floors and a roof.
2. Where interior basement and foundation walls are constructed at intervals not exceeding 50 feet (15 240 mm) .
Wood foundations in Seismic Design Category D 0, D 1 or D 2 shall be designed in accordance with accepted engineering practice.

R401.2 Requirements. Foundation construction shall be capable of accommodating all loads in accordance with Section R301 and of transmitting the resulting loads to the supporting soil. Fill soils that support footings and foundations shall be designed, installed and tested in accordance with accepted engineering practice.

Note: See Section R301.1.1.1 for limited-density owner-built rural dwellings.

R401.3 Drainage. Surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection that does not create a hazard. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall not fewer than 6 inches (152 mm) within the first 10 feet (3048 mm).

Exception: Where lot lines, walls, slopes or other physical barriers prohibit 6 inches (152 mm) of fall within 10 feet (3048 mm), drains or swales shall be constructed to ensure drainage away from the structure. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped not less than 2 percent away from the building.

**R401.4 Soil tests.
CRC § 1808.5 High relevance — show source text
** Where machinery operations or other vibrations are transmitted through the foundation, consideration shall be given in the foundation design to prevent detrimental disturbances of the soil. 1808.5 Shifting or moving soils. Where it is known that the shallow subsoils are of a shifting or moving character, foundations shall be carried to a sufficient depth to ensure stability. 1808.6 Design for expansive soils. Foundations for buildings and structures founded on expansive soils shall be designed in accordance with Section 1808.6.1 or 1808.6.2.

Exceptions: Foundation design need not comply with Section 1808.6.1 or 1808.6.2 where one of the following conditions is satisfied:
1. The soil is removed in accordance with Section 1808.6.3.
2. The building official approves stabilization of the soil in accordance with Section 1808.6.4. 1808.6.1 Foundations. Foundations placed on or within the active zone of expansive soils shall be designed to resist differential volume changes and to prevent structural damage to the supported structure. Deflection and racking of the supported structure shall be limited to that which will not interfere with the usability and serviceability of the structure.
Foundations placed below where volume change occurs or below expansive soil shall comply with the following provisions:
1. Foundations extending into or penetrating expansive soils shall be designed to prevent uplift of the supported structure.
2. Foundations penetrating expansive soils shall be designed to resist forces exerted on the foundation due to soil volume changes or shall be isolated from the expansive soil.
1808.6.2 Slab-on-ground foundations. Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on expansive soils shall be determined in accordance with WRI/CRSI or PTI DC 10.5. Using the moments, shears and deflections determined above, nonprestressed slabs-on-ground, mat or raft foundations on expansive soils shall be designed in accordance with WRI/CRSI and post-tensioned slabs-on-ground, mat or raft foundations on expansive soils shall be designed in accordance with PTI DC 10.5. It shall be permitted to analyze and design such slabs by other methods that account for soil-structure interaction, the deformed shape of the soil support, the plate or stiffened plate action of the slab as well as both center lift and edge lift conditions. Such alternative methods shall be rational and the basis for all aspects and parameters of the method shall be available for peer review.

1808.6.3 Removal of expansive soil. Where expansive soil is removed in lieu of designing foundations in accordance with Section 1808.6.1 or 1808.6.2, the soil shall be removed to a depth sufficient to ensure a constant moisture content in the remaining soil. Fill material shall not contain expansive soils and shall comply with Section 1804.5 or 1804.6.

Exception: Expansive soil need not be removed to the depth of constant moisture, provided that the confining pressure in the expansive soil created by the fill and supported structure exceeds the swell pressure.

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1808.6.4 Stabilization. Where the active zone of expansive soils is stabilized in lieu of designing foundations in accordance with Section 1808.6.1 or 1808.6.2, the soil shall be stabilized by chemical, dewatering, presaturation or equivalent techniques.
CRC § 2.4 High relevance — show source text
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FOUNDATIONS

R404.2.4 Backfilling. Wood foundation walls shall not be backfilled until the basement floor and first floor have been constructed or the walls have been braced. For crawl space construction, backfill or bracing shall be installed on the interior of the walls prior to placing backfill on the exterior.

R404.2.5 Drainage and dampproofing. Wood foundation basements shall be drained and dampproofed in accordance with Sections R405 and R406, respectively.

R404.2.6 Fastening. Wood structural panel foundation wall sheathing shall be attached to framing in accordance with Table R602.3(1) and Section R402.1.1.

R404.3 Wood sill plates. Wood sill plates shall be not less than 2-inch by 4-inch (51 mm by 102 mm) nominal lumber. Sill plate anchorage shall be in accordance with Sections R403.1.6 and R602.11.

