ADU Regulations:
Medfield
Regulations Snapshot
Rear and Side setbacks: Depends on zone
Building Separation: 10 feet
Height: 35 feet (2.5 stories)
Stormwater management: Required based on lot coverage
Sprinkler system: Not needed
Separate utilities required: No
Impact Fees: None
Building Constraints
Number of ADU’s allowed on a single family lot
One
Maximum square footage of an ADU (detached or attached)
The maximum floor area of an ADU shall not exceed 900-square feet, or 50% of the total gross floor area of the principal dwelling unit, whichever is smaller.
Maximum Height
35 feet (2.5 stories)
Maximum lot coverage
15%, includes all impervious surfaces
Exterior appearance requirements
Congruent with primary house
Setbacks
Rear setback
Depends on the zone, typically 30 - 50 feet
Side setback
Depends on the zone, typically 12 - 15 feet
Front setback
Same as primary house
Distance between buildings
10 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.
Where can the parking be located : Parking requirement for primary dwelling
Typically two off-street parking spaces
Additional Requirements
Separate utilities required
No
Stormwater management required
Needed if lot coverage with the ADU exceeds 15%. This includes all impervious surfaces.
Sprinkler system required
Not required
Site plan review required
If in an Aquifer Protection District, Wetland, or if lot coverage exceeds 15%, ZBA approval is required
Town impact fees
None. However fees to go through ZBA are about $800
Soils report required
No, the building department will inspect the hole prior to construction of the foundation
Civil Engineering plans required for utility hookups
No
Short term rental allowed
No
ADUs on multifamily lots
Allowed
Possible overlay districts
Wetlands, Aquifer Protection District, Wellhead Protection, Historic