CBC · California Building Code
What are the requirements for excavation, grading, compaction and fills?
For a homeowner: the California Building Code requires that any excavation or fill that affects foundation support be designed or protected so foundations aren’t left unsupported; fills that will bear foundations generally require a geotechnical report specifying materials, lift thickness (commonly 12 in.), compaction targets, and testing — small fills (≤12 in.) may only need to meet a 90% ASTM D1557 in‑place density and verified inspection; CLSM can be used as an alternative but must be specified and tested in the geotechnical report (§ 1804; § 1803A.5.8; § 1803A.5.9) .
Last reviewed: July 5, 2026
What the code requires — 2–4 sentences
Under the CBC, excavation, grading and fills must be carried out so they do not reduce vertical or lateral support to existing foundations unless the affected foundations are protected or underpinned, and backfill and compacted fills that will support shallow foundations must be placed and tested per the project geotechnical report (see § 1804 and the geotechnical-report requirements in § 1803A.5). For Controlled Low‑Strength Material (CLSM) used under foundations, the geotechnical investigation must include specifications and field/laboratory tests for the CLSM (§ 1804; § 1803A.5.9) .
Requirements in detail
Excavation near foundations
- Excavation shall not reduce vertical or lateral support for any foundation or adjacent foundation unless underpinning or other protection is provided in accordance with the code (see § 1804.1). A registered design professional must assess and specify support measures when excavation will reduce support (§ 1803A.5.7) .
Backfill and placement of fill
- Backfill outside foundation walls must be free of organic material, construction debris, cobbles and boulders, or may be CLSM. Backfill is to be placed in lifts and compacted so as not to damage foundations or waterproofing/dampproofing (§ 1804.3) .
- When CLSM is used, note that CLSM need not be compacted (exception in § 1804.3) but if CLSM supports foundations the geotechnical report must specify CLSM preparation, properties and testing (§ 1803A.5.9) .
Compaction requirements and testing
- Where shallow foundations will bear on compacted fill more than 12 in. (305 mm) in depth, the geotechnical investigation must include: site preparation specs, material specifications, test methods to determine maximum dry density and optimum moisture content, maximum lift thickness, field test method for in‑place density, minimum acceptable in‑place dry density (as a percentage of lab maximum), and required field test frequency (§ 1803A.5.8) .
- The CBC allows a limited exception: compacted fill 12 in. (305 mm) deep or less need not comply with the full geotechnical report requirements provided the in‑place dry density is at least 90% of the maximum dry density at optimum moisture content per ASTM D1557; compaction shall be verified by special inspection (§ 1804A.6 exception / § 1804.A.6 in appendix text) .
- Appendix J (grading) also specifies typical compaction language used by the code: lifts not exceeding 12 in. and compaction to 90% of maximum density by ASTM D1557 for fill used in grading (J107.5) .
Site grading and drainage adjacent to foundations
- Finished grade adjacent to the foundation shall slope away from the building not less than 1 unit vertical in 20 units horizontal (5%) for a minimum horizontal distance of 10 ft (3048 mm). If 10 ft is not feasible, provide the 5% slope to an approved alternative drainage method. Swales within 10 ft must be sloped not less than 2% and impervious surfaces within 10 ft must slope not less than 2% away from the building (§ 1804.4) .
Slopes, benching and keys (from Appendix J)
- Where existing grade is steeper than 1V in 5H (20%) and fill depth exceeds 5 ft (1524 mm), benching and a key is required; a key shall be not less than 10 ft (3048 mm) wide and 2 ft (610 mm) deep (J107.3) .
- Fill slopes steeper than 1V in 2H (50% slope) must be justified by a geotechnical report or engineering data (J107.6) .
Special inspection and testing
- Special inspections and testing requirements for soils/fills (including verification of lift thickness and in‑place density) are specified in the special inspections section (e.g., Table 1705A.6 and 1705A.6.1). Where fills support foundations they shall be continuously inspected by the geotechnical engineer or qualified representative, and a verified report is required after completion (§ 1705A.6 and 1705A.6.1) .