R404.4 Retaining walls. Retaining walls that are not laterally supported at the top and that retain in excess of 48 inches (1219 mm) of unbalanced fill, or retaining walls exceeding 24 inches (610 mm) in height that resist lateral loads in addition to soil, shall be designed in accordance with accepted engineering practice to ensure stability against overturning, sliding, excessive foundation pressure and water uplift. Retaining walls shall be designed for a safety factor of 1.5 against lateral sliding and overturning. This section shall not apply to foundation walls supporting buildings.

R404.5 Precast concrete foundation walls.

R404.5.1 Design. Precast concrete foundation walls shall be designed in accordance with accepted engineering practice. The design and manufacture of precast concrete foundation wall panels shall comply with the materials requirements of Section R402.3 or ACI 318. The panel design drawings shall be prepared by a registered design professional where required by the statutes of the jurisdiction in which the project is to be constructed in accordance with Section R106.1.

R404.5.2 Precast concrete foundation design drawings. Precast concrete foundation wall design drawings shall be submitted to the building official and approved prior to installation. Drawings shall include, at a minimum, the following information:
1. Design loading as applicable.
2. Footing design and material.
3. Concentrated loads and their points of application.
4. Soil bearing capacity.
5. Maximum allowable total uniform load.
6. Seismic design category.
7. Basic wind speed.
R404.5.3 Identification. Precast concrete foundation wall panels shall be identified by a certificate of inspection label issued by an approved third-party inspection agency.

SECTION R405 —FOUNDATION DRAINAGE

R405.1 Concrete or masonry foundations. Drains shall be provided around concrete or masonry foundations that retain earth and enclose habitable or usable spaces located below grade. Drainage tiles, gravel or crushed stone drains, perforated pipe or other approved systems or materials shall be installed at or below the top of the footing or below the bottom of the slab and shall discharge by gravity or mechanical means into an approved drainage system. Gravel or crushed stone drains shall extend not less than 1 foot (305 mm) beyond the outside edge of the footing and 6 inches (152 mm) above the top of the footing and be covered with an approved filter membrane material. The top of open joints of drain tiles shall be protected with strips of building paper.
CRC § 1803.5.3 High relevance — show source text
1803.5.3 Expansive soil. In areas likely to have expansive soil, the building official shall require soil tests to determine where such soils do exist.

Soils meeting all four of the following provisions shall be considered to be expansive, except that tests to show compliance with Items 1, 2 and 3 shall not be required if the test prescribed in Item 4 is conducted:
1. Plasticity index (PI) of 15 or greater, determined in accordance with ASTM D4318.
2. More than 10 percent of the soil particles pass a No.200 sieve (75 µm), determined in accordance with ASTM D6913.
3. More than 10 percent of the soil particles are less than 5 micrometers in size, determined in accordance with ASTM D6913.
4. Expansion index greater than 20, determined in accordance with ASTM D4829.
1803.5.4 Groundwater. A geotechnical investigation shall be performed to determine if:
1. Groundwater is above or within 5 feet (1524 mm) below the elevation of the lowest floor level where such floor is located below the finished ground level adjacent to the foundation.
2. The groundwater depth will affect the design and construction of buildings and structures.
1803.5.5 Deep foundations. Where deep foundations will be used, a geotechnical investigation shall be conducted and shall include all of the following, unless sufficient data on which to base the design and installation is otherwise available:
1. Recommended deep foundation types and installed capacities.
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SOILS AND FOUNDATIONS
1. Recommended center-to-center spacing of deep foundation elements.
2. Driving criteria.
3. Installation procedures.
4. Field inspection and reporting procedures (to include procedures for verification of the installed bearing capacity where required).
5. Load test requirements.
6. Suitability of deep foundation materials for the intended environment.
7. Designation of bearing stratum or strata.
8. Reductions for group action, where necessary.
1803.5.6 Rock strata. Where foundations are to be constructed on or in rock, the geotechnical investigation shall assess variations in rock strata depth, competency and load-bearing capacity.

1803.5.7 Excavation near foundations. Where excavation will reduce support from any foundation, a registered design professional shall prepare an assessment of the structure as determined from examination of the structure, available design documents, available subsurface data, and, if necessary, excavation of test pits. The registered design professional shall determine the requirements for support and protection of any existing foundation and prepare site-specific plans, details and sequence of work for submission. Such support shall be provided by under-pinning, bracing, excavation retention systems or by other means acceptable to the building official.

