Hingham, MA Accessory Dwelling Unit (ADU) Rules

City Acceptance Rating: 4/10 (10 is most accepting)

Last updated: 10.10.2024

What You Need To Know

Currently not in compliance with the Massachusetts Affordable Homes Act.

ADUs are heavily restricted and the rules will need to be revised to comply with the Affordable Homes Act.

Type of ADU Permit Required

A special permit is required to build an ADU in Hingham

ADU Rules

ADU Cap: Total ADUs in the town cannot exceed 2.5% of total single-family dwellings.
Owner Requirement: Applicant must be the lot owner and occupy either the principal or accessory dwelling as their primary residence.
Lot Size: Minimum lot area is 5,000 sq ft for ADUs within the principal structure and 10,000 sq ft for detached ADUs.
Septic/Sewer Confirmation: Must provide confirmation of adequate water and wastewater services to support the proposed bedrooms.
One ADU per Lot: Only one accessory dwelling unit allowed per lot.
Residence District Restrictions: ADUs in District D and Business Districts A and B are only permitted with preexisting nonconforming single-family dwellings.
Architectural Integrity: The architectural character of the single-family dwelling must be maintained.
Stairway Requirements: All stairways accessing an ADU above ground floor must be enclosed within the exterior walls, with possible waivers for rear stairways.
ADU Size Limitations: Maximum area is the lesser of 875 sq ft or 35% of the gross floor area of the principal dwelling.
No Non-Conforming Extensions: ADUs cannot be created by extending non-conforming building dimensions.
Entrance Location: New entrances must be located at the side or rear of the principal dwelling.
Utility Metering: Water and sewer utilities for the ADU cannot be separately metered, with possible waivers.
Landscaping and Buffers: Additional landscaping or buffers may be required to mitigate visual/auditory impacts on neighboring properties.
Parking Requirements: One parking space per bedroom plus minimum required spaces for the principal dwelling.
Bedroom Limit: ADUs may not exceed two bedrooms.
Additional Requirements for Detached ADUs:

Dimensional Compliance: Must comply with building dimensions and setbacks, with potential waivers for nonconforming structures.
Location Requirements: Must be at least 10 ft from the principal dwelling and either behind or to the side of it.
Owner Occupancy: The owner must occupy one of the dwellings as their primary residence, with allowances for temporary absences.
Annual Recertification: Owners must submit a notarized letter annually certifying continued primary residence occupancy.
Sale Transfer Conditions: New owners must recertify within 30 days of transfer to maintain the ADU permit.
Joint Sale Requirement: Neither the principal dwelling nor the ADU can be sold separately.
Minimum Rental Term: The non-owner-occupied unit must have a minimum rental term of six months.

Resources:

https://www.hingham-ma.gov/DocumentCenter/View/11301/Section-V-K-ADU-By-Law-v2-002