Compare ADU zoning rules across 8 Texas cities. Average ADU score: 5.2/10.
Gathered from the 8 cities below, with the bill or ordinance each one names. Statewide measures are listed once with the cities they reached, rather than repeated for each.
Statewide law sets a floor; the numbers that decide your project are local. Here is the spread across the 8 Texas cities covered here, taken from each city's own ordinance rather than a state summary.
| Question | Across Texas |
|---|---|
| Are ADUs permitted? | 5 of 8 permit them, 2 only by discretionary approval, and 1 do not. |
| Detached size cap | Median 800 sq ft, from 200 to 2,300 sq ft across the 5 cities publishing a numeric cap. |
| Owner-occupancy | Required in 4 of 8. |
| Build cost | $125,000 to $350,000 depending on city and unit type. |
| Easiest and hardest here | Austin scores 8/10; Richardson scores 2/10. |
Recomputed whenever a city page changes, so this and the city pages below cannot disagree.
| City | Max Size | Setbacks | Permit Fees | Build Cost | 1BR Rent | Score |
|---|---|---|---|---|---|---|
| Austin | 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. | 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)). | 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. | $150,000-$350,000 | $1,250-$1,850/mo | 8/10 |
| Dallas | Greater of 700 sq ft or 25% of the main structure's floor area, minimum 200 sq ft (Sec. 51A-4.510(c)(2)(C)(i), overlay lots). Outside an overlay the general accessory-structure cap applies: one structure may not exceed 25% of the main building's floor area and all accessory structures together 50%, excluding parking (Sec. 51A-4.209(b)(6)(E)(vii)(dd)-(ee)). | 3 ft when the structure is under 15 ft tall (Sec. 51A-4.510(c)(2)(B)(ii)); at 15 ft or taller the base district rear yard applies, 5 ft for single-family structures in R-5(A) and R-7.5(A) (Sec. 51A-4.112). Outside an overlay Sec. 51A-4.403(b)(2) lets an accessory structure under 15 ft sit 3 ft from a rear line on an alley, or on the line where there is no alley. | $1,200-$1,400 building permit for a 600-1,000 sq ft unit: Table A-I ($1.07 per sq ft up to 700 sq ft; $0.34569 per sq ft plus $300 above) plus $577 plan review, $25 handling and $15 technology fee (fee schedule of July 1, 2025); Board of Adjustment special exception $600 (Ch. 52 Sec. 303.12.1.4). | $130,000-$320,000 | $1,300-$1,550/mo | 4/10 |
| Fort Worth | No numeric cap for a habitable accessory building in § 5.301. The limits are the district's lot coverage counting every roof on the lot (§ 5.301(a)(3): 50% in A-5, 45% in A-7.5, 40% in A-10, 30% in A-21 and A-43, 20% in A-2.5A; accessory habitable area counts, § 9.101 'lot coverage'), the district setbacks, the building code and a height no greater than the house (§ 5.301(c)(2)). The 120-to-400-square-foot table in § 5.301(b) applies only to non-habitable sheds and workshops, not to a habitable unit | 5 ft in A-5, A-7.5 and AR; 10 ft in A-10 and A-21; 25 ft in A-43 and A-2.5A. A habitable accessory building must meet the side and rear setback of the primary structure for its district (§ 5.301(a)(2)). The 3-ft reduction in § 4.705(d)(8) is for detached garages behind the rear wall of the house, not habitable space, and structures may not sit in easements | $300-$900 building permit for a 500-1,200 sq ft unit. FY2027 Table 1-C-3 (R use groups, fee ordinance on the Sept 15, 2026 Council budget agenda, effective Oct 1, 2026): an R-3 unit up to 500 sq ft pays $61.01 plus $0.45 per sq ft over 65; 65-700 sq ft $102 plus $0.74 per sq ft over 65; 700-1,400 sq ft $570 plus $0.53 per sq ft over 700. Worked: 500 sq ft about $257, 800 sq ft $623, 1,000 sq ft $729, 1,200 sq ft $835, plus a $33.08 application fee and $16.87 technology fee; no plan-review deposit for R-3 accessory structures. Until Sept 30, 2026 the FY2025-26 table (Ord. 27191-09-2024) applies: 500 sq ft $240.80, 800 sq ft $592.44, 1,000 sq ft $692.44, plus $31.50 and $16.87. A garage conversion is a residential remodel at $119 per trade ($595 for five trades, FY2027). Third-party plan review and inspection reduce the permit fee to 70%, 55% or 35% | $130,000-$320,000 | $1,250-$1,500/mo | 3/10 |
