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Can I build an ADU in Kennebunk, Maine?

Kennebunk, York County · Ordinances checked 2026-10-01 · Reviewed · 7 cited sections

Allowed

Yes. Kennebunk lists the accessory dwelling unit as a permitted use in its residential districts. It can be inside, attached to, or detached from a single-family home. One ADU is allowed per single-family lot, sized between 190 and 1,000 sq ft, and the owner must live in either the house or the ADU. The ADU can't be used as a short-term rental.

Where allowedPermitted use in RC, RR, CR, SR and VR/WKVR districts [2]
Attached or detachedWithin, attached to, or detached from a single-family home on the same parcel [1]
Number per lot1 per single-family lot [4]
Size190 sq ft minimum, 1,000 sq ft maximum [4]
Owner occupancyOwner must live in the main house or the ADU more than 6 months a year [3]
Short-term rentalNot allowed in an ADU [5]
Extra lot areaNone; an ADU doesn't raise the minimum lot area [6]

Where ADUs are allowed

Kennebunk defines an ADU as a self-contained unit "located within, attached to, or detached from a single-family dwelling unit" on the same parcel [1]. The Suburban Residential district lists it as a permitted use [2]. So do the Rural Conservation, Rural Residential, Coastal Residential and Village Residential district sections. An ADU doesn't require more lot area than the house alone [6]. It does have to meet the district's normal setbacks, height and lot coverage. A lot that already has two units (a two-family home, or a house plus an ADU) can't add another unit [7].

Standards (Article 10, Section 15)

  • Owner occupancy: the owner must live in either the main house or the ADU as a primary residence, meaning more than 6 months a year [3]. Both units must be occupied as primary residences.
  • One per lot, 190 to 1,000 sq ft [4].
  • No short-term rentals: an ADU can't be used as a short-term rental [5].
  • Shoreland: an ADU in the Shoreland Overlay District must separately meet all applicable space and bulk requirements.
  • Utilities: you must give written proof of adequate water and sewer or septic service before a certificate of occupancy is issued (Article 10, Section 8).

Parking

The parking table requires 2 spaces per dwelling unit for single-family homes and doesn't list ADUs separately. Ask Code Enforcement whether it applies extra spaces to an ADU. State law bars towns from requiring parking beyond what the house already needs.

State law

Starting July 1, 2027, state law will bar towns from requiring owner occupancy for ADUs. Kennebunk's owner-occupancy rule [3] may stop being enforceable on that date. State law already lets towns ban short-term rentals in ADUs.

See how Kennebunk compares with 8+ other Maine towns on accessory dwelling units (adus) →

Next steps

  1. Confirm your zoning district and whether your lot already has two units (a two-family home or an existing ADU).
  2. Plan an ADU of 190 to 1,000 sq ft that meets your district's setbacks, height and lot coverage.
  3. Get written proof of adequate water and sewer or septic capacity (a licensed site evaluator's design if on septic).
  4. Apply to Kennebunk Code Enforcement (207-604-1303) for the building permit, and be ready to show owner occupancy.

Common questions

Can I build an ADU in Kennebunk, Maine?
Yes. Kennebunk lists the accessory dwelling unit as a permitted use in its residential districts. It can be inside, attached to, or detached from a single-family home, with one ADU per single-family lot.
How big can an ADU be in Kennebunk, Maine?
Between 190 and 1,000 sq ft. An ADU doesn't raise the minimum lot area, but it must meet the district's normal setbacks, height and lot coverage.
Do I have to live on the property if I have an ADU in Kennebunk, Maine?
Yes, for now. The owner must live in either the main house or the ADU as a primary residence, meaning more than 6 months a year. Starting July 1, 2027, state law will bar towns from requiring owner occupancy.
Can I use my ADU as an Airbnb in Kennebunk, Maine?
No. Kennebunk's zoning says an ADU can't be used as a short-term rental.

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.

State sources: 30-A M.R.S. §4364-B (Accessory dwelling units) · 30-A M.R.S. §4364 (implementation dates) · 25 M.R.S. §2463-B (sprinklers in ADUs) · LD 2173 (P.L. 2025, c. 733) status and chaptered law · Maine Office of Community Affairs, Housing Legislation Guidance (March 2026)

What the ordinance says

Exact text from Kennebunk's published ordinances. Section numbers are as printed in the source.

  1. Article 2, Definitions: Accessory Dwelling Unit, Zoning Ordinance Article 2 - Definitions, p. 1
    ACCESSORY DWELLING UNIT: a self-contained dwelling unit located within, attached to, or detached from a single-family dwelling unit located on the same parcel of land.
  2. Article 8, Section 6.B(3) Suburban Residential permitted uses, Zoning Article 8 Sect 6 - Suburban Residential District, p. 1
    3-1 Single family detached dwellings 3-2 Accessory dwelling unit
  3. Article 10, Section 15.A(1), Zoning Ordinance Article 10 - Performance Standards, p. 54
    (1) Either the primary or converted unit shall be occupied by the owner of the property as its primary physical residence (primary residence shall be defined as occupying the property for more than 6 months per year).
  4. Article 10, Section 15.A(4)-(5), Zoning Ordinance Article 10 - Performance Standards, p. 54
    (4) No more than one accessory dwelling unit is permitted per single family lot. (5) The area of an accessory dwelling unit shall be a minimum of one hundred and ninety (190) square feet, and a maximum of one thousand (1,000) square feet.
  5. Article 10, Section 15.A(7), Zoning Ordinance Article 10 - Performance Standards, p. 55
    (7) Accessory dwelling units shall not be used as short term rentals.
  6. Article 8, Section 6.E(1) Suburban Residential space and bulk, Zoning Article 8 Sect 6 - Suburban Residential District, p. 2
    provided that accessory dwelling unit shall not require an increase in the minimum net lot area.
  7. Article 8, Section 6.D(2), Zoning Article 8 Sect 6 - Suburban Residential District, p. 2
    2. Lots with two existing units, either a two family or single family with accessory dwelling unit, are not permitted to add an additional dwelling unit as of June 14, 2023
This page summarizes Kennebunk's posted ordinances as of 2026-10-01. Ordinances are amended, and individual lots can have overlays, subdivision covenants, or HOA rules that are stricter. Confirm with Community Development Department - Code Enforcement (207-604-1303) before you build. Spot an error?