Lakeville has two ADU schemes on the books, and the Attorney General warned about both
Lakeville’s adopted text carries an ADU definition tracking the state regulation and a legacy accessory-apartment scheme at the same time, unreconciled. The Attorney General approved the article with no deletions but cautioned twice — including that Lakeville’s own accessory building rules cannot be applied to an ADU at all.
The state calls it an accessory dwelling unit. Lakeville’s older provision calls it an accessory apartment. Owners call it an in-law apartment, or a backyard apartment if it is detached. That the town holds two names for it is exactly the issue.
The Sec. 270-6.3 accessory building rules, which impose a special permit requirement and a minimum lot size.
The Attorney General was explicit: the Sec. 270-6.3 accessory building rules cannot apply to a protected-use ADU, because they impose a special permit requirement and a minimum lot size, both of which are prohibited for a single ADU. Separately the AG cautioned that the off-site improvement requirement in Sec. 270-6.7(F)(12) likely violates protected-use ADU protections and should be amended to exclude ADUs. Neither amendment has been made. So the provisions are still printed, still cautioned, and still what an official will reach for.
The two unreconciled schemes
Lakeville holds both of these in the adopted text, and they have not been reconciled:
- The state-tracking definition
- An accessory dwelling unit definition following 760 CMR 71.02, with the protected-use and 900 sq ft language.Sec. 270-2; Sec. 270-7.4B(38)
- The legacy scheme
- A separate accessory-apartment provision at Sec. 270-7.8.Sec. 270-7.8
We will be straight about a limit in our own reading: the full text of Sec. 270-7.8 has not been read. It is an open item on our Lakeville file. We know the two schemes coexist and we know they conflict; we do not yet know the exact terms of the older one, so we are not going to characterise them. On a live Lakeville project that is the first thing we settle at the Town Clerk’s office.
Sec. 270-7.8 — full text not yet read; recorded as an open itemWhere the state floor holds regardless
Whatever Sec. 270-7.8 says, and whatever Sec. 270-6.3 asks for, 760 CMR 71.00 sets a floor the town cannot go below for a protected-use ADU:
- Permission
- As of right on a lot in a single-family residential zoning district. No special permit — which is exactly what the AG said Sec. 270-6.3 cannot impose.760 CMR 71.03
- Minimum lot size
- No minimum above the district minimum may be imposed. Again, the Sec. 270-6.3 problem.760 CMR 71.03
- Size
- 900 sq ft or half the principal dwelling’s gross floor area, whichever is smaller, and the published Lakeville text carries the 900 sq ft standard.760 CMR 71.02; Sec. 270-2
- Parking
- None stated locally in the provisions we have read. State ceiling: one additional space for a protected-use ADU, zero within half a mile of transit.760 CMR 71.02
Work your size number on the ADU size calculator. The state definition at 760 CMR 71.02 governs the size of a protected-use ADU, 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.
The lot coverage definition that catches people
Lakeville measures lot coverage as the percentage of lot area covered by the horizontal projection of the largest single floor area of the principal structure plus all accessory structures, parking and loading areas and access roads.
Sec. 270-2Read that list again: parking areas and access roads are inside the coverage calculation. So a new driveway or parking apron serving the ADU eats the same 25% allowance the building does. On a constrained lot this is frequently what decides a detached unit — not the setbacks, and not the size cap. It is worth laying out the parking and the access before the building footprint, which is the reverse of the usual order.
Currency: this one is clean
No published-code lag here. The held eCode360 text carries the protected-use and 900-square-foot language, and AG case 11676 decided 2 June 2025 covers Articles 15 to 18 of the Special Town Meeting of 12 November 2024. Published text and AG decision agree.
AG MLU ADUS index, read 2 September 2026; full-text search of the held eCode360 textSo the problem in Lakeville is not that the text is out of date. It is that the text contains two schemes and two cautioned provisions, all of them current.
Septic on the ponds
Lakeville sits on Assawompset Pond, Long Pond and Great Quittacas Pond — and those are public water supply reservoirs. Parcels near them can carry constraints well beyond ordinary Title 5: watershed protection, nitrogen loading limits, and in places a substantially more expensive system. Where a property sits relative to those boundaries changes the budget more than any zoning provision on this page.
310 CMR 15.000; watershed and Zone II constraints, read per parcelThat is the measurement we go and take first in this town. Planning ranges are in our cost guide.
We 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 Lakeville Zoning Bylaw, Chapter 270 —
Sec. 270-2(definitions, including the ADU definition and LOT COVERAGE),Sec. 270-6.3(accessory buildings),Sec. 270-6.7(F)(12)(off-site improvements),Sec. 270-7.4B(38)(use),Sec. 270-7.8(legacy accessory apartment — full text not yet read, recorded as an open item). - Massachusetts Attorney General, Municipal Law Unit, case 11676, Arts. 16 and 18, decided 2 June 2025 — approved with no deletions, but cautioning that
Sec. 270-6.7(F)(12)likely violates protected-use ADU protections and that theSec. 270-6.3accessory building rules cannot apply to a protected-use ADU. Covers Arts. 15–18 of the STM of 12 November 2024. - 760 CMR 71.00 — §71.02 definitions and size, §71.03 as-of-right permission and the bar on a minimum lot size above the district minimum.
- 310 CMR 15.000 (Title 5), plus watershed and Zone II constraints on parcels near Assawompset, Long and Great Quittacas Ponds.
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 decisions say as of 8 September 2026.