CBC · California Building Code

How do I use presumptive load-bearing values of soils?

The CBC allows use of Table 1806.2 presumptive vertical and lateral soil bearing values for near‑surface soils, but you must follow §§ 1806.1–1806.3 (including the 1/3 increase allowance with certain ASD combinations, lateral‑resistance combination and depth limits), avoid using the table for organic or undocumented fill without data, and provide geotechnical testing when the building official requires it.

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Last reviewed: July 5, 2026

What the code requires

The California Building Code lets you use tabulated (presumptive) soil bearing and lateral-resistance values for near‑surface soils and rock when designing foundations, provided you do not exceed the tabulated values unless you submit supporting data. Those tabulated values and the rules for their use are in § 1806.2, with load‑combination guidance in § 1806.1 and lateral‑resistance rules in § 1806.3.

Requirements in detail

When you may use presumptive values

Use the values in Table 1806.2 for supporting soils/rock near the surface unless you have test data that justify higher values and those data are submitted and approved (§ 1806.2).
The building official may require soil investigation (see § 1803.5.2) when there is doubt about soil classification, strength or compressibility. § 1806.2 refers to that requirement.

Load combinations and allowable increase

Presumptive values are intended for use with allowable‑stress design (ASD) load combinations specified by ASCE 7, Section 2.4, or the CBC alternative ASD load combinations (§ 1605.2). If you use the CBC alternative ASD load combinations that include wind or earthquake, the vertical and lateral tabular values may be increased by one‑third (§ 1806.1).

Lateral resistance rules

When you use the table values for lateral resistance, follow §§ 1806.3.1–1806.3.4: you may combine lateral bearing pressure and lateral sliding resistance to get total lateral resistance (§ 1806.3.1); for fine, cohesive soils the sliding resistance is limited to one‑half the dead load (§ 1806.3.2); lateral bearing pressures may be increased by the tabular value for each additional foot of depth up to a maximum of 15 times the tabular value (§ 1806.3.3); and isolated poles may use 2× tabular lateral bearing when allowable by § 1806.3.4.

Materials that cannot use presumptive values

Mud, organic silt and organic clays (OL, OH), peat (Pt) and undocumented fill shall not be assumed to have a presumptive load‑bearing capacity unless supporting data are submitted and approved (§ 1806.2).

Decision‑relevant numbers (from Table 1806.2)

Class / material (USCS symbols)	Vertical foundation pressure (psf)	Lateral bearing pressure (psf/ft below natural grade)	Lateral sliding resistance	Code reference
1. Crystalline bedrock	12,000	1,200	coefficient 0.70	§ 1806.2, Table 1806.2
2. Sedimentary & foliated rock	4,000	400	coefficient 0.35	§ 1806.2, Table 1806.2
3. Sandy gravel & gravel (GW, GP)	3,000	200	coefficient 0.35	§ 1806.2, Table 1806.2
4. Sand, silty/clayey sand, silty/gravelly gravel (SW, SP, SM, SC, GM, GC)	2,000	150	coefficient 0.25	§ 1806.2, Table 1806.2
5. Clays, silts (CL, ML, MH, CH)	1,500	100	cohesion = 130 psf (see § 1806.3.2 limit)	§ 1806.2, Table 1806.2; § 1806.3.2

Notes: the table footnotes state the friction coefficient is to be multiplied by the dead load and the cohesion value is to be multiplied by the contact area as limited by § 1806.3.2; SI conversions are also provided in the table.

Exceptions & special cases

Building official discretion: the official may allow use of presumptive capacity for lightweight or temporary structures even where other materials would be disallowed (§ 1806.2 Exception).
Temporary/public‑occupancy temporary structures: the CBC (Chapter 31) includes a specific note that certain temporary supports on collapsible or very low‑strength substrates should assume reduced presumptive values (see CBC 3103.6.2 and reference to Table 1806.2).
Lateral sliding in cohesive soils: for clay and similar soils, sliding resistance from the cohesion term cannot exceed one‑half of the dead load (limit in § 1806.3.2) — you must cap sliding resistance accordingly.

If the building official has reason to doubt the tabular classification or capacity, the site must meet the geotechnical investigation requirements referenced in § 1803.5.2 — you cannot rely on the table in that circumstance.

