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Can I build an ADU in Dover, Massachusetts?

Dover, Norfolk County · Reviewed · 8 cited sections

Allowed with board review

Yes. Dover allows one attached or detached ADU with a home in its R, R-1, R-2, B, M, M-P and R-M districts after Partial Site Plan Review by the Planning Board, under § 185-43 as amended at the May 4, 2026 Town Meeting. The ADU can be no larger than 50% of the main home's gross floor area (basements count) or 900 square feet, whichever is less, and it can't be used as a short-term rental.

ApprovalPartial Site Plan Review by the Planning Board [1]
DistrictsR, R-1, R-2, B, M, M-P, R-M [1]
Max floor areaLesser of 50% of main home's gross floor area or 900 sq ft [3]
DrivewayMust share the main home's driveway opening and curb cut [5]
Board of HealthApprovals required for renovations or new construction [4]
Short-term rentalNot allowed in an ADU [8]

About this source

These rules come from the text of § 185-43 adopted at Dover's May 4, 2026 Annual Town Meeting (Article 18, passed 192-38), as attached to the Town Clerk's certificate of vote. It replaced the 2025 version.

Where and how ADUs are allowed

The owner of a principal dwelling in the R, R-1, R-2, B, M, M-P or R-M district must ask the Planning Board for Partial Site Plan Review to turn part of the home into an attached ADU, or to build or use part of a separate accessory structure as a detached ADU [1]. The Planning Board "shall approve" the site plan, with reasonable conditions, if the ADU meets the Partial Site Plan Review criteria of § 185-36 and the standards below [2]. This is site plan review, not a special permit.

Size and design standards

  • Floor area: no more than 50% of the main home's gross floor area or 900 square feet, whichever is less [3]. Gross floor area counts all stories with code-compliant ceiling height, including basements and lofts, but not crawl spaces, garage parking areas, attics or enclosed porches.
  • Board of Health: any renovation or new construction for an ADU needs all required Board of Health approvals, which in practice means septic review [4].
  • Driveway: the ADU must use the same driveway opening and curb cut as the main house [5].
  • Parking: adequate off-street parking is required, within the limits set by state law (c. 40A § 3) [6].
  • One per lot: a second ADU on the same lot needs a special permit from the Board [7].

Short-term rentals

An ADU can't be used as a short-term rental, as defined in § 185-5 [8].

Owner occupancy and state law

The bylaw has no owner-occupancy requirement. Massachusetts law (c. 40A § 3) has protected one ADU per lot since February 2, 2025. The wording of subsection B(3), "construct or use a portion of an existing separate accessory structure," could be read to limit detached ADUs to existing accessory buildings. If it is applied that way, state law may override that limit. A related change to the § 185-36 site plan review rules, also voted in May 2026, was still awaiting Attorney General approval when we checked, so confirm the current review process with the Planning Board.

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Next steps

  1. Contact the Dover Planning Board for the Partial Site Plan Review application and its Rules and Regulations for ADUs.
  2. Prepare gross floor area calculations for the main home and the ADU to show the 900 sq ft / 50% limit is met, and a site plan showing the shared driveway and off-street parking.
  3. Get Board of Health approval (septic capacity) for the renovation or new construction.
  4. After Planning Board approval, apply to the Building Department for a building permit.

Common questions

Can I build an ADU in Dover, Massachusetts?
Yes. Dover allows one attached or detached ADU with a home in its R, R-1, R-2, B, M, M-P and R-M districts after Partial Site Plan Review by the Planning Board, under § 185-43 as amended at the May 4, 2026 Town Meeting. This is site plan review, not a special permit.
How big can an ADU be in Dover, Massachusetts?
No larger than 50% of the main home's gross floor area (basements count) or 900 square feet, whichever is less.
Can I rent my ADU on Airbnb in Dover, Massachusetts?
No. An ADU can't be used as a short-term rental.
Does an ADU need its own driveway in Dover, Massachusetts?
No. The ADU must use the same driveway opening and curb cut as the main house. Adequate off-street parking is also required, and Board of Health approvals apply to renovations or new construction.

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 Dover's published bylaws. Section numbers are as printed in the source.

  1. § 185-43(B)(3), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 2
    An owner(s) of a Principal Dwelling in an R, R-1, R-2, B, M, M -P or R -M District or their authorized agent must request Partial Site Plan Review by the Planning Board to enable the use of a portion of a Principal Dwelling as an Attached ADU or to construct or use a portion of an existing separate accessory structure as a Detached ADU.
  2. § 185-43(B)(4), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 2
    The Planning Board shall approve a Partial Site Plan for an Attached or Detached ADU, subject to reasonable conditions the Board deems appropriate, as described in G.L. c. 40A, § 3, provided that the ADU complies with the Partial Site Plan Review criteria of § 185-36, and meets all the standards outlined in Subsection C below.
  3. § 185-43(C)(1), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 2
    The floor area of any ADU shall not exceed 50% of the gross floor area of the Principal Dwelling or 900 Sq. Ft., whichever is less.
  4. § 185-43(C)(2), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 3
    For any renovations or new construction related to an ADU, the applicant shall obtain all required approvals from the Board of Health.
  5. § 185-43(C)(3), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 3
    Attached and detached ADUs shall use the same driveway opening and curb cut as the Principal Dwelling.
  6. § 185-43(C)(4), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 3
    Adequate provision shall be made for off-street parking of motor vehicles associated with the ADU, as limited by c. 40A §. 3.
  7. § 185-43(C)(5), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 3
    The Board may grant a Special Permit to permit more than one ADU on the same lot or otherwise associated with a Principal Dwelling.
  8. § 185-43(C)(6), Certificate of Vote, 5-4-2026 ATM Article 18 - adopted text of Zoning Sec 185-43 Accessory Dwelling Units (Final Draft April 15, 2026), p. 3
    An ADU shall not be used as a Short -Term Rental as defined in Section 185-5 of the Zoning Bylaw.
This page summarizes Dover's posted bylaws as of the date checked. 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 Officer), Dover Town House, 5 Springdale Avenue (508-785-0032 ext. 225) before you build. Spot an error?