Decision‑relevant values (quick reference table)
| Item | Value / Limit | Code Reference |
|---|---|---|
| Minimum slope away from foundation | 1 vertical : 20 horizontal (5%) for 10 ft | § 1804.4 |
| Minimum slope for swales or impervious surfaces within 10 ft | 2% | § 1804.4 |
| Compacted fill lift maximum (typical) | 12 in. (305 mm) | § 1803A.5.8 item 4; J107.5 |
| Minimum in‑place dry density (exception / typical) | 90% of ASTM D1557 maximum dry density | § 1804A.6 exception; J107.5; 1705A references for inspection |
| Key (bench) minimum dimensions | 10 ft wide × 2 ft deep (when benching required) | J107.3 § (Appendix J) |
| Fill material exclusions | No organic, frozen or other deleterious materials; rock >12 in. not allowed in fills | J107.4 § (Appendix J) |
| When CLSM must be addressed in geotech report | When shallow foundations will bear on CLSM (specs and test methods required) | § 1803A.5.9 |
Exceptions & special cases
- Short fills (12 in. / 305 mm or less) that are to support foundations may avoid full geotechnical‑report prescriptive content if the in‑place dry density is demonstrated to be ≥90% of ASTM D1557 maximum and verified by special inspection (§ 1804A.6 exception) .
- CLSM is an accepted alternative to compacted fill; CLSM does not require mechanical compaction (exception in § 1804.3), but when CLSM will support foundations the geotechnical investigation must provide preparation/specs and field/lab acceptance tests (§ 1804.3; § 1803A.5.9) .
- Fill placed in flood hazard areas has additional constraints: grading/fill must be placed, compacted and sloped to minimize shifting/slumping/erosion in floods and wave action, and in floodways is further restricted unless hydraulic analysis shows no increase in design flood elevations (§ 1804A.5) .
Common mistakes
- Assuming any backfill is acceptable: the code explicitly prohibits organic materials, construction debris, cobbles/boulders and large rock in fills intended to support structures (§ 1804.3; J107.4) .
- Skipping geotechnical input for fills over 12 in.: any compacted fill >12 in. that will support shallow foundations requires geotechnical specifications and testing (§ 1803A.5.8) .
- Relying on surface grade only: final surface must be sloped appropriately away from the foundation and account for future settlement of backfill (§ 1804.4) .
- Not providing or documenting required special inspections: fills that support foundations generally require continuous or periodic inspection and a verified geotechnical report per the special inspection rules (§ 1705A.6 and 1705A.6.1) .
Worked example — concrete scenario applying the rule with numbers
Scenario: New single‑family house with shallow spread footings is to be built on a lot where 18 inches of engineered compacted fill will be placed under the footprint.
- Because compacted fill depth exceeds 12 in. (305 mm), the project requires a geotechnical investigation that specifies site preparation, fill material specs, lab test methods (to find maximum dry density / optimum moisture), maximum lift thickness, field test methods, a minimum acceptable in‑place density (percent of lab maximum), and the number/frequency of tests (§ 1803A.5.8) .
- Typical lift control: the geotechnical report may limit lifts to 12 in. maximum; contractor places two lifts of 9 in. each (total 18 in.), each compacted to the specified density (report will state the target, e.g., 95% of ASTM D1557 maximum). The inspector performs in‑place density tests at the required frequency; passing results are recorded in the verified geotechnical report (§ 1803A.5.8; § 1705A.6) .
- If the contractor used a CLSM layer rather than compacted granular fill, the geotechnical report must have already specified CLSM properties and the acceptance tests to be used in the field (§ 1803A.5.9). CLSM would not require mechanical compaction but would require field tests to confirm bearing/compressive strength per the report (§ 1803A.5.9; § 1804.3) .
Related provisions
- § 1804 — Excavation, grading and fill (primary)
- § 1803A.5.7 — Excavation near foundations and need for a registered design professional assessment
- § 1803A.5.8 — Compacted fill material requirements to support shallow foundations (specs and testing)
- § 1803A.5.9 — Controlled low‑strength material (CLSM) reporting and testing requirements
- Appendix J, J107 — Fills (surface preparation, benching, lift thickness, compaction to 90% ASTM D1557, material exclusions)
- § 1705A.6 / Table 1705A.6 — Special inspections and tests for soils and fills (inspection frequency and who performs verification)
Code references
Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:
CBC § 1.5. High relevance — show source text
1.5. Ground water is not encountered.
- A cut surface in bedrock shall be permitted to be at a slope of 1 unit horizontal to 1 unit vertical (100-percent slope).
