Can I build an ADU in North Yarmouth, Maine?
Yes. North Yarmouth allows one accessory dwelling unit on a lot with a single-family home, approved by the Code Enforcement Officer, in every district except Resource Protection. The ADU can be inside, attached or detached, is limited to one bedroom and 40% of the main house's living area, and the owner must live in either the ADU or the main house.
| Number allowed | 1 ADU per lot with a single-family home [1] |
| Where allowed | CEO permit (P) in Village Center, Village Residential, Farm and Forest and Residential Shoreland; not allowed (N) in Resource Protection [2] |
| Attached or detached | Inside the house, attached, a new detached building, or inside an existing accessory building [3] |
| Bedrooms | 1 bedroom maximum [4] |
| Maximum size | 40% of the main house's living area (basement excluded) [5] |
| Minimum size | 190 sq ft, unless the state board sets a different minimum [6] |
| Owner occupancy | Owner must live in the ADU or the main house [8] |
| Parking | No parking beyond what the house already requires [9] |
| Approval | Code Enforcement Officer, with proof of adequate water and septic before occupancy [7] |
Where and what kind
One ADU may be built on the same lot as a single-family home anywhere housing is allowed [1]. The land use table lists ADUs as a permitted use with Code Enforcement Officer review in the Village Center, Village Residential, Farm and Forest and Residential Shoreland districts, and as prohibited in the Resource Protection district [2]. The unit can be inside the existing house, attached to it, a new detached building, or inside an existing accessory building [3].
Size and layout
The ADU is limited to one bedroom [4]. Whether inside, attached or detached, it can't exceed 40% of the main house's living area, not counting the basement [5]. The minimum is 190 sq ft unless the state Technical Building Code and Standards Board adopts a different minimum, in which case that standard applies [6]. The state board has set 160 sq ft, so check with the Code Enforcement Officer on which figure is used.
Setbacks, density and parking
An attached or internal ADU must meet the same setbacks and dimensional rules as the house. An ADU in an accessory building that existed on July 1, 2023 follows that building's setback rules [10]. ADUs are exempt from density and lot-area limits and from the town's annual residential building permit cap. No parking is required beyond what the house already needs [9].
Owner occupancy
The property owner must live in either the ADU or the main house [8]. A state law taking effect July 1, 2027 bars towns from requiring owner occupancy for ADUs, so this provision may stop being enforceable on that date.
Approval
The Code Enforcement Officer approves ADUs. Before the unit can be occupied, you must give written proof that it connects to adequate water and wastewater service, such as a septic design by a licensed site evaluator verified by the local plumbing inspector, or a potable well test [7]. Shoreland zoning, deed restrictions and HOA rules may also apply.
See how North Yarmouth compares with 8+ other Maine towns on accessory dwelling units (adus) →
Next steps
- Confirm your zoning district on the Town of North Yarmouth Zoning Map (ADUs aren't allowed in Resource Protection).
- Measure the main house's living area (excluding basement) to find your 40% size limit, and plan a one-bedroom unit.
- Have a licensed site evaluator confirm the septic system can handle the ADU (or get a new design), or document water service or a potable well test.
- Apply for a Building/Land Use Permit with the Code Enforcement Office (207-829-3705 ext. 206) with a scaled site plan showing setbacks.
Common questions
- Can I build an ADU in North Yarmouth, Maine?
- Yes. North Yarmouth allows one accessory dwelling unit on a lot with a single-family home, approved by the Code Enforcement Officer, in every district except Resource Protection. It can be inside, attached or detached.
- How big can an ADU be in North Yarmouth, Maine?
- An ADU is limited to one bedroom and 40% of the main house's living area, not counting the basement. The minimum is 190 sq ft unless the state board sets a different minimum.
- Do I have to live on the property to have an ADU in North Yarmouth, Maine?
