Duxbury’s wetlands bylaw reaches 200 feet from any stream
Duxbury’s ADU bylaw is one of the cleanest in the state — by right, no owner-occupancy requirement, no local size restriction beyond the state figure. Then its own wetlands regulations put every acre within 200 feet of any stream under Conservation Commission jurisdiction, with no test for whether the stream runs year-round.
Section 410.6 says Protected Use Accessory Dwelling Unit. Owners say in-law apartment, or backyard apartment for a detached one. The wetlands rule below reaches every one of them.
Within the Commission’s jurisdiction: all “land within 200 feet of any river, stream, or creek.”
Note what is missing from that sentence: no perenniality test. The state Wetlands Protection Act reaches 200 feet from a perennial stream, and arguing about whether a given brook runs year-round is a normal part of a wet-parcel project. In Duxbury that argument is unavailable, because the town’s own bylaw declares the express intent to protect additional resource areas beyond the state’s. DWR 2.0(6) separately covers land within 100 feet of a resource area. On a wet Duxbury lot this is the finding that decides where — and whether — a detached unit can go, and it is why a desktop wetland screening is not good enough here.
What Duxbury does not ask of you
Set the wetlands question aside and this is a permissive bylaw. Two absences are worth naming.
- Owner occupancy
- None. No owner-occupancy requirement appears anywhere in s.410.6. Many towns wrote one and had it struck by the Attorney General. Duxbury never wrote one at all.s.410.6
- Special permit
- Not required. Nothing in s.410.6 asks for one.s.410.6
- Site plan review
- Only for an ADU in a newly constructed structure or building. A conversion inside or onto what is already standing does not trigger it.s.410.6
- Size
- 900 sq ft or half the gross floor area of the principal dwelling, whichever is smaller — importing 760 CMR 71.02 verbatim, with no additional local restriction.s.410.6 definition (b)
- Parking
- One space for the ADU, or none within a half mile of a Transit Station. This sits on top of the RC baseline of two spaces for the house.s.410.6(1); s.410.4
The short-term rental clause, and how it is enforced
Thirty-one days or more. Short-term rentals as defined by G.L. c.64G are prohibited — and Duxbury adds a drafting flourish most towns do not: advertisement in any form for less than 31 days is conclusive evidence of a violation.
s.410.6(7)That is worth reading twice. It means the listing itself is the violation; the town does not have to establish that anyone stayed. If your plan involves any short-term letting, this is not a provision to test.
Setbacks, and the front setback that is measured from the middle of the road
| Yard | Requirement in RC |
|---|---|
| Front | 25 ft from the right-of-way where the way is 40 ft or more wide — but 45 ft from the CENTERLINE where the way is narrower |
| Side | 15 ft |
| Rear | 15 ft |
The two front-setback branches do not measure from the same place. On a narrow private way — and Duxbury has many — the governing figure is 45 feet from the middle of the road rather than 25 feet from the edge of your land, which can move a building line by twenty feet or more. A single value read off the dimensional table without checking the branch is simply wrong on every narrow way in town. It is a tape-measure question and it is worth answering first.
Duxbury applies the same side and rear figures to a dwelling and an accessory structure alike, so there is no accessory relief to reach for. One item we have not closed: written confirmation from the Building Department that it applies the s.410.4 accessory-structure rules to a detached protected-use ADU. We ask on a live file rather than assume it.
s.410.4; open question with the Building DepartmentThe Board of Health report is a required step, not a formality
Section 410.6(6) requires a written Board of Health report. What the Board asks for and how long it takes is a live question we have not closed — and on a Duxbury file that timing sits on the critical path rather than beside it.
s.410.6(6); open question with the Board of HealthTitle 5 tests design flow on the bedroom count of the whole property under 310 CMR 15.000. Much of Duxbury is on private septic, and a parcel can also sit inside a Zone II wellhead protection area belonging to a neighbouring town’s water department — which the bylaw expressly anticipates. Both get checked against your address.
310 CMR 15.000; s.406.6One gap we will name
An Attorney General decision on Duxbury ADUs — case 11967, decided 12 November 2025 — has never been retrieved and is not registered in our zoning library. The published text carries s.410.6 with the 900-square-foot standard and a 2025 stamp, so the post-Act bylaw is genuinely published and nothing here rests on a stale edition. But we have not read that decision, so we cannot tell you whether the AG disapproved anything, and we are not going to imply we have.
AG MLU ADUS index, checked 2 September 2026 — case 11967 not retrievedWe 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 Duxbury Protective Bylaw —
s.410.6Protected Use Accessory Dwelling Units, inserted by June 2025 STM Art. 2, including(1)parking,(5)dimensional,(6)Board of Health report and(7)short-term rental;s.410.4(RC dimensional and parking);s.406.6(aquifer and Zone II). - Town of Duxbury Wetlands Protection Bylaw Chapter 9,
ss.9.1.1–9.1.3, and the Duxbury Wetlands RegulationsDWR 2.0(6)and2.0(8), revision approved 15 June 2023 — retrieved 4 September 2026. Broader than, and separate from, the state Wetlands Protection Act. - 760 CMR 71.00 — §71.02, imported verbatim into the Duxbury ADU definition.
- 310 CMR 15.000 (Title 5) for the design-flow and bedroom-count test.
- Not retrieved: AG MLU case 11967, decided 12 November 2025. Stated rather than glossed.
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.