SECTION J107—FILLS
J107.1 General. Unless otherwise recommended in the geotechnical report, fills shall comply with the provisions of this section.
J107.2 Surface preparation. The ground surface shall be prepared to receive fill by removing vegetation, topsoil and other unsuitable materials, and scarifying the ground to provide a bond with the fill material.
J107.3 Benching. Where existing grade is at a slope steeper than one unit vertical in five units horizontal (20-percent slope) and the depth of the fill exceeds 5 feet (1524 mm) benching shall be provided in accordance with Figure J107.3. A key shall be provided that is not less than 10 feet (3048 mm) in width and 2 feet (610 mm) in depth.
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APPENDIX J—GRADING
FIGURE J107.3—BENCHING DETAILS
For SI: 1 foot = 304.8 mm.
J107.4 Fill material. Fill material shall not include organic, frozen or other deleterious materials. Rock or similar irreducible material greater than 12 inches (305 mm) in any dimension shall not be included in fills.
J107.5 Compaction. All fill material shall be compacted to 90 percent of maximum density as determined by ASTM D1557, Modified Proctor, in lifts not exceeding 12 inches (305 mm) in depth.
J107.6 Maximum slope. The slope of fill surfaces shall be not steeper than is safe for the intended use. Fill slopes steeper than one unit vertical in two units horizontal (50-percent slope) shall be justified by a geotechnical report or engineering data.
J108.1 General. Cut and fill slopes shall be set back from the property lines in accordance with this section. Setback dimensions shall be measured perpendicular to the property line and shall be as shown in Figure J108.1, unless substantiating data is submitted justifying reduced setbacks.
FIGURE J108.1—DRAINAGE DIMENSIONS
Property Line
H/5 but 2 ft. minimum
Top of Slope
For SI: 1 foot = 304.8 mm.
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APPENDIX J—GRADING
J108.2 Top of slope. The setback at the top of a cut slope shall be not less than that shown in Figure J108.1, or than is required to accommodate any required interceptor drains, whichever is greater.
J108.3 Slope protection. Where required to protect adjacent properties at the toe of a slope from adverse effects of the grading, additional protection, approved by the building official, shall be included. Examples of such protection include but are not be limited
to:
Setbacks greater than those required by Figure J108.1.
Provisions for retaining walls or similar construction.
Erosion protection of the fill slopes.
Provision for the control of surface waters.
SECTION J109—DRAINAGE AND TERRACING
CBC § 1705A.6 High relevance — show source text
TABLE 1705A.6—REQUIRED SPECIAL INSPECTIONS AND TESTS OF SOILS Col2 Col3 TYPE CONTINUOUS
SPECIAL INSPECTIONPERIODIC SPECIAL
INSPECTION1. 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 INSPECTIONPERIODIC SPECIAL
INSPECTION1. Verify element materials, sizes and lengths comply with the requirements. X — 2. CBC § 0.5 High relevance — show source text
J104.3 Geotechnical report. A geotechnical report prepared by a registered design professional shall be provided. The report shall contain not less than the following:
- The nature and distribution of existing soils.
- Conclusions and recommendations for grading procedures.
- Soil design criteria for any structures or embankments required to accomplish the proposed grading.
- Where necessary, slope stability studies, and recommendations and conclusions regarding site geology.
Exception: A geotechnical report is not required where the building official determines that the nature of the work applied for is such that a report is not necessary.
J104.4 Liquefaction study. For sites with maximum considered earthquake spectral response accelerations at short periods (S s ) greater than 0.5g as determined by Chapter 11 of ASCE 7, a study of the liquefaction potential of the site shall be provided and the recommendations incorporated in the plans.
Exception: A liquefaction study is not required where the building official determines from established local data that the liquefaction potential is low.
SECTION J105—INSPECTIONS
J105.1 General. Inspections shall be governed by Section 110, Chapter 1, Division II.
J105.2 Special inspections. The special inspection requirements of Section 1705.6 shall apply to work performed under a grading permit where required by the building official.
SECTION J106—EXCAVATIONS
J106.1 Maximum slope. The slope of cut surfaces shall be not steeper than is safe for the intended use, and shall be not more than one unit vertical in two units horizontal (50-percent slope) unless the owner or the owner’s authorized agent furnishes a geotechnical report justifying a steeper slope.
