Can I build an ADU in York, Maine?
Yes. York allows one accessory dwelling unit (ADU) per single-family lot in every zone, inside the house, attached, or in a detached accessory building. You need a building permit and an occupancy permit from the Code Enforcement Officer, and no Planning Board approval. The ADU can be no larger than 850 sq ft or 50% of the main house's floor area, whichever is smaller, and no short-term rentals are allowed anywhere on a lot with an ADU.
| Number allowed | One ADU per lot [2] |
| Attached or detached | In the main house or in an accessory building [2] |
| Approval | Building permit and occupancy permit from the CEO; no Planning Board approval [3] |
| Maximum size | 850 sq ft or 50% of the principal residence's gross floor area, whichever is smaller [5] |
| Minimum size | 190 sq ft [10] |
| Short-term rentals | Prohibited in the ADU, the main house, or anywhere on the lot [4] |
| Parking | No extra parking beyond what the single-family home needs [8] |
| Detached ADU distance | No more than 150 ft from the main house [9] |
What counts as an ADU
An ADU is a small apartment that is part of an existing single-family home, either in the same building or in an accessory building, with its own living, sleeping, bathroom and kitchen facilities [1]. The owner may rent the ADU, the main house, or both [1].
Where and how many
Only one ADU is allowed per lot. It is exempt from base-zone density and minimum floor area rules, and the ADU permit process applies in all zones regardless of the base zone's use list [2]. Any building with an ADU must meet the principal structure's yard and setback requirements and the plumbing codes [2]. A detached ADU must be within 150 ft of the main house [9] and look like a barn, garage, carriage house or similar outbuilding [7]. An addition must match the house's facade, roof pitch, siding and windows. You can't create or increase a nonconformity to add an ADU [9]. In the Watershed Protection Overlay, a lot may hold one house and one ADU with a combined maximum of 5,000 sq ft.
Size
The ADU can't exceed 50% of the principal residence's gross floor area or 850 sq ft, whichever is more restrictive [5]. Garages and unfinished attics aren't counted. The minimum is 190 sq ft [10].
Rentals and owner rules
The ordinance has no owner-occupancy requirement. However, it bans short-term residential rentals in the ADU, the main house, or anywhere on the lot [4], and you must record a covenant at the York County Registry of Deeds saying neither unit will be used as a short-term rental [6]. Buyers must keep meeting these rules or stop using the ADU.
Parking, water and permits
No parking beyond the single-family home's requirement is needed [8]. If you aren't on Town water, you must submit a well water test before the occupancy permit is issued. A CEO building permit is required, and a CEO occupancy permit is needed before anyone moves in [3].
State law
Maine's ADU law separately sets a state minimum size that may be smaller than York's 190 sq ft floor; see the statewide summary.
See how York compares with 8+ other Maine towns on accessory dwelling units (adus) →
Next steps
- Check your lot's zone and whether it is in the Shoreland, Watershed or Wetland overlays, which add their own limits.
- Measure the main house's gross floor area to find your ADU size cap (50% or 850 sq ft, whichever is smaller).
- Apply to the York Code Enforcement Office for a building permit with plans showing setbacks, floor area and design.
- Prepare and record the no-short-term-rental covenant (in a form the Town attorney accepts) at the York County Registry of Deeds.
- Before move-in, get a CEO occupancy permit; submit a well water test if you aren't on Town water.
Common questions
- Can I build an ADU in York, Maine?
- Yes. York allows one accessory dwelling unit per single-family lot in every zone, inside the house, attached, or in a detached accessory building. You need a building permit and an occupancy permit from the Code Enforcement Officer, and no Planning Board approval.
- How big can an ADU be in York, Maine?
- No larger than 850 sq ft or 50% of the principal residence's gross floor area, whichever is more restrictive. The minimum is 190 sq ft. A detached ADU must be within 150 ft of the main house.
- Can I use an ADU as an Airbnb in York, Maine?
- No. York bans short-term residential rentals in the ADU, the main house, or anywhere on the lot, and you must record a covenant at the York County Registry of Deeds saying so.
- Does an ADU need extra parking in York, Maine?
- No. No parking beyond the single-family home's requirement is needed. The ordinance also has no owner-occupancy requirement.
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
- Art. 2, Definitions: Accessory Dwelling Unit, Zoning Ordinance (Revised through May 16, 2026), p. 14
ACCESSORY DWELLING UNIT: A small apartment which is part of an existing single-family home, in the same building as the principal dwelling unit or in a building accessory to the principal dwelling unit, and which is clearly secondary to the single- family home. The ADU shall have living, sleeping, sanitary and kitchen facilities for the exclusive use of the unit occupants. The owner may rent the ADU and/or the principal dwelling unit.
- §7.17.2(C)(1), Zoning Ordinance (Revised through May 16, 2026), p. 143
Only one ADU is permitted per lot. The ADU shall be located in the same building as the principal dwelling unit or in a building accessory to the principal dwelling unit and shall be exempt from base zone density requirements for dwelling units and the minimum floor area requirements as specified in section 5.3 of this ordinance. Any structure containing an ADU must meet the minimum yard and setback requirements for the principal structure, and must meet all relevant sections of the state and local Plumbing Codes. The ADU permit process shall be applicable to all zones town wide, regardless of underlying base zone use requirements.
- §7.17.2(C)(2), Zoning Ordinance (Revised through May 16, 2026), p. 143
A building permit is required for the creation of a new ADU and is issued by the CEO. Planning Board approval is not required for an ADU. An occupancy permit must be issued by the CEO prior to occupancy of an ADU created or modified pursuant to this section.
- §7.17.2(C)(3), Zoning Ordinance (Revised through May 16, 2026), p. 143
This ADU ordinance is intended to create year-round housing. Therefore, a short-term residential rental is prohibited within the ADU, principal dwelling unit or anywhere on a lot where an ADU is constructed.
- §7.17.2(C)(5), Zoning Ordinance (Revised through May 16, 2026), p. 143
The total gross floor area of the ADU unit shall not exceed 50% of the total gross floor area of the principal residence or 850 square feet, whichever is more restrictive. Calculation of total gross floor area for an ADU shall not include: garage areas or unfinished attic space.
- §7.17.2(C)(9), Zoning Ordinance (Revised through May 16, 2026), p. 144
To ensure continued compliance by current and subsequent owners, the applicant shall provide and record in the York County Registry of Deeds a covenant in a form acceptable to the Town attorney that the ADU and principal dwelling shall not be utilized as a short-term residential rental or for transient occupancy as defined in this ordinance.
- §7.17.2(C)(12)(d), Zoning Ordinance (Revised through May 16, 2026), p. 144
A detached accessory structure housing an ADU must be designed and constructed in the style of a barn, garage, carriage house, or similar structure customarily located on the same lot with a single family residence.
- §7.17.2(C)(14), Zoning Ordinance (Revised through May 16, 2026), p. 144
An accessory dwelling unit is not subject to additional motor vehicle parking requirements beyond the parking requirements of the single-family dwelling unit on the lot where the accessory dwelling unit is located.
- §7.17.2(C)(18)-(19), Zoning Ordinance (Revised through May 16, 2026), p. 144
A detached accessory structure containing an ADU shall be located no further than 150 feet from the nearest point of the principal structure. 19. Non-conformities shall not be created or increased in the creation of an accessory dwelling unit.
- §7.17.2(C)(5), Zoning Ordinance (Revised through May 16, 2026), p. 143
Total floor area of an ADU shall be measured from the interior faces of the inside walls. The minimum gross floor area for an ADU shall not be less than 190 square feet.