Guides
Guides
Plain answers to the questions San Diego homeowners ask before they build. Each guide names who it applies to, cites the rules it relies on and shows the day it was last reviewed.
What changed
Dated notes when a San Diego rule changes, with the guides it affects.
Takes effect January 1, 2027
Two detached ADUs by right, and lower impact fees on larger ADUs
From January 1, 2027, AB 956 lets a single-family lot have two newly built detached ADUs and extends the HOA rule to lots zoned to allow a house. SB 1117 limits impact fees on an ADU over 750 square feet to the area above 750 when the lot has one or two ADUs. Both were signed September 29, 2026.
In these guides: What changes for ADUs in San Diego on January 1, 2027?, Can I build an ADU on my lot in San Diego?, San Diego's ADU bonus program in 2026: what changed and how many ADUs you can build
New conditions on selling an ADU in the unincorporated County
Each sale of an ADU condominium in the unincorporated County now needs a 30-day public listing, a recorded right of first refusal for a tenant or co-owner, and the buyer's affidavit that they or family will live there for at least a year. The Board adopted the conditions on August 19, 2026.
In these guides: Can I sell my ADU separately in San Diego County?
Expected in 2026
The City's 2025 ADU changes and the Coastal Zone
The City of San Diego's 2025 ADU amendments are not yet in effect in the Coastal Overlay Zone. The City sent them to the Coastal Commission in July 2025 and expects certification in 2026. Until then a coastal lot follows the earlier rules, including Housing Action Package 2.0, in effect there since March 11, 2026.
In these guides: San Diego's ADU bonus program in 2026: what changed and how many ADUs you can build, Can I sell my ADU separately in San Diego County?
Not yet in effect
The state's Zone 0 rules for the first five feet around a home
The Board of Forestry adopted Zone 0 rules on August 19, 2026, then withdrew them from the state's legal review on September 8, 2026. No new filing was listed on October 19, 2026. The City of San Diego's own Zone 0 rule has applied to new buildings in its Very High fire zones since February 28, 2026.
In these guides: Fire hazard zones after the 2025 maps: what changes for ADUs, additions and rebuilds
SB 543's fee rules for small ADUs and junior ADUs
SB 543 extended the state's ADU fee limits to junior ADUs and took ADUs and junior ADUs under 500 square feet out of school fees. It was signed on October 10, 2025 and, with no urgency clause, took effect on January 1, 2026.
In these guides: San Diego's ADU bonus program in 2026: what changed and how many ADUs you can build
Guides
ADUs
Permits
- Can I build an ADU on my lot in San Diego?
- How long does an ADU take in San Diego, from permit to move-in?
- San Diego's ADU bonus program in 2026: what changed and how many ADUs you can build
- Can I sell my ADU separately in San Diego County?
- Legalizing an unpermitted ADU or garage conversion in San Diego
- What changes for ADUs in San Diego on January 1, 2027?