ADU Rules in Brockton, MA
Brockton follows the Massachusetts state baseline with local regulations.
State Baseline: Affordable Homes Act
Up to 900 sq ft or 50% of principal dwelling (whichever is smaller). By-right approval statewide.
Zoning Districts
R-1C — Single-Family Residential R-1C
Single-family residential district, 30,000 sqft min lot, 175ft frontage, 25% lot coverage
| Type | Approval | Max Size | Height | Parking | Owner Occ. |
|---|---|---|---|---|---|
| Detached ADU | By Right | 900 sq ft | 20 ft | 1 space | No |
| Attached ADU | By Right | 900 sq ft | 35 ft | 1 space | No |
| Interior Conversion | By Right | 900 sq ft | — | None | No |
R-2 — Two/Three-Family Residential R-2
Two/three-family residential district, 7,500 sqft min lot, 100ft frontage, 30% lot coverage
| Type | Approval | Max Size | Height | Parking | Owner Occ. |
|---|---|---|---|---|---|
| Detached ADU | By Right | 900 sq ft | 30 ft | 1 space | No |
| Attached ADU | By Right | 900 sq ft | 45 ft | 1 space | No |
| Interior Conversion | By Right | 900 sq ft | — | None | No |
Transit Stations
Properties near transit stations may qualify for parking exemptions.
Brockton
Campello
Montello
Building Department
Explore ADU Topics in Brockton
ADU Zoning in Brockton, MA
ADU Permit Process in Brockton, MA
ADU Costs in Brockton, MA
ADU Size Limits in Brockton, MA
ADU Setback Requirements in Brockton, MA
ADU Parking Requirements in Brockton, MA
ADU Types Explained in Brockton, MA
ADU Financing in Brockton, MA
ADU Timeline in Brockton, MA
ADU Property Value Impact in Brockton, MA
ADU Rental Income in Brockton, MA
Frequently Asked Questions
Are ADUs allowed by right in Brockton, MA?
Yes. ADUs in Brockton are approved by right — you submit your plans to the building department and receive a building permit without a public hearing or special permit process. This is guaranteed by the Affordable Homes Act.
What types of ADUs can I build in Brockton?
Brockton allows detached, attached, conversion ADUs. With up to 900 sq ft allowed, a detached ADU gives you the most flexibility for a full living space.
Do I need to live on the property to build an ADU in Brockton?
No. Brockton does not require owner occupancy — this is a right guaranteed by the Affordable Homes Act. You can rent both your main home and the ADU, making this a pure investment property if you choose.
How big can I build an ADU in Brockton, MA?
In Brockton, you can build an ADU up to 900 square feet or 50% of your home's living area, whichever is larger. With 900 sq ft, you have enough room for a full 2-bedroom cottage with a kitchen, bathroom, and living area. This is guaranteed by the Affordable Homes Act.
Does Brockton have historic district rules for ADUs?
Yes. Brockton has historically significant areas including South Street Historic District. If your property is in or near a historic district, your ADU design may require review by the local historical commission for architectural compatibility. This can affect timelines and design choices.
Can I rent out my ADU in Brockton?
Yes, long-term rentals are allowed for ADUs in Brockton. However, short-term rentals (like Airbnb) are not currently allowed for ADUs. With a population of 105,643, Brockton has strong rental demand.