County directory

Napa County ADU rules

Each place name links to that city or county's own ADU page. Places with a 'See our rules summary' button also have our plain-language summary of the local ADU rules, with sources. Each place below says whether we show local rules or California state rules.

Places in Napa County

American Canyon (planning page) (opens the government site in a new tab)See our rules summary
Showing American Canyon city rules
These are American Canyon's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a American Canyon rule may conflict with state law or is being challenged, we show the California state rule instead. This covers a rule that applicants report the expected rent and household size of a new ADU.
Calistoga (opens the government site in a new tab)
Showing California state rules because Calistoga's local rules may conflict with state law or are being challenged
We show the state rules for ADU rules from 2020 that limit single-family lots to one ADU and one junior ADU and multifamily lots to two detached ADUs. Check with Calistoga about how it handles this today.
Napa (opens the government site in a new tab)See our rules summary
Showing Napa city rules
These are Napa's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a Napa rule may conflict with state law or is being challenged, we show the California state rule instead. This covers a size cap on attached ADUs and an owner-occupancy rule for every junior ADU.
St. Helena (opens the government site in a new tab)See our rules summary
Showing California state rules, plus St. Helena details
The size, setback, height, and parking figures are California state rules. The St. Helena section lists the local details we have on file, like plans, forms, and contacts.
Yountville (opens the government site in a new tab)See our rules summary
Showing California state rules because Yountville's local rules may conflict with state law or are being challenged
The size, setback, height, and parking figures are California state rules. The Yountville section lists the local details we have on file, like plans, forms, and contacts.
Where a Yountville rule may conflict with state law or is being challenged, we show the California state rule instead. This covers a definition that bars ADUs from having direct access to the main home.
Unincorporated Napa County (opens the government site in a new tab)
Showing California state rules because Napa County's local rules may conflict with state law or are being challenged
We show the state rules for ADU rules (Ordinance 1495, September 2024) that a June 2026 state housing department letter found do not meet state ADU law. Check with Napa County about how it handles this today.

All counties in the ADU directory