- Yes, for now. The owner must live in either the ADU or the main house. A state law taking effect July 1, 2027 bars towns from requiring owner occupancy, so this provision may stop being enforceable then.
- Does an ADU need extra parking in North Yarmouth, Maine?
- No. No parking is required beyond what the house already needs. Before occupancy you must give written proof of adequate water and wastewater service.
Maine's statewide ADU law
Under 30-A M.R.S. §4364-B (first passed as LD 2003 in 2022), a town must allow at least one accessory dwelling unit (ADU) on a lot with a single-family home anywhere homes are allowed. Towns had to comply by 2024.
Rules in effect now:
- It can be inside the house, attached, or a new detached building.
- One ADU per lot is exempt from density limits.
- No extra parking can be required beyond what the house already needs.
- Setbacks are the same as for the house.
- Minimum size: the state building codes board set 160 sq ft in 2025. Towns may set a maximum size.
- Before you can move in, you must show the ADU has adequate water and septic/sewer.
- In the shoreland zone ADUs must meet shoreland rules, but towns can't ban them there outright.
- Sprinklers aren't required unless the ADU is in or attached to a building with more than 2 units.
Coming July 1, 2027 (LD 1829 of 2025, pushed back by LD 2173 in 2026): towns can no longer require the owner to live on the property, ADUs must also be allowed next to 2- and 3-unit buildings, and towns can't require planning board approval for an ADU. Towns may still regulate short-term rentals in ADUs. Private covenants and HOA rules can be stricter.
What the ordinance says
- Sec. 11.1(B), Land Use Ordinance, p. 248
One (1) accessory dwelling unit may be constructed on the same lot as a single-family dwelling unit in any area in which housing is allowed, subject to the requirements of the following criteria:
- Table 7-1, Land Uses by Zoning District (Residential Uses), Land Use Ordinance, p. 76
Accessory Dwelling Unit4 [Amended 5/17/08] P P P N P P P
- Sec. 11.1(B)(2), Land Use Ordinance, p. 248
An accessory dwelling unit may be constructed only: a. Within an existing dwelling unit on a lot; b. Attached to a single-family dwelling unit; c. As a new structure on a lot for the primary purpose of creating an accessory dwelling unit; or d. Within an existing accessory structure.
- Sec. 11.1(B)(5), Land Use Ordinance, p. 248
The accessory dwelling unit is limited to one (1) bedroom.
- Sec. 11.1(B)(6)(a), Land Use Ordinance, p. 248
An accessory dwelling unit, whether constructed within, attached to, or detached from the single-family dwelling, shall not exceed forty (40) percent of the available living area of the principal single-family dwelling (excluding the basement of the single-family dwelling).
- Sec. 11.1(B)(6)(b), Land Use Ordinance, p. 248
An accessory dwelling unit must be at least 190 square feet in size, unless the Technical Building Code and Standards Board, pursuant to 10 M.R.S. § 9722, adopts a different minimum standard; if so, that standard applies.
- Sec. 11.1(B)(7), Land Use Ordinance, p. 249
The Code Enforcement Officer (CEO) approves the accessory dwelling unit. The CEO shall require an owner of an accessory dwelling unit to provide writing verification that the proposed accessory dwelling unit is to be connected to adequate water and wastewater services prior to certification of the accessory dwelling unit for occupancy.
- Sec. 11.1(B)(8), Land Use Ordinance, p. 249
The owner of the property must occupy either the accessory dwelling unit or the principal dwelling unit.
- Sec. 11.1(B)(10), Land Use Ordinance, p. 249
Accessory dwelling units are not subject to any additional vehicle parking requirements beyond the parking requirements of the single-family dwelling unit on the lot where the accessory dwelling unit is located.
- Sec. 11.1(B)(3)(b), Land Use Ordinance, p. 248
For an accessory dwelling unit permitted in an accessory structure existing as of July 1, 2023, the required setback requirements in this Ordinance of the existing accessory structure apply.