Attached addition ADU Cost
An ADU that shares one or more walls with the main house. Slightly cheaper than detached because it reuses an existing wall and is closer to utilities.
Nationally a attached addition ADU runs $200–$330/sq ft turnkey. Below is a 600 sq ft example for every state, adjusted for local construction costs.
| State | 600 sq ft estimate | $/sq ft |
|---|---|---|
| Mississippi | $99,500–$164,500 | $166–$274 |
| Arkansas | $101,000–$166,500 | $168–$277 |
| Alabama | $102,000–$168,500 | $170–$281 |
| Oklahoma | $103,000–$170,500 | $172–$284 |
| South Carolina | $104,500–$172,500 | $174–$287 |
| North Carolina | $105,500–$174,000 | $176–$290 |
| Tennessee | $105,500–$174,000 | $176–$290 |
| Kansas | $105,500–$174,000 | $176–$290 |
| Louisiana | $105,500–$174,000 | $176–$290 |
| Georgia | $108,000–$178,000 | $180–$297 |
| Kentucky | $108,000–$178,000 | $180–$297 |
| Nebraska | $108,000–$178,000 | $180–$297 |
| New Mexico | $108,000–$178,000 | $180–$297 |
| South Dakota | $108,000–$178,000 | $180–$297 |
| West Virginia | $108,000–$178,000 | $180–$297 |
| Texas | $110,500–$182,000 | $184–$304 |
| Indiana | $110,500–$182,000 | $184–$304 |
| Iowa | $110,500–$182,000 | $184–$304 |
| Missouri | $110,500–$182,000 | $184–$304 |
| Florida | $114,000–$188,000 | $190–$314 |
| Ohio | $114,000–$188,000 | $190–$314 |
| Michigan | $114,000–$188,000 | $190–$314 |
| Idaho | $114,000–$188,000 | $190–$314 |
| North Dakota | $114,000–$188,000 | $190–$314 |
| Wyoming | $114,000–$188,000 | $190–$314 |
| Montana | $117,500–$194,000 | $196–$323 |
| Utah | $117,500–$194,000 | $196–$323 |
| Arizona | $117,500–$194,000 | $196–$323 |
| Virginia | $117,500–$194,000 | $196–$323 |
| Delaware | $120,000–$198,000 | $200–$330 |
| Wisconsin | $120,000–$198,000 | $200–$330 |
| Maine | $122,500–$202,000 | $204–$337 |
| Pennsylvania | $122,500–$202,000 | $204–$337 |
| Nevada | $122,500–$202,000 | $204–$337 |
| New Hampshire | $126,000–$208,000 | $210–$347 |
| Vermont | $126,000–$208,000 | $210–$347 |
| Colorado | $126,000–$208,000 | $210–$347 |
| Minnesota | $126,000–$208,000 | $210–$347 |
| Maryland | $126,000–$208,000 | $210–$347 |
| Oregon | $129,500–$214,000 | $216–$356 |
| Washington | $132,000–$218,000 | $220–$363 |
| Illinois | $132,000–$218,000 | $220–$363 |
| Rhode Island | $134,500–$222,000 | $224–$370 |
| Connecticut | $138,000–$227,500 | $230–$379 |
| New Jersey | $138,000–$227,500 | $230–$379 |
| Massachusetts | $144,000–$237,500 | $240–$396 |
| New York | $144,000–$237,500 | $240–$396 |
| Washington DC | $144,000–$237,500 | $240–$396 |
| California | $150,000–$247,500 | $250–$413 |
| Alaska | $156,000–$257,500 | $260–$429 |
| Hawaii | $162,000–$267,500 | $270–$446 |
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Other ADU types
Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.