Exceptions:
- A cut surface shall be permitted to be at a slope of 1.5 units horizontal to 1 unit vertical (67-percent slope) provided that all of the following are met: 1.1. It is not intended to support structures or surcharges. 1.2. It is adequately protected against erosion. 1.3. It is not more than 8 feet (2438 mm) in height. 1.4. It is approved by the building code official.
1.5. Ground water is not encountered.
- A cut surface in bedrock shall be permitted to be at a slope of 1 unit horizontal to 1 unit vertical (100-percent slope).
SECTION J107—FILLS
J107.1 General. Unless otherwise recommended in the geotechnical report, fills shall comply with the provisions of this section.
J107.2 Surface preparation. The ground surface shall be prepared to receive fill by removing vegetation, topsoil and other unsuitable materials, and scarifying the ground to provide a bond with the fill material.
J107.3 Benching. Where existing grade is at a slope steeper than one unit vertical in five units horizontal (20-percent slope) and the depth of the fill exceeds 5 feet (1524 mm) benching shall be provided in accordance with Figure J107.3. A key shall be provided that is not less than 10 feet (3048 mm) in width and 2 feet (610 mm) in depth.
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APPENDIX J—GRADING
FIGURE J107.3—BENCHING DETAILS
For SI: 1 foot = 304.8 mm.
CBC § 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
INSPECTIONPERIODIC
SPECIAL
INSPECTION1. 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 17-12 2025 CALIFORNIA BUILDING CODE
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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.
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.
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 INSPECTIONPERIODIC
SPECIAL
INSPECTION1. CBC § 1202.4. High relevance — show source text
The procedure used to establish the final ground level adjacent to the foundation shall account for additional settlement of the backfill.
1804 A .5 Grading and fill in flood hazard areas. In flood hazard areas established in Section 1612 A .3, grading, fill, or both, shall not be approved:
- Unless such fill is placed, compacted and sloped to minimize shifting, slumping and erosion during the rise and fall of flood water and, as applicable, wave action.
- In floodways, unless it has been demonstrated through hydrologic and hydraulic analyses performed by a registered design professional in accordance with standard engineering practice that the proposed grading or fill, or both, will not result in any increase in flood levels during the occurrence of the design flood.
- In coastal high hazard areas, unless such fill is conducted or placed to avoid diversion of water and waves toward any building or structure.
- Where design flood elevations are specified but floodways have not been designated, unless it has been demonstrated that the cumulative effect of the proposed flood hazard area encroachment, when combined with all other existing and anticipated flood hazard area encroachment, will not increase the design flood elevation more than 1 foot (305 mm) at any point.
1804 A .6 Compacted fill material. Where shallow foundations will bear on compacted fill material, the compacted fill shall comply with the provisions of an approved geotechnical report, as set forth in Section 1803 A .
Exception: Compacted fill material 12 inches (305 mm) in depth or less need not comply with an approved report, provided that the in-place dry density is not less than 90 percent of the maximum dry density at optimum moisture content determined in accordance with ASTM D1557. The compaction shall be verified by special inspection in accordance with Section 1705 A .6.
1804 A .7 Controlled low-strength material (CLSM). Where shallow foundations will bear on controlled low-strength material (CLSM), the CLSM shall comply with the provisions of an approved geotechnical report, as set forth in Section 1803 A .
SECTION 1805 A —DAMPPROOFING AND WATERPROOFING
1805 A .1 General. Walls or portions thereof that retain earth and enclose interior spaces and floors below grade shall be waterproofed and dampproofed in accordance with this section, with the exception of those spaces containing groups other than residential and institutional where such omission is not detrimental to the building or occupancy.
Ventilation for crawl spaces shall comply with Section 1202.4.
1805 A .1.1 Story above grade plane. Where a basement is considered a story above grade plane and the finished ground level adjacent to the basement wall is below the basement floor elevation for 25 percent or more of the perimeter, the floor and walls shall be dampproofed in accordance with Section 1805 A .2 and a foundation drain shall be installed in accordance with Section 1805 A .4.2. The foundation drain shall be installed around the portion of the perimeter where the basement floor is below ground level. The provisions of Sections 1803 A .5.4, 1805 A .3 and 1805 A .4.1 shall not apply in this case.
CBC § 105.3 High relevance — show source text
BENCH. A relatively level step excavated into earth material on which fill is to be placed.
