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Lot splits under SB 9 in San Diego

In single-unit zones, urban lot split lots must be at least 1,200 square feet, and a second home is limited to 800 square feet.

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Key points

  • Lot splits: In single-unit zones, urban lot split lots must be at least 1,200 square feet, and a second home is limited to 800 square feet.

Each rule below links to the section of the San Diego Municipal Code it was read from, with the code text one click away (checked October 2026). General information, not legal advice.

What San Diego's code says

San Diego code What San Diego's code adds
Unit size
  • A second home of up to 800 square feet of gross floor area.
    Applies: Each urban lot split lot in single-unit zones; some base zone rules are waived; floor area ratio limits apply, with exceptions for existing structures.
    § 143.1315 · code text
    construction of a second dwelling unit with a maximum gross floor area of 800 square feet shall be permitted on each of the lots created by an urban lot split
Minimum new lot size
  • Each new lot must be at least 1,200 square feet.
    Applies: Both lots from an urban lot split in a zone that allows single but not multiple homes.
    § 143.1315 · code text
    The two lots shall each be no smaller than 1,200 square feet.
Standards
  • If buildings remain, split so each lot meets, or comes as close as possible to, the zone's floor area ratio.
    Applies: Urban lot splits in single-unit zones; if street frontage or driveway width rules are not met, an access easement must be recorded.
    § 143.1315 · code text
    regulations of the base zone in which the lot is located shall apply, except as specified in Section 143.1310(a) and this section. Ch. Art. Div. 14 3 13 9 San Diego Municipal Code Chapter 14: General Regulations (2-2025) (1) The minimum lot area and minimum lot dimensions regulations of the base zone shall not apply and are replaced with the following regulations: (A) The two lots shall be approximately equal in size, provided that one lot shall not be smaller than 40 percent of the lot area of the original lot. (B) The two lots shall each be no smaller than 1,200 square feet. (C) If the lot contains existing structures that will remain as part of the development, the lot shall be split in a manner that complies with or comes as close as possible to compliance with the floor area ratio of the underlying base zone, consistent with Section 143.1315(f)(1)(A) and (B). (2) A lot should be subdivided in a manner that complies with the street frontage and driveway width requirements of the base zone wherever feasible. Development that does not comply with the street frontage and driveway width requirements of the base zone shall record an access easement on the lot to the satisfaction of the City Engineer.

Who this affects

HomeownersContractorsDesigners

Frequently asked questions

Can I split my lot under SB 9 in San Diego?

In single-unit zones, urban lot split lots must be at least 1,200 square feet, and a second home is limited to 800 square feet.

General information, not legal advice.

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Ask GoCodebook how San Diego's lot splits under SB 9 rules apply to your situation and get an answer that cites the section.

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