York County · Maine
ADU rules in Biddeford, ME
Biddeford is a York County city on the Saco River.
This is a reference guide. Biddeford is not on our service-area list, so call to ask whether we can take on a build there.
Town ADU rules
What’s allowed on your lot in Biddeford.
Biddeford allows an ADU with an administrative building permit. The limit is 35% of the house or 900 sq ft, whichever is greater.
- Size limit
- 300 sq ft minimum; maximum 35% of the house's gross floor area or 900 sq ft, whichever is greater; max two bedrooms
- Where it can go
- Within, attached to, or detached from a single-family home
- Owner on site
- Owner must live in the house or the ADU
- Parking
- 1 off-street space unless legal on-street or public parking is within 1,000 ft
- Approval
- Code Enforcement Office building permit (administrative review; $200 ADU fee)
- Rentals
- No short-term rental rule in the ADU section; max three occupants
- Water setback
- 100 ft from water bodies, tributary streams and wetlands (25 ft in Waterfront Renaissance and General Development 1 and 2)
Allowed
- Attached or detachedThe CEO may permit an ADU within or attached to an existing or new owner-occupied single-family dwelling, or in a detached structure on a single-family home lot.§78.C(1)
- How manyOne ADU per residentially zoned parcel (per Table A), except within the RP Overlay District. Only one ADU per single-family house or house lot.§78.B(1)(a); §78.C(1)(b)
- SizeAt least 300 sq ft of gross floor area. No more than 35% of the principal dwelling's gross floor area or 900 sq ft, whichever is greater, including additions. Never enlarged past that limit. No more than two bedrooms.§78.C(1)(e), (f), (g), (j)
- Owner on siteThe owner must keep living in either the ADU or the principal dwelling. If not, the owner must remove the features that make the ADU a dwelling unit. Maximum three occupants in the ADU.§78.D(1)-(3)
- ParkingOne off-street parking space required for the ADU unless legal on-street parking or publicly supplied off-street parking is within 1,000 ft. Tandem parking allowed.§78.C(1)(l)
- LotThe lot must meet the district's minimum lot size for a single-family dwelling, or be legally nonconforming as of January 1, 2017.§78.C(1)(c)
- ApprovalThe Code Enforcement Office reviews applications administratively and may issue the permit if all standards are met. Decisions are final except for appeal to the Zoning Board of Appeals. ADU fee $200, non-refundable, plus building, electrical and plumbing fees. A certificate of occupancy is required before occupancy.§78.B(1)(a)-(b), B(2)(a), E(2)
- DesignNo rooftop decks. Balconies may not face interior side lot lines. Internal and attached ADUs: no added entrances facing a public street, and stairways enclosed. Attached ADUs: primary exterior materials match the main house. Detached ADUs: at least 10% of the facade facing an alley or street must be windows, and exterior stair railings must match the unit's finish or trim (no raw lumber).§78.C(1)(h), (i), (m), (n), (o)
- OtherMust be a complete separate housekeeping unit with kitchen and bath. The CEO may allow reasonable deviation for accessibility features.§78.C(1)(a); §78.C(2)
- OtherADUs are also allowed on nonresidentially zoned parcels with a single nonconforming (as to use) dwelling unit that existed as of January 1, 2017. All ADUs must meet Article XIV Shoreland Zoning.§78.B(1)(a); Table A note 27
- ShorelandAll new principal and accessory structures must be set back at least 100 ft from the normal high-water line of GPA great ponds and rivers flowing to them, and 100 ft from other water bodies, tributary streams and wetland edges. Exceptions: 25 ft in the Waterfront Renaissance District (excluding areas west of Elm Street) and in General Development 1 and 2; no minimum in Commercial Fisheries/Maritime Activities; 75 ft for essential-services structures in Limited Residential and in part of the IN Zone. All ADUs must comply with Article XIV, and §78 excludes ADUs from the RP Overlay District.LDR Art. XIV §15.B(1); Art. VI §78.B(1)(a)
- State lawThe city text asks for one off-street space for the ADU. Maine law already bars parking beyond what the single-family home requires.30-A M.R.S. §4364-B(4)(C)
Not allowed
- Not allowedNo ADU within the RP Overlay District.§78.B(1)(a)
- Not allowedADU may not be sold; it must stay in common ownership with the principal dwelling.§78.C(1)(d)
- Not allowedOnly one ADU per single-family house or lot.§78.C(1)(b)
- Not allowedNo rooftop decks; no balconies facing interior side lot lines.§78.C(1)(h), (i)
- Not allowedADU may not be enlarged beyond the 35% / 900 sq ft cap after it is created.§78.C(1)(g)
- Not allowedNo more than three people may occupy an ADU.§78.D(3)
Read 2026-11-15 from City of Biddeford Land Development Regulations (Code Part III, Chapter LDR), Art. VI §78 Accessory dwelling units; Art. V Tables A and B; Art. XIV Shoreland Zoning (§78 [Added 3-7-2017 by Ord. No. 2017.16; §78.B(1)(a) amended 6-20-2017 by Ord. No. 2017.57 and 12-19-2023 by 2023.143]. Table A last amended 8-20-2024 (Ord. No. 2024.136); Table B last amended 11-7-2024 (Ord. No. 2024.171), Supp 13, Jan 2026. eCode360 shows legislation through 08-18-2026; read live 2026-11-15.). Anything not listed here, we check with the Biddeford land-use office for your lot.
