Town Permit Guide

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Can I build an ADU in Falmouth, Maine?

Falmouth, Cumberland County · Ordinances checked 2026-10-15 · Reviewed · 15 cited sections

Allowed with a permit

Yes. Falmouth allows one accessory dwelling unit (an in-house apartment or a separate cottage) per single-family home as a permitted use in its residential districts. The ADU must be at least 190 square feet and no larger than 850 square feet or the size of the house, whichever is less, must stay in the same ownership as the house, and needs no extra parking.

Number allowedOne ADU per single-family dwelling [1]
OwnershipADU and house must be held in the same ownership [1]
Minimum size190 sq ft gross floor area [2]
Maximum size850 sq ft, or 100% of the house's floor area (excluding garages, porches, decks, unfinished areas), whichever is less [2]
ParkingTown may not impose any parking requirement for ADUs [5]
Density and lot areaADUs exempt from density, net residential area and lot-area requirements [4]
Where allowedPermitted use in FF, RA, RB, RC, RD, HL, MUC, VMU and Tidewater (TWMP) districts (see details for each district's citation) [6]
Before occupancyWritten proof of adequate water and wastewater service for a certificate of occupancy [7]

Where ADUs are allowed

In the district use tables reproduced in Ordinance No. 9-2024, an accessory dwelling unit is a permitted use, not a conditional use, in Farm and Forest [8], RA [6], RB [9], RC [10], RD [11], Highland Lake (HL) [12], MUC [13] and VMU [14], and the ordinance added ADUs to the Tidewater (TWMP) district [15]. The ordinance brought Falmouth's zoning into line with Maine's LD 2003; our copy is the Council agenda version, and its December 11, 2023 adoption comes from the Council's meeting minutes. Tables for other districts weren't included, so check with Code Enforcement if you're elsewhere.

Size, ownership and design

Falmouth's ADUs include both Accessory Apartments (inside or attached to the house) and Accessory Cottages (separate buildings). Only one ADU is allowed per single-family dwelling, and the ADU and the house must be held in the same ownership [1]. That's an ownership rule, not a requirement that the owner live there. An ADU must have at least 190 square feet of gross floor area and can't exceed 850 square feet or 100% of the house's gross floor area (not counting garages, porches, decks or unfinished areas), whichever is less [2]. A house with an Accessory Apartment must keep a single main entrance, with other entrances subordinate to it [3].

Density, parking and growth limits

ADUs are exempt from density, net residential area and lot-area requirements [4], and the town may not impose any parking requirements for them [5]. The same ordinance struck the annual caps on ADU development permits from the growth-cap section (Sec. 19-69).

What these sources don't cover

We only have the amended sections in Ord. 9-2024, not the full zoning code. The remaining accessory-cottage standards (Sec. 19-55.2 and following, such as placement and design) are only in the online code we couldn't review, so check them with Code Enforcement. Our sources also don't say whether an accessory cottage needs Planning Board review. Before anyone moves in, the town needs written proof that the unit has adequate water and wastewater service [7].

State law

Maine's building codes board set a 160 sq ft statewide ADU minimum in 2025, so state law may allow a smaller unit than Falmouth's 190 sq ft minimum. Starting July 1, 2027, state law will also require towns to allow ADUs on lots with 2- and 3-unit buildings and will bar towns from requiring planning board approval for an ADU, which may override Falmouth's rule limiting ADUs to single-family homes. Falmouth's same-ownership rule isn't an owner-occupancy requirement.

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

Next steps

  1. Confirm your zoning district and ask Code Enforcement (207-699-5310) for the full Sec. 19-55 accessory apartment/cottage standards that apply to your design.
  2. Size the unit between 190 sq ft and the lesser of 850 sq ft or your house's finished floor area.
  3. Apply for a building permit with Code Enforcement, plus separate electrical and plumbing permits.
  4. Before occupancy, provide written verification of sewer or septic capacity and water supply (public water or a potable well test) to get a certificate of occupancy.

Common questions

Can I build an ADU in Falmouth, Maine?
Yes. Falmouth allows one accessory dwelling unit, either an in-house apartment or a separate cottage, per single-family home as a permitted use in the FF, RA, RB, RC, RD, HL, MUC, VMU and Tidewater districts. The ADU and the house must stay in the same ownership. Tables for other districts weren't available, so check with Code Enforcement if you're elsewhere.
How big can an ADU be in Falmouth, Maine?
An ADU must have at least 190 square feet of gross floor area and can't exceed 850 square feet or 100% of the house's gross floor area (not counting garages, porches, decks or unfinished areas), whichever is less. Maine set a 160 sq ft statewide ADU minimum in 2025, so state law may allow a smaller unit.
Does an ADU in Falmouth, Maine need extra parking or a bigger lot?
No. The town may not impose any parking requirement for ADUs, and ADUs are exempt from density, net residential area and lot-area requirements.
Do I have to live on the property to have an ADU in Falmouth, Maine?
Not under the rules reviewed. Falmouth requires the ADU and the house to be held in the same ownership, but that's an ownership rule, not a requirement that the owner live there.
What permits do I need for an ADU in Falmouth, Maine?
A building permit from Code Enforcement plus separate electrical and plumbing permits, and written proof of adequate water and wastewater service before a certificate of occupancy. The remaining accessory-cottage standards, and whether a cottage needs Planning Board review, weren't in the sources reviewed, so confirm them with Code Enforcement (207-699-5310).

