Rockland · Plymouth County

Can you build an ADU in Rockland?

Rockland rewrote its accessory apartment bylaw wholesale at the May 2025 town meeting, replacing it with Section 415-32 and tightening accessory structure setbacks in the same sitting. Every ADU here goes in front of the Planning Board, though the bylaw is explicit that the board may not use that to say no.

What the state guarantees you

Since 2 February 2025 this applies in every Massachusetts community. A town may be more generous than this. It may not be less.

Rule	What it means
Allowed by right	One ADU in single-family zoning districts, statewideNo special permit and no public hearing for a protected-use ADU
Maximum size	900 sq ft, or 50% of the principal dwelling, whichever is smallerA town may allow larger. It cannot allow smaller
Owner occupancy	A town cannot require itSo you may rent both units, or live in the ADU and rent out the house
Parking	One space at most, and none at all within half a mile of transitA town cannot ask for more than this
Short-term rental	The state leaves this to each townAll six towns documented here ban it, and two of them ban it for the main house too
In force since	2 February 2025Any conflicting local zoning became unenforceable that day

What Rockland adds on top

Rule	In Rockland
Where allowed	By right in R-1, R-2, R-3 and R-4, subject to site plan review
Review	Site Plan Review by the Planning Board as a regular agenda item at a posted meeting. The bylaw limits the board to reasonable terms and conditions and bars it from prohibiting the use
Maximum size	Half the principal dwelling's gross floor area or 900 sq ft, whichever is smaller
How many	One per lot
Parking	One space for the ADU
Setback from the house	A detached unit must sit at least 10 ft from the principal dwelling
Height of a new outbuilding	Two storeys and 24 ft maximum where it is built to house an ADU
Lot line setbacks	10 ft where the structure is under 24 ft tall and under 400 sq ft, 15 ft once it reaches either figure, under Section 415-22.B(4)
Front yard	No detached accessory structure in the front yard area between the street and the principal building, across the width of the house
Yard coverage	An accessory building may not occupy more than 30% of a required yard
Converting an old outbuilding	Permitted, but a pre-existing nonconforming accessory structure needs a special permit from the Zoning Board of Appeals under Section 415-89
Nonconforming structures	An ADU must not increase the nonconforming nature of the principal structure
Still a single family	A single-family dwelling with an ADU is not deemed a two-family dwelling
Short-term rental	Prohibited for the ADU and the principal dwelling
Separate sale	Neither may be sold, conveyed or transferred apart from the other
Septic	Compliance with Title 5 at 310 CMR 15.000 and Board of Health policy

Rockland sits in the middle of the three towns we have documented on the question that decides most projects, which is whether the garage can become the unit. Braintree allows that conversion by right. Whitman effectively bars it, by requiring the outbuilding to already meet principal-dwelling dimensions. Rockland allows it with a Zoning Board special permit under Section 415-89, so it is possible, slower, and discretionary. The other number to watch is 400 sq ft, because crossing it moves your lot line setback from 10 ft to 15 ft, as does going over 24 ft in height. On a narrow lot that single threshold can decide where the building goes, or whether it fits at all. Note too that the bylaw states plainly that a single family with an ADU is not a two-family, which matters for how the property is later classified and financed.

Questions people ask

Does Rockland require a hearing for an ADU?

An ADU is allowed by right but requires Site Plan Review by the Planning Board, taken as a regular agenda item at a posted meeting. The bylaw restricts the board to imposing reasonable terms and conditions and bars it from prohibiting the use.

Can I convert an existing garage into an ADU in Rockland?

Yes, but a pre-existing nonconforming accessory structure requires a special permit from the Zoning Board of Appeals under Section 415-89, and the conversion must not increase the nonconforming nature of the principal structure.

What setback applies to a detached ADU in Rockland?

Ten feet from a side or rear lot line where the structure is under 24 feet tall and under 400 square feet. At or above either threshold it becomes 15 feet. A detached unit must also sit at least 10 feet from the principal dwelling.

Does an ADU make my house a two-family in Rockland?

No. Section 415-32 states that a single-family dwelling with an accessory dwelling unit shall not be deemed a two-family dwelling.

Can I short-term rent a Rockland ADU?

No, and the prohibition covers the principal dwelling as well as the ADU. Neither may be sold or transferred separately from the other either.