Common mistakes

Applying tabular values to organic soils, peat or undocumented fill without tests — the code forbids that unless data are submitted (§ 1806.2).
Forgetting the 1/3 increase allowance (or failing to apply it) when using the CBC alternative ASD load combinations that include wind/quake — § 1806.1 explicitly permits a 1/3 increase in that case.
Treating tabular lateral bearing as unlimited with depth; the code allows increases per foot but caps the increase at 15× the tabular value (§ 1806.3.3).
Misusing lateral sliding coefficients: the coefficient in the table is multiplied by dead load (per table footnote) and, for clays, must obey the one‑half dead‑load cap (§ 1806.3.2).
Confusing allowable stress design context: the presumptive values are stated for use with ASD load combinations (ASCE 7 §2.4 or the CBC alternative); do not mix LRFD factors without justification (§ 1806.1).

Worked example — shallow footing on sandy gravel (Class 3)

Situation (assumptions):

Soil classification at bearing level is sandy gravel (Class 3, GW/GP). Table gives vertical allowable = 3,000 psf and lateral bearing = 200 psf/ft (§ 1806.2).
Column factored service load to be supported (dead+live for sizing under ASD) = 60,000 lb (60 kips). (This is an assumed applied load for the example; project loads and combinations must match your design practice and § 1806.1 guidance.)

Step 1 — footing area for vertical support

Required plan area = applied vertical load / allowable bearing = 60,000 lb ÷ 3,000 psf = 20.0 ft².
A square footing ≈ √20 ≈ 4.47 ft; pick a 5.0 ft × 5.0 ft footing (25 ft²) to provide margin. This sizing follows the vertical allowable from Table 1806.2 (§ 1806.2).

Step 2 — lateral resistance (overview; compute rigorously per project needs)

Tabular lateral bearing = 200 psf/ft. Per § 1806.3.3 you may increase the lateral bearing pressure by the tabular value for each additional foot of depth, up to 15× the tabular value. For example, if you assume embedment of 3 ft and interpret the tabular value as applying at 1 ft (so added twice), a common practice calculation would be lateral bearing ≈ 200 × 3 = 600 psf (capped at 15 × 200 = 3,000 psf). Use the code limit language in § 1806.3.3 when applying depth increases.
Lateral sliding resistance may also be used: the table gives a friction coefficient of 0.35 for Class 3; sliding resistance = 0.35 × dead load (table footnote) but observe the clay sliding cap in § 1806.3.2 if soils are cohesive. Combine sliding and bearing per § 1806.3.1 to obtain total lateral resistance.

Important: the above lateral arithmetic illustrates use of the table values and the depth/increase rule in § 1806.3.3; for design you must apply the precise embedment geometry, contact area, the correct dead load for sliding calculations, and the combined method in § 1806.3.1. If there is any doubt about classification or strength, satisfy § 1803.5.2 (geotechnical investigation).

Related provisions

§ 1806.1 — Load combinations and the 1/3 increase when using alternative ASD that include wind/earthquake.
§ 1806.2 — Presumptive load‑bearing values and materials excluded from presumptive use (Table 1806.2).
§ 1806.3 (and § 1806.3.1–.4) — Lateral load resistance, combined resistance, sliding limit, increase for depth, poles.
§ 1803.5.2 — Geotechnical investigation requirement when the building official doubts soil classification/strength/compressibility (referenced from § 1806.2).
§ 1605.2 — CBC alternative allowable stress design load combinations (referenced by § 1806.1).
R401.4.1 (CRC) — Residential presumptive bearing table that parallels CBC Table 1806.2 for one‑ and two‑family dwellings (useful for residential work).

Code references

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

CBC § 4.3 High relevance — show source text

1805 A .4.3 Drainage discharge. The floor base and foundation perimeter drain shall discharge by gravity or mechanical means into an approved drainage system that complies with the California Plumbing Code .

Exception: Where a site is located in well-drained gravel or sand/gravel mixture soils, a dedicated drainage system is not required.

SECTION 1806 A —PRESUMPTIVE LOAD-BEARING VALUES OF SOILS

1806 A .1 Load combinations. The presumptive load-bearing values provided in Table 1806 A .2 shall be used with the allowable stress design load combinations specified in ASCE 7, Section 2.4 or the alternative allowable stress design load combinations of Section 1605 A .2. The values of vertical foundation pressure and lateral bearing pressure given in Table 1806 A .2 shall be permitted to be increased by one-third where used with the alternative allowable stress design load combinations of Section 1605 A .2 that include wind or earthquake loads.

