CBC · California Building Code

How is the structural integrity of deep foundation elements verified when defects are suspected?

If a pile or deep foundation is suspected to be defective, the CBC (§ 1705.10) requires an engineering assessment that uses approved ASTM defect‑detection tests (for example ASTM D4945) and, when capacity is in doubt, control load tests per the deep foundation rules (for example § 1810.3.3.1.2). A registered design professional and the geotechnical engineer evaluate results and the code limits allowable design loads (for load tests the allowable is capped at one‑half the assessed ultimate).

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Last reviewed: July 5, 2026

What the code requires — 2-4 sentences

When there is reasonable doubt about a deep foundation element’s structural integrity the CBC requires an engineering assessment that includes defect-detection tests performed to specified ASTM methods. The requirement is stated in § 1705.10: the assessment shall include tests for defects in accordance with ASTM D4945, ASTM D5882, ASTM D6760, ASTM D7949 or another approved method.

Requirements in detail

Trigger and scope: when an assessment is required

Trigger: “reasonable doubt” as to the structural integrity of a deep foundation element requires an engineering assessment under § 1705.10.
Scope: the engineering assessment must address the suspected defect(s) and include appropriate testing methods for the element type (cast‑in‑place, driven, grouted, steel, micropile, helical, etc.). For related test/acceptance and load‑test rules see the deep foundation provisions in Chapter 18 (for example, load test requirements in § 1810.3.3.1.2).

Approved test methods

The CBC explicitly names ASTM D4945, D5882, D6760 and D7949 as acceptable procedures for detecting defects and states that other approved methods may be used per § 1705.10. Use the method appropriate to the element type and the suspected defect.
Where the design load or capacity is in doubt, the code also prescribes load testing (for example ASTM D1143 or ASTM D4945 for certain cast‑in‑place or control test elements) under § 1810.3.3.1.2.

Who performs the assessment and reporting

An engineering assessment is required (a registered design professional is implied by context of the chapter and the requirements for control tests and load evaluations). The geotechnical engineer or responsible registered design professional typically directs or performs the assessment and prepares the report for the building official. The code also describes duties of the geotechnical engineer and verified reporting requirements elsewhere in the chapter.

How test results are evaluated and limits used

If load testing is performed to establish capacity the resulting allowable loads for subsequent elements are limited by the code: the allowable loads shall not exceed one‑half of the test element’s ultimate axial load capacity as assessed by the published evaluation methods listed in § 1810.3.3.1.3 (Davisson, Brinch‑Hansen 90% criterion, Butler‑Hoy, or other approved methods). Use a registered design professional to determine ultimate capacity with consideration for settlement and test details.
The code also limits assumed shaft resistance for uncased cast‑in‑place elements (shaft resistance shall not exceed one‑sixth of the bearing value at minimum depth, up to 500 psf), which affects interpretations of integrity when tests indicate degraded shaft/end bearing.

Decision‑relevant dimensions / values

Decision item	Key value or threshold	Code reference
Tests explicitly accepted for defect detection	ASTM D4945, D5882, D6760, D7949 (or other approved method)	§ 1705.10
When load testing required for capacity in doubt	Control test elements tested in accordance with ASTM D1143 or ASTM D4945 (where prescribed)	§ 1810.3.3.1.2
Allowable load from a successful load test	≤ 1/2 of the ultimate axial load assessed from the load test	§ 1810.3.3.1.2
Load test evaluation methods	Davisson offset limit, Brinch‑Hansen 90% criterion, Butler‑Hoy, or other approved methods	§ 1810.3.3.1.3
Assumed shaft resistance (uncased cast‑in‑place)	≤ 1/6 of bearing value at minimum depth, up to 500 psf	§ 1810.3.3.1.4
Maximum allowable compressive load (driven piles by formula) without wave equation	40 tons (356 kN) limit when using driving formulas; above this, wave equation analysis required	§ 1810.3.3.1.1
Minimum diameters (cast‑in‑place uncased)	Specified diameter not less than 12 in.; with permanent casing nominal OD not less than 8 in.	§ 1810.3.5.2.1–2.2

Exceptions & special cases

Building official discretion: where approved by the building official, load testing may not be required (exception noted in the allowable load/determination provisions). Always verify with the local enforcement agency.
Element type specifics: micropiles, helical piles and specialty elements have additional or different testing and production test requirements elsewhere in Chapter 18 (for example, micropile and helical pile test references and production testing rules). The engineering assessment should follow the element‑specific rules and the geotechnical report.
Bent or sharply curved elements: when piles are bent there are explicit requirements to confirm capacity either by approved analysis or by load testing a representative element. § 1810.3.3.1.8 addresses bent deep foundation elements.

