Can You Build an ADU in Lewiston?
Yes — Lewiston is governed by Maine's statewide ADU law, which limits what the city can restrict. A 700 sq ft detached ADU here runs about $157,000–$257,000.
Construction costs in Lewiston track close to the Maine state average.
Detached ADU (700 sq ft)
$157,000–$257,000
Garage conversion (400 sq ft)
$49,000–$90,000
Statewide protection
Yes
What applies in Lewiston
Maine's LD 2003 (2022) requires municipalities to allow at least one ADU per single-family lot and prohibits owner-occupancy requirements. Size and setback standards are set locally within state limits.
Because Maine has a statewide ADU law (30-A M.R.S. §4364-B (LD 2003, 2022)), Lewiston must follow these minimums even where its older zoning code is stricter. Confirm fees and design standards with the Lewiston planning department.
Estimate your Lewiston ADU cost
Your property
ADU typeEstimated cost in Maine
$157,000 – $257,000
≈ $224–$367/sq ft turnkey · midpoint $207,000
- $140,700
- Construction
- $37,300
- Design & permits
- $29,000
- Site work
- iSize set locally. This state leaves ADU size limits to your city — typical caps run 600–1,200 sq ft. Check your local code.
- ✓No extra parking likely required. Set by local ordinance — commonly 1 space per ADU unless near transit.
- ✓No owner-occupancy requirement. You can rent out both the main home and the ADU — you do not have to live on the property.
- ✓Lot has room. A 700 sq ft ADU uses about 12% of your 6,000 sq ft lot — comfortably within typical coverage limits.
Rule basis: 30-A M.R.S. §4364-B (LD 2003, 2022)
If you rent it out
$1,100–$1,775
est. rent/mo
8.4%
gross yield
12.8 yrs
payback
~$16,182/yr after a 7% vacancy allowance, before financing & maintenance.
Financed over 20 yrs at 7.5%, the build is about $1,668/mo — vs ~$1,450/mo in estimated rent.
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.
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Other Maine cities
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.