Contra Costa County · California
Blackhawk ADU guide: local rules, permits & property planning
A Blackhawk mailing address should be checked against County jurisdiction before borrowing Danville’s permit process. Start with the County parcel record, serving sanitary district and access arrangements for the proposed unit.
Local planning guide · Reviewed October 2, 2026
What matters for an ADU in Blackhawk
Permitting authority: Contra Costa County — unincorporated Blackhawk
Official local guidanceLocal rules and design checks
| Topic | Local guidance |
|---|---|
| County parcel review | Use the County property and zoning lookup to establish jurisdiction and the parcel’s zoning record. |
| Sanitary coordination | The County’s agency directory lists Blackhawk within Central Contra Costa Sanitary’s service area; confirm service for the specific parcel. |
| Existing-unit legalization | The County publishes an AB 2533 path with construction-date evidence and a substandard-conditions checklist for qualifying older units. |
Selected local requirements, not a complete zoning determination. Confirm the current rules for your address with the responsible agency.
Fees and budget checks
Request a County fee assessment for the exact conversion or new-build scope and a separate sanitary-district assessment. Use the County permit record for billed fees and payments; a neighboring town’s rebate or fee schedule does not establish a Blackhawk charge.
Contra Costa County permit portalHow to start the permit process
Locate the parcel through County property research, confirm the serving agencies, then use the digital ePermits process. For an older unpermitted unit, prepare the County’s required age evidence and safety checklist.
Public records resource
County property and permit research
The County provides zoning, permit status and payment lookup. Use an address-specific record to compare a relevant Blackhawk proposal rather than assuming a Danville project has the same approvals.
View the original sourceBlackhawk ADU questions
- Does a Danville postal address decide the permit agency?
- No. Confirm the parcel’s jurisdiction in the County lookup before selecting the application.
- Who handles the sewer approval?
- The County directory identifies Central Contra Costa Sanitary for Blackhawk. Ask the district to confirm the property’s connection and project requirements.
Sources for this guide
- Contra Costa County — ADU permitting
- Contra Costa County permit portal
- County property and permit research
- Blackhawk sanitary agency listing
Local sources reviewed October 2, 2026. Historical examples retain their stated dates. Contact ADU California to confirm project availability; this guide does not establish an office location or property approval.
A useful first review
Separate what is available from what still needs verification.
01
Confirm the property
Start with a complete address and review the available parcel, building, and map context.
02
Identify the unknowns
Keep missing setbacks, easements, utilities, access, hazards, and local requirements visible.
03
Choose the next review
Use the preliminary result to prepare a focused conversation with the required professionals and agencies.
Explore project types
Compare the scope before choosing a solution.
These pages explain the questions each project type introduces. They do not assert that a particular scope is permitted or suitable for your address.
Compare planning footprints
See common ADU sizes before choosing a design.
These model pages are planning references only. They are not a statement that a particular size is allowed or buildable at a Blackhawk address.
California directory
Explore more city guides.
The next useful action
Put your address at the center of the conversation.
The online review is preliminary and is not a permit decision, survey, engineering opinion, construction document, final price, or guaranteed schedule.