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Can I build an ADU in Auburn, Maine?

Auburn, Androscoggin County · Ordinances checked 2026-10-19 · Reviewed · 11 cited sections

Allowed with a permit

Yes. Auburn allows one accessory dwelling unit of 190 to 1,500 square feet, inside, attached to or detached from a single-family home, in its residential districts, with a building permit. ADUs aren't allowed in the Lake Auburn Watershed Overlay where it lies over the Agriculture & Resource Protection district.

Size190 to 1,500 sq ft (minimum may follow the state board's standard) [1]
TypeWithin, attached to, or detached from a single-family home on the same parcel [1]
Detached ADU as a second buildingAllowed where two-family homes are permitted and a single-family home exists (Sec. 60-34) [11]
Min. lot area, Suburban Residence21,780 sq ft for the house plus ADU [4]
Min. lot area, Urban Residence10,000 sq ft for the house plus ADU [5]
Min. lot area, Low Density Rural Residence1 acre for the house plus ADU [10]
SetbacksNot reduced for additional units [3]
Lake Auburn Watershed over AG/RPAdditional units prohibited [7]
ParkingCity may require no more than 1 off-street space per unit (LD 427) [9]

Where ADUs are allowed

Auburn defines an accessory dwelling unit as a self-contained unit of 190 to 1,500 square feet, inside, attached to, or detached from a single-family home on the same parcel [1]. The housing table in Sec. 60-53 (Ord. 23-12022024, effective January 6, 2025) lists ADUs as permitted in every residential district [4][5][10]. The minimum lot area is stated "for the first unit with accessory dwelling unit": 21,780 sq ft in Suburban Residence [4], 10,000 sq ft in Urban Residence [5] and 1 acre in Low Density Rural Residence [10]. In Agriculture & Resource Protection, an ADU is allowed only if it meets the single-family home rules for that district [6]. The buildings-per-lot rule (Sec. 60-34) also allows, as an exception to its one-principal-building limit, "the addition of an accessory dwelling unit in a zoning district where two-family dwelling units are permitted, and a single-family dwelling currently exists on the lot" [11]. Which districts permit two-family homes is in Article IV, which we couldn't review, so confirm a detached ADU is allowed in your district. State law requires towns to allow an ADU with a single-family home wherever homes are allowed, and may override a narrower reading.

Size and setbacks

The minimum size is 190 sq ft above grade unless the state Technical Building Codes and Standards Board adopts a different minimum, in which case that standard applies [2]. The state board set 160 sq ft in 2025, so 160 sq ft may now govern. The maximum is 1,500 sq ft [1]. Setbacks can't be reduced to fit an additional unit [3].

Lake Auburn Watershed

Additional units are prohibited in the Lake Auburn Watershed Overlay where the underlying zone is Agriculture & Resource Protection [7]. Maine's ADU and density provisions don't apply anywhere in the overlay, a drinking-water watershed [8].

Parking and owner occupancy

Since April 2026 the city can require no more than one off-street space per dwelling unit [9]. The sources we reviewed contain no owner-occupancy rule for ADUs. However, we couldn't download the district regulations (Article IV) from Municode, so check with the city. Starting July 1, 2027, state law will bar towns from requiring the owner to live on the property.

Pending changes (not adopted)

An August 2026 Planning Board draft would add a new ADU section (Sec. 60-56) for LD 1829, allowing an ADU on any lot with a residential use. No hearing had been held as of October 2026, so don't rely on it yet.

Approvals

The city text we reviewed doesn't call for Planning Board review of a single ADU. Apply for building, plumbing and electrical permits through SmartGov.

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

Next steps

  1. Check your zoning district and whether your lot is in the Lake Auburn or Taylor Pond Watershed Overlay on the city's zoning map, or ask the Planning, Permitting & Code Department at Auburn Hall, 60 Court Street (207-333-6601).
  2. Confirm the lot meets the district's minimum lot area and setbacks for the house plus ADU, and that the unit will be 1,500 sq ft or less.
  3. Apply for building, plumbing and electrical permits through the city's SmartGov portal (questions: permits@auburnmaine.gov). Bring plans showing the ADU's size and location, plus water and sewer or septic details.
  4. Ask Code staff about the status of the pending LD 1829 ADU amendments (proposed Sec. 60-56) before you finalize plans.