Common mistakes

Running the wrong test: using a non‑approved or inappropriate ASTM procedure for the suspected defect. § 1705.10 names specific ASTM standards; other methods must be approved.
Treating a nondestructive integrity test as a capacity test: sonic or cross‑hole tests (e.g., ASTM D4945) detect defects or anomalies but do not by themselves establish axial capacity unless code‑required load testing or other capacity evaluations are also performed per § 1810.3.3.1.2.
Misreading allowable vs. ultimate: after a load test the code caps allowable design loads at one‑half of the assessed ultimate from the test—do not assume ultimate equals allowable. § 1810.3.3.1.2.
Failing to involve the geotechnical engineer / registered design professional: the code anticipates qualified design professionals direct testing, evaluate results and submit verified reports.

Worked example — application with numbers

Scenario: A cast‑in‑place concrete pile is suspected of having a necking/void at mid‑depth after visual and drilling records raise “reasonable doubt.” The RDP orders an integrity test and, because capacity is also in question, a control load test.

Integrity test: Perform ASTM D4945 sonic/impulse echo testing per § 1705.10 to map anomalies and guide whether a load test is required. § 1705.10 names ASTM D4945 as an acceptable test.
Load test: A control element is load tested in accordance with ASTM D1143 (code reference for cast‑in‑place control test requirement is § 1810.3.3.1.2). If the load test evaluation (for example Butler‑Hoy or Davisson) yields an ultimate axial capacity of 200 kips, then the code limits the allowable axial load used for design/acceptance to no more than one‑half of that ultimate (≤ 100 kips) for subsequent like elements. § 1810.3.3.1.2.
Interpretation: If the integrity test indicates a localized void but the load test shows ultimate ≥ 200 kips and the registered design professional judges settlements acceptable, the element group may be accepted at an allowable ≤ 100 kips (per § 1810.3.3.1.2) provided elements are of comparable type, installation, and subsoil conditions.

Related provisions

§ 1705.10 — Structural integrity of deep foundation elements (ASTM test methods).
§ 1810.3.3.1.2 — Load tests for deep foundations (ASTM D1143, ASTM D4945 referenced).
§ 1810.3.3.1.3 — Load test evaluation methods (Davisson, Brinch‑Hansen, Butler‑Hoy).
§ 1810.3.3.1.4 — Allowable shaft resistance limits for uncased cast‑in‑place elements.
§ 1810.3.3.1.1 — Driving criteria and 40‑ton threshold for driven piles when using driving formulas.
§ 1810.3.5.2 — Minimum diameters and dimensional requirements for cast‑in‑place elements.
Geotechnical engineer duties and verified reporting requirements (special inspections context).

Code references

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

CBC § 1705.10 High relevance — show source text
1705.10 Structural integrity of deep foundation elements. Whenever there is a reasonable doubt as to the structural integrity of a deep foundation element, an engineering assessment shall be required. The engineering assessment shall include tests for defects performed in accordance with ASTM D4945, ASTM D5882, ASTM D6760 or ASTM D7949, or other approved method.

1705.11 Fabricated items. Special inspections of fabricated items shall be performed in accordance with Section 1704.2.5.

1705.12 Special inspections for wind resistance. Special inspections for wind resistance specified in Sections 1705.12.1 through 1705.12.3, unless exempted by the exceptions to Section 1704.2, are required for buildings and structures constructed in the following areas:
1. In wind Exposure Category B, where basic wind speed, V, is 150 mph (67 m/sec) or greater.
2. In wind Exposure Category C or D, where basic wind speed, V, is 140 mph (62.6 m/sec) or greater.
1705.12.1 Structural wood. Continuous special inspection is required during field gluing operations of elements of the main windforce-resisting system. Periodic special inspection is required for nailing, bolting, anchoring and other fastening of elements of the main windforce-resisting system, including wood shear walls, wood diaphragms, drag struts, braces and hold-downs.

Exception: Special inspections are not required for wood shear walls, shear panels and diaphragms, including nailing, bolting, anchoring and other fastening to other elements of the main windforce-resisting system, where the lateral resistance is provided by structural sheathing and the specified fastener spacing at panel edges is more than 4 inches (102 mm) on center.

