ADU reform: Reshaping residential development landscape in Mass.? - by Anthony Susi

More than a year has passed since Massachusetts enacted its landmark Affordable Homes Act, a reform that included a provision making it significantly easier to build Accessory Dwelling Units (ADUs). Aimed at expanding affordable housing across the state, the ADU provision looks to benefit homeowners, property managers, and communities by unlocking new, flexible housing options.

Often referred to as in-law apartments, an ADU by definition is a small, independent residential space located on the same lot as a primary residential home. It can be internal (basement or attic apartment); attached (addition to the main house); or detached (backyard cottage or converted garage). While their original intent was to house family members as a less expensive alternative to senior housing, ADUs have become a key strategy at the state level to boost housing supply and address rising demand. 

The provision included in the Affordable Homes Act of 2024 legalized ADU by-right statewide, (except for the City of Boston which has its own ADU by right ordinance) meaning homeowners can now build one ADU up to 900 square feet in single-family zoning districts without the previously required maze of design reviews, special permits or zoning board approval. As of February of this year, that “by right” law officially went into effect.

So, what does this mean to homeowners, property managers, and communities? 

This change allows homeowners to add rental units or create housing for family members or individuals with disabilities, without navigating zoning approvals – a considerable step toward increasing housing supply and affordability in Massachusetts.

It also expands building and rental opportunities for property owners and managers.

As far as communities – they benefit from increased housing supply without altering neighborhood character.

What hasn’t changed are compliance standards. ADUs must still meet local building codes, fire safety requirements, and that 900 s/f maximum size limit. 

This new provision has already gained considerable traction. According to information recently posted on www.Mass.gov, in the first six months of 2025, homeowners in 170 communities filed 844 applications to build ADUs on their properties. An estimated 550 of those applications have been approved as of July.

For the real estate industry, the statewide legalization of ADUs by right represents a pivotal shift in development potential – offering new opportunities for rental income and portfolio diversification. 

With early adoption already gaining speed, ADUs may become a cornerstone of Massachusetts’ housing strategy for years to come.

Anthony Susi is the 2025 IREM Boston Chapter president and is the director of property management at The Simon Companies, Braintree, Mass.