ADU Rules in Austin, TX (2026)
ADU rules, permit requirements, size limits, and fees for Austin, TX. Source-cited from official municipal code.
Yes, ADUs are allowed in Austin, TX.
Austin, TX permits accessory dwelling units (ADUs) on residential properties. ADUs — also called granny flats, in-law units, backyard cottages, or secondary suites — are secondary housing units on a single-family or multifamily lot. State and local law governs the approval process. In Austin, the Austin Development Services Department (DSD) handles ADU permit applications. Below you will find the current size limits, setbacks, fees, and timeline for building an ADU in Austin.
ADU Size Limits
ADU Size Limits in Austin: Detached ADU: up to 1100 sq ft (max height: 32 feet). Attached ADU: No greater than main house floor area. Austin Development Code Section 25-2-774. Detached secondary apartments (ADUs) limited to 1,100 sqft or 0.15 FAR of lot area, whichever is greater. Austin does not use the JADU terminology from California.
| Type | Max Size | Max Height |
|---|---|---|
| Detached ADU | 1100 sq ft | 32 feet |
| Attached ADU | No greater than main house floor area | Per zone height limit |
Permit Fees
ADU Permit Fees in Austin: Plan check fee: $300–$2,000. Building permit fee: Based on construction value — typically $1,000–$4,000. Impact fees: Varies significantly — Austin charges Transportation, Water/Wastewater, Drainage impact fees. School fees: None or N/A. Total estimated permit cost: $3,000–$15,000 total fees including impact fees. Austin impact fees are significant — water/wastewater impact fees for secondary apartments can be $3,000–$8,000 depending on connection size. Transportation impact fee depends on location and trip generation. Fee estimator: https://abc.austintexas.gov/
| Fee Type | Amount |
|---|---|
| Plan Check | $300–$2,000 |
| Building Permit | Based on construction value — typically $1,000–$4,000 |
| Impact Fees | Varies significantly — Austin charges Transportation, Water/Wastewater, Drainage impact fees |
| School Fees | None |
| Total Estimate | $3,000–$15,000 total fees including impact fees |
Permit Timeline
Austin ADU Permit Timeline: Austin DSD building permit: typically 2-4 months plan review. Austin has electronic permit review (Austin Build + Connect portal). Construction 4-12 months. Apply through the Austin Development Services Department (DSD) online permit portal. Phone: (512) 978-4000.
Setback Requirements
ADU Setback Requirements in Austin: Front setback: follows zone standard. Side setback: 5 feet. Rear setback: 10 feet. Secondary apartments must maintain 10 ft rear setback and 5 ft side setbacks. If accessory structure (detached garage converted to ADU), different setback standards may apply per Austin Development Code Section 25-2-492. Alley access available on many lots — ADU can be placed over garage near alley.
Parking Requirements
Parking Requirements: 1 parking space required per secondary apartment unit unless within one-quarter mile of CapMetro urban rail station. Reduced parking available in transit-oriented development zones.
Restrictions & Requirements
- Secondary apartment must be on same lot as main residence
- Minimum lot size requirements by zone (SF-2 requires 5,750 sqft minimum)
- Impervious cover limits by watershed — development cannot exceed basin-specific limits
- Tree preservation requirements may limit placement — Heritage Trees (19+ inch diameter) cannot be removed
- Secondary apartment unit cannot be separately conveyed (sold separately) from main lot
- Short-term rental of secondary apartment requires STR license
How Many ADUs Are Allowed?
Number of ADUs Allowed in Austin: Single-family lots: 1 secondary apartment per lot (plus HOME initiative allows up to 3 total units). Multifamily properties: Multiple units allowed per zoning in MF zones. HOME Ordinance (2023) allows up to 3 units on any SF-zoned lot citywide. Secondary apartments and duplexes allowed by-right in most SF zones. This effectively allows: main house + secondary apartment + additional unit.
Single-Family Lots
1 secondary apartment per lot (plus HOME initiative allows up to 3 total units)
Multifamily Properties
Multiple units allowed per zoning in MF zones
Historic District Considerations
Historic District Requirements: Austin has 12 historic districts where additional design review may be required for ADU construction. Design review approval is required before obtaining a building permit for properties in historic overlay zones. Austin Historic Landmark Commission designates approximately 600 individual Austin Historic Landmarks and oversees 12+ National Register Historic Districts including Hyde Park, Clarksville, and Old West Austin. Certificate of Appropriateness (CoA) required for exterior changes to landmarks and contributing structures in historic districts. Austin Heritage Tourism: https://www.austintexas.gov/department/heritage-tourism Look up historic district boundaries at: https://www.austintexas.gov/page/historic-landmark-and-contributing-structure-resources
Frequently Asked Questions
Can I build an ADU in Austin?
Yes. Austin, TX allows accessory dwelling units. On a single-family lot you can build 1 secondary apartment per lot (plus HOME initiative allows up to 3 total units).
How big can an ADU be in Austin?
The maximum size for a detached ADU in Austin is 1,100 square feet.
How long does it take to get an ADU permit in Austin?
The typical ADU permit timeline in Austin is Austin DSD building permit: typically 2-4 months plan review. Austin has electronic permit review (Austin Build + Connect portal). Construction 4-12 months.. Total estimated permit fees are $3,000–$15,000 total fees including impact fees.
Do I need extra parking for an ADU in Austin?
No, Austin does not require additional parking for ADUs.
Do I have to live on-site to have an ADU in Austin?
No, owner-occupancy is not required for ADUs in Austin.
Source: Austin City Code Title 25, Section 25-2-774 — Secondary Apartments; HOME Ordinance 2023-05-18. Last verified April 3, 2026. View source