COMPACTION. The densification of a fill by mechanical means.
CUT. See “Excavation.”
DOWN DRAIN. A device for collecting water from a swale or ditch located on or above a slope, and safely delivering it to an approved drainage facility.
EROSION. The wearing away of the ground surface as a result of the movement of wind, water or ice.
EXCAVATION. The removal of earth material by artificial means, also referred to as a cut.
FILL. Deposition of earth materials by artificial means.
GRADE. The vertical location of the ground surface.
GRADE, EXISTING. The grade prior to grading.
GRADE, FINISHED. The grade of the site at the conclusion of all grading efforts.
GRADING. An excavation or fill or combination thereof.
KEY. A compacted fill placed in a trench excavated in earth material beneath the toe of a slope.
SLOPE. An inclined surface, the inclination of which is expressed as a ratio of horizontal distance to vertical distance.
TERRACE. A relatively level step constructed in the face of a graded slope for drainage and maintenance purposes.
SECTION J103—PERMITS REQUIRED
J103.1 Permits required. Except as exempted in Section J103.2, grading shall not be performed without first having obtained a permit therefor from the building official. A grading permit does not include the construction of retaining walls or other structures.
J103.2 Exemptions. A grading permit shall not be required for the following:
Grading in an isolated, self-contained area, provided that the public is not endangered and that such grading will not adversely affect adjoining properties.
Excavation for construction of a structure permitted under this code.
Cemetery graves.
Refuse disposal sites controlled by other regulations.
Excavations for wells, or trenches for utilities.
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APPENDIX J—GRADING
- Mining, quarrying, excavating, processing or stock-piling rock, sand, gravel, aggregate or clay controlled by other regulations, provided that such operations do not affect the lateral support of, or significantly increase stresses in, soil on adjoining properties.
- Exploratory excavations performed under the direction of a registered design professional.
Exemption from the permit requirements of this appendix shall not be deemed to grant authorization for any work to be done in any manner in violation of the provisions of this code or any other laws or ordinances of this jurisdiction.
SECTION J104—PERMIT APPLICATION AND SUBMITTALS
J104.1 Submittal requirements. In addition to the provisions of Section 105.3 and 1.8.4, as applicable, the applicant shall state the estimated quantities of excavation and fill.
J104.2 Site plan requirements. In addition to the provisions of Section 107, a grading plan shall show the existing grade and finished grade in contour intervals of sufficient clarity to indicate the nature and extent of the work and show in detail that it complies with the requirements of this code. The plans shall show the existing grade on adjoining properties in sufficient detail to identify how grade changes will conform to the requirements of this code.
CBC § 1010.1.4 High relevance — show source text
1804 A .3 Placement of backfill. The excavation outside the foundation shall be backfilled with soil that is free of organic material, construction debris, cobbles and boulders or with a controlled low-strength material (CLSM). The backfill shall be placed in lifts and compacted in a manner that does not damage the foundation or the waterproofing or dampproofing material.
Exception: CLSM need not be compacted.
1804 A .4 Site grading. The ground immediately adjacent to the foundation shall be sloped away from the building at a slope of not less than 1 unit vertical in 20 units horizontal (5-percent slope) for a minimum distance of 10 feet (3048 mm) measured perpendicular to the face of the wall. If physical obstructions or lot lines prohibit 10 feet (3048 mm) of horizontal distance, a 5-percent slope shall be provided to an approved alternative method of diverting water away from the foundation. Swales used for this purpose shall be sloped not less than 2 percent where located within 10 feet (3048 mm) of the building foundation. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped not less than 2 percent away from the building.
Exceptions:
- Where climatic or soil conditions warrant, the slope of the ground away from the building foundation shall be permitted to be reduced to not less than 1 unit vertical in 48 units horizontal (2-percent slope).
- Impervious surfaces shall be permitted to be sloped less than 2 percent where the surface is a door landing or ramp that is required to comply with Section 1010.1.4, 1012.3 or 1012.6.1.
The procedure used to establish the final ground level adjacent to the foundation shall account for additional settlement of the backfill.
1804 A .5 Grading and fill in flood hazard areas. In flood hazard areas established in Section 1612 A .3, grading, fill, or both, shall not be approved:
- Unless such fill is placed, compacted and sloped to minimize shifting, slumping and erosion during the rise and fall of flood water and, as applicable, wave action.
