AUSTIN — ADU Guide — Your Guide to Accessory Dwelling Units in Austin Get Listed as a Trusted Pro

The ADU Process, Step by Step

A general roadmap from idea to move-in. Exact steps and timelines vary by project.

  1. 1. Check Property Eligibility

    Confirm your lot's zoning, size, deed restrictions, and HOA rules. Austin context: the HOME Initiative allows up to three units on most single-family lots, but private HOA and deed restrictions can still override city code.

  2. 2. Define Your Project

    Choose your ADU type (detached, garage conversion, or attached), target square footage, and budget.

  3. 3. Hire a Contractor or Architect

    Develop site plans, architectural drawings, and MEP (mechanical, electrical, plumbing) layouts that meet Austin's building codes.

  4. 4. Submit for Permits

    Submit residential plan review to the City of Austin Development Services Department, covering zoning, building, structural, electrical, plumbing, and mechanical.

  5. 5. Permit Review & Revisions

    Address formal review comments, update drawings, and secure approved building and trade permits.

  6. 6. Construction

    Foundation, framing, rough-in trades, insulation, drywall, and finishes — each phase requires a staged city trade inspection.

  7. 7. Final Inspection & Certificate of Occupancy (CO)

    Final building and trade sign-offs, followed by issuance of the Certificate of Occupancy before the unit can be legally occupied or rented.

Estimated ADU Cost Ranges

ADU budgets vary significantly based on project type, site conditions, utility connections, and finish levels. Below are typical turnkey planning benchmarks for standard residential builds.

ADU Type Typical Cost Range Average Cost / Sq Ft Ideal For
Garage Conversion $50,000–$150,000 $125–$250 Reusing an existing foundation/framing shell for the lowest initial cost.
Attached Addition $120,000–$250,000 $200–$325 Expanding living space directly tied to the primary home's footprint.
Prefab / Modular DADU $130,000–$260,000 $225–$350 Faster on-site assembly and predictable off-site manufacturing.
Custom Detached Build (DADU) $175,000–$400,000+ $250–$400+ Maximum layout flexibility, privacy, and long-term rental value.

Top Factors That Influence Total Cost

  • Site Preparation & Grading: Sloped lots, soil composition, and protected tree root zones (Critical Root Zone mitigations).
  • Utility Infrastructure: Distance from main lines for water and sewer tap connections, and electrical sub-panel upgrades.
  • Soft Costs: Architectural design, structural engineering, boundary surveys, and municipal permit fees.
  • Interior Finishes: Standard vs. custom cabinetry, countertop materials, appliance packages, and multi-zone HVAC split systems.

These figures reflect general planning estimates. Final pricing requires a site feasibility assessment and formal architectural review.

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