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October 5, 2021

Updated ADU Code Revision for SB 9

"4 MEANS 4"

Sen. Atkins lot-splitting bill, Senate Bill 9, goes into effect January 1, 2022.

Neighbors For A Better San Diego has analyzed how San Diego's Accessory Dwelling Unit (ADU) code would be applied to SB 9, and we have found that San Diego's current code allows an unlimited number of market-rate ADUs to be added to the four units allowed statewide.

Based on the statements made by our legislators during passage of SB 9, the allowance of more than 4 units on a single dwelling property is contrary to the intent of the law, and we call on Mayor Gloria and the San Diego City Council to act immediately to close the ADU loophole. We also call on Senate President pro Tempore Atkins and our local Assembly Members to support these revisions in order to deliver on her repeated promises that SB 9 would not result in more than 4 units per lot. "4 MEANS 4"


SB 9 allows a single family property owner in an urban area of California to split their existing lot into two separate lots and then build new units, so as to produce up to 2 units on each resulting lot. (Note: San Diego is classified by the census as an urban area.)

During its passage through the state legislature, concerns were raised about the possibility of adding accessory dwelling units (ADUs) to the properties created under SB 9. The response of California Senate President pro Tempore Toni Atkins, was that there would only be four units (two on each lot) created under SB 9, effectively that "4 means 4".

However, the actual wording of the bill (now Sections 65852.21, 66411.7, and 66452.6 of the California Government Code) is much more open-ended:

"(f) Notwithstanding Section 65852.2 or 65852.22, a local agency shall not be required to permit an accessory dwelling unit or a junior accessory dwelling unit on parcels that use both the authority contained within this section and the authority contained in Section 66411.7."

In short, ADUs are permitted on split lots UNLESS a city prohibits it by ordinance.

In the case of San Diego, the city's ADU code (141.0302) has explicit code for the addition of ADUs to multiple dwelling unit properties, such as would be created by building duplexes on lots split under SB 9 rules. This code, 141.0302(b)(2)(C), is much more permissive than even the density bonus, 141.0302(b)(2)(G), that NFABSD has previously documented.

NFABSD has constructed scenarios whereby more than 10 ADUs could be added to a lot split under SB 9. While this is comparable in units to what can be done on a single dwelling property in a Transit Priority Area (TPA), exploitation of the multiple dwelling unit code can be done ANYWHERE in San Diego and WITHOUT designating any of the units as affordable.

We know from implementation of the current ADU code that the Development Services Department is likely to apply the most permissive interpretation of city code, and hence the only recourse to preventing these types of overbuilt projects is to revise the code to close this loophole.

Again, SB 9 goes into effect January 1, so time is of the essence. We have already seen webinars and mailers revving up developers to take advantage of SB 9 -- Mayor Gloria and the City Council need to act now to get ahead of this issue, and they need to hear from the public to make sure that they prioritize this issue.


For contact information for your council member or the mayor, visit:

NFABSD's proposed revisions to San Diego's ADU code are summarized here:

Our example markup of the code (141.0302) can be viewed here:

The full text of SB 9 (Sections 65852.21, 66411.7, and 66452.6 of the California Government Code) is posted here:

The full text of San Diego's ADU code (Municipal Code §141.0302) is posted here:

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