1806 A .2 Presumptive load-bearing values. The load-bearing values used in design for supporting soils and rock near the surface shall not exceed the values specified in Table 1806 A .2 unless data to substantiate the use of higher values are submitted and approved. Where the building official has reason to doubt the classification, strength or compressibility of the soil or rock, the requirements of Section 1803 A .5.2 shall be satisfied.

Presumptive load-bearing values shall apply to materials with similar physical and engineering characteristics. Mud, organic silt and organic clays (OL, OH), peat (Pt) and undocumented fill shall not be assumed to have a presumptive load-bearing capacity unless data to substantiate the use of such a value are submitted.

Exception: A presumptive load-bearing capacity shall be permitted to be used where the building official deems the load-bearing capacity is adequate for the support of lightweight or temporary structures.

TABLE 1806A.2—PRESUMPTIVE LOAD-BEARING VALUES	Col2	Col3	Col4	Col5
CLASS OF MATERIALS	VERTICAL FOUNDATION PRESSURE (psf)	LATERAL BEARING PRESSURE (psf/ft below natural grade)	LATERAL SLIDING RESISTANCE	LATERAL SLIDING RESISTANCE
CLASS OF MATERIALS	VERTICAL FOUNDATION PRESSURE (psf)	LATERAL BEARING PRESSURE (psf/ft below natural grade)	Coefficient of frictiona	Cohesion (psf)b
1. Crystalline bedrock	12,000	1,200	0.70	—
2. Sedimentary and foliated rock	4,000	400	0.35	—
3. Sandy gravel and gravel (GW and GP)	3,000	200	0.35	—
4. Sand, silty sand, clayey sand, silty gravel and clayey gravel (SW, SP, SM, SC, GM and GC)	2,000	150	0.25	—
5.

CBC § 1805.4.1 High relevance — show source text

The top of joints or the top of perforations shall be protected with an approved filter membrane material. The pipe or tile shall be placed on not less than 2 inches (51 mm) of gravel or crushed stone complying with Section 1805.4.1, and shall be covered with not less than 6 inches (152 mm) of the same material.

1805.4.3 Drainage discharge. The floor base and foundation perimeter drain shall discharge by gravity or mechanical means into an approved drainage system that complies with the California Plumbing Code .

Exception: Where a site is located in well-drained gravel or sand/gravel mixture soils, a dedicated drainage system is not required.

SECTION 1806—PRESUMPTIVE LOAD-BEARING VALUES OF SOILS

1806.1 Load combinations. The presumptive load-bearing values provided in Table 1806.2 shall be used with the allowable stress design load combinations specified in ASCE 7, Section 2.4 or the alternative allowable stress design load combinations of Section 1605.2. The values of vertical foundation pressure and lateral bearing pressure given in Table 1806.2 shall be permitted to be increased by one-third where used with the alternative allowable stress design load combinations of Section 1605.2 that include wind or earthquake loads.

1806.2 Presumptive load-bearing values. The load-bearing values used in design for supporting soils and rock near the surface shall not exceed the values specified in Table 1806.2 unless data to substantiate the use of higher values are submitted and approved. Where the building official has reason to doubt the classification, strength or compressibility of the soil or rock, the requirements of Section 1803.5.2 shall be satisfied.

TABLE 1806.2—PRESUMPTIVE LOAD-BEARING VALUES	Col2	Col3	Col4	Col5
CLASS OF MATERIALS	VERTICAL FOUNDATION PRESSURE (psf)	LATERAL BEARING PRESSURE (psf/ft below natural grade)	LATERAL SLIDING RESISTANCE	LATERAL SLIDING RESISTANCE
CLASS OF MATERIALS	VERTICAL FOUNDATION PRESSURE (psf)	LATERAL BEARING PRESSURE (psf/ft below natural grade)	Coefficient of frictiona	Cohesion (psf)b
1. Crystalline bedrock	12,000	1,200	0.70	—
2. Sedimentary and foliated rock	4,000	400	0.35	—
3. Sandy gravel and gravel (GW and GP)	3,000	200	0.35	—
4.