Common questions

Are ADUs allowed in Auburn, Maine?
Yes. Auburn allows one accessory dwelling unit of 190 to 1,500 square feet, inside, attached to or detached from a single-family home, in its residential districts, with a building permit. The buildings-per-lot rule allows an added ADU where two-family homes are permitted; we couldn't review which districts those are, so confirm a detached ADU with the city.
What is the minimum lot size for an ADU in Auburn, Maine?
It depends on the district. The minimum lot area for the house plus ADU is 21,780 sq ft in Suburban Residence, 10,000 sq ft in Urban Residence and 1 acre in Low Density Rural Residence. Setbacks can't be reduced to fit the unit.
How big can an accessory dwelling unit be in Auburn, Maine?
Up to 1,500 square feet. The local minimum is 190 sq ft unless the state building codes board sets a different minimum; the board set 160 sq ft in 2025, so 160 sq ft may now govern.
Can I build an ADU near Lake Auburn in Auburn, Maine?
Not where the Lake Auburn Watershed Overlay lies over the Agriculture & Resource Protection district: additional units are prohibited there. Maine's ADU and density provisions don't apply anywhere in the overlay, so check the zoning map and ask the city.
Does the owner have to live on the property to have an ADU in Auburn, Maine?
It's unclear. The sources we reviewed contain no owner-occupancy rule, but we couldn't review Auburn's district regulations, so check with the city. Starting July 1, 2027, state law will bar towns from requiring the owner to live on the property.

