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Sonoma County · ADU permit data · Updated 2026-10-20

How long does an ADU permit take in Unincorporated Sonoma County?

4.3months median, application to building permit, 2023–2025

Bay Area
6.0 mo
Slow quarter
7.5+ mo
Rank
12 of 52

That is 28% shorter than the Bay Area median of 6.0 months. One in four applicants waited more than 7.5 months.

State limit
60 days
Uninc. Sonoma Co.
4.3 mo
Bay Area
6.0 mo
months
Months from application to ADU permit, 2023–2025, drawn to one scale. The state's 60-day clock starts once an application is complete.
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Permit wait

Rank 12 of 52 · full ranking

Months from ADU application to building permit

ADUs permitted in 2023–2025, 232 matched on parcel number. Includes time owners spent revising plans.

Source: California HCD Annual Progress Reports, filed by Sonoma County

Estimate my dates

Fast quarter, median and slow quarter, in months

Unincorporated Sonoma County 2.3–7.5 mo

Sonoma County

Bay Area 3.8–10.5 mo

Median Fast quarter to slow quarter

Median wait

  • Unincorporated Sonoma County 4.3 mo
  • Sonoma County 4.7 mo
  • Bay Area 6.0 mo
  • Santa Rosa fastest nearby 6.4 mo

Where Uninc. Sonoma Co. sits among 52 ranked cities

Uninc. Sonoma Co. 4.3

Uninc. Sonoma Co. Other ranked cities Bay Area 6.0

Unincorporated Sonoma County

4.3months

median wait, 2023–2025

Took longer than 60 days

State law gives the city 60 days to act once an application is complete. Counted from first submission, this share of ADUs took longer. Ask for the completeness letter, which is due within 15 business days, and keep its date.

Source: HCD Annual Progress Reports, 2023–2025; Gov. Code 66317

Unincorporated Sonoma County

84%

of matched ADUs

Slow quarter waited longer than

One applicant in four took longer than this. Plan on it if the city sends your plans back for another round of corrections.

Source: HCD Annual Progress Reports, 2023–2025, 75th percentile

Unincorporated Sonoma County

7.5months

Fast quarter had a permit within

One applicant in four had a building permit within this time from first submission.

Source: HCD Annual Progress Reports, 2023–2025, 25th percentile

Unincorporated Sonoma County

2.3months

Permits issued

364 ADU permits, 2023–2025

ADU building permits issued and ADUs finished, by year

Source: units by calendar year, as reported by Sonoma County to California HCD

Unincorporated Sonoma County, units per year

0 75 150 2018: 101 Permits issued2019: 75 Permits issued2020: 82 Permits issued2021: 116 Permits issued2022: 134 Permits issued2023: 120 Permits issued2024: 134 Permits issued2025: 110 Permits issued 2018: 45 ADUs completed2019: 65 ADUs completed2020: 65 ADUs completed2021: 58 ADUs completed2022: 98 ADUs completed2023: 114 ADUs completed2024: 93 ADUs completed2025: 102 ADUs completed 110 Permits issued 102 ADUs completed 20182020202220242025

ADU permits a year, 2023–2025 average

  • Unincorporated Sonoma County 121
  • Santa Rosa 79
  • Petaluma 25
  • Windsor 10
  • Sonoma County, all 268
  • Bay Area, all 4,316

ADU permits a year per 1,000 houses, 109 places

Uninc. Sonoma Co. 2.3

Uninc. Sonoma Co. Other Bay Area places

Unincorporated Sonoma County

121a year

ADU permits, 2023–2025 average

Share of new homes that are ADUs

Of every home Unincorporated Sonoma County permitted in 2023–2025, this share was an ADU.

Source: HCD Annual Progress Reports, 2023–2025

Unincorporated Sonoma County

40%

ADU permits per 1,000 houses

Permits a year for every 1,000 detached houses, so small and large cities can be compared.

