ADU Regulations:
Brookline
Regulations Snapshot
Rear and Side setbacks: 6 feet
Building Separation: 6 feet
Height: 2 stories
Separate utilities required: No
Stormwater management required: If disturbing 2,500 sf of land (should not apply)
Specialized Stretch Energy Code: Yes
Impact Fees: Potentially for tree removal, additional trash pickup and water meter
Building Constraints
Number of ADU’s allowed on a single family lot
One ADU is allowed per single-family lot, whether interior, detached, or attached
Maximum square footage of an ADU (detached or attached)
900 square feet or 50% of the total gross floor area of the principal dwelling unit, whichever is smaller.
Maximum Height
2 stories
Maximum lot coverage
Not regulated
Exterior appearance requirements
Congruent with the primary house and neighborhood
Setbacks
Rear setback
6 feet
Side setback
6 feet
Front setback
Level with or behind primary home
Distance between buildings
6 feet
Parking
Parking requirement for an ADU
Each ADU requires one off-street parking space in addition to what is required for the primary dwelling. No parking space is required for an Accessory Dwelling Unit on a Lot if any portion of such Lot is located within a 0.5-mile radius of a Transit Station.
Specific parking requirements (location)
No
Where can the parking be located : Parking requirement for primary dwelling
Normally 1 off street parking space per dwelling unit
Additional Requirements
Separate utilities required
No hard rule. The water department likes a separate water meter or submeter. It is allowed to connect to the sewer of the primary home. Same with electric, it is recommended to contact the local electric utility company to learn the procedure.
Stormwater management required
Stormwater management is needed if 2,500 square feet (50×50) of land area is disturbed. This should not apply to most ADU builds
Site plan review required
Yes, the utility plan will be reviewed for the engineering department. The building application is reviewed by the Building Commissioner and Deputy Building Commissioner and a decision is made.
Town impact fees
Potentially for tree removal, additional trash pickup and water meter
Soils report required
No, the building department will just inspect the hole prior to foundation build
Civil plans required
Yes
Short term rental allowed
No
Possible overlay districts
Historical zones that would require approval by the town Preservation Department
ADUs on multifamily lots
If your property is in any zone that allows single family homes then you are allowed to build a by-right ADU
Resources
As of 9/24 town bylaws regarding ADUs are being contested by the state Attorney General’s office. They plan to be finalized over the coming months.