Town Permit Guide

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Can I build an ADU in Scarborough, Maine?

Scarborough, Cumberland County · Ordinances checked 2026-10-01 · Reviewed · 9 cited sections

Allowed with a permit

Yes. Scarborough allows one accessory dwelling unit per single-family home in all residential zones with a permit from the Code Enforcement Officer. The owner must live on the property, the ADU must be at least 190 sq ft (max generally 750 sq ft or a percentage of the house, whichever is greater), occupancy is limited to two people, and no extra parking is required.

Zones where allowedPermitted by right in all residential districts (RF, RFM, R2, R3, R4, R4A, VR2, VR4) and most village/mixed districts [1]
ApprovalPermit from the Code Enforcement Officer [2]
Owner occupancyOwner must live in the main house or the ADU (may be seasonal) [3]
Minimum rental termNeither unit may be rented for less than 28 continuous days [3]
Max occupants2 [4]
SizeMin 190 sq ft; max 40% of a house under 2,000 sq ft or 750 sq ft, whichever is greater (larger caps for larger homes) [5]
Number per lot1 per principal structure [6]
Detached ADU locationWithin 100 feet of the main house [8]
ParkingNone required [9]

Where ADUs are allowed

The combined use table lists Accessory Dwelling Unit as permitted by right ("P") in every residential district (RF, RFM, R2, R3, R4, R4A, VR-2, VR-4) and in most village and mixed-use districts [1]; the table row is just a string of "P" marks, one per district column. The Code Enforcement Officer issues the permit if the unit meets the Section IX.J standards [2].

Owner occupancy and renting

The lot owner must live in either the main house or the ADU, and either residence may be seasonal; neither the ADU nor the house may be rented for less than 28 continuous days [3]. Starting July 1, 2027, state law bars towns from requiring the owner to live on an ADU property, so this owner-occupancy rule may be overridden then; towns can still restrict short-term rentals in ADUs. The separate short-term rental registration ordinance also bars short-term rentals in an ADU or in the house on the same lot. Occupancy of the ADU is capped at two people [4].

Size

The ADU must be at least 190 sq ft. The maximum depends on the main house: under 2,000 sq ft, 40% or 750 sq ft (whichever is greater); 2,000–3,000 sq ft, 35% or 750 sq ft; 3,000–5,000 sq ft, 30% or 1,050 sq ft; over 5,000 sq ft, 20% or 1,500 sq ft [5].

Attached vs. detached

Only one ADU per principal structure is allowed [6]. It can be inside the house, attached to it, or a new structure built mainly to create the ADU [7]. A detached ADU must be within 100 feet of the house and look like a garage, barn, carriage house, cottage or similar building [8]. A new detached ADU structure must meet the dimensional requirements for an accessory structure, while an attached or internal unit follows the setbacks for the house. ADUs are exempt from density and lot-area requirements and can go on nonconforming lots if lot coverage is met. The Zoning Board of Appeals can grant a limited yard reduction where reasonably necessary.

Utilities and parking

The ADU and house must share utility meters unless the utility refuses. Unsewered lots must meet the state minimum lot size law and plumbing code, and you must document adequate water and wastewater service before occupancy. The parking table requires no spaces for an accessory unit [9].

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

Next steps

  1. Confirm your zone and lot coverage with Scarborough Planning & Codes, (207) 730-4040.
  2. If on septic, have a licensed site evaluator confirm the system can handle the added flow (and the lot meets state minimum lot size).
  3. Prepare a scaled plot plan and floor plans showing the ADU's living space versus the main house and the distance to the house if detached.
  4. Apply to the Code Enforcement Officer for the ADU/building permit; apply to the Zoning Board of Appeals only if you need a limited yard-size reduction.
  5. Before occupancy, submit written verification of water and wastewater service.

Common questions

Can I build an ADU in Scarborough, Maine?
Yes. Scarborough allows one accessory dwelling unit per single-family home in all residential zones, with a permit from the Code Enforcement Officer. It can be inside the house, attached, or a new detached structure.
How big can an ADU be in Scarborough, Maine?
The ADU must be at least 190 sq ft. For a house under 2,000 sq ft, the maximum is 40% of the house or 750 sq ft, whichever is greater. Larger houses get different caps.
Do I have to live on the property to have an ADU in Scarborough, Maine?
Currently yes. The owner must live in the main house or the ADU, and either may be seasonal. State law bars towns from requiring this starting July 1, 2027, so the rule may be overridden then.
Can I rent my ADU in Scarborough, Maine?
Not short-term. Neither the ADU nor the house may be rented for less than 28 continuous days, and short-term rentals are barred in an ADU or the house on the same lot. Occupancy of the ADU is capped at 2 people.
Does an ADU need extra parking in Scarborough, Maine?
No. The parking table requires no spaces for an accessory unit. A detached ADU must be within 100 feet of the main house.

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

  1. Section XIII.A Use Tables – Accessory Dwelling Unit, Zoning Ordinance Section XIII.A – Combined Zoning District Use Tables, p. 3
    Accessory Dwelling Unit Section IX.J P P P P P P P P P P P P P P P P
  2. Section IX.J Performance Standards – Accessory Dwelling Units, Zoning Ordinance Section IX – Performance Standards, p. 24
    The Code Enforcement Officer may issue a permit for the construction on an accessory dwelling unit only if the accessory dwelling unit adheres to the following standards:
  3. Section IX.J.1, Zoning Ordinance Section IX – Performance Standards, p. 24
    The owner(s) of the lot on which the principal structure is located must reside in the principal structure or the accessory dwelling unit, either of which residence may be seasonal. An accessory dwelling unit may be located on a lot which the owner occupies as a seasonal residence; however, neither the accessory dwelling unit nor the single- family dwelling shall be rented for less than 28 continuous days.
  4. Section IX.J.2, Zoning Ordinance Section IX – Performance Standards, p. 24
    The number of occupants of the accessory dwelling unit is limited to two.
  5. Section IX.J.3, Zoning Ordinance Section IX – Performance Standards, p. 24
    The living space of an accessory dwelling unit shall be a minimum of 190 square feet and not exceed the following percentage of living space of the single-family dwelling to which the unit is accessory or the following maximum amounts, whichever are applicable:
  6. Section IX.J.6, Zoning Ordinance Section IX – Performance Standards, p. 24
    Only one accessory dwelling unit per principal structure shall be permitted on a lot.
  7. Section IX.J.7, Zoning Ordinance Section IX – Performance Standards, p. 24
    An accessory dwelling unit may be constructed only: a) Within an existing dwelling unit on the lot; b) Attached to or sharing a wall with a single-family dwelling unit; or c) As a new structure on the lot for the primary purpose of creating an accessory dwelling unit.
  8. Section IX.J.16, Zoning Ordinance Section IX – Performance Standards, p. 25
    The detached accessory structure must be located no further than 100 feet from the nearest point of the principal structure;
  9. Section XI Off-Street Parking – Residential Uses, Zoning Ordinance (Chapter 405), compiled, p. 156
    Accessory Unit None required
This page summarizes Scarborough'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 Planning & Codes (Code Enforcement) ((207) 730-4040) before you build. Spot an error?