Chapter 18 — SOILS AND FOUNDATIONS

(Matrix Adoption Tables are nonregulatory, intended only as an aid to the code user.

See Chapter 1 for state agency authority and building applications.)

Adopting agency	BSC	BSC- CG	SFM	HCD			DSA			OSHPD						BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting agency	BSC	BSC- CG	SFM	1	2	1/AC	AC	SS	SS/CC	1	1R	2	3	4	5	5	5	5	5	5	5	5	5
Adopt entire chapter	X
Adopt entire chapter as amended (amended sections listed below)				X	X						X	X			X
Adopt only those sections that are listed below
Chapter / Section
1801.1.1– 1801.1.3											X	X			X
1802.1				X
1803.1											X	X			X
1803.1.1– 1803.1.1.5				X
1803.2												X
1803.3.1											X	X			X
1803.3.5.4 Exception											X	X			X
1803.6											X	X			X
1803.7											X	X			X
1804.4.1				X
1805.2											X	X			X
1805.4.1,Exception 2				X
1805.4.3
1807.1.3											X	X			X
1807.1.4											X	X			X
1807.1.5 Exception											X	X			X
1807.1.6											X	X			X
1807.2											X	X			X
1807.2.2											X	X			X
1807.2.4											X	X			X
1808.8 Exception											X	X			X
Table 1808.8.1											X	X			X
1808.8.6											X	X			X
1809.3											X	X			X
1809.7											X	X			X
1809.8											X	X			X
1809.9											X	X			X
1809.12											X	X			X
1809.14											X	X			X
1810.3.1.5.1											X	X			X
1810.3.2.4											X	X			X
1810.3.5.3.3											X	X			X
1810.3.8.3.3 Exception											X	X			X
1810.3.8.3.4 Exception											X	X			X
1810.3.9.4.2.1											X	X			X
1810.3.10.4	X			X
1810.3.10.4.1											X	X			X
1810.3.11											X	X			X
1810.4.1.5											X	X			X
1811											X	X			X
1812											X	X			X
1813											X	X			X

The state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.

Copyright © 2019 ICC. ALL RIGHTS RESERVED. Accessed by Kevin Day (kevin.day@dgs.ca.gov), (California Building Standards Commission) Order Number #100735044 on Jul 24, 2019 03:54 PM (PDT) pursuant to License Agreement with ICC. No further reproduction or distribution authorized. Single user only, copying and networking prohibited. ANY UNAUTHORIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT, AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.

100735044

142 2019 CALIFORNIA BUILDING CODE Copyright © 2019 ICC. ALL RIGHTS RESERVED. Accessed by Kevin Day (kevin.day@dgs.ca.gov), (California Building Standards Commission) Order Number #100735044 on Jul 24, 2019 03:54 PM (PDT) pursuant to License Agreement with ICC. No further reproduction or distribution authorized. Single user only, copying and networking prohibited. ANY UNAUTHORIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT, AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.

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CHAPTER 18

SOILS AND FOUNDATIONS

User notes:

About this chapter: Chapter 18 provides criteria for geotechnical and structural considerations in the selection, design and installation of foundation systems to support the loads imposed by the structure above. This chapter includes requirements for soils investigation and site preparation for receiving a foundation, including the load-bearing values for soils and protection for the foundation from frost and water intru- sion. Section 1808 addresses the basic requirements for all foundation types while subsequent sections address foundation requirements that are specific to shallow foundations and deep foundations.

Code development reminder: Code change proposals to this chapter will be considered by the IBC—Structural Code Development Commit- tee during the 2019 (Group B) Code Development Cycle. See explanation on page ix.

1809.6 Location of footings.¶

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

1809.7 Prescriptive footings for light-frame construction.¶

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

TABLE 1809.7 PRESCRIPTIVE FOOTINGS SUPPORTING WALLS OF LIGHT-FRAME CONSTRUCTION ^{a, b, c, d, e}

NUMBER OF FLOORS SUPPORTED BY THE FOOTINGf	WIDTH OF FOOTING (inches)	THICKNESS OF FOOTING (inches)
1	12	6
2	15	6
3	18	8g

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm. a. Depth of footings shall be in accordance with Section 1809.4. b. The ground under the floor shall be permitted to be excavated to the

elevation of the top of the footing. c. Interior stud-bearing walls shall be permitted to be supported by isolated

footings. The footing width and length shall be twice the width shown in this table, and footings shall be spaced not more than 6 feet on center. d. See Section 1905 for additional requirements for concrete footings of

structures assigned to Seismic Design Category C, D, E or F. e. For thickness of foundation walls, see Section 1807.1.6. f. Footings shall be permitted to support a roof in addition to the stipulated

number of floors. Footings supporting roof only shall be as required for supporting one floor. g. Plain concrete footings for Group R-3 occupancies shall be permitted to

be 6 inches thick.

