Town Permit Guide

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Can I build an ADU in Lewiston, Maine?

Lewiston, Androscoggin County · Ordinances checked 2026-10-16 · Reviewed · 11 cited sections

Allowed with a permit

Yes. Lewiston allows one accessory dwelling unit (ADU) per lot with a house, duplex, multi-family building or mobile home, and it can be inside, attached or detached. It must be 190 to 900 square feet of habitable area with no more than 2 bedrooms, the owner must live in either the ADU or the main home, and no extra parking is required. You need a building permit and, before move-in, recorded deed documentation and an occupancy permit.

Number allowedOne ADU per lot [2]
DistrictsPermitted (P) in every zoning district except Resource Conservation (RC) [11]
Attached or detachedEither (same parcel, permanent foundation) [2]
Size190 to 900 sq ft habitable area, max 2 bedrooms [4]
Owner occupancyOwner must live in the ADU or the main dwelling [6]
ParkingNo additional parking required [7]
DrivewayMust share the existing driveway opening; curb cut max 24 ft wide [3]
Detached ADU placementSide or rear of the main home, front setback at least equal to the main home [5]

Where and what kind

Lewiston's zoning code defines an ADU as a self-contained unit within, attached to or detached from a single-family, two-family or multi-family dwelling or a mobile home on the same parcel [1]. One ADU is permitted on any lot with one of those principal dwellings, attached or detached, on a permanent foundation [2]. The Article XI Land Use Table lists ADUs "in accordance with the standards of Article XII" as a permitted use (P) in all 16 base districts from Rural Agricultural through Mill, including every residential district (RA, LDR, SR, MDR, NCA, NCB, DR); only Resource Conservation (RC) has no entry [11]. In the Riverfront, Centreville and Mill districts the entry carries note (2), which bars new dwelling units on the first floor facing certain downtown streets. No extra frontage or lot size is needed and the ADU doesn't count against the district's lot-area-per-unit rule, but setbacks for a structure still apply.

Size and design

  • Habitable area of 190 to 900 square feet, with no more than 2 bedrooms [4].
  • An attached ADU shares one main front entrance with the house; other entrances must look subordinate. The ADU must use the existing driveway opening, with no new curb cuts, and any new or expanded curb cut can't exceed 24 feet wide [3].
  • A detached ADU goes to the side or rear of the main home, with a front setback at least equal to the house's. On lots over one acre where the house is set back at least twice the required front setback, it can sit closer to the street if it meets the district setback [5].

Occupancy, parking and ownership

Either the ADU or the main dwelling must be owner-occupied [6]. Maine state law will bar towns from requiring owner occupancy starting July 1, 2027, so this rule may be overridden then. No additional parking is required [7]. The ADU and main dwelling must stay in common ownership, and you must record documentation at the Androscoggin Registry of Deeds and give the City evidence of it before an occupancy permit is issued [8]. ADUs on private septic must meet the state subsurface wastewater rules, and fire safety and egress laws apply.

Permits

Building an ADU is construction of a structure, which needs a permit from Planning & Code Enforcement [9]. The posted fee schedule (dated 2013) charges single-family new construction or additions $25 plus $0.25 per square foot [10]; staff confirm the fee once your application is complete.

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

Next steps

  1. Look up your zoning district on the City's GIS map and confirm the lot has a principal home that qualifies.
  2. Draw a plan showing the ADU's habitable area (190-900 sq ft, max 2 bedrooms), its location relative to the house, setbacks and the shared driveway.
  3. Submit a Building Permit application to Planning & Code Enforcement (PlanningCode@lewistonmaine.gov or 27 Pine St., 3rd floor; 207-513-3125). Add a septic design if you're not on public sewer.
  4. Before move-in, record the ADU deed documentation at the Androscoggin Registry of Deeds and give the City proof so it can issue the occupancy permit.

Common questions

Are ADUs allowed in Lewiston, Maine?
Yes. Lewiston allows one accessory dwelling unit per lot with a house, duplex, multi-family building or mobile home, and it can be inside, attached or detached. The zoning Land Use Table lists ADUs as permitted in every zoning district except Resource Conservation, including all residential districts.
How big can an ADU be in Lewiston, Maine?
An ADU in Lewiston must have 190 to 900 square feet of habitable area and no more than 2 bedrooms. A detached ADU goes to the side or rear of the main home, with a front setback at least equal to the house's.
Does the owner have to live on the property to build an ADU in Lewiston, Maine?
For now, yes. Lewiston requires either the ADU or the main home to be owner-occupied. Maine law will bar towns from requiring owner occupancy starting July 1, 2027, so this rule may be overridden then. The ADU and main home must also stay in common ownership.
Do I need a permit and extra parking for an ADU in Lewiston, Maine?
You need a building permit from Planning & Code Enforcement, but no additional parking is required. The ADU must share the existing driveway opening. Before move-in, you record documentation at the Androscoggin Registry of Deeds and give the City proof so it can issue an occupancy permit.