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 Falmouth's published ordinances. Section numbers are as printed in the source.

  1. Sec. 19-55.1.a, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 23
    Only one Accessory Dwelling Unit shall be permitted per single family dwelling. The accessory dwelling unit and the single-family dwelling to which it is accessory must be held in the same ownership.
  2. Sec. 19-55.1.b, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 23
    An Accessory Dwelling Unit shall have a minimum gross floor area of 190 square feet. An Accessory Dwelling Unit shall not exceed 100% of the gross floor area of the single family dwelling to which it is accessory, not including garages, porches, decks or unfinished areas, or 850 square feet of gross floor area, whichever is less.
  3. Sec. 19-55.1.c, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 23
    The single family dwelling unit in which an Accessory Apartment is located shall have only one main entrance and all other entrances shall appear subordinate to the main entrance.
  4. Sec. 19-55.1.d, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 23
    Accessory Dwelling Units are exempt from the density and net residential area requirements of Sec.19-64 and are exempt from all requirements related to lot area in Div.II-19-1-3.
  5. Sec. 19-38.a, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 22
    Parking for uses not listed shall be determined by the permitting authority except that the permitting authority may not impose any parking requirements for accessory dwelling units and may not require more than two parking spaces for every three units in an Affordable Housing Development.
  6. Sec. 19-8 Residential A District (RA), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 4
    Permitted Structures and Uses A. Accessory Structures & Uses [Amended 7/25/22] B. Accessory Dwelling Units [Adopted 7/11/16]
  7. Sec. 19-166 Certificates of Occupancy, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 26
    Prior to issuance of a certificate of occupancy for any dwelling unit, the Town must receive written verification that the structure is connected to adequate water and wastewater services.
  8. Sec. 19-7 Farm and Forest District (FF), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 2
    Permitted Structures and Uses. A. Accessory animal husbandry use [Adopted 7/10/17] B. Accessory structures & uses [Amended 7/25/22] C. Accessory dwelling unit [Adopted 7/11/16]
  9. Sec. 19-9 Residential B District (RB), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 5
    Permitted Structures and Uses. Accessory Structures & Uses [Amended 7/25/22] Accessory Dwelling Units
  10. Sec. 19-10 Residential C District (RC), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 7
    Permitted Structures and Uses. A. Accessory Structures & Uses [Amended 7/25/22] B. Accessory Dwelling Unit
  11. Sec. 19-10.1 Residential D District (RD), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 8
    Permitted Structures and Uses. A. Accessory Structures & Uses [Amended 7/25/22] B. Accessory Dwelling Unit
  12. Sec. 19-10.2 Highland Lake Residential District (HL), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 10
    Permitted Structures and Uses. A. Accessory Structures & Uses [Amended 7/25/22] B. Accessory Dwelling Unit
  13. Sec. 19-13 Mixed Use Cluster District (MUC), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 14
    Permitted Structures and Uses. A. Accessory structures & uses [Amended 7/25/22] B. Accessory Dwelling Unit
  14. Sec. 19-14 Village Mixed Use District (VMU), Permitted Structures and Uses, Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 15
    N. Accessory structures and uses [Amended 7/25/22] O. Accessory Dwelling Units
  15. Table 19-23.1 Tidewater Master Planned Development District (TWMP), item 27 (added by Ord. 9-2024), Ordinance No. 9-2024 - Amendments to Ch. II-19 implementing LD 2003 (30-A MRSA 4364, 4364-A, 4364-B): definitions, district use/dimensional tables, Sec. 19-38 parking, Sec. 19-55.1 Accessory Dwelling Units, Sec. 19-69 growth cap, Sec. 19-166 - adopted Dec 11, 2023, p. 21
    26. Grocery Retail [Adopted 11/26/12] 27. Accessory Dwelling Units
This page summarizes Falmouth's posted ordinances as of 2026-10-15. Ordinances are amended, and individual lots can have overlays, subdivision covenants, or HOA rules that are stricter. Confirm with Code Enforcement Division (Community Development) (207-699-5310) before you build. Spot an error?