As of October 2026, Angi puts a garage-to-ADU conversion at roughly $58,000 to $173,000 nationally, and one 2026 Texas guide built on RSMeans data estimates a 600 sq ft detached unit in Dallas at about $80,000 to $166,000 before permits. Zoning approval, utility work and finishes come on top.
What do published estimates say?
| Project | Published estimate | Source |
|---|---|---|
| Garage-to-ADU conversion, national | About $58,000 to $173,000; average about $115,000 | Angi |
| Detached ADU, 600 sq ft, Dallas | About $80,000 (basic) to $166,000 (high-end), before permits | CostToBuildHouse 2026 Texas guide, RSMeans-based |
| Permit estimate, Dallas | About $3,800 | Same 2026 Texas guide |
| Board of Adjustment filing, City of Dallas | $600 | City of Dallas |
We found no published source that tracks Dallas ADU prices from real contracts. The Texas figures above are model estimates and the guide that publishes them is not fully consistent, so treat them as a low-side reference, not a price.
What costs come before construction?
- Approval. A Board of Adjustment special exception means a filing fee, notification signs and drawings for the hearing.
- Survey and design. A current survey, a plan set and structural engineering.
- Permits. Building and trade permits, which vary by city.
- Utility work. Sewer and water taps or extensions, and often an electrical service upgrade.
What makes a North Texas ADU cost more?
- Foundation design for expansive clay soils.
- Distance from the street to the back of the lot for sewer and power.
- A second story for a garage apartment.
- HOA requirements to match brick, roofing or trim on the main house.
- Replacing parking when a garage conversion removes required spaces.
Is a garage conversion always cheaper?
In construction cost, usually. In total cost, not always: the approval step is the same, and a city that requires a replacement garage can erase the savings. We price both when both are open to you.
Sources, as of October 2026:
- Angi, garage-to-ADU conversion cost guide (2025 data).
- CostToBuildHouse, "2026 Texas ADU Cost Guide" (RSMeans-based estimates).
- City of Dallas Planning and Development, Accessory Dwelling Units page.
- Figures are published estimates, not our quotes.