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Can I build an ADU in Burlington, Massachusetts?

Burlington, Middlesex County · Bylaws checked 2026-10-15 · Reviewed · 10 cited sections

Allowed with a permit

Yes. Under the January 2025 version of Burlington's zoning bylaw (the newest copy we have; a September 2026 Town Meeting article may have changed it), one "Protected Use ADU" per lot is allowed by right in the One-Family Dwelling (RO) district with a building permit from the Inspector of Buildings. It can be attached or detached, no larger than 900 sq ft or half the main house's floor area (whichever is smaller), and may not be used as a short-term rental.

Where allowedRO One-Family Dwelling district, by right [3]
Number per lotOne ADU [4]
Max size900 sq ft or half the principal dwelling's gross floor area, whichever is smaller [1]
Attached or detachedEither is allowed [10]
Detached ADU locationNot between the street and the front of the main house [2]
ParkingOff-street driveway or garage for ADU occupants' cars (except within 1/2 mile of transit) [6]
Short-term rentalProhibited for Protected ADUs [4]
ApprovalInspector of Buildings, as part of the building permit [8]

These rules come from the zoning bylaw as consolidated through the January 2025 Town Meeting; our copy does not yet show the Attorney General's approval of the ADU amendment, and later changes (see Pending changes) may not be reflected.

Where and how many

The bylaw defines an ADU as a self-contained unit with its own sleeping, cooking and sanitary facilities, a separate entrance, and a size cap of half the main home's gross floor area or 900 sq ft, whichever is smaller [1]. A "Protected Use ADU" can be attached or detached and sits on a lot in a single-family district with no other ADU [10]. The accessory use schedule lists the Protected Use ADU as allowed (YES) in the RO district [3]. Section 11.2.2 says Protected ADUs are permitted as of right, only one per lot, and none may be used as a short-term rental [4]. State law protects one ADU per lot, so the one-per-lot limit matches it; the state leaves a second ADU to local special-permit rules, and Burlington doesn't allow one.

Design and siting

  • The house must still look like a single-family home, and any new ADU entry must be on the side or rear [5].
  • A detached ADU can't be placed between the road and the front of the main house, and a separate-entrance ADU needs a path or walkway [2].
  • Both units must connect to public water and sewer, must stay on one lot, and the ADU can't be sold separately as a condo [7].
  • Normal RO dimensional rules (setbacks, height) still apply under the definition [1].

Parking

All vehicles of ADU occupants must have a designated off-street driveway area or garage, except for properties within half a mile of a transit station [6]. State law bars towns from requiring more than one parking space for a protected ADU (none within half a mile of transit), so state law may override this "all vehicles" requirement. Likewise, the public sewer and water connection requirement [7] may be overridden by state law, which lets towns require Title 5 septic compliance but bars unreasonable restrictions on ADUs; confirm with the Building Department if your lot is on septic.

Approval

The Inspector of Buildings is the permit granting authority, and review happens with the building permit application [8]. No owner-occupancy requirement appears in the section.

Pending changes

A September 2026 Town Meeting article (Article 9, outcome not confirmed) would revise Section 11.2, including replacing the parking rule with "at least one (1) off-street parking space" outside a half mile of transit [9]. It also keeps the short-term rental ban. Treat it as proposed until the Town Clerk confirms adoption.

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

Next steps

  1. Confirm your lot is in the RO One-Family Dwelling district and has no other ADU.
  2. Check the size: the ADU's gross floor area must be no more than half the main house's or 900 sq ft, whichever is smaller.
  3. Plan the layout: new entries on the side or rear, no detached unit in front of the house, a walkway to a separate entrance, and off-street parking.
  4. Apply for a building permit with the Building Department (Inspector of Buildings, 781-270-1615); ADU review happens as part of that application.
  5. If the site is near a wetland or in the floodplain, contact the Conservation Commission before applying.

Common questions

Can I build an ADU on my property in Burlington, Massachusetts?
Yes, in the RO One-Family Dwelling district. Under the January 2025 zoning bylaw (the newest copy we have), one Protected Use ADU per lot is allowed by right with a building permit. A September 2026 Town Meeting article may have changed the rules; treat it as proposed until the Town Clerk confirms adoption.
How big can an ADU be in Burlington, Massachusetts?
An ADU can be no larger than 900 sq ft or half the main house's gross floor area, whichever is smaller. It can be attached or detached, but a detached ADU can't sit between the street and the front of the main house. This is from the January 2025 zoning copy and may have changed.
Do I need a permit for an ADU in Burlington, Massachusetts?
Yes. The Inspector of Buildings is the permit granting authority, and ADU review happens as part of the building permit application with the Building Department. No owner-occupancy requirement appears in the ADU section. If the site is near a wetland or in the floodplain, contact the Conservation Commission first.
Can I Airbnb my ADU in Burlington, Massachusetts?
No. The zoning bylaw says no Protected ADU may be used as a short-term rental, and the proposed September 2026 ADU article (outcome not confirmed) keeps that ban.
What are the ADU parking requirements in Burlington, Massachusetts?
It depends. The January 2025 bylaw requires a designated off-street driveway area or garage for all ADU occupants' vehicles, except within half a mile of a transit station, but state law may override this. A proposed September 2026 article would require at least one off-street space outside a half mile of transit; its adoption isn't confirmed.

Massachusetts' statewide ADU law

Since February 2, 2025, the Affordable Homes Act (St. 2024, c. 150, §8) has protected one accessory dwelling unit (ADU) per lot in any zoning district that allows single-family homes (M.G.L. c. 40A, §3). Your town cannot ban it, require a special permit or other discretionary approval, or "unreasonably restrict" building or renting it.