- In floodways, unless it has been demonstrated through hydrologic and hydraulic analyses performed by a registered design professional in accordance with standard engineering practice that the proposed grading or fill, or both, will not result in any increase in flood levels during the occurrence of the design flood.
- In coastal high hazard areas, unless such fill is conducted or placed to avoid diversion of water and waves toward any building or structure.
- Where design flood elevations are specified but floodways have not been designated, unless it has been demonstrated that the cumulative effect of the proposed flood hazard area encroachment, when combined with all other existing and anticipated flood hazard area encroachment, will not increase the design flood elevation more than 1 foot (305 mm) at any point.
1804 A .6 Compacted fill material. Where shallow foundations will bear on compacted fill material, the compacted fill shall comply with the provisions of an approved geotechnical report, as set forth in Section 1803 A .
CBC § 18-6 High relevance — show source text
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SOILS AND FOUNDATIONS
SECTION 1804—EXCAVATION, GRADING AND FILL
1804.1 Excavation near foundations. Excavation for any purpose shall not reduce vertical or lateral support for any foundation or adjacent foundation without first underpinning or protecting the foundation against detrimental lateral or vertical movement, or both, in accordance with Section 1803.5.7.
1804.2 Underpinning. Where underpinning is chosen to provide the protection or support of adjacent structures, the underpinning system shall be designed and installed in accordance with provisions of this chapter and Chapter 33.
1804.2.1 Underpinning sequencing. Underpinning shall be installed in a sequential manner that protects the neighboring structure and the working construction site. The sequence of installation shall be identified in the approved construction documents.
1804.3 Placement of backfill. The excavation outside the foundation shall be backfilled with soil that is free of organic material, construction debris, cobbles and boulders or with a controlled low-strength material ( CLSM ). The backfill shall be placed in lifts and compacted in a manner that does not damage the foundation or the waterproofing or dampproofing material.
Exception: CLSM need not be compacted.
1804.4 Site grading. The ground immediately adjacent to the foundation shall be sloped away from the building at a slope of not less than 1 unit vertical in 20 units horizontal (5-percent slope) for a minimum distance of 10 feet (3048 mm) measured perpendicular to the face of the wall. If physical obstructions or lot lines prohibit 10 feet (3048 mm) of horizontal distance, a 5-percent slope shall be provided to an approved alternative method of diverting water away from the foundation. Swales used for this purpose shall be sloped not less than 2 percent where located within 10 feet (3048 mm) of the building foundation. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped not less than 2 percent away from the building.
Exceptions:
- Where climatic or soil conditions warrant, the slope of the ground away from the building foundation shall be permitted to be reduced to not less than 1 unit vertical in 48 units horizontal (2-percent slope).
- Impervious surfaces shall be permitted to be sloped less than 2 percent where the surface is a door landing or ramp that is required to comply with Section 1010.1.4, 1012.3 or 1012.6.1.
The procedure used to establish the final ground level adjacent to the foundation shall account for additional settlement of the backfill.
1804.4.1 [HCD 1] Construction plans. Construction plans shall indicate how the site grading or drainage system will manage all surface water flows to keep water from entering buildings in accordance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.1.
1804.5 Grading and fill in flood hazard areas. In flood hazard areas established in Section 1612.3, grading, fill, or both, shall not be approved:
- Unless such fill is placed, compacted and sloped to minimize shifting, slumping and erosion during the rise and fall of flood water and, as applicable, wave action.
CBC § 1803A.8 High relevance — show source text
1803A.8 Geotechnical peer review. [DSA-SS and DSA-SS/CC] When alternate foundations designs or ground improvements are employed or where slope stabilization is required, a qualified peer review by a California-licensed geotechnical engineer, in accordance with Section 322 of Part 10, Title 24, CCR, may be required by the enforcement agency. In Section 322 of Part 10, Title 24, CCR, where reference is made to structural or seismic-resisting system, it shall be replaced with geotechnical, foundation or ground improvement, as appropriate.
18A-6 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
SOILS AND FOUNDATIONS
SECTION 1804 A —EXCAVATION, GRADING AND FILL
1804 A .1 Excavation near foundations. Excavation for any purpose shall not reduce vertical or lateral support for any foundation or adjacent foundation without first underpinning or protecting the foundation against detrimental lateral or vertical movement, or both, in accordance with Section 1803 A .5.7.
