ADU rules in Freetown, and the setback nobody has to meet
Freetown allows one accessory dwelling unit by right on every single-family lot in town — a backyard apartment, an in-law apartment, a garage or barn conversion. The setback rule printed in the town’s own published bylaw was struck down by the Attorney General in May 2026, and the published text still shows it. On most lots that is the difference between a unit that fits and one that doesn’t.
“The lot coverage and setback requirements applicable to the lot shall apply to an ADU on the same lot.”
The Attorney General’s Municipal Law Unit disapproved that subsection on 29 May 2026 (case 12191), holding that it conflicts with G.L. c.40A §3 and 760 CMR 71.00. A disapproved provision has no legal effect — but it is still in the text on the town’s website, so anyone reading the bylaw straight through applies a 20-foot side and rear setback to an ADU that is not actually required to meet it.
What the setbacks actually are
With Sec. 300-5.11(D)(2) removed, a detached ADU is an accessory structure and takes the accessory setbacks. On a lot recorded before 22 September 1986 — which is most of Assonet and much of East Freetown — the older-lot relief in Sec. 300-6.1G(1) applies instead, and it is more generous again.
| Setback | If you read the published bylaw | What applies | Lot recorded pre-1986 |
|---|---|---|---|
| Front / street | 50 ft | 50 ft | 30 ft |
| Side | 20 ft | 10 ft | 6 ft |
| Rear | 20 ft | 10 ft | 6 ft |
Ten feet against twenty, or six against twenty, decides whether a 900-square-foot cottage fits behind an existing house on a normal Assonet lot. It is the single most consequential thing about building an ADU in this town, and it is not what the published bylaw says.
Where an ADU is allowed
One protected use ADU is permitted as of right on each lot in a single-family residential zoning district. No special permit, no zoning board.
Sec. 300-5.11C(2)- Residential (R)
- Qualifies. Single-family detached is permitted as of right. Table of Use Regulations — “Y” in the R column
- Village Res. (VR)
- Qualifies. Lot requirements are the same as the Residential District. Sec. 300-3.1A; Sec. 300-3.3B(1)
- STOD overlay
- Does not qualify. The Science and Technology Overlay column reads “N” for single-family detached, so it is not a single-family residential district under 760 CMR 71.02. Sec. 300-4.4E → Sec. 300-5.1 Table of Use Regulations
- Floodplain overlay
- Separate constraint layer. Overlay status is a map reading, not a text reading — it has to be checked against the Zoning Map for your parcel. Sec. 300-4.1
How big it can be
Half the gross floor area of your house, or 900 square feet, whichever is smaller. A 1,600-square-foot house gives you 800 square feet, not 900.
Sec. 300-5.11D(1)Freetown’s bylaw carries its own definition of gross floor area, and it is not the one that governs the size of a protected-use ADU. The state definition at 760 CMR 71.02 controls, and a local definition cannot shrink a state entitlement. We compute the half-GFA figure on the state definition and carry the local number alongside it, because a local official may well reach for the local one.
Septic: you may share the system
This is the most valuable line in the Freetown bylaw and it is easy to miss. The ADU and the principal dwelling may share the same septic system and the same water service. Freetown has no town sewer across most of its area, so in towns that require a dedicated system this single sentence is worth tens of thousands of dollars.
Sec. 300-5.11C(5)Sharing is permitted, not automatic. The existing system still has to carry the added design flow under Title 5, which is a bedroom-count test on the whole property, not on the new unit alone. Where the existing system has spare capacity, an ADU can often be added with no septic work at all. Where it does not, the system is the largest line in the budget — and knowing which of those two you are in is most of what a feasibility study is for.
Parking, occupancy, and two provisions we would contest
Parking — one space, in practice
One additional off-street space is required only if all portions of the lot sit outside a half-mile radius of a transit station. Freetown has no commuter rail station, so in practice plan on one space.
Sec. 300-5.11C(4); cf. 760 CMR 71.03Owner occupancy — required as written
The bylaw requires owner occupancy, and it restricts rental of the unit. Worth knowing before you plan around a tenant: short-term rental is not the intended use here.
Sec. 300-5.11C(6); Sec. 300-5.11C(7)Common ownership — approved, but flagged
The Attorney General approved the common-ownership requirement in Sec. 300-5.11C(2) while expressly flagging it as vulnerable, on the ground that it is written around ownership rather than around use. It stands today. It is the kind of provision that does not survive a challenge, and if your situation turns on it, it is worth raising with the building department rather than assuming.
AG MLU case 12191, decided 2026-05-29If your lot is smaller than the zoning minimum
Freetown’s Residential District asks for 70,000 square feet of lot, 175 feet of frontage, and 52,000 square feet of contiguous upland. A great many Assonet and East Freetown lots are nothing like that, and it does not disqualify them: a single-family dwelling is allowed on an undersized or wetland-containing lot where the lot was legally created and recorded before those minimums went up, is not held in common ownership with abutting land, and meets Board of Health requirements. Conservation Commission review applies where wetland is present.
Sec. 300-6.1D; Sec. 300-6.1E (30% building coverage); Sec. 300-6.1FWe will tell you whether it works before you spend anything
Southcoast Building is an approved Feasibility Study Provider under the Massachusetts Housing Partnership ADU Incentive Program. A licensed builder walks your property, reads your parcel against the bylaw, checks the septic and the grading, and tells you whether an ADU works here and roughly what it would cost. Thirteen of our studies have been approved by MHP to date.
Request your free study$0 to you under the MHP ADU Incentive Program · One study per property · Michael Bicho · (508) 269-2131
Where these figures come from
- Town of Freetown Zoning Bylaw, Chapter 300 —
Sec. 300-5.11(ADUs),Sec. 300-6.1(dimensional regulations),Sec. 300-3.3BandSec. 300-4.4(districts and overlays). Published text retrieved 31 August 2026; the section header reads[Amended 5-1-1999 ATM; 10-27-2008 STM; 10-27-2015 STM; 2-2-2026 STM by Art. 25], so the published text does include the 2026 ADU article. - Massachusetts Attorney General, Municipal Law Unit, case 12191, decided
29 May 2026 — Article 25 partially approved;
Sec. 300-5.11(D)(2)disapproved and deleted;Sec. 300-5.11(C)(2)approved and flagged. Reasoning cites Amherst v. Attorney General, 398 Mass. 793, 795–96 (1986). - 760 CMR 71.00 (Accessory Dwelling Units) — §71.02 definitions and the gross floor area measure; §71.03 on parking and dimensional relief.
- 310 CMR 15.000 (Title 5) for the design-flow and bedroom-count test.
Zoning changes, and a building inspector’s reading of it is the one that governs your permit. Nothing here is a determination about your property. It is what the adopted text and the Attorney General’s decision say as of 8 September 2026.