1705.12.2 Cold-formed steel light-frame construction. Periodic special inspection is required for welding operations of elements of the main windforce-resisting system. Periodic special inspection is required for screw attachment, bolting, anchoring and other fastening of elements of the main windforce-resisting system, including shear walls, braces, diaphragms, collectors (drag struts) and hold-downs.

Exception: Special inspections are not required for cold-formed steel light-frame shear walls and diaphragms, including screwing, bolting, anchoring and other fastening to components of the windforce-resisting system, where either of the following applies:
1. The sheathing is gypsum board or fiberboard.
2. The sheathing is wood structural panel or steel sheets on only one side of the shear wall, shear panel or diaphragm assembly and the specified fastener spacing at the panel or sheet edges is more than 4 inches (102 mm) on center (o.c.).
1705.12.3 Wind-resisting components. Periodic special inspection is required for fastening of the following systems and components:
1. Roof covering, roof deck and roof framing connections.
2. Exterior wall covering and wall connections to roof and floor diaphragms and framing.
1705.13 Special inspections for seismic resistance. Special inspections for seismic resistance shall be required as specified in Sections 1705.13.1 through 1705.13.9, unless exempted by the exceptions of Section 1704.2.

Exception: The special inspections specified in Sections 1705.13.1 through 1705.13.9 are not required for structures designed and constructed in accordance with one of the following: 1.
CBC § 2.5. High relevance — show source text
1705 A .10 Structural integrity of deep foundation elements. Whenever there is a reasonable doubt as to the structural integrity of a deep foundation element, an engineering assessment shall be required. The engineering assessment shall include tests for defects performed in accordance with ASTM D4945, ASTM D5882, ASTM D6760 or ASTM D7949, or other approved method.

1705 A .11 Fabricated items. Special inspections of fabricated items shall be performed in accordance with Section 1704 A .2.5.

1705 A .12 Special inspections for wind resistance. Special inspections for wind resistance specified in Sections 1705 A .12.1 through 1705 A .12.3, unless exempted by the exceptions to Section 1704 A .2, are required for buildings and structures constructed in the following areas:
1. In wind Exposure Category B, where basic wind speed, V, is 150 mph (67 m/sec) or greater.
2. In wind Exposure Category C or D, where basic wind speed, V, is 140 mph (62.6 m/sec) or greater.
1705 A .12.1 Structural wood. Continuous special inspection is required during field gluing operations of elements of the main windforce-resisting system. Periodic special inspection is required for nailing, bolting, anchoring and other fastening of elements of the main windforce-resisting system, including wood shear walls, wood diaphragms, drag struts, braces and hold-downs.

1705 A .12.2 Cold-formed steel light-frame construction. Periodic special inspection is required for welding operations of elements of the main windforce-resisting system. Periodic special inspection is required for screw attachment, bolting, anchoring and other fastening of elements of the main windforce-resisting system, including shear walls, braces, diaphragms, collectors (drag struts) and hold-downs. [DSA-SS, DSA-SS/CC] Requirements specified in Section 1705A.2.9 shall also apply.

1705 A .12.3 Wind-resisting components. Periodic special inspection is required for fastening of the following systems and components:
1. Roof covering, roof deck and roof framing connections.
2. Exterior wall covering and wall connections to roof and floor diaphragms and framing.
1705 A .13 Special inspections for seismic resistance. Special inspections for seismic resistance shall be required as specified in Sections 1705 A .13.1 through 1705 A .13.9, unless exempted by the exceptions of Section 1704 A .2.

1705 A .13.1 Structural steel. Special inspections for seismic resistance shall be in accordance with Section 1705 A .13.1.1 or 1705 A .13.1.2, as applicable.

1705 A .13.1.1 Seismic force-resisting systems. Special inspections of structural steel in the seismic force-resisting systems in buildings and structures assigned to Seismic Design Category D, E or F shall be performed in accordance with the quality assurance requirements of AISC 341 and this code.

CBC § 1705.8 High relevance — show source text

TABLE 1705.8—REQUIRED SPECIAL INSPECTIONS AND TESTS OF CAST-IN-PLACE DEEP FOUNDATION ELEMENTS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1. Inspect drilling operations and maintain complete and accurate records for each element.	X	—
2. Verify placement locations and plumbness, confirm element diameters, bell diameters (if applicable), lengths, embedment into bedrock (if applicable) and adequate end-bearing strata capacity. Record concrete or grout volumes.	X	—
3. For concrete elements, perform tests and additional special inspections in accordance with Section 1705.3.	In accordance with Section 1705.3	In accordance with Section 1705.3

1705.9 Helical pile foundations. Continuous special inspections shall be performed during installation of helical pile foundations. The information recorded shall include installation equipment used, pile dimensions, tip elevations, final depth, final installation torque and other pertinent installation data as required by the registered design professional in responsible charge. The approved

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SPECIAL INSPECTIONS AND TESTS

geotechnical report and the construction documents prepared by the registered design professional shall be used to determine compliance.