1804 A .2 Underpinning. Where underpinning is chosen to provide the protection or support of adjacent structures, the underpinning system shall be designed and installed in accordance with provisions of this chapter and Chapter 33.
1804 A .2.1 Underpinning sequencing. Underpinning shall be installed in a sequential manner that protects the neighboring structure and the working construction site. The sequence of installation shall be identified in the approved construction documents.
1804 A .3 Placement of backfill. The excavation outside the foundation shall be backfilled with soil that is free of organic material, construction debris, cobbles and boulders or with a controlled low-strength material (CLSM). The backfill shall be placed in lifts and compacted in a manner that does not damage the foundation or the waterproofing or dampproofing material.
Exception: CLSM need not be compacted.
1804 A .4 Site grading. The ground immediately adjacent to the foundation shall be sloped away from the building at a slope of not less than 1 unit vertical in 20 units horizontal (5-percent slope) for a minimum distance of 10 feet (3048 mm) measured perpendicular to the face of the wall. If physical obstructions or lot lines prohibit 10 feet (3048 mm) of horizontal distance, a 5-percent slope shall be provided to an approved alternative method of diverting water away from the foundation. Swales used for this purpose shall be sloped not less than 2 percent where located within 10 feet (3048 mm) of the building foundation. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped not less than 2 percent away from the building.
Exceptions:
- Where climatic or soil conditions warrant, the slope of the ground away from the building foundation shall be permitted to be reduced to not less than 1 unit vertical in 48 units horizontal (2-percent slope).
- Impervious surfaces shall be permitted to be sloped less than 2 percent where the surface is a door landing or ramp that is required to comply with Section 1010.1.4, 1012.3 or 1012.6.1.
CBC § 1612.3 High relevance — show source text
2025 CALIFORNIA BUILDING CODE APPENDIX J-1
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
J GRADING
The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency or referenced in the adopting ordinance.
User notes:
About this appendix: Appendix J provides standards for the grading of properties. The appendix also provides standards for the administration and enforcement of a grading program, including permit and inspection requirements. Appendix J was originally developed in the 1960s and used for many years in jurisdictions throughout the western United States. It is intended to provide consistent and uniform code requirements anywhere grading is considered an issue.
ICC code development note: Code change proposals to this appendix will be considered by the IBC—Structural Code Development Committee during the
2025 (Group B) Code Development Cycle.
SECTION J101—GENERAL
J101.1 Scope. The provisions of this chapter apply to grading, excavation and earthwork construction, including fills and embankments. Where conflicts occur between the technical requirements of this chapter and the geotechnical report, the geotechnical report shall govern.
J101.2 Flood hazard areas. Unless the applicant has submitted an engineering analysis, prepared in accordance with standard engineering practice by a registered design professional, that demonstrates the proposed work will not result in any increase in the level of the base flood, grading, excavation and earthwork construction, including fills and embankments, shall not be permitted in floodways that are in flood hazard areas established in Section 1612.3 or in flood hazard areas where design flood elevations are specified but floodways have not been designated.
SECTION J102—DEFINITIONS
J102.1 Definitions. The following words and terms shall, for the purposes of this appendix, have the meanings shown herein. Refer to Chapter 2 of this code for general definitions.
BENCH. A relatively level step excavated into earth material on which fill is to be placed.
COMPACTION. The densification of a fill by mechanical means.
CUT. See “Excavation.”
DOWN DRAIN. A device for collecting water from a swale or ditch located on or above a slope, and safely delivering it to an approved drainage facility.
EROSION. The wearing away of the ground surface as a result of the movement of wind, water or ice.
EXCAVATION. The removal of earth material by artificial means, also referred to as a cut.
FILL. Deposition of earth materials by artificial means.
GRADE. The vertical location of the ground surface.
GRADE, EXISTING. The grade prior to grading.
GRADE, FINISHED. The grade of the site at the conclusion of all grading efforts.
GRADING. An excavation or fill or combination thereof.
KEY. A compacted fill placed in a trench excavated in earth material beneath the toe of a slope.
SLOPE. An inclined surface, the inclination of which is expressed as a ratio of horizontal distance to vertical distance.
TERRACE. A relatively level step constructed in the face of a graded slope for drainage and maintenance purposes.