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

  1. Art. II, Sec. 2 Definitions, Accessory dwelling unit, Zoning and Land Use Code (Appendix A) Article II - Definitions (as amended through Ord. 26-02, eff. 2026-03-05), p. 2
    Accessory dwelling unit means a self-contained dwelling unit located within, attached to or detached from a single-family dwelling unit, two-family dwelling unit, multi-family dwelling, or mobile home located on the same parcel of land.
  2. Art. XII, Sec. 11 Accessory dwelling unit standards, Zoning and Land Use Code (Appendix A) Article XII - Performance Standards (as amended through Ord. 26-05, eff. 2026-03-05), p. 59
    The accessory dwelling unit may be attached to or detached from the principal dwelling, but must be located on the same parcel and be on a permanent foundation.
  3. Art. XII, Sec. 11(2)b, Zoning and Land Use Code (Appendix A) Article XII - Performance Standards (as amended through Ord. 26-05, eff. 2026-03-05), p. 60
    The ADU must share the same driveway opening that serves the principal dwelling; no additional curb cuts or driveways may be created to facilitate the creation of the accessory dwelling unit and any new or expanded driveway entrance curb cut on the property must not exceed twenty-four (24) feet in width;
  4. Art. XII, Sec. 11(2)c, Zoning and Land Use Code (Appendix A) Article XII - Performance Standards (as amended through Ord. 26-05, eff. 2026-03-05), p. 60
    The habitable area of the ADU shall not exceed 900 square feet and shall not contain more than two (2) bedrooms. The ADU must be a minimum of 190 square feet;
  5. Art. XII, Sec. 11(2)d, Zoning and Land Use Code (Appendix A) Article XII - Performance Standards (as amended through Ord. 26-05, eff. 2026-03-05), p. 60
    A detached ADU shall be located to the side or rear of the principal dwelling and must have a front setback that is equal to or greater than the principal dwelling.
  6. Art. XII, Sec. 11(3), Zoning and Land Use Code (Appendix A) Article XII - Performance Standards (as amended through Ord. 26-05, eff. 2026-03-05), p. 60
    Either the ADU or the primary dwelling must be owner-occupied.
  7. Art. XII, Sec. 11(6), Zoning and Land Use Code (Appendix A) Article XII - Performance Standards (as amended through Ord. 26-05, eff. 2026-03-05), p. 60
    No additional parking is required for the ADU.
  8. Art. XII, Sec. 11(7), Zoning and Land Use Code (Appendix A) Article XII - Performance Standards (as amended through Ord. 26-05, eff. 2026-03-05), p. 60
    The principal dwelling and the ADU must remain in common ownership.
  9. Art. V, Sec. 5(a)(1) Administrative procedures, Zoning and Land Use Code (Appendix A) Article V - Administration and Enforcement (as amended through Ord. 26-03, eff. 2026-03-05), p. 8
    A permit shall be required for all activities regulated by this code including, but not limited to the following: (1) The construction, alteration, relocation, demolition, placement, or removal of or the addition to any structure or building or part thereof;
  10. Building Permit Fee Schedule, Single Family, Building Permit Fee Schedule (updated 4/16/2013, effective 7/01/2013), p. 1
    New construction/Additions $25 base + $0.25 sf
  11. Art. XI, Sec. 22 Land Use Table (6.04.2026), Residential: Accessory dwelling units row, Zoning and Land Use Code (Appendix A) Article XI - District Regulations incl. Land Use Table and Space & Bulk Table (as amended through Ord. 26-19, eff. 2026-08-20), p. 9
    Accessory dwelling units in accordance with the standards of Article XII P P P P P (2) P P P P P P P P (2) P P P (2)
This page summarizes Lewiston's posted ordinances as of 2026-10-16. Ordinances are amended, and individual lots can have overlays, subdivision covenants, or HOA rules that are stricter. Confirm with Planning & Code Enforcement Department (City Hall, 27 Pine St., 3rd floor) (207-513-3125) before you build. Spot an error?