An ADU builder in Austin is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Austin's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in Texas.
What ADU Builders Cost in Austin [14][15][16]
Based on our Austin cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $150,000-$350,000 |
| Cost per Sq Ft | $250-$450 |
| Garage Conversion | $30,000-$100,000 |
| Prefab / Modular ADU (installed) | $125,000-$300,000 |
| City Permit & Plan Review | 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. |
| Impact Fees | No City impact fee for an ADU on an already-built lot: the Street Impact Fee applies only to redevelopment adding 10 or more PM-peak trips, and Transportation and Public Works states an ADU on a site with an existing structure owes none. Austin Water capital recovery (impact) fees are assessed per service unit only when a new or larger tap is added: $7,700 combined on lots platted after Oct 1, 2023, $7,200 for 2018-2023 plats, $800-$3,900 by zone for pre-2014 plats. |
For a full line-item breakdown, see our Austin ADU cost guide. To confirm what you're allowed to build before you hire, review the Austin ADU rules (max detached size: 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.; owner-occupancy: 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.).
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How to Vet an ADU Builder in Austin
- License: Confirm a current contractor's license in Texas and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Austin and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (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.), 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.), and impact fees (No City impact fee for an ADU on an already-built lot: the Street Impact Fee applies only to redevelopment adding 10 or more PM-peak trips, and Transportation and Public Works states an ADU on a site with an existing structure owes none. Austin Water capital recovery (impact) fees are assessed per service unit only when a new or larger tap is added: $7,700 combined on lots platted after Oct 1, 2023, $7,200 for 2018-2023 plats, $800-$3,900 by zone for pre-2014 plats.) are included.
- Permit handling: Confirm they manage Austin's permit process ("Residential New Construction or Addition building-permit application through DSD's AB+C portal: 1) confirm zoning and lot area on Property Profile, 2) get a new address from Address Management Services, 3) submit plans through the web form, 4) pay plan-review fees, 5) pay and activate the building and trade permits, 6) inspections, 7) Certificate of Occupancy. Fee-based Expedited Residential Plan Review (one sitting with all disciplines) and an AI 'Pre-Check' beta are optional.", 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.) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Austin in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (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.) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent Texas ADU client references?
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