ADU Regulations in Maine (ME)
Maine is rated Easy for ADU construction with an ADU-friendliness score of 80/100 (Very ADU-Friendly). Maine has a statewide ADU law that sets baseline rules across all municipalities. No owner-occupancy requirement. No additional parking required for ADUs. Maine passed LD 2003 in 2022, one of the most progressive ADU laws in the US. The law requires all municipalities to allow up to 2 ADUs per lot, prohibits owner-occupancy requirements, and bans parking mandates for ADUs. Municipal design review must be objective. Effective July 2023.
Full ADU Regulations Summary for Maine
| ADUs Allowed | Yes |
| Statewide ADU Law | Yes |
| Maximum ADU Size | Set locally |
| Owner Occupancy Required | No |
| Parking Required | No |
| Minimum Setback | Set locally |
| Permitting Timeline | Varies by municipality |
| Impact Fees | None for ADUs |
| Long-Term Rental Allowed | Yes |
| Short-Term Rental (Airbnb) Allowed | Yes |
| Ease of Building | Easy |
ADU Regulations by City in Maine
ADU rules can vary by city even within the same state. While Maine's statewide law sets minimum standards, some cities have additional local provisions. Below are ADU details for 3 cities in Maine.
Portland
ADUs allowed by right on all residential lots. Portland was already ADU-friendly before the state law. Up to 2 ADUs permitted per lot.
Bangor
ADUs permitted per state law. Bangor updated zoning in 2023 to comply with LD 2003.
South Portland
ADUs allowed on residential lots. No owner-occupancy requirement per state law.
How Maine Compares to Other States
Below is a comparison of Maine with five states that have similar ADU-friendliness scores. This comparison helps illustrate where Maine stands nationally.
| State | Score | Statewide Law | Parking Req? | Owner Occ? | Ease |
|---|---|---|---|---|---|
| Maine (ME) | 80 | Yes | No | No | Easy |
| Florida (FL) | 78 | Yes | No | No | Easy |
| Montana (MT) | 78 | Yes | No | No | Easy |
| Nevada (NV) | 78 | Yes | No | No | Moderate |
| Connecticut (CT) | 83 | Yes | No | No | Easy |
| New York (NY) | 76 | Yes | No | Yes | Easy |
Frequently Asked Questions About ADUs in Maine
Can I build an ADU in Maine?
Yes, ADUs are allowed in Maine. Maine has a statewide ADU law that requires local jurisdictions to permit ADUs on residential lots. This means your city cannot outright ban ADUs. The ease of building is rated "Easy" with a friendliness score of 80/100.
Do I need to live on the property to have an ADU in Maine?
No, Maine does not require owner occupancy for ADUs. You can rent out both the main house and the ADU, which maximizes rental income potential.
How big can an ADU be in Maine?
Maine does not set a statewide maximum ADU size — this is determined by your local jurisdiction. Common local limits range from 600 to 1,200 square feet. Check your city's zoning code for the specific maximum.
Do I need extra parking for an ADU in Maine?
No, Maine does not require additional parking for ADUs. This is a significant advantage, as parking requirements are often the biggest barrier to ADU construction on smaller lots.
Can I rent out my ADU in Maine?
Yes, long-term rentals of ADUs are allowed in Maine. Short-term rentals (like Airbnb) are also generally permitted, though your city may have separate short-term rental regulations.
How long does it take to get an ADU permit in Maine?
The permitting timeline in Maine is: Varies by municipality. The statewide law sets maximum review periods that cities must comply with. Actual timelines can be affected by plan review backlogs, inspection scheduling, and the complexity of your project. Pre-approved ADU plans, where available, can significantly speed up the process.
Check ADU Rules for Your City
Use our ADU regulations lookup tool to find the specific rules for your city in Maine, or browse all 50 states to compare ADU regulations across the country. Remember that local rules may be more specific than state-level regulations.