Setbacks
Front, side and rear in Biddeford.
Maine 30-A M.R.S. §4364-B - at least one ADU with a single-family home; from July 1, 2027, also with a two- or three-unit building, and at least three units per lot
Biddeford's dimensional table, as printed in the ordinance.
| District | Front | Side | Rear | Lot / cover / height |
|---|---|---|---|---|
| SR-1primarySuburban ResidentialLDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. SR-1 frontage 100 ft water & sewer; 100 ft water or sewer; 200 ft neither. | 40 ft from major R.O.W.; 25 ft from other R.O.W. | 10 ft | 10 ft | 15,000 sq ft/unit water & sewer; 20,000 water no sewer; 20,000 sewer no water; 40,000 neither (note C: dwelling units only; other uses 10,000 sq ft) · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| CRCoastal ResidentialLDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A; Art. V §6A Table C. CR frontage 150 ft (all utility cases). | 40 ft from major R.O.W.; 25 ft from other R.O.W. | 25 ft | 25 ft | Table C (Art. V §6A): on private septic with municipal water, 20,000 to 80,000 sq ft by soil profile/condition; 80,000 sq ft without municipal water; 20,000 sq ft with municipal sewer · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| R-1-AResidential R-1-ALDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. R-1-A frontage 100 ft (all cases). | 40 ft major R.O.W.; 25 ft other | 10 ft | 10 ft | 10,000 sq ft/unit water & sewer; 20,000 water no sewer; 10,000 sewer no water; 20,000 neither · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| R-1-BResidential R-1-BLDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. R-1-B frontage 50 ft (all cases). | 25 ft major R.O.W.; 10 ft other | 5 ft | 5 ft | 5,000 sq ft/unit water & sewer; 20,000 water no sewer; 5,000 sewer no water; 20,000 neither · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| R-2Residential R-2LDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. R-2 frontage 45 ft with water & sewer. | 25 ft major R.O.W.; 15 ft other | 5 ft | 5 ft | 4,500 sq ft/unit with water & sewer; other utility cases N/A (not allowed) · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| R-3Residential R-3 (single-family row)LDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. R-3 frontage 100 ft water & sewer; 120 ft water or sewer; 200 ft neither. | 40 ft major R.O.W.; 25 ft other | 10 ft | 10 ft | 10,000 sq ft water & sewer; 20,000 water no sewer; 20,000 sewer no water; 40,000 neither · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| W-1Waterfront W-1LDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. W-1 frontage 100 ft (all cases). | 40 ft major R.O.W.; 25 ft other | 25 ft | 25 ft | 15,000 sq ft/unit water & sewer; 20,000 water no sewer; 20,000 sewer no water; 40,000 neither (note C) · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| W-3Waterfront W-3 (Biddeford Pool Village Waterfront)LDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. W-3 frontage Not shown in Table B. | Not shown in Table B | Not shown in Table B | Not shown in Table B | Not shown in Table B · Not set in Table B (no lot coverage column) · Height Not shown in Table B |
| R-FRural-Farm (single-family row)LDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. R-F frontage 120 ft water & sewer; 120 ft water or sewer; 200 ft neither. R-F accessory buildings: Note M: accessory structures must meet setbacks, max three per lot, no taller than the primary structure, plumbing limited to a utility sink (farm structures exempt). | 40 ft major R.O.W. (note H); 25 ft other | 25 ft | 25 ft | 20,000 sq ft water & sewer; 20,000 water no sewer; 20,000 sewer no water; 40,000 neither · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| OROffice ResidentialLDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. OR frontage 75 ft with water & sewer. | 10 ft major R.O.W.; 10 ft other | 10 ft | 10 ft | 4,500 sq ft/unit with water & sewer; other cases N/A · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
| MSRD-2Main Street Revitalization District 2 (residential conservation)LDR Art. V, Table B Dimensional Requirements (Supp 13, Jan 2026); single-family permission from Table A. MSRD-2 frontage 50 ft with water & sewer. | 15 ft major R.O.W.; 15 ft other (note R: may reduce to average of adjacent lots) | None | None | 2,000 sq ft/unit with water & sewer; other cases N/A · Not set in Table B (no lot coverage column) · Height 3 stories / 35 ft |
Verified 2026-11-15 against City of Biddeford Land Development Regulations (Code Part III, Chapter LDR), Art. VI §78 Accessory dwelling units; Art. V Tables A and B; Art. XIV Shoreland Zoning. Towns amend ordinances, so confirm with the land-use office before you build. Official source
FAQ
ADUs in Biddeford.
- How big can an ADU be in Biddeford?
- 300 sq ft minimum; maximum 35% of the house's gross floor area or 900 sq ft, whichever is greater; max two bedrooms, per §78.C(1)(e), (f), (g), (j) as read 2026-11-15.
- Does the owner have to live on the lot in Biddeford?
- Owner must live in the house or the ADU (§78.D(1)-(3)).
- Can an ADU in Biddeford be detached?
- Within, attached to, or detached from a single-family home, under §78.C(1).
Planning an ADU in Biddeford?
Call (978) 987-0089 and we will say whether we can build there. See the ADU models