1705.10 Structural integrity of deep foundation elements. Whenever there is a reasonable doubt as to the structural integrity of a deep foundation element, an engineering assessment shall be required. The engineering assessment shall include tests for defects performed in accordance with ASTM D4945, ASTM D5882, ASTM D6760 or ASTM D7949, or other approved method.

1705.11 Fabricated items. Special inspections of fabricated items shall be performed in accordance with Section 1704.2.5.

1705.12 Special inspections for wind resistance. Special inspections for wind resistance specified in Sections 1705.12.1 through 1705.12.3, unless exempted by the exceptions to Section 1704.2, are required for buildings and structures constructed in the following areas:

In wind Exposure Category B, where basic wind speed, V, is 150 mph (67 m/sec) or greater.
In wind Exposure Category C or D, where basic wind speed, V, is 140 mph (62.6 m/sec) or greater.

1705.12.1 Structural wood. Continuous special inspection is required during field gluing operations of elements of the main windforce-resisting system. Periodic special inspection is required for nailing, bolting, anchoring and other fastening of elements of the main windforce-resisting system, including wood shear walls, wood diaphragms, drag struts, braces and hold-downs.

Exception: Special inspections are not required for wood shear walls, shear panels and diaphragms, including nailing, bolting, anchoring and other fastening to other elements of the main windforce-resisting system, where the lateral resistance is provided by structural sheathing and the specified fastener spacing at panel edges is more than 4 inches (102 mm) on center.

CBC § 1705A.8 High relevance — show source text

TABLE 1705A.8—REQUIRED SPECIAL INSPECTIONS AND TESTS OF CAST-IN-PLACE DEEP FOUNDATION ELEMENTS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1. Inspect drilling operations and maintain complete and accurate records for each element.	X	—
2. Verify placement locations and plumbness, confirm element diameters, bell diameters (if applicable), lengths, embedment into bedrock (if applicable) and adequate end-bearing strata capacity. Record concrete or grout volumes.	X	—
3. For concrete elements, perform tests and additional special inspections in accordance with Section 1705_A_.3.	In accordance with Section 1705_A_.3	In accordance with Section 1705_A_.3

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1705A.8.1 Micropile tests. Micropile preproduction and production load tests shall be in accordance with Section 1810A.3.10.4.

1705 A .9 Helical pile foundations. Continuous special inspections shall be performed during installation of helical pile foundations. The information recorded shall include installation equipment used, pile dimensions, tip elevations, final depth, final installation torque and other pertinent installation data as required by the registered design professional in responsible charge. The approved geotechnical report and the construction documents prepared by the registered design professional shall be used to determine compliance.

1705A.9.1 Helical pile tests. Helical pile preproduction and production load tests shall be in accordance with Section 1810A.3.1.5.1.

1705 A .10 Structural integrity of deep foundation elements. Whenever there is a reasonable doubt as to the structural integrity of a deep foundation element, an engineering assessment shall be required. The engineering assessment shall include tests for defects performed in accordance with ASTM D4945, ASTM D5882, ASTM D6760 or ASTM D7949, or other approved method.

1705 A .11 Fabricated items. Special inspections of fabricated items shall be performed in accordance with Section 1704 A .2.5.

1705 A .12 Special inspections for wind resistance. Special inspections for wind resistance specified in Sections 1705 A .12.1 through 1705 A .12.3, unless exempted by the exceptions to Section 1704 A .2, are required for buildings and structures constructed in the following areas:

In wind Exposure Category B, where basic wind speed, V, is 150 mph (67 m/sec) or greater.
In wind Exposure Category C or D, where basic wind speed, V, is 140 mph (62.6 m/sec) or greater.

1705 A .12.1 Structural wood. Continuous special inspection is required during field gluing operations of elements of the main windforce-resisting system. Periodic special inspection is required for nailing, bolting, anchoring and other fastening of elements of the main windforce-resisting system, including wood shear walls, wood diaphragms, drag struts, braces and hold-downs.