1803.5.8 Compacted fill material. Where shallow foundations will bear on compacted fill material more than 12 inches (305 mm) in depth, a geotechnical investigation shall be conducted and shall include all of the following:
1. Specifications for the preparation of the site prior to placement of compacted fill material.
2. Specifications for material to be used as compacted fill.
3. Test methods to be used to determine the maximum dry density and optimum moisture content of the material to be used as compacted fill.
4. Maximum allowable thickness of each lift of compacted fill material.
5. Field test method for determining the in-place dry density of the compacted fill.
CRC § 1809.2 High relevance — show source text
1809.2 Supporting soils. Shallow foundations shall be built on undisturbed soil, compacted fill material or controlled low-strength material (CLSM). Compacted fill material shall be placed in accordance with Section 1804.6. CLSM shall be placed in accordance with Section 1804.7.

1809.3 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).

[OSHPD 1R, 2 & 5] 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.

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SOILS AND FOUNDATIONS

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.

1809.4 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 1809.5 shall be satisfied. The minimum width of footings shall be 12 inches (305 mm).

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:
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.

1809.5.1 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.
CRC § 3.1 High relevance — show source text
1808 A .3.1 Seismic overturning. Where foundations are proportioned using the load combinations of Section 2.3 or 2.4 of ASCE 7 and the computation of seismic over-turning effects is by equivalent lateral force analysis or modal analysis, the proportioning shall be in accordance with Section 12.13.4 of ASCE 7.

1808 A .3.2 Surcharge. Fill or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by the fill or the surcharge. Existing footings or foundations that will be affected by any excavation shall be underpinned or otherwise protected against settlement and shall be protected against detrimental lateral or vertical movement or both.

Exception: Minor grading for landscaping purposes shall be permitted where done with walk-behind equipment, where the grade is not increased more than 1 foot (305 mm) from original design grade or where approved by the building official.

1808 A .4 Vibratory loads. Where machinery operations or other vibrations are transmitted through the foundation, consideration shall be given in the foundation design to prevent detrimental disturbances of the soil.

1808 A .5 Shifting or moving soils. Where it is known that the shallow subsoils are of a shifting or moving character, foundations shall be carried to a sufficient depth to ensure stability.

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SOILS AND FOUNDATIONS

1808 A .6 Design for expansive soils. Foundations for buildings and structures founded on expansive soils shall be designed in accordance with Section 1808 A .6.1 or 1808 A .6.2.

Exceptions: Foundation design need not comply with Section 1808 A .6.1 or 1808 A .6.2 where one of the following conditions is satisfied:
1. The soil is removed in accordance with Section 1808 A .6.3.
2. The building official approves stabilization of the soil in accordance with Section 1808 A .6.4.
1808 A .6.1 Foundations. Foundations placed on or within the active zone of expansive soils shall be designed to resist differential volume changes and to prevent structural damage to the supported structure. Deflection and racking of the supported structure shall be limited to that which will not interfere with the usability and serviceability of the structure.

Foundations placed below where volume change occurs or below expansive soil shall comply with the following provisions:
1. Foundations extending into or penetrating expansive soils shall be designed to prevent uplift of the supported structure.
2. Foundations penetrating expansive soils shall be designed to resist forces exerted on the foundation due to soil volume changes or shall be isolated from the expansive soil.
1808 A .6.2 Slab-on-ground foundations. Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on expansive soils shall be determined in accordance with WRI/CRSI or PTI DC 10.5.
CRC § 3.5 High relevance — show source text
1. The use of fill for structural support is prohibited.
2. Minor grading, and the placement of minor quantities of fill, shall be permitted for landscaping and for drainage purposes under and around buildings and for support of parking slabs, pool decks, patios and walkways.
3. Walls and partitions enclosing areas below the elevation required in this section shall meet the requirements of Sections R306.3.5 and R306.3.6.
R306.3.3 Foundations. Buildings and structures erected in coastal high-hazard areas and Coastal A Zones shall be supported on pilings or columns and shall be adequately anchored to such pilings or columns and shall comply with the following:
1. The space below the elevated building shall be either free of obstruction or, if enclosed with walls, the walls shall meet the requirements of Section R306.3.5.
2. Pilings shall be designed in accordance with ASCE 24 to have adequate soil penetrations to resist the combined wave and wind loads (lateral and uplift) and pile embedment shall include consideration of decreased resistance capacity caused by scour of soil strata surrounding the piling.
3. Columns and their supporting foundations shall be designed in accordance with ASCE 24 to resist combined wave and wind loads, lateral and uplift, and shall include consideration of decreased resistance capacity caused by scour of soil strata surrounding the columns. Spread footing, mat, raft or other foundations that support columns shall not be permitted where soil investigations that are required in accordance with Section R401.4 indicate that soil material under the spread footing, mat, raft or other foundation is subject to scour or erosion from wave-velocity flow conditions. If permitted, spread footing, mat, raft or other foundations that support columns shall be designed in accordance with ASCE 24.
4. Flood and wave loads shall be determined in accordance with ASCE 7 and shall include loads associated with the design flood. Wind loads shall be those required by this code.
5. Foundation designs and construction documents shall be prepared and sealed in accordance with Section R306.3.9.
Exception: In Coastal A Zones, stem wall foundations supporting a floor system above and backfilled with soil or gravel to the underside of the floor system shall be permitted provided that the foundations are designed to account for wave action, debris impact, erosion and local scour. Where soils are susceptible to erosion and local scour, stem wall foundations shall have deep footings to account for the loss of soil.

