Thanks to Ryan Castle of the Cape and Islands Association of REALTORS for sharing his summary of the new regulations permitting accessory dwelling units (ADUs) by-right in all single-family residential zones statewide. We know Berkshire communities are studying the implementation of these rules and addressing requests for additional allowable provisions.
This significant policy shift aims to address housing shortages and provide homeowners with more flexibility.
Understanding ADUs
ADUs, often referred to as in-law suites or granny flats, are secondary housing units located on the same lot as a primary residence. They can be attached to the main home, such as a converted basement or garage, or exist as separate structures within the property’s boundaries.
ADU Examples
Key Provisions of the New Regulations
The Affordable Homes Act amends the Zoning Act to allow ADUs up to 900 square feet to be built by right in single-family zoning districts:
- Maintain a separate entrance, either directly from the outside or through an entry hall or corridor shared with the principal dwelling, sufficient to meet the requirements of the state building code for safe egress;
- Be either no larger than half the gross floor area of the principal dwelling or 900 square feet, whichever is smaller;
- Meet local municipal restrictions, including, but not limited to, additional size restrictions and/or restrictions or prohibitions on short-term rental if the city or town decides to impose these
Additional Regulations Explained
Here is a more detailed list of what is and is not allowed to be regulated on ADUs:
- Design Standards
They cannot be stricter than those applied to single-family homes. Regulations that increase costs excessively or make ADU construction impractical are not allowed. - Dimensional Standards
Setback, lot coverage, open space, bulk, height, and story limits must be equal to or more permissive than those for single-family homes. No minimum lot size can be required for ADU construction. - Utilities, Safety, and Emergency Access
No requirement for a separate water, sewer, or electric connection unless mandated by state law or a utility provider. Local emergency access rules cannot be stricter than state fire code. - Environmental Regulations
Rules regarding environmental protection (e.g., wastewater treatment, stormwater management) cannot be stricter than those applied to single-family homes in the same zoning district. Must comply with state environmental regulations (Title 5 septic standards, etc.). - Site Plan Review
The process must be clear, objective, and fair. Municipalities cannot impose subjective conditions or discretionary reviews that hinder ADU approval. - Impact Analysis, Studies, and Fees
Municipalities cannot require extra studies, reports, or fees for ADUs if these are not also required for single-family homes. - Modular Dwelling Units
Prefabricated or modular homes used as ADUs must be allowed if they comply with the Massachusetts Building Code. Cities cannot impose additional restrictions just because an ADU is modular. - Historic Districts
Municipalities may impose stricter design and dimensional standards on ADUs in historic districts. However, these standards must still be reasonable and cannot outright prevent ADU construction. - Pre-existing Nonconforming Structures
If a principal dwelling, existing structure, or lot is already nonconforming with zoning rules (e.g., due to setback violations), a Protected Use ADU cannot be prohibited solely for this reason. The ADU must be allowed if it complies with the Building Code and state law.
Additional Considerations
While the new regulations streamline the approval process for ADUs, homeowners should be mindful of local zoning laws and building codes. It’s advisable to consult with local planning departments to ensure compliance with all requirements.
Again, thanks to Ryan Castle of the Cape Cod and Islands Association of REALTORS for this great summary!