County directory

Contra Costa 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 Contra Costa County

Antioch (opens the government site in a new tab)
Showing California state rules
We couldn't read this city's ADU code yet, so we're showing California state rules. Check with the city before you plan.
City ADU page: https://www.antiochca.gov/327/Accessory-Dwelling-Units-ADUs
Brentwood (opens the government site in a new tab)
Showing California state rules because a local rule change is pending
A local rule change is pending. The City adopted new ADU rules on March 10, 2026 (Ordinance 1092), after an October 2025 state housing department letter on its earlier rules, and its online code still shows the earlier text. We'll add the new local rules after they take effect and we've reviewed them.
Clayton (planning page) (opens the government site in a new tab)
Showing California state rules because Clayton's local rules may conflict with state law or are being challenged
We show the state rules for an ADU ordinance from 2022 that cites the old state ADU law and limits multifamily lots to two detached ADUs. Check with Clayton about how it handles this today.
Concord (opens the government site in a new tab)See our rules summary
Showing California state rules, plus Concord details
The size, setback, height, and parking figures are California state rules. The Concord section lists the local details we have on file, like plans, forms, and contacts.
Danville (opens the government site in a new tab)
Showing California state rules
We don't have Danville's own ADU rules on file, so this shows the California state rules that apply across the state. Check with Danville for local details.
El Cerrito (opens the government site in a new tab)See our rules summary
Showing California state rules, plus El Cerrito details
The size, setback, height, and parking figures are California state rules. The El Cerrito section lists the local details we have on file, like plans, forms, and contacts.
Hercules (opens the government site in a new tab)See our rules summary
Showing Hercules city rules
These are Hercules's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a Hercules rule may conflict with state law or is being challenged, we show the California state rule instead. This covers owner-occupancy rules for junior ADUs and a rule that ADUs match the main home's design.
Lafayette (opens the government site in a new tab)See our rules summary
Showing California state rules, plus Lafayette details
The size, setback, height, and parking figures are California state rules. The Lafayette section lists the local details we have on file, like plans, forms, and contacts.
Martinez (opens the government site in a new tab)See our rules summary
Showing Martinez city rules
These are Martinez's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a Martinez rule may conflict with state law or is being challenged, we show the California state rule instead. This covers a front-setback rule for some ADUs.
Moraga (opens the government site in a new tab)See our rules summary
Showing Moraga city rules
These are Moraga's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Oakley (opens the government site in a new tab)See our rules summary
Showing Oakley city rules
These are Oakley's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a Oakley 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 that can fall below the sizes state law protects.
Orinda (opens the government site in a new tab)
Showing California state rules because Orinda's local rules may conflict with state law or are being challenged
We show the state rules for an ADU ordinance from 2020 that cites the old state ADU law and limits single-family lots to one ADU and one junior ADU. Check with Orinda about how it handles this today.
Pinole (opens the government site in a new tab)See our rules summary
Showing Pinole city rules
These are Pinole's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a Pinole rule may conflict with state law or is being challenged, we show the California state rule instead. This covers a rule that detached ADUs sit at the rear or side of the main home.
Pittsburg (opens the government site in a new tab)
Showing California state rules because Pittsburg's local rules may conflict with state law or are being challenged
We show the state rules for ADU rules (Ordinance 20-1476) that a December 2021 state housing department letter found do not meet state ADU law, including a cap on attached ADUs at 50% of the home or 1,200 sq ft, whichever is less. Check with Pittsburg about how it handles this today.
Pleasant Hill (opens the government site in a new tab)See our rules summary
Showing California state rules, plus Pleasant Hill details
The size, setback, height, and parking figures are California state rules. The Pleasant Hill section lists the local details we have on file, like plans, forms, and contacts.
Richmond (opens the government site in a new tab)See our rules summary
Showing California state rules, plus Richmond details
The size, setback, height, and parking figures are California state rules. The Richmond section lists the local details we have on file, like plans, forms, and contacts.
San Pablo (opens the government site in a new tab)
Showing California state rules because San Pablo's local rules may conflict with state law or are being challenged
We show the state rules for ADU rules (Ordinance 2025-005, December 2025) that a May 2026 state housing department letter found do not meet state ADU law. Check with San Pablo about how it handles this today.
San Ramon (opens the government site in a new tab)See our rules summary
Showing San Ramon city rules
These are San Ramon's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a San Ramon rule may conflict with state law or is being challenged, we show the California state rule instead. This covers a one-ADU limit on single-family lots, a 50% size cap for attached ADUs, a 20-foot front setback, and a parking rule that covers junior ADUs.
Walnut Creek (opens the government site in a new tab)See our rules summary
Showing California state rules because a local rule change is pending
The size, setback, height, and parking figures are California state rules. The Walnut Creek section lists the local details we have on file, like plans, forms, and contacts.
Where a Walnut Creek rule may conflict with state law or is being challenged, we show the California state rule instead. This covers owner-occupancy rules for junior ADUs.
A local rule change is pending. The City Council adopted Ordinance No. 2258 on October 6, 2026. It rewrites the City's ADU rules (for example, it allows up to four ADUs on a single-family lot and requires the owner to live on site with a junior ADU only when the junior ADU shares a bathroom with the house). It takes effect November 6, 2026. We'll add the new local rules after they take effect and we've reviewed them.
Unincorporated Contra Costa County (opens the government site in a new tab)See our rules summary
Showing Contra Costa County rules
These are Contra Costa County's own ADU rules on file, shown with the California state rules they build on. Each item says which is which.
Where a Contra Costa County rule may conflict with state law or is being challenged, we show the California state rule instead. This covers front setbacks for ADUs.

All counties in the ADU directory