R306.3.4 Concrete slabs. Concrete slabs used for parking, floors of enclosures, landings, decks, walkways, patios and similar uses that are located beneath structures, or slabs that are located such that if undermined or displaced during base flood conditions could cause structural damage to the building foundation, shall be designed and constructed in accordance with one of the following:
1. To be structurally independent of the foundation system of the structure, to not transfer flood loads to the main structure, and to be frangible and break away under flood conditions prior to base flood conditions. Slabs shall be a maximum of 4 inches (102 mm) thick, shall not have turned-down edges, shall not contain reinforcing, shall have isolation joints at pilings and columns, and shall have control or construction joints in both directions spaced not more than 4 feet (1219 mm) apart.
2. To be self-supporting, structural slabs capable of remaining intact and functional under base flood conditions, including erosion and local scour, and the main structure shall be capable of resisting any added flood loads and effects of local scour caused by the presence of the slabs.

CRC § 1.3.3.7.6 High relevance — show source text

Vertical reinforcement with a yield strength of less
than 60,000 psi and bars of a different size than specified in the table are permitted in accordance with Section R404.1.3.3.7.6 and Table R404.1.3.2(9).
d. Deflection criterion is_L_/240, where_L_ is the height of the basement wall in inches.
e. Interpolation is not permitted.
f. Where walls will retain 4 feet or more of unbalanced backfill, they shall be laterally supported at the top and bottom before backfilling.
g. See Section R404.1.3.2 for minimum reinforcement required for basement walls supporting above-grade concrete walls.
h. See Table R608.3 for thicknesses and dimensions of waffle-grid walls.
i. DR means design is required in accordance with the applicable building code, or in the absence of a code, in accordance with ACI 318.
j. The use of this table shall be prohibited for soil classifications not shown.|

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FOUNDATIONS

TABLE R404.1.3.2(6)—MINIMUM VERTICAL REINFORCEMENT FOR 8-INCH WAFFLE-GRID BASEMENT WALLSb, c, d, e, f, h, i, j, k	Col2	Col3	Col4	Col5
MAXIMUM UNSUPPORTED WALL HEIGHT (feet)	MAXIMUM UNBALANCED BACKFILL HEIGHTg (feet)	MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (inches)	MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (inches)	MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (inches)
MAXIMUM UNSUPPORTED WALL HEIGHT (feet)	MAXIMUM UNBALANCED BACKFILL HEIGHTg (feet)	Soil classesa and design lateral soil (psf per foot of depth)	Soil classesa and design lateral soil (psf per foot of depth)	Soil classesa and design lateral soil (psf per foot of depth)
MAXIMUM UNSUPPORTED WALL HEIGHT (feet)	MAXIMUM UNBALANCED BACKFILL HEIGHTg (feet)	GW, GP, SW, SP 30	GM, GC, SM, SM-SC and ML 45	** SC,

CRC § 1803.5.9 High relevance — show source text
1. Field test method for determining the in-place dry density of the compacted fill.
2. Minimum acceptable in-place dry density expressed as a percentage of the maximum dry density determined in accordance with Item 3.
3. Number and frequency of field tests required to determine compliance with Item 6.
1803.5.9 Controlled low-strength material (CLSM). Where shallow foundations will bear on controlled low-strength material (CLSM), a geotechnical investigation shall be conducted and shall include all of the following:
1. Specifications for the preparation of the site prior to placement of the CLSM.
2. Specifications for the CLSM.
3. Laboratory or field test method(s) to be used to determine the compressive strength or bearing capacity of the CLSM .
4. Test methods for determining the acceptance of the CLSM in the field.
5. Number and frequency of field tests required to determine compliance with Item 4.
1803.5.10 Alternate setback and clearance. Where setbacks or clearances other than those required in Section 1808.7 are desired, the building official shall be permitted to require a geotechnical investigation by a registered design professional to demonstrate that the intent of Section 1808.7 would be satisfied. Such an investigation shall include consideration of material, height of slope, slope gradient, load intensity and erosion characteristics of slope material.