CBC § 1805.4.1 High relevance — show source text
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

SOILS AND FOUNDATIONS

1805.4.1 Floor base course. Floors of basements, except as provided for in Section 1805.1.1, shall be placed over a floor base course not less than 4 inches (102 mm) in thickness that consists of gravel or crushed stone containing not more than 10 percent of material that passes through a No. 4 (4.75 mm) sieve.

Exception s:
1. Where a site is located in well-drained gravel or sand/gravel mixture soils, a floor base course is not required. 2. [HCD 1] When a capillary break is installed in accordance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.5.
1805.4.2 Foundation drain. A drain shall be placed around the perimeter of a foundation that consists of gravel or crushed stone containing not more than 10-percent material that passes through a No. 4 (4.75 mm) sieve. The drain shall extend not less than 12 inches (305 mm) beyond the outside edge of the footing. The thickness shall be such that the bottom of the drain is not higher than the bottom of the base under the floor, and that the top of the drain is not less than 6 inches (152 mm) above the top of the footing. The top of the drain shall be covered with an approved filter membrane material. Where a drain tile or perforated pipe is used, the invert of the pipe or tile shall not be higher than the floor elevation. The top of joints or the top of perforations shall be protected with an approved filter membrane material. The pipe or tile shall be placed on not less than 2 inches (51 mm) of gravel or crushed stone complying with Section 1805.4.1, and shall be covered with not less than 6 inches (152 mm) of the same material.

1805.4.3 Drainage discharge. The floor base and foundation perimeter drain shall discharge by gravity or mechanical means into an approved drainage system that complies with the California Plumbing Code .

Exception: Where a site is located in well-drained gravel or sand/gravel mixture soils, a dedicated drainage system is not required.

SECTION 1806—PRESUMPTIVE LOAD-BEARING VALUES OF SOILS

1806.1 Load combinations. The presumptive load-bearing values provided in Table 1806.2 shall be used with the allowable stress design load combinations specified in ASCE 7, Section 2.4 or the alternative allowable stress design load combinations of Section 1605.2. The values of vertical foundation pressure and lateral bearing pressure given in Table 1806.2 shall be permitted to be increased by one-third where used with the alternative allowable stress design load combinations of Section 1605.2 that include wind or earthquake loads.

1806.2 Presumptive load-bearing values. The load-bearing values used in design for supporting soils and rock near the surface shall not exceed the values specified in Table 1806.2 unless data to substantiate the use of higher values are submitted and approved. Where the building official has reason to doubt the classification, strength or compressibility of the soil or rock, the requirements of Section 1803.5.2 shall be satisfied.
CBC § 4.1 High relevance — show source text
1805 A .4.1 Floor base course. Floors of basements, except as provided for in Section 1805 A .1.1, shall be placed over a floor base course not less than 4 inches (102 mm) in thickness that consists of gravel or crushed stone containing not more than 10 percent of material that passes through a No. 4 (4.75 mm) sieve.

Exception: Where a site is located in well-drained gravel or sand/gravel mixture soils, a floor base course is not required.

18A-8 2025 CALIFORNIA BUILDING CODE

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

SOILS AND FOUNDATIONS

1805 A .4.2 Foundation drain. A drain shall be placed around the perimeter of a foundation that consists of gravel or crushed stone containing not more than 10-percent material that passes through a No. 4 (4.75 mm) sieve. The drain shall extend not less than 12 inches (305 mm) beyond the outside edge of the footing. The thickness shall be such that the bottom of the drain is not higher than the bottom of the base under the floor, and that the top of the drain is not less than 6 inches (152 mm) above the top of the footing. The top of the drain shall be covered with an approved filter membrane material. Where a drain tile or perforated pipe is used, the invert of the pipe or tile shall not be higher than the floor elevation. The top of joints or the top of perforations shall be protected with an approved filter membrane material. The pipe or tile shall be placed on not less than 2 inches (51 mm) of gravel or crushed stone complying with Section 1805.4.1, and shall be covered with not less than 6 inches (152 mm) of the same material.

1805 A .4.3 Drainage discharge. The floor base and foundation perimeter drain shall discharge by gravity or mechanical means into an approved drainage system that complies with the California Plumbing Code .

Exception: Where a site is located in well-drained gravel or sand/gravel mixture soils, a dedicated drainage system is not required.