Source: HCD Annual Progress Reports; DOF housing estimates

Unincorporated Sonoma County

2.3

rank 53 of 92

Change since 2019–2021

Yearly ADU permits in 2023–2025, up 33% from 2019–2021.

Source: HCD Annual Progress Reports

Unincorporated Sonoma County

+33%

Build time

261 finished ADUs

Building permit to finished ADU

Median time from building permit to certificate of occupancy for ADUs finished in 2023–2025. Add it to the permit wait for a full timeline.

Source: HCD Annual Progress Reports, 2023–2025

Unincorporated Sonoma County

14.9months

median of 261

Slow quarter of builds took longer than

One ADU in four took longer than this to reach a certificate of occupancy after the permit.

Source: HCD Annual Progress Reports, 2023–2025, 75th percentile

Unincorporated Sonoma County

25.1months

Sonoma County

10 cities and areas · all cities
Months from ADU application to building permit

Median Fast quarter to slow quarter Bay Area median, 6.0 months Number is the rank out of 52 cities

06121824
median
  1. 12Unincorporated Sonoma County
    4.3
  2. 34Santa Rosa
    6.4

Every page in Sonoma County: median wait where we can measure it, otherwise ADU permits a year

Planning an ADU in Unincorporated Sonoma County

  1. 1 State law gives the city 60 days to act once your application is complete. Counting from first submission, 84% of ADUs here took longer than 60 days to reach an issued permit (Bay Area: 93%). Ask for the completeness letter, which the city owes you within 15 business days, and keep its date.
  2. 2 Plan for about 4.3 months to get your permit, and up to 7.5 if the city sends your plans back for another round. Those numbers include the time owners spent revising drawings.
  3. 3 After the permit, ADUs here took a median of 14.9 months to reach a certificate of occupancy (Bay Area: 13.0).
  4. 4 Unincorporated Sonoma County permits about 121 ADUs a year, up 33% from 2019–2021. Local designers and builders have recent examples to show you; ask for permitted ADUs in Unincorporated Sonoma County, not elsewhere.
  5. 5 The part of the wait you control is the first submission. Complete drawings, a site plan that matches the survey, and answers to the city's ADU checklist cut down on correction rounds.
  6. Read next: why home plans get sent back · permit drawings vs. full plans · architect fee calculator

Timeline tool

When would your permit come through?

Pick a start date and see the fast, likely and slow dates for Unincorporated Sonoma County, from the numbers on this page.

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Next step

Not sure who to call first?

Answer a few questions about your lot and your plans. We point you to the right kind of help for an ADU in Unincorporated Sonoma County: an architect, a permit-drawing team, or a design-build firm. About two minutes, no call list.

Find the right first call

Start with the city's own rules: County ADU and JADU page.

Sheet
C-202
Drawing
ADU permit record, unincorporated Sonoma County
Source
California HCD Annual Progress Reports, filed by Sonoma County
Date
2026-10-20
Scale
Not to scale

Source: Bay Area ADU Permit Clock 2026, our analysis of the California HCD Housing Element Annual Progress Reports (data.ca.gov) filed by Sonoma County, and DOF housing estimates. Wait times are matched on parcel number and include applicant revision time. The 60-day rule is in Government Code section 66317. How we measured it · See all 109 jurisdictions

Common questions

How long does it take to get an ADU permit in Unincorporated Sonoma County?

For ADUs permitted in 2023–2025, the median time from application to building permit in unincorporated Sonoma County was 4.3 months (132 days), based on 232 permits we could match. A quarter took longer than 7.5 months.

How many ADUs does Unincorporated Sonoma County approve?

Unincorporated Sonoma County issued 364 ADU building permits in 2023–2025, about 121 a year. ADUs were 40% of all new homes permitted there.

How long does it take to build an ADU in Unincorporated Sonoma County?

The median time from building permit to certificate of occupancy was 14.9 months for ADUs completed in 2023–2025.