Can I build an ADU in Cumberland, Maine?
Yes. Cumberland allows one accessory dwelling unit, attached or detached, with a single-family home or multifamily structure on any lot in any zoning district, approved by the Code Enforcement Officer through an ADU permit. The ADU must meet the district's setbacks and the Plumbing Inspector must confirm adequate septic or sewer capacity.
| Number allowed | 1 ADU per lot [1] |
| Where allowed | Any lot in any zoning district [1] |
| Attached vs detached | Either; may be inside the house, attached, or a separate building [1] |
| Approval | ADU permit from the Code Enforcement Officer [2] |
| Lot size | No extra lot area needed if Plumbing Inspector confirms capacity [3] |
| Setbacks | Same district setbacks that apply to the house [4] |
| Variances | None allowed for ADU size, height, setbacks, lot coverage or frontage [5] |
| Residential parking (general table) | 2.5 spaces per dwelling unit (1 in designated growth area) [7] |
What's allowed
Cumberland's ADU rules (§ 315-45A, amended November 24, 2025) allow one accessory dwelling unit as an attached or detached structure accessory to a single-family home or multifamily structure, on any lot in any zoning district [1]. It can be part of the main house or a separate building on the same lot. Existing basement, attic or over-garage space used by family members doesn't count as an ADU. The residential district use lists also include "an accessory dwelling unit as permitted in § 315-45A" as a permitted use [9]. The definition ties the term to the state ADU statute [8].
Approval
Every ADU needs an accessory dwelling unit permit from the Code Enforcement Officer [2]. The text we reviewed doesn't set a maximum size, a Planning Board review or an owner-occupancy requirement.
Lot and setback rules
An ADU doesn't need its own minimum lot area if the local Plumbing Inspector confirms adequate capacity under the State Plumbing Code [3]. It also doesn't need extra frontage, but must meet all district setbacks that apply to the house [4]. A nonconforming house can be expanded for an ADU under the nonconforming-structure rules (or § 226-14 in the shoreland zone), but no ADU is allowed on a lot with a nonconforming use. No variances may be granted for ADU size, height, setbacks, lot coverage or frontage [5]. In a subdivision, the ADU must sit within the approved building envelope.
Parking
The ADU section itself has no parking rule. The general parking table requires 2.5 spaces per residential dwelling unit, or 1 in a designated growth area [7]. Maine's ADU law bars towns from requiring parking beyond what the house already needs, so state law may override that table if applied to an ADU.
Guesthouses
Separately, a guesthouse may be built if each guesthouse meets the district's lot standards and setbacks [6].
A further Chapter 315 amendment adopted August 10, 2026 may not be reflected in the online text we reviewed.
See how Cumberland compares with 8+ other Maine towns on accessory dwelling units (adus) →
Next steps
- Call the Cumberland Code Enforcement Office (207-829-2207) to confirm your zone, setbacks and any subdivision building envelope.
- Get the Plumbing Inspector's sign-off that your septic system or sewer connection can serve both units.
- Apply to the Code Enforcement Officer for an accessory dwelling unit permit with a site plan showing the lot, buildings, setbacks and parking.
- Ask the Code Enforcement Office how many parking spaces it will require for the ADU.
Common questions
- Can I build an ADU in Cumberland, Maine?
- Yes. Cumberland allows one accessory dwelling unit, attached or detached, with a single-family home or multifamily structure on any lot in any zoning district. The Code Enforcement Officer approves it through an ADU permit.
- What setbacks apply to an ADU in Cumberland, Maine?
- An ADU must meet all the district setbacks that apply to the house. It needs no extra frontage, and no variances may be granted for ADU size, height, setbacks, lot coverage or frontage.
- Does an ADU need septic or sewer approval in Cumberland, Maine?
- Yes. The Plumbing Inspector must confirm adequate capacity under the State Plumbing Code. If so, the ADU doesn't need its own minimum lot area.
- How much parking does an ADU need in Cumberland, Maine?
- The ADU section itself has no parking rule. The general table requires 2.5 spaces per residential dwelling unit, or 1 in a designated growth area, but Maine's ADU law bars towns from requiring parking beyond what the house needs. Ask Code Enforcement.
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
- § 315-45A, Chapter 315 Zoning, Article VI General Regulations
One accessory dwelling unit may be constructed as an attached or detached structure that is accessory to a primary single-family dwelling unit or multifamily-structure on any lot in any zoning district.
- § 315-45A(1), Chapter 315 Zoning, Article VI General Regulations
Review and approval. All accessory dwelling units must satisfy the standards set forth in this section and must be approved by the Code Enforcement Officer pursuant to an accessory dwelling unit permit.
- § 315-45A(2)(a), Chapter 315 Zoning, Article VI General Regulations
An accessory dwelling unit shall not be required to independently meet the minimum lot size requirements of the zoning district within which it is located; provided that the local Plumbing Inspector indicates adequate capacity and conformity with the State Plumbing Code for the accessory dwelling unit in addition to the primary dwelling unit.
- § 315-45A(2)(b), Chapter 315 Zoning, Article VI General Regulations
An accessory dwelling unit shall not be required to independently meet the lot frontage requirements of the zoning district within which it is located, but shall be required to meet all setbacks of the zoning district within which it is located that are otherwise applicable to the existing structure within which the primary dwelling unit is located.
- § 315-45A(2)(d), Chapter 315 Zoning, Article VI General Regulations
no variances may be granted with respect to the dimensional requirements related to size and height of structures, setback distances, lot coverage, or lot frontage required for accessory dwelling units.
- § 315-51 Guesthouses, Chapter 315 Zoning, Article VI General Regulations
A guesthouse may be constructed, provided that the lot standards and setback requirements for the district in which it is located are met for each guesthouse.
- § 315-57A Parking, Chapter 315 Zoning, Article VI General Regulations
Residential 2.5 per dwelling unit Residential in designated growth area 1 per dwelling unit
- § 315-4 Definitions, Accessory dwelling unit (ADU), Chapter 315 Zoning, Article I Title, Purpose and Definitions
A self-contained dwelling unit located within, attached to or detached from a single-family dwelling unit or multi-unit structure located on the same parcel of land in accordance with 30-A M.R.S.A. § 4301, sub-§ 1-C as amended.
- § 315-6A(1)(d) (Rural Residential District 1), Chapter 315 Zoning, Article II Zoning Districts
An accessory dwelling unit as permitted in § 315-45A