SECTION 1806 A —PRESUMPTIVE LOAD-BEARING VALUES OF SOILS

1806 A .1 Load combinations. The presumptive load-bearing values provided in Table 1806 A .2 shall be used with the allowable stress design load combinations specified in ASCE 7, Section 2.4 or the alternative allowable stress design load combinations of Section 1605 A .2. The values of vertical foundation pressure and lateral bearing pressure given in Table 1806 A .2 shall be permitted to be increased by one-third where used with the alternative allowable stress design load combinations of Section 1605 A .2 that include wind or earthquake loads.

1806 A .2 Presumptive load-bearing values. The load-bearing values used in design for supporting soils and rock near the surface shall not exceed the values specified in Table 1806 A .2 unless data to substantiate the use of higher values are submitted and approved. Where the building official has reason to doubt the classification, strength or compressibility of the soil or rock, the requirements of Section 1803 A .5.2 shall be satisfied.

CBC § 1806.2 High relevance — show source text

TABLE 1806.2—PRESUMPTIVE LOAD-BEARING VALUES	Col2	Col3	Col4	Col5
CLASS OF MATERIALS	VERTICAL FOUNDATION PRESSURE (psf)	LATERAL BEARING PRESSURE (psf/ft below natural grade)	LATERAL SLIDING RESISTANCE	LATERAL SLIDING RESISTANCE
CLASS OF MATERIALS	VERTICAL FOUNDATION PRESSURE (psf)	LATERAL BEARING PRESSURE (psf/ft below natural grade)	Coefficient of frictiona	Cohesion (psf)b
1. Crystalline bedrock	12,000	1,200	0.70	—
2. Sedimentary and foliated rock	4,000	400	0.35	—
3. Sandy gravel and gravel (GW and GP)	3,000	200	0.35	—
4. Sand, silty sand, clayey sand, silty gravel and clayey gravel (SW, SP, SM, SC, GM and GC)	2,000	150	0.25	—
5. Clay, sandy clay, silty clay, clayey silt, silt and sandy silt (CL, ML, MH and CH)	1,500	100	—	130
For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m. a. Coefficient to be multiplied by the dead load. b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.	For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m. a. Coefficient to be multiplied by the dead load. b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.	For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m. a. Coefficient to be multiplied by the dead load. b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.	For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m. a. Coefficient to be multiplied by the dead load. b.

CBC § 0.35 High relevance — show source text
Sandy gravel and gravel (GW and GP)|3,000|200|0.35|—| |4. Sand, silty sand, clayey sand, silty gravel and
clayey gravel (SW, SP, SM, SC, GM and GC)|2,000|150|0.25|—| |5. Clay, sandy clay, silty clay, clayey silt, silt and
sandy silt (CL, ML, MH and CH)|1,500|100|—|130| |For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m.
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.|For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m.
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.|For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m.
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.|For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m.
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.|For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m.
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.|

1806.3 Lateral load resistance. Where the presumptive values of Table 1806.2 are used to determine resistance to lateral loads, the calculations shall be in accordance with Sections 1806.3.1 through 1806.3.4.

1806.3.1 Combined resistance. The total resistance to lateral loads shall be permitted to be determined by combining the values derived from the lateral bearing pressure and the lateral sliding resistance specified in Table 1806.2.

1806.3.2 Lateral sliding resistance limit. For clay, sandy clay, silty clay, clayey silt, silt and sandy silt, the lateral sliding resistance shall not exceed one-half the dead load.

1806.3.3 Increase for depth. The lateral bearing pressures specified in Table 1806.2 shall be permitted to be increased by the tabular value for each additional foot (305 mm) of depth to a value that is not greater than 15 times the tabular value.

2025 CALIFORNIA BUILDING CODE 18-9

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

SOILS AND FOUNDATIONS
CBC § 1806.3.2. High relevance — show source text
Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.|For SI: 1 pound per square foot = 0.0479 kPa, 1 pound per square foot per foot = 0.157 kPa/m.
a. Coefficient to be multiplied by the dead load.
b. Cohesion value to be multiplied by the contact area, as limited by Section 1806.3.2.|

1806.3 Lateral load resistance. Where the presumptive values of Table 1806.2 are used to determine resistance to lateral loads, the calculations shall be in accordance with Sections 1806.3.1 through 1806.3.4.

