Accessory Dwelling Unit

Additional Dwelling Units

An Additional Dwelling Unit (ADU) is a separate dwelling unit on the same property as a single-family home that is smaller in size and regulated by the City of Austin’s Land Development Code.

The information you will find on this page includes: 

Definition of an Additional Dwelling Unit (ADU)

A structure or portion of a structure is a "dwelling unit" if it contains:

  • a habitable space,
  • a full bathroom, and
  • a sink or a dishwasher outside of a full bathroom

A structure that meets these criteria must follow all regulations applicable to a dwelling unit, including zoning, utility meter, internal access, occupancy, and address requirements. Visit the Code Interpretation Library webpage for more information about the definition and components of the dwelling unit. 

If the structure does not contain all criteria, schedule an appointment for Residential Zoning Questions to discuss what is proposed and if it's permitted on the property. 

Can I build an ADU on my property?

An ADU may be built on a residential property if the minimum requirements are met:

  1. The property is zoned SF-1, SF-2, or SF-3. Check the zoning of your property using Property Profile.
  2. The minimum lot area of the property is 5,750 square feet or greater.
  3. The required size of an additional dwelling is based on the zoning district and geographic location within the City of Austin.
  4. Zoning regulations have changed about how close units can be to each other. There is no longer a minimum distance required between units by zoning regulations. However, you must still follow applicable technical codes. This includes ensuring the minimum space between units required by the Fire Code. 
  5. A unique address or building number is required for each new dwelling unit. Visit the Address Management Services webpage to confirm or obtain a new address for an ADU before submitting the residential building permit application.
  6. Additional requirements and regulations for additional dwelling units (two-unit residential or three-unit residential) can be found in the City of Austin’s Land Development Code. 
If you do not meet the minimum requirements for an ADU (two-unit residential or three-unit residential), schedule an appointment for Residential Zoning Questions to discuss your options for the property. 
If you have questions on building code requirements for the ADU, including structural, foundation, roofing, and wall-bracing plan requirements, schedule an appointment for Residential Building Code Technical Questions
Can I use an ADU as a Short-Term Rental?

An ADU may be used as a short-term rental under specific conditions. Visit the Short-Term Rental License Program webpage to learn more about the program and requirements and to renew or apply for a short-term rental license.

Before applying for a license, please note the following conditions. 

  • The ADU may not be used as a short-term rental for more than 30 days in a calendar year if constructed after October 1, 2015. 
  • A Certificate of Occupancy (CO) for the ADU must be submitted with the short-term rental license application. The CO is issued at the end of the development process upon passing all Final Inspections with the Development Services Department. Visit the Certificate of Occupancy webpage to learn more and to request the CO. 
How to Apply for an ADU

step 1   Verify that an ADU can be built on the property

Before applying for the permit, verify that an ADU is allowed to be built on the residential property by visiting the Can I Build an ADU on my property? section.

If you have general questions about your proposed development, schedule an appointment for Residential Zoning Questions or Residential Building Code Technical Questions.

  • If an ADU is allowed to be built on the property, continue with Step 2. 
  • If an ADU is not allowed to be built on the property, please schedule an appointment for Residential Zoning Questions to discuss your options for the property.

step 2   Request a New Address or Building Number

The new additional dwelling unit requires a unique address or building number. Please visit the Address Management Services webpage to request a new Address, Building, or Unit before you apply.

Once the new address is verified with Address Management Services, continue with Step 3. 

step 3   Do you have an Austin Build + Connect (AB+C) Account?

(If yes, go to Step 4)

The Applicant listed on the permit must have an AB+C account to pay fees and manage the application. If you do not have an AB+C account, please register for an AB+C account. Additional help can be found in the Web Help Manual (PDF).

Please make a note of the email address used for this new account. You will need this for Step 4.

step 4   Apply for the Building Permit

Go to the Residential Plan Review webpage for the New Construction and Addition Building Permit Application. The application is linked in the web form. 

Once you submit the permit application and required documentation, Residential Intake staff will check the submission to verify all required documentation is provided.

step 5   Pay the Plan Review Fees and complete the Review Process

After Residential Intake staff verifies that all required documentation is provided, they will contact the Applicant designated on the permit application. The Applicant will need to log into their AB+C account to pay for the invoiced plan review fees. 

Once the invoiced plan review fees are paid, the permit application review will begin. Please coordinate with the assigned staff to work toward permit application approval. 

step 6   Pay the Permit Fees and Activate the Permits

Once the Residential New Construction and Addition Building Permit Application has been approved, the Building Permit and associated trade permits will be generated by the Residential Plan Review staff. The generated permits will be in a "Pending" status and ready for activation. Permit Activation Instructions are sent to the Applicant at this time. 

The registered General and Trade Contractors can then pay for and activate the "pending" permits with Service Center staff. Please visit the Activating a Permit webpage to learn how to pay for the permits, activate the building permit and related trade permits, and print and post the Building Permit.


step 7   Begin Construction and Schedule Inspections

Once the permit(s) are in an "Active" status, the contractor(s) can begin construction and schedule the inspections. Construction cannot occur until the permits have been paid for and activated. 

  • Learn how to schedule inspections, understand the building inspections process, and find the assigned Inspector by visiting our Building Inspections webpage.
  • Once a permit is in an "Active" status, it expires on the 181st day if the project has not been scheduled nor received an inspection. Upon the performance of an inspection, the permit expiration date will be extended 180 days. A "Canceled" or "Failed/No Work Performed" inspection result does not extend the expiration date. Learn more about building permit inspections by visiting our Building Inspections webpage.


 step 8   Receive Certificate of Occupancy (CO)

Once the Final Building Inspection receives a "Pass" inspection, the Building Permit will be in a "Final" status and be closed out. The Certificate of Occupancy (CO) will then be issued by the Building Inspector. 

Review Timeline and Fees

The length of review time and fees will vary based on the specific property and scope of work. The following provides some general guidance. 

  • Adding a new additional dwelling unit to a property is permitted as new construction. Visit the Residential Review webpage to learn more about the review timelines. 
  • Fees are required for the plan review of the building permit application and for the permit(s) once the permit application review is approved.
    • The plan review fees for the permit application will be determined when the application is submitted.
    • The permit fees will be determined once the application is approved and the permit is ready to be activated. 
  • Additional application review fees may apply in addition to the minimum plan review fees.
  • View the Residential Building Plan Review and Permit Fee chart on the Fees webpage to determine the applicable fees.

Schedule an appointment for Residential Submittal Application Questions for questions about application review fees and timelines. 


Residential Zoning Questions

For general questions about an Additional Dwelling Unit (ADU), including its definition and zoning requirements, schedule a virtual or in-person appointment with Residential Zoning. 

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Residential Building Code Technical Questions

For general building and technical code questions for the Additional Dwelling Unit (ADU), including structural, foundation, roofing, and wall-bracing plan requirements, schedule a virtual or in-person appointment with Residential Building Code. 

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Residential Submittal Application Questions

For general questions about application review fees, review timelines, and new construction application submittal questions, schedule a virtual or in-person appointment with Residential Intake. 

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