ADU Rulebook

City · Texas

ADU rules in Austin

6 sources

These are the primary sources for accessory dwelling unit regulations in Austin: the city's own zoning code, planning department pages, and permit guides. Start here before talking to anyone: the rules below are what your permit reviewer will apply.

Rules at a glance

Detached (backyard) ADU
Allowed

Detached second units are the 'two-unit residential use': the use of a lot for two dwelling units, each in a separate building. Permitted by right in SF-1, SF-2, SF-3 and most multifamily districts. A third unit (three-unit residential use) is permitted in SF-1 through SF-3.

LDC § 25-2-3(16) (definition); § 25-2-491 (use table); § 25-2-773
Attached or internal ADU
Allowed

Two units within a single building is the 'duplex residential use' (§ 25-2-3(4)), permitted in SF-1, SF-2, SF-3 and multifamily districts per the § 25-2-491 use table, and governed by the same § 25-2-773 standards as two-unit use.

LDC § 25-2-3(4); § 25-2-491; § 25-2-773
Maximum size
Within the Subchapter F (central-city 'McMansion') boundary: each new unit capped at the greater of 0.4 FAR or 2,300 sq ft; total site FAR capped at the greater of 0.55 or 3,200 sq ft for two-unit use (0.65 or 4,350 sq ft for three-unit). Outside that boundary, base zoning district limits control. Preserving a qualifying older dwelling excludes its preserved square footage from FAR.

Minimum lot area for duplex/two-unit/three-unit use is 5,750 sq ft; max building coverage 40 percent; max impervious cover 45 percent. There is no longer a 1,100 sq ft ADU cap; the old ADU section (§ 25-2-774) was repealed.

LDC § 25-2-773(B), (E)(3)-(4), (F)
Owner occupancy
Not required

§ 25-2-773 contains no owner-occupancy requirement, and the former ADU section that once carried unit-specific conditions (§ 25-2-774) was repealed by Ord. 20231207-001 effective Dec 18, 2023. No owner-occupancy condition appears anywhere in the current two-unit/three-unit framework I read.

LDC § 25-2-773 (full text read); § 25-2-774 (reserved; editor's note)
Extra parking
None. Austin eliminated off-street parking minimums citywide (Ord. 20231102-028, Nov 2023): 'off-street motor vehicle parking is not required' except accessible spaces tied to what would formerly have been required. If parking is provided, placement rules in § 25-2-773(C)(2)-(3) apply (max four spaces in the front street yard; garage placement limits).

Chapter 25-6 Appendix A is now titled 'Tables of Off-Street Loading Requirements and Former Off-Street Parking Requirements'.

LDC § 25-6-471(A)-(B); § 25-2-773(C)
Approval process
Permitted use

Two-unit residential is a 'P' (permitted) use in SF-1, SF-2, SF-3, SF-5, SF-6, MF-1 through MF-6, CBD, and DMU in the § 25-2-491 use table; three-unit is P in SF-1 through SF-3. Standard residential building permit through the AB+C portal; no discretionary hearing. Not permitted in LA (Lake Austin) or RR (Rural Residence) districts.

LDC § 25-2-491
Rental restrictions
No minimum lease term found. Short-term rental of an ADU is allowed: § 25-2-904 (rewritten effective Oct 1, 2025) makes STR an accessory use to residential use in all districts, states STR 'cannot be prohibited', and requires an operator's license under City Code Chapter 4-23. The city's ADU page still states that ADUs built after Oct 1, 2015 may not be short-term rented more than 30 days per calendar year; that restriction lived in the repealed § 25-2-774 and conflicts with current § 25-2-904(D), which controls over conflicting provisions.

Treat the 30-day limit as likely stale guidance; the operative code text no longer contains it.

LDC § 25-2-904 (Ord. 20250227-039, Pt. 6, eff. 10-1-25)
The fine print: 8 caveats that can change the picture
  • Austin no longer has a standalone ADU ordinance. Since HOME Phase 1 (Ord. 20231207-001, effective Dec 18, 2023) a second (or third) unit on a single-family lot is regulated as 'two-unit' or 'three-unit residential use' under § 25-2-773; the old ADU section § 25-2-774 is repealed and reserved.
  • The per-unit size cap (greater of 0.4 FAR or 2,300 sq ft) applies only within the Subchapter F Residential Design and Compatibility Standards boundary (roughly the central city); outside it, base zoning district site development regulations control unit size.
  • Minimum lot area of 5,750 sq ft applies to duplex, two-unit, and three-unit uses; smaller lots cannot add a second unit under this section (small-lot pathways under HOME Phase 2, § 25-2-779, are a separate single-unit-per-lot regime).
  • Two-unit and three-unit uses are not permitted in LA (Lake Austin), RR (Rural Residence), SF-4A, or SF-4B districts.
  • Preservation incentive: preserving 50 percent or more of a qualifying existing dwelling (pre-1961, or 20+ years old) lets the owner exclude preserved square footage from FAR, changing effective size limits per § 25-2-773(E)-(F).
  • Traditional Neighborhood District (TND) areas have their own accessory dwelling rule, § 25-3-88(B), which caps an accessory dwelling unit at 700 sq ft; this applies only inside TND zoning, not citywide.
  • Private deed restrictions and restrictive covenants can still prohibit ADUs; the city's ADU page expressly flags this as the applicant's responsibility.
  • The city ADU page still advertises a 30-day-per-year STR cap for ADUs built after Oct 1, 2015, but the current code (§ 25-2-904, effective Oct 1, 2025) contains no such limit and states it controls over conflicting provisions.

Summarized from Austin's ordinance text, read July 2026; every row links the code section it came from. Rules often vary by zone and lot, so treat this as orientation, not a permit determination, and confirm with the planning department before you commit to a design.

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ADU regulations

Short-term rental rules

Planning to rent your ADU on Airbnb or VRBO? Austin regulates short-term rentals separately; check these before counting on nightly rental income.

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