Everything homeowners ask about building an ADU in Austin — answered with 2026 data.
Yes, ADUs are allowed in SF-1, SF-2 and SF-3: two-unit and three-unit residential are permitted uses (§ 25-2-491 use table). Two-unit residential is also permitted in SF-5, SF-6, MF-1 to MF-6, CBD and DMU. The lot must be at least 5,750 sq ft (§ 25-2-773(B)(1)); small lots of 1,800-5,749 sq ft get one home only (§ 25-2-779). Deed restrictions, NCCDs and historic districts can still block a second unit. in Austin, TX. The maximum size for a detached ADU is No fixed cap outside the Subchapter F (McMansion) boundary: only 40% building cover and 45% impervious cover (§ 25-2-773(B)). Inside that central-Austin boundary a new unit may not exceed the greater of 0.4 FAR or 2,300 sq ft; the lot total is the greater of 0.55 FAR or 3,200 sq ft for two units and 0.65 FAR or 4,350 sq ft for three (§ 25-2-773(E), as amended by Ord. 20250424-073, eff. May 5, 2025). Garages and lofts count toward gross floor area; carports and porches do not. Attached ADUs can be up to An attached second unit is a duplex residential use under the same § 25-2-773 limits: greater of 0.4 FAR or 2,300 sq ft per new unit and 0.55 FAR or 3,200 sq ft for the lot inside the Subchapter F boundary; no unit-size cap outside it. The old 1,100 sq ft / 15%-of-lot ADU limit in former § 25-2-774 was repealed by HOME Phase 1. Austin has an ADU-friendliness score of 8/10. Check our full Austin ADU rules page for complete zoning details.
ADU construction in Austin typically costs $150,000-$350,000. The cost per square foot averages $250-$450. Garage conversions are more affordable at $30,000-$100,000, while prefab ADUs cost $125,000-$300,000. Permit fees add About $1,850-$2,150 in DSD fees for an 800-1,200 sq ft unit (FY2025-26 residential schedule, eff. Oct 1, 2025): $106.72 processing + $896.50-$1,220 plan review + roughly $840-$885 in building, electrical, mechanical, plumbing and energy permits; Austin Energy adds $220-$440. to your budget. See our detailed Austin ADU cost guide.
Detached ADUs in Austin can be up to No fixed cap outside the Subchapter F. Attached ADUs are limited to An attached second unit is a duplex residential use under the same § 25-2-773 limits: greater of 0.4 FAR or 2,300 sq ft per new unit and 0.55 FAR or 3,200 sq ft for the lot inside the Subchapter F boundary; no unit-size cap outside it. The old 1,100 sq ft / 15%-of-lot ADU limit in former § 25-2-774 was repealed by HOME Phase 1. Junior ADUs (JADUs) have a cap of Austin has no junior-ADU category. A unit of 400 sq ft or less is a 'tiny home' (§ 25-1-21; IRC Appendix AQ) that counts as one of the two or three units and is permitted through the same residential application with a Request for Modification or Alternate Method of Compliance form. Maximum height is 35 ft: the SF-1, SF-2 and SF-3 base-district limit in the § 25-2-492(D) table. Subchapter F's 32-ft 'McMansion' height applies only to single-family residential use, not to duplex, two-unit or three-unit residential (Subchapter F § 1.2.2; DSD HOME Amendments page). You are allowed up to 3 dwelling units per SF-1, SF-2 or SF-3 lot on a qualifying lot.
Rear setback: 10 ft (SF-1/SF-2/SF-3 base district, § 25-2-492), reduced to 5 ft when the lot is adjacent to an alley or to a lot with a use permitted in a multifamily or less restrictive district (§ 25-2-773(B)(3)). Side setback: 5 ft interior side yard (§ 25-2-492). On a corner lot the street side yard is 10 ft from the property line on a Level 2, 3 or 4 street, or the greater of 5 ft from the line or 10 ft from the curb on a Level 1 street (§ 25-2-773(B)(4)). Front setback: 15 ft for duplex, two-unit and three-unit uses (§ 25-2-773(B)(2)); an open porch may sit 15 ft from the front lot line with its roof 13 ft. The 25-ft figure in the § 25-2-492 table applies only to single-family use. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None required. Austin repealed minimum off-street parking citywide in Ord. 20231102-028: § 25-6-471(A) reads 'off-street motor vehicle parking is not required'. If you build parking anyway, no more than four spaces may sit in the front yard and front-yard impervious cover is capped at 40% (§ 25-2-773(C)(2)). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required. HOME Phase 1 removed the primary/secondary use distinction, so any of the units may be rented or sold as a condominium; the pre-2023 owner-occupancy and 'accessory apartment' language is gone from Chapter 25-2. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Austin is typically DSD's published target is 10 business days for the first review of a New Construction application and 7 business days per update (Residential Plan Review page, targets revised July 1, 2026); garage conversions are 5 business days. Time to permit depends on how many review cycles you need. Plan check: 10 business days for the first review (New Construction and Additions), 7 business days for each update submittal, 5 business days for garage conversions: DSD Residential Plan Review targets in force since July 1, 2026. Expedited review is a paid single-session alternative. Pre-approved plans availability: None. The City has no pre-approved ADU plan library (Council Resolutions 20200409-080 and 20211209-064 only directed staff to study one, and DSD's ADU page lists none as of Sept 2026). What does exist: fee-based Expedited Residential Plan Review, the AI Pre-Check beta, and free 20-minute Residential Zoning appointments.
Average ADU rental income in Austin: 1-bedroom units rent for $1,250-$1,850/month, 2-bedroom units for $1,600-$2,300/month. Short-term rentals: Yes, with a City STR operator's license (Code Ch. 4-23, in force Oct 1, 2025): up to two STRs on a lot of three or fewer units, $836.30 new / $385.30 renewal, two-year term, hotel occupancy tax applies. Expected ROI: 5-9% gross rent yield (annual rent divided by build cost).
The minimum lot size for an ADU in Austin is 5,750 sq ft for a second or third unit (§ 25-2-773(B)(1)). Lots of 1,800 to 5,749 sq ft in SF-3 or more restrictive districts may hold one 'small lot single-family' home only (§ 25-2-779(F), HOME Phase 2, Ord. 20240516-006). Lots may be re-subdivided down to 1,800 sq ft through the residential infill plat process (applications since June 16, 2025). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Austin, a garage conversion typically costs $30,000-$100,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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