1806.3.1 Combined resistance. The total resistance to lateral loads shall be permitted to be determined by combining the values derived from the lateral bearing pressure and the lateral sliding resistance specified in Table 1806.2.

1806.3.2 Lateral sliding resistance limit. For clay, sandy clay, silty clay, clayey silt, silt and sandy silt, the lateral sliding resistance shall not exceed one-half the dead load.

1806.3.3 Increase for depth. The lateral bearing pressures specified in Table 1806.2 shall be permitted to be increased by the tabular value for each additional foot (305 mm) of depth to a value that is not greater than 15 times the tabular value.

2025 CALIFORNIA BUILDING CODE 18-9

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

SOILS AND FOUNDATIONS

1806.3.4 Increase for poles. Isolated poles for uses such as flagpoles or signs and poles used to support buildings that are not adversely affected by a [1] / 2 -inch (12.7 mm) motion at the ground surface due to short-term lateral loads shall be permitted to be designed using lateral bearing pressures equal to two times the tabular values.

SECTION 1807—FOUNDATION WALLS, RETAINING WALLS AND EMBEDDED POSTS AND POLES

1807.1 Foundation walls. Foundation walls shall be designed and constructed in accordance with Sections 1807.1.1 through 1807.1.6. Foundation walls shall be supported by foundations designed in accordance with Section 1808.

1807.1.1 Design lateral soil loads. Foundation walls shall be designed for the lateral soil loads set forth in Section 1610.

1807.1.2 Unbalanced backfill height. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation wall or the interior finish ground level. Where an interior concrete slab on grade is provided and is in contact with the interior surface of the foundation wall, the unbalanced backfill height shall be permitted to be measured from the exterior finish ground level to the top of the interior concrete slab.

1807.1.3 Rubble stone foundation walls. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. Foundation walls of rough or random rubble stone shall be not less than 16 inches (406 mm) thick. Rubble stone shall not be used for foundation walls of structures assigned to Seismic Design Category C, D, E or F.
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 § 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 § 3103.6.1.5 Medium relevance — show source text
3103.6.1.5 Ice loads. Ice loads on public-occupancy temporary structures shall be permitted to be determined with a maximum nominal thickness of 0.5 inch (13 mm), for all risk categories. Where the public-occupancy temporary structure is not subject to ice loads or not constructed and occupied during times when ice is to be expected, ice loads need not be considered, provided that where the period of time when the public-occupancy temporary structure is in service shifts to include times when ice is to be expected, one of the following conditions is met:
1. The design is reviewed and modified, as appropriate, to account for ice loads.
2. Controlled occupancy procedures in accordance with Section 3103.8 are implemented.
3103.6.1.6 Tsunami loads. Public-occupancy temporary structures in a tsunami design zone are not required to be designed for tsunami loads specified in Section 1615. Controlled occupancy procedures in accordance with Section 3103.8 shall be implemented.

3103.6.2 Foundations. Public-occupancy temporary structures shall be permitted to be supported on the ground with temporary foundations where approved by the building official. Consideration shall be given for the impacts of differential settlement where foundations do not extend below the ground or where foundations are supported on compressible materials. The presumptive load-bearing value for public-occupancy temporary structures supported on a pavement, slab on grade or on other collapsible or controlled low-strength substrate soils such as beach sand or grass shall be assumed not to exceed 1,000 pounds per square foot (47.88 kPa) unless determined through testing and evaluation by a registered design professional. The presumptive load-bearing values listed in Table 1806.2 shall be permitted to be used for other supporting soil conditions.

3103.6.3 Installation and maintenance inspections. A qualified person shall inspect public-occupancy temporary structures that are assembled using transportable and reusable materials. Components shall be inspected when purchased or acquired and at least once per year. The inspection shall evaluate individual components, and the fully assembled structure, to determine suitability for use based on the requirements in ESTA ANSI E1.21. Inspection records shall be kept and shall be made available for verification by the building official. Additionally, public-occupancy temporary structures shall be inspected at regular intervals when in service to ensure that the structure continues to perform as designed and initially erected.

3103.6.4 Durability. Reusable components used in the erection and the installation of public-occupancy temporary structures shall be manufactured of durable materials necessary to withstand environmental conditions at the service location. Components damaged during transportation or installation or due to the effects of weathering shall be replaced or repaired.

