Fees
Estimated city fees
Baseline for a simple permitted adu: Austin does not publish a simple flat ADU fee on the ADU page; plan review fees are generated at submittal and permit fees are generated at approval/activation.
| Fee | Amount | Notes |
|---|---|---|
| Residential plan review fee | Varies | Austin says plan review fees are determined when the residential building permit application is submitted. Additional application review fees may apply depending on the scope and review comments. |
| Building permit activation fee | Varies | Austin says permit fees are determined after the application is approved and the permit is ready to be activated. |
| Austin Water / utility-related fees | Project-specific | If a new utility tap or similar utility service work is required, Austin notes that separate Austin Water Utility tap requirements can apply. |
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Conditions
The rules that apply
- Austin treats an ADU as a separate dwelling unit on the same property as a single-family home, not as a simple accessory structure.
- Austin Development Services says an ADU may be built on residential property if the lot is zoned SF-1, SF-2, or SF-3 and the minimum lot area is 5,750 square feet or greater.
- The permit path is residential new construction / addition review through Austin Build + Connect (AB+C), with plan review and permit activation required before construction starts.
- Austin's ADU page says required size is based on zoning district and geographic location within the city rather than one citywide posted square-foot cap.
- Austin says zoning no longer requires a minimum distance between units, but applicants still must satisfy applicable International Residential Code spacing and fire-separation rules.
- Each new dwelling unit needs a unique address or building number before the permit application is submitted.
- A structure that includes habitable space, a full bathroom, and a sink or dishwasher outside the bathroom is treated as a dwelling unit and must follow dwelling-unit zoning, utility meter, internal-access, occupancy, and address requirements.
- Austin's ADU guidance also points applicants to HOME Amendment rules for projects adding multiple dwelling units on a lot.
Documents
What you'll need to file
- Residential New Construction and Addition building permit application submitted through Austin Build + Connect (AB+C).
- Unique address or building-number approval for the new dwelling unit from Address Management Services before permit filing.
- Site plan / plot plan showing lot lines, existing structures, proposed ADU location, setbacks, and access.
- Residential building plans and supporting documents required for new-construction residential review.
- Any reviewer-specific supporting materials requested during intake or correction cycles.
- Trade-permit documents if the ADU scope includes separate mechanical, electrical, or plumbing work requiring associated permits.
Process
How the permit process works
Sequential — each step gates the next.
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Confirm the lot qualifies for an ADU Use Austin's Property Profile and ADU guidance to confirm the parcel is zoned SF-1, SF-2, or SF-3, has at least 5,750 square feet of lot area, and can satisfy current HOME / Land Development Code rules for additional dwelling units.
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Request a unique address or building number Austin requires each new dwelling unit to have a unique address or building number. Get that from Address Management Services before filing the permit application.
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Prepare the residential permit package Assemble the Residential New Construction and Addition application, site plan, building plans, and any reviewer-specific supporting documents required for the proposed ADU.
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Submit through AB+C and pay plan review fees File through the Austin Build + Connect portal. Austin says plan review starts after intake verifies the submission and the invoiced plan review fees are paid.
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Work through plan review comments Coordinate with the assigned Austin reviewers and resubmit any corrections needed for zoning, technical code, drainage, utilities, or other review disciplines.
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Activate the permit and begin construction After approval, Austin generates the building permit and any associated trade permits in pending status. The registered contractor then pays the activation fees and activates the permits before construction begins.
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Schedule inspections and obtain the certificate of occupancy After inspections pass, Austin closes the permit and issues the certificate of occupancy for the ADU. Austin's ADU page notes the CO is required for any later short-term-rental license request.
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Tools & materials
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Provenance
Code basis & official sources
Last verified 2026-04-18.
City of Austin Land Development Code Article 23-3D and related HOME Amendment standards for additional dwelling units / two-unit and three-unit residential uses, plus Austin's adopted residential technical codes and review criteria.
Residential permit page: https://www.austintexas.gov/development-services/residential-plan-review
If you skip the permit
- Austin can stop work on an unpermitted dwelling-unit build and require full after-the-fact review before the structure can be occupied.
- A non-permitted backyard structure that actually meets Austin's dwelling-unit definition can trigger additional zoning, utility, and occupancy issues beyond a typical accessory-building violation.
- You may be forced to expose completed work so inspectors can verify code compliance after the fact.
- A missing certificate of occupancy can block lawful occupancy and complicate any later rental or resale use.
- Unpermitted dwelling-unit work can become a title, insurance, and disclosure problem during refinance or sale.
FAQ
Common Austin adu permit questions
Do I need a permit for a detached backyard ADU in Austin?
Yes. Austin routes ADUs through its Residential New Construction and Addition permit path. The city treats an ADU as a dwelling unit, not as a simple accessory shed or studio shell.
Can I build an ADU on any Austin single-family lot?
No. Austin's ADU guidance says the property must meet minimum conditions including SF-1, SF-2, or SF-3 zoning and at least 5,750 square feet of lot area, with additional Land Development Code and HOME requirements still applying.
What is the maximum ADU size in Austin?
Austin's ADU page does not publish one simple citywide maximum square footage. It says the required size depends on zoning district and geographic location within the city, with additional GFA, coverage, and site-development constraints under current code.
Do I need a new address for an Austin ADU?
Yes. Austin says each new dwelling unit requires a unique address or building number, and you should obtain that before submitting the residential building permit application.
How long does Austin take to review an ADU permit?
Austin's Residential Plan Review page lists 15 business days for new construction and additions per review cycle. Total project timing is usually longer because corrections, utility reviews, permit activation, inspections, and the certificate of occupancy all sit on top of the initial review clock.
Can I use an Austin ADU as a short-term rental?
Austin says an ADU may be used as a short-term rental only under specific conditions. If the ADU was constructed after October 1, 2015, it may not be used as a short-term rental for more than 30 days in a calendar year, and a certificate of occupancy is required for the license application.
Why mention Texas HB 2127 on an Austin ADU page?
HB 2127 is part of the current Texas state-law backdrop limiting some local regulatory approaches. It matters as context, but homeowners still need to file against Austin's current Development Services process and the city's active Land Development Code / HOME rules that govern the permit review.
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Disclaimer: Informational only — not legal advice. Rules change; verify with Austin permitting staff before you build.