CBC § 1705.7 High relevance — show source text

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 INSPECTION	PERIODIC SPECIAL INSPECTION
1. Verify element materials, sizes and lengths comply with the requirements.	X	—
2. Determine capacities of test elements and conduct additional load tests, as required.	X	—
3. Inspect driving operations and maintain complete and accurate records for each element.	X	—
4. Verify placement locations and plumbness, confirm type and size of hammer, record number of blows per foot of penetration, determine required penetrations to achieve design capacity, record tip and butt elevations and document any damage to foundation element.	X	—
5. For steel elements, perform additional special inspections in accordance with Section 1705.2.	In accordance with Section 1705.2	In accordance with Section 1705.2
6. For concrete elements and concrete-filled elements, perform tests and additional special inspections in accordance with Section 1705.3.	In accordance with Section 1705.3	In accordance with Section 1705.3
7.For specialty elements, perform additional inspections as determined by the registered design professional in responsible charge.	In accordance with Statement of Special Inspections	In accordance with Statement of Special Inspections

1705.7.1 Driven deep foundations observation. [OSHPD 1R, 2 & 5] The installation of driven deep foundations shall be continu- ously observed by a qualified representative of the geotechnical engineer responsible for that portion of the project.

The representative of the geotechnical engineer shall make a report of the deep foundation pile-driving operation giving such pertinent data as the physical characteristics of the deep foundation pile-driving equipment, identifying marks for each deep founda- tion pile, total depth of embedment for each deep foundation; and when the allowable deep foundation pile loads are determined by a dynamic load formula, the design formula used, and the permanent penetration under the last 10 blows. One copy of the report shall be sent to the enforcement agency.

California Building Code Medium relevance — show source text

5
10
15|64
99
126
NA|613
594
565
NA|336
313
296
281|77
118
148
171|779
759
727
698|441
416
394
375|92
139
173
198|968
946
912
880|562
533
567
485|127
186
229
259|1376
1352
1315
1280|841
828
777
742| |20|2
5
10
15
20|61
95
122
NA
NA|678
658
627
NA
NA|375
350
332
314
296|73
113
143
165
186|867
845
811
780
750|491
463
440
418
397|87
133
167
191
214|1083
1059
1022
987
955|627
597
566
541
513|121
179
221
251
277|1548
1523
1482
1443
1406|953
933
879
840
807| |30|2
5
10
15
20
30|57
90
115
NA
NA
NA|762
741
709
NA
NA
NA|421
393
373
353
332
288|68
106
135
156
176
NA|985
962
927
893
860
NA|558
526
500
476
450
416|81
125
158
181
203
249|1240
1216
1176
1139
1103
1035|717
683
648
621
592
555|111
169
210
239
264
318|1793
1766
1721
1679
1638
1560|1112
1094
1025
981
940
877| |50|2
5

CBC § 1705A.6.2 Medium relevance — show source text

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

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

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

TABLE 1705A.7—REQUIRED SPECIAL INSPECTIONS AND TESTS OF DRIVEN DEEP FOUNDATION ELEMENTS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1. Verify element materials, sizes and lengths comply with the requirements.	X	—
2. Determine capacities of test elements and conduct additional load tests, as required.	X	—
3. Inspect driving operations and maintain complete and accurate records for each element.	X	—
4. Verify placement locations and plumbness, confirm type and size of hammer, record number of blows per foot of penetration, determine required penetrations to achieve design capacity, record tip and butt elevations and document any damage to foundation element.	X	—
5. For steel elements, perform additional special inspections in accordance with Section 1705_A_.2.	In accordance with Section 1705_A_.2	In accordance with Section 1705_A_.2
6. For concrete elements and concrete-filled elements, perform tests and additional special inspections in accordance with Section 1705_A_.3.	In accordance with Section 1705_A_.3	In accordance with Section 1705_A_.3
7. For specialty elements, perform additional inspections as determined by the registered design professional in responsible charge.	In accordance with Statement of Special Inspections	In accordance with Statement of Special Inspections

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1705A.7.1 Driven deep foundations observation. The installation of driven deep foundations shall be continuously observed by a qualified representative of the geotechnical engineer responsible for that portion of the project.

CBC § 1810.3.3.1.7 Medium relevance — show source text
1. The proposed individual allowable uplift load times the number of elements in the group.
2. Two-thirds of the effective weight of the group and the soil contained within a block defined by the perimeter of the group and the length of the element, plus two-thirds of the ultimate shear resistance along the soil block.
1810.3.3.1.7 Load-bearing capacity. Deep foundation elements shall develop ultimate load capacities of not less than twice the design working loads in the designated load-bearing layers. Analysis shall show that soil layers underlying the designated load-bearing layers do not cause the load-bearing capacity safety factor to be less than two.

