Building an ADU in Austin

What you can build: HOME Phase 1

The Austin City Council adopted HOME ("Home Options for Mobility and Equity") Phase 1 on December 7, 2023. The city began accepting applications under it on February 5, 2024.

On a lot zoned SF-1, SF-2 or SF-3, Phase 1:

• allows up to three housing units, including tiny homes;
• revises the rules for lots with two units;
• removes limits on the number of unrelated adults living in a unit.

A three-unit residential use can be up to three units on a lot, attached or detached in any combination. HOME also dropped the old "primary" versus "secondary" (accessory) unit distinction. Guest houses, on-site employee housing and accessory apartments are no longer separate categories.

Austin's ADU page still uses the term "additional dwelling unit." It says the property must be zoned SF-1, SF-2 or SF-3 and have at least 5,750 square feet of lot area. Check your zoning with the city's Property Profile map. [1][2]

Size, setbacks and coverage

For a duplex, two-unit or three-unit residential use, the HOME Phase 1 ordinance sets:

• minimum lot area of 5,750 sq ft;
• minimum front yard setback of 15 feet;
• rear setback per the base zoning district, or 5 feet if the lot is next to an alley or a lot with a multifamily-type use;
• maximum building coverage of 40% and impervious cover of 45%.

Height is set by the base zoning district. The city says there is no longer a zoning minimum distance between units, but you must still meet the International Residential Code's separation and fire separation rules.

Inside the "McMansion" area (Subchapter F), floor area is capped. Under the 2023 ordinance, a three-unit site may have the greater of 0.65 floor-to-area ratio or 4,350 sq ft. Each new unit may be no more than the greater of 0.4 or 2,300 sq ft. For two units, the site cap is the greater of 0.55 or 3,200 sq ft. Garages count toward floor area there; carports and porches don't. There is a floor-area bonus for preserving an older existing home.

These numbers come from the adopted ordinances and city guidance. Confirm current limits for your lot at a Residential Zoning appointment. [1][2][4]

Parking

The City Council passed Ordinance 20231102-028 on November 2, 2023. It eliminated minimum motor vehicle parking requirements and took effect November 13, 2023.

Front-yard parking is still limited for two- and three-unit lots. No more than four parking spaces may sit in the front street yard. Front-yard impervious cover is capped at 40%. [4][5]

Small lots and lot splits: HOME Phase 2

HOME Phase 2 was adopted May 16, 2024 and has applied citywide since November 16, 2024. It created a "small lot single-family residential use" in SF-1, SF-2 and SF-3. That allows one home on a lot of at least 1,800 sq ft but less than 5,750 sq ft. A small lot can have only one dwelling unit.

To use the smaller lot sizes, you generally need a subdivision application to divide your lot, unless it is already under 5,750 sq ft. In that case you apply for a building permit. A simpler "residential infill" subdivision is available for sites of no more than one acre that are a replat of land already platted as a residential subdivision.

Under the Phase 2 ordinance, small lots in SF-3 or more restrictive zones must be at least 15 feet wide. The minimum setbacks are generally 10 feet in front, 5 feet on the sides and 5 feet in back, with some zero setbacks where new small lots meet. Inside the McMansion area, gross floor area is capped at the greater of 1,650 sq ft or 0.55 floor-to-area ratio, and the maximum unit size is 2,300 sq ft.

Two- and three-unit uses must still meet the minimum lot area, so a new small lot can't hold extra units. The city's HOME Phase 2 Guide helps you check eligibility.

Separately, the state's 2025 small-lot law, SB 15, limits minimum lot sizes in new, unplatted subdivisions of five acres or more in large Texas cities. See our Texas ADU guide. [1][6][7]

Tiny homes

Austin defines a tiny home as a dwelling unit of 400 square feet or less, not counting loft space. A tiny home can be one of the up to three units on an SF lot.

To permit one, submit the Tiny House Request for Modification or Alternate Method of Compliance form with your residential new construction application, through either standard or expedited review. See our backyard tiny house guide. [1]

Fees and timeline

An ADU is permitted as new construction. You pay plan review fees when you submit and permit fees once the plans are approved. The amounts depend on your project; the city's fee page has the Residential Building Plan Review and Permit Fee chart. Our ADU cost guide covers construction costs.

Since July 1, 2026, the city's posted review time for residential new construction and additions is 10 business days, and 7 business days for update submittals. The review clock starts after you pay the plan review invoice. Expedited review is also available.

Once your permit is active, it expires on the 181st day if no inspection has been scheduled or received. Each passed inspection extends it 180 days. [1][2][8]

Renting it out and short-term rentals

An ADU can be used as a short-term rental only under specific conditions. If it was built after October 1, 2015, it may not be rented short term for more than 30 days in a calendar year. You need a short-term rental license and must submit the ADU's Certificate of Occupancy with the application. See the city's Short-Term Rental program. [2]

Deed restrictions

City zoning is not the only limit. Some Austin properties have deed restrictions or restrictive covenants that can block or limit extra units, and the city says checking them is your responsibility. See the city's Deed Restrictions and Development page. [1][2]

Permit steps in Austin

1. Check that an ADU is allowed on your lot

   Confirm the lot is zoned SF-1, SF-2 or SF-3 and is at least 5,750 sq ft using Property Profile. If it isn't, book a Residential Zoning Questions appointment to discuss options. [2]

2. Get a new address

   Each new unit needs its own address or building number. Request it from Address Management Services before you apply. [2]

3. Set up an AB+C account and apply

   Register on the Austin Build + Connect portal, then submit the Residential New Construction and Addition application through the Residential Plan Review web form. [2][8]

4. Pay plan review fees and complete review

   Intake staff check the submission and invoice plan review fees. Review starts once you pay, and you work with assigned reviewers to resolve comments. [2][8]

5. Activate the permits

   After approval, the building and trade permits are created in Pending status. Your registered contractors pay for and activate them. [2]

6. Build and schedule inspections

   Construction can start once permits are Active. A permit expires on day 181 without an inspection; each inspection extends it 180 days. [2]

7. Get the Certificate of Occupancy

   When the final building inspection passes, the inspector issues the Certificate of Occupancy. [2]

Who to call

• Austin Development Services Department

  Development-related questions, residential plan review and permits

  512-978-4000

  [8]

• Residential Zoning Questions appointments (DSD)

  Zoning questions for ADUs, two- and three-unit lots: setbacks, impervious cover, Subchapter F

  [1][2]

• Land Use Assistance (DSD)

  Subdivision and small-lot (HOME Phase 2) questions, land status determinations

  [1]

• Address Management Services

  New address or building number for an ADU

  [2]

Questions people ask