SECTION J103—PERMITS REQUIRED
J103.1 Permits required. Except as exempted in Section J103.2, grading shall not be performed without first having obtained a permit therefor from the building official. A grading permit does not include the construction of retaining walls or other structures.
CBC § 5.5. High relevance — show source text
The report shall_ contain the results of the analyses of problem areas identified in the geohazard report. The geotechnical report shall incorporate esti- mates of the characteristics of site ground motion provided in the geohazard report. This geotechnical report shall include, but need not be limited to, the following information:
- A plot showing the location of the soil investigations.
- A complete record of the soil boring and penetration test logs and soil samples.
- A record of the soil profile.
- Elevation of the water table, if encountered. Historic high ground water elevations shall be addressed in the report to adequately evaluate liquefaction and settlement potential.
- Recommendations for foundation type and design criteria, including but not limited to: bearing capacity of natural or compacted soil; provisions to mitigate the effects of expansive soils; mitigation of the effects of liquefaction, differential settlement and varying soil strength; and the effects of adjacent loads.
- Expected total and differential settlement.
- Deep foundation information in accordance with Section 1803 A .5.5.
- Special design and construction provisions for foundations of structures founded on expansive soils, as necessary.
- Compacted fill material properties and testing in accordance with Section 1803 A .5.8.
- Controlled low-strength material properties and testing in accordance with Section 1803 A .5.9. 11. The report shall consider the effects of stepped footings addressed in Section 1809A.3. 12. The report shall consider the effects of seismic hazards in accordance with Section 1803A.6 and shall incorporate the associ- ated geohazard report.
1803A.8 Geotechnical peer review. [DSA-SS and DSA-SS/CC] When alternate foundations designs or ground improvements are employed or where slope stabilization is required, a qualified peer review by a California-licensed geotechnical engineer, in accordance with Section 322 of Part 10, Title 24, CCR, may be required by the enforcement agency. In Section 322 of Part 10, Title 24, CCR, where reference is made to structural or seismic-resisting system, it shall be replaced with geotechnical, foundation or ground improvement, as appropriate.
18A-6 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
SOILS AND FOUNDATIONS
SECTION 1804 A —EXCAVATION, GRADING AND FILL
1804 A .1 Excavation near foundations. Excavation for any purpose shall not reduce vertical or lateral support for any foundation or adjacent foundation without first underpinning or protecting the foundation against detrimental lateral or vertical movement, or both, in accordance with Section 1803 A .5.7.
1804 A .2 Underpinning. Where underpinning is chosen to provide the protection or support of adjacent structures, the underpinning system shall be designed and installed in accordance with provisions of this chapter and Chapter 33.
1804 A .2.1 Underpinning sequencing. Underpinning shall be installed in a sequential manner that protects the neighboring structure and the working construction site. The sequence of installation shall be identified in the approved construction documents.
Frequently asked questions
When do I need a geotechnical report for fills?
If compacted fill that will support shallow foundations is more than 12 in. (305 mm) deep, the CBC requires a geotechnical investigation that includes site prep specs, material specs, lab and field test methods, lift thickness limits, minimum acceptable in‑place density and test frequency (§ 1803A.5.8) .
Can I use CLSM instead of compacted fill under a foundation?
Yes; CLSM is permitted and does not require mechanical compaction, but when foundations bear on CLSM the geotechnical investigation must specify CLSM preparation, properties and field/lab acceptance testing (§ 1804.3; § 1803A.5.9) .
What minimum compaction level is commonly required?
The code provides a commonly referenced threshold of 90% of maximum dry density (ASTM D1557) for certain fills (and as the exception threshold for fills ≤12 in. supporting foundations), and the geotechnical report will specify the required minimum for fills >12 in. (§ 1804A.6 exception; J107.5; § 1803A.5.8) .
How far must I slope the ground away from my foundation?
Finished grade must slope away at least 1 vertical to 20 horizontal (5%) for a horizontal distance of 10 ft (3048 mm) perpendicular to the wall; if 10 ft is not possible provide the 5% slope to an approved alternative drainage method (§ 1804.4) .
Who verifies compaction and fills?
Fills that will support foundations generally require special inspection by the geotechnical engineer or their qualified representative; Table/section 1705A.6 specifies continuous or periodic inspection duties and reporting requirements (§ 1705A.6 and 1705A.6.1) .
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