| Frisco | No floor-area cap: §4.06.03 sets location, permit, rental and setback standards for a Garage Apartment or Guest House but no maximum size. What binds is the district's maximum lot coverage for all buildings: 45% in SF-7, SF-8.5 and SF-10, 40% in SF-12.5, 30% in SF-16, 20% in RE and 55% in OTR (§2.06.04). A detached unit is a Guest House, defined in §7.01.01 only as "an accessory building used to house guests of the owner(s)" — confirm with Development Services before adding a kitchen | Same as the primary structure. Figure 4.06.04.1 gives the row "Guest House or Garage Apartment" setback note D, "Same as Primary Structure Setback", for front, side and rear, so it does not get the 3-foot (note A) or 10-foot (note B) rear setback ordinary accessory buildings use (§4.06.03(D), §4.06.04(G)). That is 30 feet in AG, RE, SF-16, SF-12.5, SF-10, SF-8.5, SF-7 and 2F, and 8 feet (20 feet for a garage facing an alley) in OTR (§2.06.04) | Building permit $150 for the first 300 sq ft plus $0.50 per added sq ft ($400 for 800 sq ft), plus a $300 application fee and $50-per-trade electrical, mechanical and plumbing permits, per the FY26 Comprehensive Fee Ordinance 2025-09-48 (effective Oct 1, 2025); FY27 figures apply from Oct 1, 2026. | $140,000-$350,000 | $1,500-$2,100/mo | 5/10 |
| Houston | 1,500 sq ft. § 42-1 defines single-family residential to include 'a detached second dwelling unit of not more than 1500 square feet'; the cap was increased by the Livable Places amendments (Ord. 2023-801, eff. Nov 27, 2023). The code does not say how the area is measured; deed restrictions may set a lower cap or bar a second unit entirely. | Chapter 42 sets no interior rear building line for a single-family lot; it sets 10 ft along a rear lot line that abuts a collector or local street (§ 42-156) and 3 ft along a shared driveway 18 ft or wider (§ 42-159). Interior rear lines are governed by deed restrictions, the plat and the Building Code's fire-separation rules — confirm with the Houston Permitting Center. | Set by the City Fee Schedule (CPI increase of 1.391% on Jan 1, 2026): minimum building permit $91.06, minimum plumbing permit $97.56, administrative fee $33.56; the full residential fee formula was not readable this pass, so price your project with HPC's Fee Calculator. | $140,000-$260,000 | $1,250-$1,900/mo | 7/10 |
| Plano | 400 sq ft minimum; maximum 1,100 sq ft or 50% of the gross habitable floor area of the main dwelling, whichever is more restrictive, and never above the district's maximum lot coverage (§15.1800.2.C–E). The city's permit handout lists 45% total coverage in SF-6, SF-7, SF-9 and 2F with garage and accessory buildings capped at 10% of the lot (25%/10% in SF-20) — confirm current coverage limits with Building Inspections | §15.1800 sets no cottage-specific rear setback — the rear-yard rule of your zoning district and the accessory-building placement rules of Article 13 apply. The current Article 9 and 13 text could not be read in September 2026, so confirm your district's rear-yard figure with Plano Planning before designing | Set by City Council fee resolution rather than in the Code (Code §6-653 amends UAC §304.2), plus a fire-protection plan-review fee on all construction (§304.2.1); the current schedule could not be read in September 2026 — get the figure from Building Inspections | $140,000-$350,000 | $1,350-$2,050/mo | 6/10 |
| Richardson | N/A: a detached second dwelling is not a permitted use. Detached accessory buildings are capped instead: all detached structures together, garages included, may occupy no more than 8% of the lot area and may not exceed 40% of the floor area of the principal dwelling (Art. IV, Sec. 4(d)(2); Art. VII, Sec. 4(d)(2)). Servants' quarters, the only accessory living space allowed, may not have kitchen facilities or separate utility connections (Art. I, Sec. 2) | N/A for ADUs. The district rear setback is 25 ft, but a detached garage, carport or other accessory building may extend into it with a minimum 3 ft from the rear lot line, or 18 in where the rear lot line adjoins an alley (Art. IV, Sec. 4(g)(2); Art. VII, Sec. 4(g)(2)). Building Inspection measures these to the roof overhang | Accessory building permit: $100 for a structure of 150 sq ft or less, $200 for one larger than 150 sq ft; a room addition is $200 up to 500 sq ft, then $200 plus $0.10/sq ft (Appendix B, Master Fee Schedule, Ord. 4559, Sept. 15, 2025). | $140,000-$350,000 | $1,450-$1,950/mo | 2/10 |
| San Antonio | The larger of 800 sq ft gross floor area or 50% of the main house's gross floor area, capped at 1,600 sq ft (UDC 35-371; IB 402 FAQ 1). Every lot may therefore have an ADU of at least 800 sq ft regardless of the size of the main house. | 5 ft standard for a detached ADU; may be reduced to 3 ft if the structure has no eave overhang within 3 ft of the line, and walls within 5 ft of the line must be fire-rated under the IRC (IB 402 FAQ 2; DSD ADU page). The ADU must be located in the rear of the lot (IB 402 FAQ 4). | FY2026 DSD fee schedule (rev. Oct 2025), new residential construction by size: $988 total basic permit fees for 501-1,000 sq ft, $1,022 for 1,001-1,250 and $1,201 for 1,251-1,500 sq ft (building, trade and sewer permits plus a $200 plan review). 100% waivable for income-qualified ADUs. | $125,000-$320,000 | $950-$1,250/mo | 7/10 |
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