Section 508C — ALLOWABLE DESIGN VALUES

508C.7 Foundations.

San Francisco Building Inspection Commission Codes · 2022 edition · ingested 2026-07-08 · San Francisco

508C.7 Foundations. For existing foundations, new total dead loads may be increased over existing dead load by 25 percent. New total dead load plus live load plus seismic forces may be increased over existing dead load plus live load by 50 percent.

EXCEPTION: In buildings located in poor soil areas as defined in Chapter 5B, any increase in dead load shall require an evaluation of the existing foundation system.

Higher values may be justified only in conjunction with a geotechnical investigation. A foundation investigation shall be also submitted with the building permit application when:

  1. A building has an existing full or partial pile supported, or similar foundation system or whenever the installation of such a system is proposed as part of the strengthening.

  2. Whenever there is evidence of significant distress attributable to foundation or geotechnical conditions.

  3. An investigation is required by San Francisco Building Code Section 1803 or 1804.

  4. It is desired to prove that the building is not on poor soil as permitted by the exception to Section 503B.

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