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

  1. Sec. 60-2 Definitions, "Accessory dwelling unit" (Supp. No. 34 text reprinted in the 2026-08-11 Planning Board packet), PROPOSAL (not adopted): Planning Board workshop packet 2026-08-11 - draft Chapter 60 amendments for LD 1829/LD 2173 (Sec. 60-2 definitions and Article II General Provisions, redline on Supp. No. 34 text), p. 2
    Accessory dwelling unit means a self-contained dwelling unit meeting a minimum of 190 square feet and not to exceed 1,500 square feet, that can be located within, attached to or detached from a single-family dwelling unit located on the same parcel of land.
  2. Sec. 60-2 Definitions, "Dwelling, one-family detached" (Supp. No. 34), PROPOSAL (not adopted): Planning Board workshop packet 2026-08-11 - draft Chapter 60 amendments for LD 1829/LD 2173 (Sec. 60-2 definitions and Article II General Provisions, redline on Supp. No. 34 text), p. 7
    Each one family detached dwelling unit must be at least 400 square feet above grade in size, and an accessory detached dwelling unit must be 190 square feet, above grade in size, unless the Technical Building Code and Standards Board, pursuant to 10 M.R.S.A. 9722, adopts a different minimum standard; if so, that standard applies.
  3. Ord. 23-12022024, Sec. 60-53 Additional dwellings permitted to increase housing opportunity, City Council Ordinances adopted in 2024 (compilation) - incl. Ord. 21-11182024 Lake Auburn Watershed Overlay text/map amendments and Ord. 23-12022024 LD 2003 housing/ADU amendments, p. 83
    Setback standards shall not be reduced to allow for additional dwelling units and shall not be increased for subsequent dwelling units.
  4. Sec. 60-53 table, Suburban Residence row (Supp. No. 34), PROPOSAL (not adopted): Planning Board workshop packet 2026-08-11 - draft Chapter 60 amendments for LD 1829/LD 2173 (Sec. 60-2 definitions and Article II General Provisions, redline on Supp. No. 34 text), p. 27
    Suburban Residence 21,780 square feet for the first unit with accessory dwelling unit. 21,780 square feet for each subsequent unit.
  5. Sec. 60-53 table, Urban Residence row (Supp. No. 34), PROPOSAL (not adopted): Planning Board workshop packet 2026-08-11 - draft Chapter 60 amendments for LD 1829/LD 2173 (Sec. 60-2 definitions and Article II General Provisions, redline on Supp. No. 34 text), p. 27
    Urban Residence 10,000 square feet for the first unit with accessory dwelling unit. 10,000 additional square feet per unit for each subsequent unit.
  6. Sec. 60-53 table, Agriculture & Resource Protection row (Supp. No. 34), PROPOSAL (not adopted): Planning Board workshop packet 2026-08-11 - draft Chapter 60 amendments for LD 1829/LD 2173 (Sec. 60-2 definitions and Article II General Provisions, redline on Supp. No. 34 text), p. 26
    Agriculture & Resource Protection 10 acres 250 feet Permitted if unit meets requirements for single family home in Article IV, Division 2 of this Chapter*.
  7. Ord. 23-12022024, Sec. 60-53, City Council Ordinances adopted in 2024 (compilation) - incl. Ord. 21-11182024 Lake Auburn Watershed Overlay text/map amendments and Ord. 23-12022024 LD 2003 housing/ADU amendments, p. 83
    Additional dwelling units allowed under this section are prohibited in the Lake Auburn Watershed Overlay District where the underlying zoning district is Agriculture and Resource Protection.
  8. Ord. 21-11182024, Sec. 60-952(1)(a) Lake Auburn Watershed Overlay District, City Council Ordinances adopted in 2024 (compilation) - incl. Ord. 21-11182024 Lake Auburn Watershed Overlay text/map amendments and Ord. 23-12022024 LD 2003 housing/ADU amendments, p. 64
    Pursuant to 30-A M.R.S.A. §§ 4364(9), 4364-A(1-A), and 4364-B(1-A), each as may be amended from time to time, the affordable housing density, residential density and accessory dwelling unit provisions of P.L. 2021, ch. 672, "An Act to Implement the Recommendations of the Commission to Increase Housing Opportunities in Maine by Studying Zoning and Land Use Restrictions" and any related state regulations do not apply in the Lake Auburn Watershed Overlay District.
  9. Ord. 06-04062026 (LD 427 parking), passed second reading 4/21/26, City Council Ordinances adopted in 2026 (Ords. 01-01052026 through 14-08032026; compilation posted 2026-08-25), p. 16
    BE IT ORDAINED, that THE CITY OF AUBURN hereby amends Auburn’s Code of City Ordinances Chapter 60 to comply with LD-427 “An Act to Regulate Municipal Parking Space Minimums”, which prohibits a municipality from requiring more than one off-street parking space per dwelling unit and allows a developer to satisfy parking requirements through an off-site parking agreement within existing facilities located within a ¼ mile of the development site.
  10. Sec. 60-53 table, Low Density Rural Residence row (Supp. No. 34), PROPOSAL (not adopted): Planning Board workshop packet 2026-08-11 - draft Chapter 60 amendments for LD 1829/LD 2173 (Sec. 60-2 definitions and Article II General Provisions, redline on Supp. No. 34 text), p. 27
    Low Density Rural Residence 1 acre for the first unit with accessory dwelling unit. 1 acre for each subsequent unit.
  11. Sec. 60-34(2) Buildings per lot (Supp. No. 34 text; shown struck in red in the 2026-08-11 packet = current law a pending draft would replace), PROPOSAL (not adopted): Planning Board workshop packet 2026-08-11 - draft Chapter 60 amendments for LD 1829/LD 2173 (Sec. 60-2 definitions and Article II General Provisions, redline on Supp. No. 34 text), p. 20
    (2) The addition of an accessory dwelling unit in a zoning district where two-family dwelling units are permitted, and a single-family dwelling currently exists on the lot.
This page summarizes Auburn's posted ordinances as of 2026-10-19. Ordinances are amended, and individual lots can have overlays, subdivision covenants, or HOA rules that are stricter. Confirm with Planning, Permitting & Code Department (Building, Plumbing & Code Services), Auburn Hall, 60 Court Street (207-333-6601 (Code Supervisor ext. 1150)) before you build. Spot an error?