1810.3.3.1.8 Bent deep foundation elements. The load-bearing capacity of deep foundation elements discovered to have a sharp or sweeping bend shall be determined by an approved method of analysis or by load testing a representative element.

1810.3.3.1.9 Helical piles. The allowable axial design load, P a, of helical piles shall be determined as follows:

Equation 18-4 P a = 0.5 P u

where P u is the least value of:

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SOILS AND FOUNDATIONS
1. Base capacity plus shaft resistance of the helical pile . The base capacity is equal to the sum of the areas of the helical bearing plates times the ultimate bearing capacity of the soil or rock comprising the bearing stratum. The shaft resistance is equal to the area of the shaft above the uppermost helical bearing plate times the ultimate skin resistance.
2. Ultimate capacity determined from well-documented correlations with installation torque.
3. Ultimate capacity determined from load tests where required by Section 1810.3.3.1.2. [OSHPD 1R, 2 & 5] Load tests are required to determine the ultimate capacity.
4. Ultimate axial capacity of pile shaft.
5. Ultimate axial capacity of pile shaft couplings.
6. Sum of the ultimate axial capacity of helical bearing plates affixed to pile.
1810.3.3.2 Allowable lateral load. Where required by the design, the lateral load capacity of a single deep foundation element or a group thereof shall be determined by an approved method of analysis or by lateral load tests to not less than twice the proposed design working load. The resulting allowable lateral load shall not be more than one-half of the load that produces a gross lateral movement of 1 inch (25 mm) at the lower of the top of the foundation element and the ground surface, unless it can be shown that the predicted lateral movement shall cause neither harmful distortion of, nor instability in, the structure, nor cause any element to be loaded beyond its capacity. Group effects shall be evaluated where required by Section 1810.2.5.

1810.3.4 Subsiding soils or strata. Where deep foundation elements are installed through subsiding soils or other subsiding strata and derive support from underlying firmer materials, consideration shall be given to the downward frictional forces potentially imposed on the elements by the subsiding upper strata.

Where the influence of subsiding soils or strata is considered as imposing loads on the element, the allowable stresses specified in this chapter shall be permitted to be increased where satisfactory substantiating data are submitted.
CBC § 3.3.1.3 Medium relevance — show source text
One element or more shall be load tested in each area of uniform subsoil conditions. Where required by the building official, additional elements shall be load tested where necessary to establish the safe design capacity. The resulting allowable loads shall not be more than one-half of the ultimate axial load capacity of the test element as assessed by one of the published methods listed in Section 1810 A .3.3.1.3 with consideration for the test type, duration and subsoil. The ultimate axial load capacity shall be determined by a registered design professional with consideration given to tolerable total and differential settlements at design load in accordance with Section 1810 A .2.3. In subsequent installation of the balance of deep foundation elements, all elements shall be deemed to have a supporting capacity equal to that of the control element where such elements are of the same type, size and relative length as the test element; are installed using the same or comparable methods and equipment as the test element; are installed in similar subsoil conditions as the test element; and, for driven elements, where the rate of penetration (for example, net displacement per blow) of such elements is equal to or less than that of the test element driven with the same hammer through a comparable driving distance, or where the downward pressure and torque on such elements is greater than or equal to that applied to the test element that determined the ultimate axial load capacity at a comparable driving distance.

1810 A .3.3.1.3 Load test evaluation methods. It shall be permitted to evaluate load tests of deep foundation elements using any of the following methods:
1. Davisson Offset Limit.
2. Brinch-Hansen 90-percent Criterion.
3. Butler-Hoy Criterion.
4. Other methods approved by the building official.
1810 A .3.3.1.4 Allowable shaft resistance. The assumed shaft resistance developed by any uncased cast-in-place deep foundation element shall not exceed one-sixth of the bearing value of the soil material at minimum depth as set forth in Table 1806 A .2, up to 500 psf (24 kPa), unless a greater value is allowed by the building official on the basis of a geotechnical investigation as specified in Section 1803 A or a greater value is substantiated by a load test in accordance with Section 1810 A .3.3.1.2. Shaft resistance and end-bearing resistance shall not be assumed to act simultaneously unless determined by a geotechnical investigation in accordance with Section 1803 A .

