Santa Clara County · ADU permit data · Updated 2026-10-20
7.2months median, application to building permit, 2023–2025
That is 18% longer than the Bay Area median of 6.0 months. One in four applicants waited more than 10.4 months.
ADUs permitted in 2023–2025, 182 matched on parcel number. Includes time owners spent revising plans.
Source: California HCD Annual Progress Reports, filed by the City of Los Altos
Fast quarter, median and slow quarter, in months
Los Altos 4.4–10.4 mo
Santa Clara County
Bay Area 3.8–10.5 mo
Median Fast quarter to slow quarter
Median wait
Where Los Altos sits among 52 ranked cities
Los Altos Other ranked cities Bay Area 6.0
Los Altos
7.2months
median wait, 2023–2025
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
Los Altos
99%
of matched ADUs
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
Los Altos
10.4months
One applicant in four had a building permit within this time from first submission.
Source: HCD Annual Progress Reports, 2023–2025, 25th percentile
Los Altos
4.4months
Source: units by calendar year, as reported by the City of Los Altos to California HCD
Of every home Los Altos permitted in 2023–2025, this share was an ADU.
Source: HCD Annual Progress Reports, 2023–2025
Los Altos
42%
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
Los Altos
8.6
rank 7 of 92
Yearly ADU permits in 2023–2025, up 108% from 2019–2021.
Source: HCD Annual Progress Reports
Los Altos
+108%
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
Los Altos
14.6months
median of 156
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
Los Altos
21.8months
Median Fast quarter to slow quarter Bay Area median, 6.0 months Number is the rank out of 52 cities
Every page in Santa Clara County: median wait where we can measure it, otherwise ADU permits a year
Timeline tool
Pick a start date and see the fast, likely and slow dates for Los Altos, from the numbers on this page.
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Source: Bay Area ADU Permit Clock 2026, our analysis of the California HCD Housing Element Annual Progress Reports (data.ca.gov) filed by the City of Los Altos, 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
For ADUs permitted in 2023–2025, the median time from application to building permit in Los Altos was 7.2 months (218 days), based on 182 permits we could match. A quarter took longer than 10.4 months.
Los Altos issued 249 ADU building permits in 2023–2025, about 83 a year. ADUs were 42% of all new homes permitted there.
The median time from building permit to certificate of occupancy was 14.6 months for ADUs completed in 2023–2025.