3103.7 Serviceability. The effects of structural loads or conditions shall not adversely affect the serviceability or performance of the public-occupancy temporary structure.

3103.8 Controlled occupancy procedures. Where controlled occupancy procedures are required to be implemented for publicoccupancy temporary structures in Section 3103.6.1, the procedures shall comply with this section and ANSI ES1.7. An operations management plan in accordance with ANSI E1.21 shall be submitted to the building official for approval as a part of the permit documents. In addition, the operations management plan shall include an emergency action plan that documents the following information, where applicable:
1. Surfaces on which snow or ice accumulates shall be monitored before and during occupancy of the public-occupancy temporary structure.
CBC § 3.2 Medium relevance — show source text
Wood poles shall be treated in accordance with AWPA U1 for sawn timber posts (Commodity Specification A, Use Category 4B) and for round timber posts (Commodity Specification B, Use Category 4B).

1807 A .3.2 Design criteria. The depth to resist lateral loads shall be determined using the design criteria established in Sections 1807 A .3.2.1 through 1807 A .3.2.3, or by other methods approved by the building official.

1807 A .3.2.1 Nonconstrained. The following formula shall be used in determining the depth of embedment required to resist lateral loads where lateral constraint is not provided at the ground surface, such as by a rigid floor or rigid ground surface pavement, and where lateral constraint is not provided above the ground surface, such as by a structural diaphragm. Equation 18 A -1 d = 0.5 A {1 + [1 + (4.36 h/A )] [1/2] }

18A-10 2025 CALIFORNIA BUILDING CODE

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

SOILS AND FOUNDATIONS

where:

A = 2.34 P /( S 1 b ).

b = Diameter of round post or footing or diagonal dimension of square post or footing, feet (m).

d = Depth of embedment in earth in feet (m) but not over 12 feet (3658 mm) for purpose of computing lateral pressure.

h = Distance in feet (m) from ground surface to point of application of “ P .”

P = Applied lateral force in pounds (kN).

S 1 = Allowable lateral soil-bearing pressure as set forth in Section 1806 A .2 based on a depth of one-third the depth of embedment in pounds per square foot (psf) (kPa).

1807 A .3.2.2 Constrained. The following formula shall be used to determine the depth of embedment required to resist lateral loads where lateral constraint is provided at the ground surface, such as by a rigid floor or slab-on-ground.

Equation 18 A -2

or alternatively

Equation 18 A -3 d = ----------------- g - where: 3

M g = Moment in the post at grade, in foot-pounds (kN-m). S 3 = Allowable lateral soil-bearing pressure as set forth in Section 1806.2 based on a depth equal to the depth of embedment in pounds per square foot (kPa).

1807 A .3.2.3 Vertical load. The resistance to vertical loads shall be determined using the vertical foundation pressure set forth in Table 1806 A .2.

Frequently asked questions

Do I ever have to do soil testing if I want to use the presumptive values?

If the building official has reason to doubt soil classification, strength or compressibility you must satisfy the geotechnical investigation requirement in § 1803.5.2; otherwise the table may be used as allowed in § 1806.2.

Can I increase the tabular vertical bearing when seismic or wind loads are included?

Yes — § 1806.1 permits increasing the vertical foundation pressure and lateral bearing pressure from Table 1806.2 by one‑third when those values are used with the CBC alternative ASD load combinations that include wind or earthquake (see § 1605.2).

Can I use the table on undocumented fill or peat?

No. § 1806.2 explicitly states that mud, organic silt, organic clays (OL, OH), peat (Pt) and undocumented fill shall not be assumed to have a presumptive capacity unless supporting data are submitted and approved.

How do I combine lateral bearing and sliding resistance?

Combine the two contributions per § 1806.3.1. Note limits: sliding resistance for clays is limited to one‑half the dead load (§ 1806.3.2) and lateral bearing increases with depth are limited to 15× the tabular value (§ 1806.3.3).

Are the tabular coefficients applied to dead load or total load?

The table footnote states the coefficient of friction is to be multiplied by the dead load (not the full factored lateral load). Use the table footnote rules and the sliding‑limit language in § 1806.3.2 when computing sliding resistance.

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Foundation Design: Capacity, Settlement & Expansive Soils

California Building Code