1809.8 Plain concrete footings.¶

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

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

1809.9 Masonry-unit footings.¶

[OSHPD 1R, 2 & 5] Not permitted by OSHPD. The design, materials and construction

1808.8.6 Seismic requirements. [OSHPD 1R, 2 & 5] See Section 1905 for additional requirements for foundations of structures assigned to Seismic Design Category D, E or F.

For structures assigned to Seismic Design Category D, E or F, provisions of Section 18.13 of ACI 318 shall apply where not in conflict with the provisions of Sections 1808 through 1810.

Exceptions: [OSHPD 1R, 2 & 5] Not permitted by OSHPD.

Detached one- and two-family dwellings of lightframe construction and two stories or less above grade plane are not required to comply with the provisions of Section 18.13 of ACI 318.
Section 18.13.4.3(a) of ACI 318 shall not apply.

1808.9 Vertical masonry foundation elements.¶

Vertical masonry foundation elements that are not foundation piers as defined in Section 202 shall be designed as piers, walls or columns, as applicable, in accordance with TMS 402.

1803A.6 Geohazard reports.¶

Geohazard reports shall be required for all proposed construction.

Exceptions:

1. Reports are not required for one-story, wood-frame and light-steel-frame buildings of Type II or Type V construction and 4,000 square feet (371 m ² ) or less in floor area, not located within Earthquake Fault Zones or Seismic Hazard Zones as shown in the most recently published maps from the California Geological Survey (CGS) or in seismic hazard zones as defined in the Safety Element of the local General Plan; nonstructural, associated structural or volun- tary structural alterations, and incidental structural additions or alterations, and structural repairs for other than earthquake damage.

2. A previous report for a specific site may be resub- mitted, provided that a reevaluation is made and the report is found to be currently appropriate.

The purpose of the geohazard report shall be to identify geologic and seismic conditions that may require project mit- igations. The reports shall contain data which provide an assessment of the nature of the site and potential for earth- quake damage based on appropriate investigations of the regional and site geology, project foundation conditions and the potential seismic shaking at the site. The report shall be prepared by a California-certified engineering geologist in consultation with a California-registered geotechnical engi- neer.

The preparation of the geohazard report shall consider the most recent CGS Note 48: Checklist for the Review of Engineering Geology and Seismology Reports for Califor- nia Public School, Hospitals, and Essential Services Build- ings. In addition, the most recent version of CGS Special Publication 42, Fault Rupture Hazard Zones in California, shall be considered for project sites proposed within an Alquist-Priolo Earthquake Fault Zone. The most recent ver- sion of CGS Special Publication 117, Guidelines for Evalu- ating and Mitigating Seismic Hazards in California, shall be considered for project sites proposed within a Seismic

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SOILS AND FOUNDATIONS

Hazard Zone. All conclusions shall be supported by satis- factory data and analysis.

In addition to requirements in Sections 1803A.5.11 and 1803A.5.12, the report shall include, but shall not be limited to, the following:

1. Site geology.

2. Evaluation of the known active and potentially active faults, both regional and local.

3. Ground-motion parameters, as required by Sections 1613A and 1617A, and ASCE 7.

The Next Generation Attenuation West 2 (NGA-West 2) relations used for the 2014 USGS seismic hazards maps for Western United States (WUS) shall be utilized to determine the site-specific ground motion. When supported by data and analysis, and approved by the enforcement agency, other attenuation relations that were not used for the 2014 USGS maps shall be permitted as additions or substitutions. No fewer than three NGA attenuation relations shall be utilized.

1803A.7 Geotechnical¶

reporting. Where geotechnical investigations are required, a written report of the investigations shall be submitted to the building official by the permit applicant at the time of permit application. The geotechnical report shall provide completed evaluations of the foundation conditions of the site and the potential geo- logic/seismic hazards affecting the site. The geotechnical report shall include, but shall not be limited to, site-specific evaluations of design criteria related to the nature and extent of foundation materials, groundwater conditions, liq- uefaction potential, settlement potential and slope stability. The report shall contain the results of the analyses of prob- lem areas identified in the geohazard report. The geotechni- cal report shall incorporate estimates 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 set- tlement 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 foot- ings addressed in Section 1809A.3.

12. The report shall consider the effects of seismic haz- ards in accordance with Section 1803A.6 and shall incorporate the associated geohazard report.

1803A.8 Geotechnical peer review. [DSA-SS and DSA-SS/¶

CC] When alternate foundations designs or ground improve- ments 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, C.C.R., may be required by the enforcement agency. In Sec- tion 322 of Part 10, Title 24, C.C.R., where reference is made to structural or seismic-resisting system, it shall be replaced with geotechnical, foundation, or ground improvement, as appropriate.