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Building Code Reference

Got a CBC 1803.6 correction?

Geotechnical report contents

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CBC 1803.6 sets what goes in the geotechnical (soils) report and when it is due. Where a geotechnical investigation is required, the permit applicant must submit a written report to the building official at the time of permit application. The report must include a plot of the investigation locations, the boring and penetration test logs, the soil profile, the water table elevation if encountered, foundation type and design criteria such as bearing capacity and how to handle expansive soil, liquefaction and differential settlement, and expected total and differential settlement. Investigations are required under Section 1803, for example for structures in Seismic Design Category C through F, unless the building official waives one.

How to fix it

  1. Confirm your project needs a geotechnical report

    Read the correction and the jurisdiction's submittal requirements. CBC 1803.2 calls for a geotechnical investigation and lets the building official waive it where satisfactory data from adjacent areas shows one is not needed, and 1803.5 lists conditions it must address, including questionable soil, expansive soil and structures in Seismic Design Category C through F. If you are unsure, ask the building department whether your project needs a report before the foundation is designed, not after the first correction.

  2. Submit the full report with the permit application

    CBC 1803.6 requires the written report to be submitted to the building official by the permit applicant at the time of permit application. Upload the complete signed report with the first submittal, not an excerpt or a cover letter. Reference it by firm, report number and date in the structural general notes so the reviewer can tie the drawings to it.

  3. Check the report against the 1803.6 contents list

    Before you submit, confirm the report includes a plot showing where the soil investigations were done, the boring and penetration test logs and soil samples, the soil profile, the water table elevation if encountered, foundation type and design criteria (bearing capacity, expansive soil mitigation, liquefaction, differential settlement and varying soil strength, and the effects of adjacent loads), and expected total and differential settlement. Where it applies, it also needs deep foundation information, special provisions for expansive soil, and compacted fill or controlled low-strength material properties and testing. If an item is missing, ask the geotechnical engineer for an addendum.

  4. Carry the report's numbers onto the foundation plan

    Cross-check the allowable bearing pressure, footing depth and width, slab and moisture recommendations, and any expansive soil or fill provisions in the report against the foundation plan and structural calculations. If the structural engineer designed to 2,000 psf and the soils report allows 1,500 psf, you have a discrepancy that must be resolved in writing before permit issuance. CBC 1806.2 does not let design values exceed the presumptive values in Table 1806.2 unless data to substantiate higher values are submitted and approved.

  5. Add the soils special inspection note where it applies

    Where special inspections apply, add a general note on the foundation plan sheet that reads something like: 'Soils special inspection per CBC 1705.6 and Table 1705.6: verify materials below shallow foundations are adequate to achieve the design bearing capacity, and verify excavations are extended to proper depth and have reached proper material, per the approved geotechnical report.' List the same items in the statement of special inspections, which CBC 1704.2.3 requires as a condition of permit issuance. If the report asks for the geotechnical engineer to observe the footing excavations, repeat that requirement in the note.

  6. Get a written update when the design or site changes

    If the foundation design changes after the report was written, or the site has been graded or filled since, ask the geotechnical engineer for a signed update letter or addendum that addresses the change, and submit it with the revised drawings. A letter confirming the original recommendations still apply is often enough when nothing material has changed. If the update changes a recommendation, the foundation plan has to be revised to match.

  7. Resubmit with page and sheet references

    In the response letter, cite the report by firm, number and date, give the report page where each 1803.6 item appears, and point to the sheet and note where its recommendations are carried into the foundation design. Cloud the revised notes on the foundation plan. A reviewer who can find each item in one pass clears the correction faster than one who has to hunt through a 40-page report.

Take the CBC 1803.6 fix steps with you

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Why you got flagged

The most common reason plans get flagged on CBC 1803.6 is that the soils report is missing from the submittal. The section requires the report to be submitted by the permit applicant at the time of permit application, so a reviewer who sees a foundation designed to specific soil values with no report in the file will stop and ask for it.