What counts as a protected ADU:

  • A self-contained unit with its own sleeping, cooking and bathroom facilities, on the same lot as the main home.
  • No larger than 900 sq ft or half the main home's floor area, whichever is smaller.
  • It can be attached or detached, and it needs a separate entrance that meets the building code.

What towns cannot require:

  • That the owner live in the main home or the ADU.
  • More than 1 extra parking space, or any extra space if the lot is within 0.5 miles of a subway, commuter rail, ferry or bus station.
  • A minimum lot size, caps on the number of ADUs, or limits on who may live there (age, income, relationship).

What towns can still do: use reasonable site plan review, setback, height and bulk rules, require Title 5 septic compliance, and restrict or ban short-term rentals of ADUs. A second ADU on the same lot needs a special permit. State regulations at 760 CMR 71.00 (in effect since January 31, 2025) explain which rules count as unreasonable.

State sources: M.G.L. c. 40A, §3 (protected ADU paragraph) · M.G.L. c. 40A, §1A (ADU definition) · EOHLC, Accessory Dwelling Units (law, FAQ, 2026 draft regulations) · 760 CMR 71.00, Protected Use Accessory Dwelling Units

What the bylaw says

Exact text from Burlington's published bylaws. Section numbers are as printed in the source.

  1. Art. II §2.4, Dwelling Unit, Accessory (ADU), Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 14
    A self-contained housing unit, inclusive of sleeping, cooking and sanitary facilities on the same lot as a principal dwelling, subject to otherwise applicable dimensional and parking requirements, that: (i) maintains a separate entrance, either directly from the outside or through an entry hall or corridor shared with the principal dwelling sufficient to meet the requirements of the state building code for safe egress; (ii) is not larger in gross floor area than 1/2 the gross floor area of the principal dwelling or 900 square feet, whichever is smaller; and (iii) is subject to such additional restrictions as may be imposed by a municipality, including, but not limited to, additional size restrictions and restrictions or prohibitions on short-term rental, as defined in section 1 of M.G.L chapter 64G; provided, however, that no municipality shall unreasonably restrict the creation or rental of an accessory dwelling unit that is not a short-term rental.
  2. §11.2.2.3 Siting Standards, Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 137
    a. A detached Protected Use ADU shall not be located between a roadway and the designated frontage of the Principal One-Family Dwelling. b. When a Protected Use ADU has a separate exterior entrance from the Principal One-Family Dwelling or is a separate Building, the ADU shall be accessible from a path or walkway.
  3. §4.3.2.23 Accessory Use Regulation Schedule, Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 51
    4.3.2.23 Dwelling, Protected Use ADU YES NO NO NO NO NO NO NO NO NO NO NO YES YES YES YES NO
  4. §11.2.2.1-11.2.2.2, Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 136
    c. No Protected ADU unit may be utilized as Short-Term Rental. (See Section 4.3.1.2) 11.2.2.2 Applicability and Requirements a. Only one (1) Protected Use ADU per lot may be created As-of-Right. No more than one ADU shall be permitted on any lot.
  5. §11.2.2.2(b), Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 136
    b. The Protected Use ADU and any modifications to the Principal Single Family Dwelling on the lot shall be designed so that the appearance of the Principal Dwelling remains that of a Single Family Dwelling. Any new entry to a Protected Use ADU shall be located on the side or in the rear of the Principal Dwelling.
  6. §11.2.2.2(e), Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 136
    e. All motor vehicles owned or maintained by occupants of a Protected Use ADU, with the exception of properties within one-half (1/2) mile of a transit station as defined in 760 CMR 71.02, shall be provided with a designated off-street driveway area or garage.
  7. §11.2.2.2(f)-(h), Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 136
    f. Both the Principal Single Family Dwelling and the Protected Use ADU shall be connected to the public water and sanitary sewer systems. g. The Protected Use ADU and the Principal One-Family Dwelling shall remain on the same Lot and shall not be divided into two (2) separate lots. h. No Protected Use ADU unit may be separately sold as a condominium, or otherwise.
  8. §11.2.2.4 Permitting Regulations and Permit Review Authority, Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 137
    a. The Inspector of Buildings shall be the permit granting authority for Protected Use ADUs. Such review shall be conducted concurrently as part of a Building Permit application.
  9. Sept 2026 TM Article 9 (proposed), §11.2.2.2(e), Sept 2026 Town Meeting Article 9 - ADU Bylaw Amendment (Sec. 11.2 / 4.3), proposed 2026-06-30, p. 2
    At least one (1) off-street parking space shall be provided for all Protected Use ADUs outside of one-half (1/2) mile of a transit stop.
  10. Art. II §2.4, Dwelling, Protected Use ADU, Burlington Zoning Bylaws (as amended through January 2025, pending AG approval at posting), p. 15
    An attached or detached Accessory Dwelling Unit that is located, or is proposed to be located, on a Lot in a Single-Family Residential Zoning District and no other Accessory Dwelling Unit is located on said Lot and which is protected from Prohibited Regulation and Unreasonable Regulations pursuant to M.G.L c. 40A, s. 3, para. 11 and 760 CMR 71.00.
This page summarizes Burlington's posted bylaws as of 2026-10-15. Bylaws are amended, and individual lots can have overlays, subdivision covenants, or HOA rules that are stricter. Confirm with Building Department (Inspector of Buildings / zoning enforcement) (781-270-1615) before you build. Spot an error?