Site Preparation, Excavation, Grading, Fill & Moisture Protection

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.

  2. 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:

  1. Setbacks greater than those required by Figure J108.1.

  2. Provisions for retaining walls or similar construction.

  3. Erosion protection of the fill slopes.

  4. Provision for the control of surface waters.

  SECTION J109—DRAINAGE AND TERRACING

• CBC § 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

  2. Recommended center-to-center spacing of deep foundation elements.
  3. Driving criteria.
  4. Installation procedures.
  5. Field inspection and reporting procedures (to include procedures for verification of the installed bearing capacity where required).
  6. Load test requirements.
  7. Suitability of deep foundation materials for the intended environment.
  8. Designation of bearing stratum or strata.
  9. 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.
• 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:

  1. 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).
  2. 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:

  1. 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.
  2. 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.
  3. In coastal high hazard areas, unless such fill is conducted or placed to avoid diversion of water and waves toward any building or structure.
  4. 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 § 17A-4 High relevance — show source text

  1704A Special Inspections and Tests, Contractor Responsibility and Structural Observation . . . . . . . . . . . . . . . . . . .17A-4

  1705A Required Special Inspections and Tests . . . . . . . . . .17A-6

  1706A Design Strengths of Materials . . . . . . . . . . . . . . . . . .17A-22

  1707A Alternative Test Procedure . . . . . . . . . . . . . . . . . . . . .17A-22

  1708A In-Situ Load Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17A-22

  1709A Preconstruction Load Tests . . . . . . . . . . . . . . . . . . . .17A-22

  1710A Off-Site Construction [OSHPD 1 & 4] . . . . . . . . . . . . .17A-23

  CHAPTER 18 SOILS AND FOUNDATIONS. . . . . . . . . . . . . . 18-1

  1801 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3

  1802 Design Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3

  1803 Geotechnical Investigations. . . . . . . . . . . . . . . . . . . . 18-3

  1804 Excavation, Grading and Fill. . . . . . . . . . . . . . . . . . . . 18-7

  1805 Dampproofing and Waterproofing . . . . . . . . . . . . . . 18-7

  1806 Presumptive Load-Bearing Values of Soils . . . . . . . 18-9

  1807 Foundation Walls, Retaining Walls and Embedded Posts and Poles . . . . . . . . . . . . . . . . . 18-10

  1808 Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-16

  1809 Shallow Foundations . . . . . . . . . . . . . . . . . . . . . . . . . 18-18

  1810 Deep Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20

  1811 Prestressed Rock and Soil Foundation

  Anchors [OSHPD 1R, 2 & 5]. . . . . . . . . . . . . . . . . . . . . 18-31

  1812 Earth Retaining Shoring

  [OSHPD 1R, 2 & 5] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-32

  1813 Vibro Stone Columns for Ground Improvement

• CBC § 18-6 High relevance — show source text

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  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:

  1. 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).
  2. 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:

  1. 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 § 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:

  1. 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.
  2. 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.
  3. In coastal high hazard areas, unless such fill is conducted or placed to avoid diversion of water and waves toward any building or structure.
  4. 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 § 5.4 High relevance — show source text

  4. Expansion index greater than 20, determined in accordance with ASTM D4829.

  1803 A .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 A .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.
  2. Recommended center-to-center spacing of deep foundation elements.
  3. Driving criteria.
  4. Installation procedures.
  5. Field inspection and reporting procedures (to include procedures for verification of the installed bearing capacity where required).
  6. Load test requirements.
  7. Suitability of deep foundation materials for the intended environment.
  8. Designation of bearing stratum or strata.
  9. Reductions for group action, where necessary.

  1803 A .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 A .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

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  for submission. Such support shall be provided by under-pinning, bracing, excavation retention systems or by other means acceptable to the building official.

  1803 A .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.

  6. Minimum acceptable in-place dry density expressed as a percentage of the maximum dry density determined in accordance with Item 3.

  7. Number and frequency of field tests required to determine compliance with Item 6.

• CBC § 1612.3 High relevance — show source text

  2025 CALIFORNIA BUILDING CODE APPENDIX J-1

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  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 § 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:

  1. Grading in an isolated, self-contained area, provided that the public is not endangered and that such grading will not adversely affect adjoining properties.

  2. Excavation for construction of a structure permitted under this code.

  3. Cemetery graves.

  4. Refuse disposal sites controlled by other regulations.

  5. Excavations for wells, or trenches for utilities.

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  APPENDIX J—GRADING

  6. 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.
  7. 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 § 18-3 High relevance — show source text

  1803 Geotechnical Investigations. . . . . . . . . . . . . . . . . . . . 18-3

  1804 Excavation, Grading and Fill. . . . . . . . . . . . . . . . . . . . 18-7

  1805 Dampproofing and Waterproofing . . . . . . . . . . . . . . 18-7

  1806 Presumptive Load-Bearing Values of Soils . . . . . . . 18-9

  1807 Foundation Walls, Retaining Walls and Embedded Posts and Poles . . . . . . . . . . . . . . . . . 18-10

  1808 Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-16

  1809 Shallow Foundations . . . . . . . . . . . . . . . . . . . . . . . . . 18-18

  1810 Deep Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20

  1811 Prestressed Rock and Soil Foundation

  Anchors [OSHPD 1R, 2 & 5]. . . . . . . . . . . . . . . . . . . . . 18-31

  1812 Earth Retaining Shoring

  [OSHPD 1R, 2 & 5] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-32

  1813 Vibro Stone Columns for Ground Improvement

  [OSHPD 1R, 2 & 5] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-35

  CHAPTER 18A SOILS AND FOUNDATIONS. . . . . . . . . . . . . .18A-1

  1801A General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18A-3

  1802A Design Basis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18A-3

  1803A Geotechnical Investigations. . . . . . . . . . . . . . . . . . . . . . 18A-3

  1804A Excavation, Grading and Fill . . . . . . . . . . . . . . . . . . . . . 18A-7

  1805A Dampproofing and Waterproofing . . . . . . . . . . . . . . . 18A-7

  1806A Presumptive Load-Bearing Values of Soils. . . . . . . . 18A-9

  CONTENTS

  1807A Foundation Walls, Retaining Walls and Embedded Posts and Poles . . . . . . . . . . . . . . . . . . . 18A-10

• 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:

  1. A plot showing the location of the soil investigations.
  2. A complete record of the soil boring and penetration test logs and soil samples.
  3. A record of the soil profile.
  4. 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.
  5. 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.
  6. Expected total and differential settlement.
  7. Deep foundation information in accordance with Section 1803 A .5.5.
  8. Special design and construction provisions for foundations of structures founded on expansive soils, as necessary.
  9. Compacted fill material properties and testing in accordance with Section 1803 A .5.8.
  10. 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.

• CBC § 1803A.8 Medium 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:

  1. 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).
  2. 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.