1803.5.11 Seismic Design Categories C through F. For structures assigned to Seismic Design Category C, D, E or F, a geotechnical investigation shall be conducted, and shall include an evaluation of all of the following potential geologic and seismic hazards:
1. Slope instability.
2. Liquefaction.
3. Total and differential settlement.
4. Surface displacement due to faulting or seismically induced lateral spreading or lateral flow.
1803.5.12 Seismic Design Categories D through F. For structures assigned to Seismic Design Category D, E or F, the geotechnical investigation required by Section 1803.5.11 shall include all of the following as applicable:
1. The determination of dynamic seismic lateral earth pressures on foundation walls and retaining walls supporting more than 6 feet (1.83 m) of backfill height due to design earthquake ground motions.
2. The potential for liquefaction and soil strength loss evaluated for site peak ground acceleration, earthquake magnitude and source characteristics consistent with the maximum considered earthquake ground motions. Peak ground acceleration shall be determined based on one of the following: 2.1. A site-specific study in accordance with Chapter 21 of ASCE 7.
2.2. In accordance with Section 11.8.3 of ASCE 7.
1. An assessment of potential consequences of liquefaction and soil strength loss including, but not limited to, the following:
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SOILS AND FOUNDATIONS

3.1. Estimation of total and differential settlement.

3.2. Lateral soil movement.

3.3. Lateral soil loads on foundations.

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

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

Frequently asked questions

When can I use the CRC presumptive bearing values instead of a geotechnical report?

You may use the code’s presumptive values (Table R401.4.1(1)) when no site conditions trigger required soil testing; however, if expansive, compressible, shifting soils, groundwater issues, or seismic category C+ conditions exist, the code requires a geotechnical investigation and site‑specific recommendations. § R401.4 / § R401.4.1.

Who is responsible for inspecting engineered fill that supports a foundation?

The project’s geotechnical engineer or their qualified representative is responsible to inspect and verify fills used to support foundations; continuous inspection and a verified report are required where applicable. See special inspection provisions and § R401.2 / special inspections tables.

What minimum grading slopes should I provide to protect the foundation?

Grade should fall not fewer than 6 inches within the first 10 feet away from foundation walls; if physical barriers prevent that, provide drains or swales. Impervious surfaces within 10 feet must slope not less than 2% away from the building. § R401.3.

If I find expansive soil, what does the CRC require?

Where expansive soils are indicated, soil tests and a geotechnical report are required and the report must recommend mitigation; the CRC points you to further design provisions and the need to design foundations to resist differential volume changes. § R401.4 (and referenced expansive soil provisions).

Are there special inspection requirements for fill placement?

Yes — fills that support foundations commonly require continuous inspection and testing by the geotechnical engineer in accordance with the special inspection provisions (see the special inspection tables and the geotechnical‑inspection language).

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Related in the CRC

What foundations and foundation spaces does the CRC chapter cover?

How must the site be graded and surface drainage directed away from foundations?

When are soil tests required and how is bearing value handled?

General foundation requirements

California Residential Code

TABLE R404.1.3.2(6)—MINIMUM VERTICAL REINFORCEMENT FOR 8-INCH WAFFLE-GRID BASEMENT WALLSb, c, d, e, f, h, i, j, k	Col2	Col3	Col4	Col5
MAXIMUM UNSUPPORTED WALL HEIGHT (feet)	MAXIMUM UNBALANCED BACKFILL HEIGHTg (feet)	MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (inches)	MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (inches)	MINIMUM VERTICAL REINFORCEMENT-BAR SIZE AND SPACING (inches)
MAXIMUM UNSUPPORTED WALL HEIGHT (feet)	MAXIMUM UNBALANCED BACKFILL HEIGHTg (feet)	Soil classesa and design lateral soil (psf per foot of depth)	Soil classesa and design lateral soil (psf per foot of depth)	Soil classesa and design lateral soil (psf per foot of depth)
MAXIMUM UNSUPPORTED WALL HEIGHT (feet)	MAXIMUM UNBALANCED BACKFILL HEIGHTg (feet)	GW, GP, SW, SP 30	GM, GC, SM, SM-SC and ML 45	** SC,