A second scenario is a report that is missing required contents. A short letter that states a bearing value but has no boring logs, no plot of where the borings were taken, no soil profile or no settlement estimate does not meet the list in 1803.6. Plan-checkers also flag reports that are silent on expansive soil or liquefaction when the site conditions call for it, and reports that leave out compacted fill specifications when the footings will bear on fill.

A third is a mismatch between the report and the drawings. The report recommends a footing type, depth, bearing value or slab treatment, and the foundation plan or structural calculations use something different. Plan-checkers compare the two. Under CBC 1806.2, a bearing value higher than the code's presumptive values needs approved data to back it, so a foundation designed to a higher pressure than the report allows draws a correction until the drawings or the report are revised in writing.

A fourth is construction-phase follow-through. Where special inspections apply, CBC 1705.6 and Table 1705.6 call for verifying that materials below shallow foundations can achieve the design bearing capacity and that excavations reach proper depth and material, judged against the approved geotechnical report. When the report recommends that the geotechnical engineer observe the footing excavations, reviewers often ask for that to be noted on the foundation plan and listed in the statement of special inspections. That observation comes from special inspection and the report's own recommendations, not from 1803.6.

The official code

California Building Code 2025 (Title 24 Part 2), Section 1803.6 Reporting, geotechnical report contents

Read the source →

Common questions

What does CBC 1803.6 require the soils report to include?
At minimum: a plot showing the location of the soil investigations, a complete record of the boring and penetration test logs and soil samples, a record of the soil profile, the water table elevation if encountered, recommendations for foundation type and design criteria, and expected total and differential settlement. The design criteria include bearing capacity, provisions to mitigate expansive soil, mitigation of liquefaction, differential settlement and varying soil strength, and the effects of adjacent loads. Where they apply, the report also covers deep foundations, special provisions for expansive soil, and compacted fill or controlled low-strength material properties and testing.
When is the geotechnical report due?
At the time of permit application. CBC 1803.6 requires the permit applicant to submit the written report to the building official when the application is made, because the foundation design depends on it. Submitting the report late is one of the most common reasons for a first-round correction. If the structural engineer is still waiting on the report, hold the submittal or ask the building department how they want to sequence it.
Does CBC 1803.6 apply to single-family homes and ADUs?
CBC 1803.6 governs projects reviewed under the California Building Code. Homes reviewed under the California Residential Code follow CRC R401.4 instead: where data indicate expansive, compressible, shifting or other questionable soils, the building official decides whether to require a soil test. Where soil testing is performed and the seismic design category is C or greater, the report must include the site class and SDS in accordance with CBC 1613. Without a complete geotechnical evaluation, the presumptive values in CRC Table R401.4.1(1) are assumed. Check your permit conditions or ask the building department directly.
Does CBC 1803.6 require the soils engineer to inspect the footing excavations?
No. CBC 1803.6 covers the report submitted with the permit application. Excavation verification comes from special inspection: CBC Table 1705.6 lists periodic special inspection to verify that materials below shallow foundations can achieve the design bearing capacity and that excavations extend to proper depth and have reached proper material, using the approved geotechnical report to judge compliance. Under CBC 1704.2, the owner or the owner's agent, not the contractor, employs the approved agency, and some work is exempt, such as Group U buildings accessory to a residence unless the building official requires it. Many soils reports also recommend that the geotechnical engineer observe the excavations; when yours does, put it on the foundation plan.
What if the report's bearing value doesn't match the foundation design?
Resolve it in writing before permit issuance. Either the structural engineer revises the design to the value the report allows, or the geotechnical engineer issues an addendum supporting the value used. CBC 1806.2 does not allow design values above the presumptive values in Table 1806.2 unless data to substantiate the higher values are submitted and approved, so a higher design value with no report behind it will not clear plan check.
My soils report is several years old. Is it still valid?
CBC 1803.6 does not set an expiration date for a report, but plan-checkers may question an older one, especially on sites that have been graded, filled or affected by drainage changes since. If nothing has changed on the lot, the geotechnical engineer can typically write a letter stating the original report still applies to the current design. If conditions have changed, expect a site visit and an updated evaluation. Check with your building department before submitting to avoid a correction.

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