1810 A .3.3.1.5 Uplift capacity of a single deep foundation element. Where required by the design, the uplift capacity of a single deep foundation element shall be determined by an approved method of analysis based on a minimum factor of safety of three or by load tests conducted in accordance with ASTM D3689. The maximum allowable uplift load shall not exceed the ultimate load capacity as determined in Section 1810 A .3.3.1.2, using the results of load tests conducted in accordance with ASTM D3689 divided by a factor of safety of two.

Exception: Where uplift is due to wind or seismic loading, the minimum factor of safety shall be two where capacity is determined by an analysis and one and one-half where capacity is determined by load tests.
CBC § 2.3.6 Medium relevance — show source text
1. In the case of rotational restraint, the anchorage shall be designed to resist the axial and shear forces, and moments resulting from the seismic load effects including overstrength factor in accordance with Section 2.3.6 or 2.4.5 of ASCE 7 or the anchorage shall be capable of developing the full axial, bending and shear nominal strength of the element.
2. The connection between the pile cap and the steel H-piles or unfilled steel pipe piles in structures assigned to Seismic Design Category D, E or F shall be designed for a tensile force of not less than 10 percent of the pile compression capacity.
2025 CALIFORNIA BUILDING CODE 18-29

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

SOILS AND FOUNDATIONS

Exceptions:
1. Connection tensile capacity need not exceed the strength required to resist seismic load effects including overstrength of ASCE 7 Section 12.4.3 or 12.14.3.2.
2. Connections need not be provided where the foundation or supported structure does not rely on the tensile capacity of the piles for stability under the design seismic force. [OSHPD 1R, 2 & 5] Not permitted by OSHPD.
Where the vertical lateral-force-resisting elements are columns, the pile cap flexural strengths shall exceed the column flexural strength. The connection between batter piles and pile caps shall be designed to resist the nominal strength of the pile acting as a short column. Batter piles and their connection shall be designed to resist forces and moments that result from the application of seismic load effects including overstrength factor in accordance with Section 2.3.6 or 2.4.5 of ASCE 7.

1810.3.12 Grade beams. Grade beams shall comply with the provisions of ACI 318.

Exception: Grade beams not subject to differential settlement exceeding one-fourth of the thresholds specified in ASCE 7 Table 12.13-3 and designed to resist the seismic load effects including overstrength factor in accordance with Section 2.3.6 or 2.4.5 of ASCE 7 need not comply with ACI 318 Section 18.13.3.1.

1810.3.13 Seismic ties. Seismic ties shall comply with the provisions of ACI 318.

Exception: In Group R-3 and U occupancies of light-frame construction, deep foundation elements supporting foundation walls, isolated interior posts detailed so the element is not subject to lateral loads or exterior decks and patios are not subject to interconnection where the soils are of adequate stiffness, subject to the approval of the building official.

1810.4 Installation. Deep foundations shall be installed in accordance with Section 1810.4. Where a single deep foundation element comprises two or more sections of different materials or different types spliced together, each section shall satisfy the applicable conditions of installation.

1810.4.1 Structural integrity. Deep foundation elements shall be installed in such a manner and sequence as to prevent distortion or damage that would adversely affect the structural integrity of adjacent structures or of foundation elements being installed or already in place and as to avoid compacting the surrounding soil to the extent that other foundation elements cannot be installed properly.
CBC § 3.3.1.4 Medium relevance — show source text
1. Davisson Offset Limit.
2. Brinch-Hansen 90-percent Criterion.
3. Butler-Hoy Criterion.
4. Other methods approved by the building official.
1810 A .3.3.1.4 Allowable shaft resistance. The assumed shaft resistance developed by any uncased cast-in-place deep foundation element shall not exceed one-sixth of the bearing value of the soil material at minimum depth as set forth in Table 1806 A .2, up to 500 psf (24 kPa), unless a greater value is allowed by the building official on the basis of a geotechnical investigation as specified in Section 1803 A or a greater value is substantiated by a load test in accordance with Section 1810 A .3.3.1.2. Shaft resistance and end-bearing resistance shall not be assumed to act simultaneously unless determined by a geotechnical investigation in accordance with Section 1803 A .

1810 A .3.3.1.5 Uplift capacity of a single deep foundation element. Where required by the design, the uplift capacity of a single deep foundation element shall be determined by an approved method of analysis based on a minimum factor of safety of three or by load tests conducted in accordance with ASTM D3689. The maximum allowable uplift load shall not exceed the ultimate load capacity as determined in Section 1810 A .3.3.1.2, using the results of load tests conducted in accordance with ASTM D3689 divided by a factor of safety of two.

