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Accessory Dwelling Units
Accessory Dwelling Units (ADU)
Accessory Dwelling Units (ADUs) are known by many names: granny flats, in-law units, backyard cottages, secondary units and more. No matter what you call them, ADUs are an innovative, affordable, effective option for adding much-needed housing.
State Guidance for ADUs
As of January 1, 2019, homeowners who created accessory dwelling units (ADUs) without the required building permits may have the opportunity to bring their ADUs into compliance.
Learn more about the State Law and Guidance for ADUs
Planning Approvals
- Accessory Dwelling Unit (ADU) Permit Application Form (PDF)
- ADU Application Submittal Checklist (PDF)
- ADU Application Processing Guidelines (PDF)
- County ADU Ordinance
- ADU are not allowed to be permitted for Short Term Rental Use. Read the Summary of the Short Term Rental Ordinance (PDF)
Building Permit Requirements
- Applying for a Building Permit web page. **All contractors must have an active business license with Contra Costa County if doing work in Unincorporated areas of the County. Visit the County Business License link for additional information on how to apply for a license.
If you are thinking about making any improvements to your home or parcel, and you have a septic system, you need to have your plans reviewed by Environmental Health.
Learn more about Septic System permitting.
Types of ADU and Legalization Process
- Legalizing Addition to Existing Residence as an ADU (PDF)
- Legalizing Detached Structure as an ADU (PDF)
- Legalizing ADU Within Existing Building Footprint (PDF)
ADU are not allowed to be permitted for Short Term Rental Use. Read the Summary of the Short Term Rental Ordinance (PDF)
Process
Schedule an Initial Meeting
The Initial Meeting is an opportunity to meet with Planning, Building, and Inspection staff to better understand what permits and fees are required to for your existing ADU.
Schedule an Appointment for Help
Contact us at 925-655-2700
Preparing for the meeting
The more information you provide at the meeting, the better staff will be able to assist you. Please bring
- Photos
- Site plan (drawing of all property lines and structures on the property
- Floor plan of the ADU
Next Steps
Planning Approvals
- Accessory Dwelling Unit (AD) Permit Application Form (PDF)
- ADU Application Submittal Checklist (PDF)
- ADU Development Standards (PDF)
- County ADU Ordinance
Building Permit Requirements
- Applying for a Building Permit web page. **All contractors must have an active business license with Contra Costa County if doing work in Unincorporated areas of the County. Visit the County Business License link for additional information on how to apply for a license.
Required Forms for Owner / Builder Permit Applications
Forms below are required for submission prior to permit issuance
- Authorization of Agent to Act on Property Owner's Behalf (PDF)
- Owner-Builder Acknowledgement and Verification of Information (PDF)
If you are thinking about making any improvements to your home or parcel, and you have a septic system, you need to have your plans reviewed by Environmental Health.
Learn more about Septic System permitting.