Exception: Where uplift is due to wind or seismic loading, the minimum factor of safety shall be two where capacity is determined by an analysis and one and one-half where capacity is determined by load tests.

1810 A .3.3.1.6 Allowable uplift load of grouped deep foundation elements. For grouped deep foundation elements subjected to uplift, the allowable uplift load for the group shall be calculated by a generally accepted method of analysis.

18A-18 2025 CALIFORNIA BUILDING CODE

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

SOILS AND FOUNDATIONS

Where the deep foundation elements in the group are placed at a center-to-center spacing less than three times the least horizontal dimension of the largest single element, the allowable uplift load for the group is permitted to be calculated as the lesser of:
1. The proposed individual allowable uplift load times the number of elements in the group.
2. Two-thirds of the effective weight of the group and the soil contained within a block defined by the perimeter of the group and the length of the element, plus two-thirds of the ultimate shear resistance along the soil block.
1810 A .3.3.1.7 Load-bearing capacity. Deep foundation elements shall develop ultimate load capacities of not less than twice the design working loads in the designated load-bearing layers. Analysis shall show that soil layers underlying the designated load-bearing layers do not cause the load-bearing capacity safety factor to be less than two.

1810 A .3.3.1.8 Bent deep foundation elements. The load-bearing capacity of deep foundation elements discovered to have a sharp or sweeping bend shall be determined by an approved method of analysis or by load testing a representative element.

1810 A .3.3.1.9 Helical piles. The allowable axial design load, P a, of helical piles shall be determined as follows:

CBC § 17A-15 Medium relevance — show source text

For steel elements, perform additional special inspections in accordance with Section 1705_A_.2.|In accordance with Section 1705_A_.2|In accordance with Section 1705_A_.2| |6. For concrete elements and concrete-filled elements, perform tests and additional special
inspections in accordance with Section 1705_A_.3.|In accordance with Section 1705_A_.3|In accordance with Section 1705_A_.3| |7. For specialty elements, perform additional inspections as determined by the registered design
professional in responsible charge.|In accordance with Statement of Special
Inspections|In accordance with Statement of Special
Inspections|

2025 CALIFORNIA BUILDING CODE 17A-15

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

SPECIAL INSPECTIONS AND TESTS

1705 A .8 Cast-in-place deep foundations. Special inspections and tests shall be performed during installation of cast-in-place deep foundation elements as specified in 1810A.3.3.1.2 and Table 1705 A .8. The approved geotechnical report and the construction documents prepared by the registered design professionals shall be used to determine compliance.

TABLE 1705A.8—REQUIRED SPECIAL INSPECTIONS AND TESTS OF CAST-IN-PLACE DEEP FOUNDATION ELEMENTS	Col2	Col3
TYPE	CONTINUOUS SPECIAL INSPECTION	PERIODIC SPECIAL INSPECTION
1. Inspect drilling operations and maintain complete and accurate records for each element.	X	—
2. Verify placement locations and plumbness, confirm element diameters, bell diameters (if applicable), lengths, embedment into bedrock (if applicable) and adequate end-bearing strata capacity. Record concrete or grout volumes.	X	—
3. For concrete elements, perform tests and additional special inspections in accordance with Section 1705_A_.3.	In accordance with Section 1705_A_.3	In accordance with Section 1705_A_.3

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1705A.8.1 Micropile tests. Micropile preproduction and production load tests shall be in accordance with Section 1810A.3.10.4.

Frequently asked questions

Who decides whether a proposed alternative test method is acceptable?

The building official must approve alternative or other test methods beyond the ASTM standards listed in § 1705.10.

Does an integrity test alone establish pile capacity?

No. Integrity (nondestructive) tests detect defects or anomalies; where capacity is in doubt the code calls for control load testing or other approved capacity evaluations per § 1810.3.3.1.2.

Can a building official waive load testing?

Yes—where approved by the building official load testing may not be required; verify local enforcement interpretations and conditions in the project documents.

If a load test shows ultimate capacity, how is allowable derived?

The CBC caps allowable load from a load test at no more than one‑half of the assessed ultimate axial load (with proper evaluation methods), per § 1810.3.3.1.2.

Who must prepare the assessment report?

A registered design professional / geotechnical engineer or their qualified representative typically directs testing and prepares the verified report required by the code. § 1705.10 triggers the assessment and other sections describe geotechnical engineer duties and reporting.

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Foundations & Soils — Required Inspections and Testing

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