The Healey-Driscoll Administration announced that municipalities across Massachusetts have approved 854 accessory dwelling units, or ADUs, during the first six months of 2026, building on strong early momentum following the signing of Governor Healey’s Affordable Homes Act and bringing the statewide total to 2,084 approved ADUs since the start of 2025.
70 percent of communities in Massachusetts have approved at least one ADU and an updated interactive map tracking ADU applications and approvals is available at Mass.gov/ADUtracker.
ADUs, also known as in-law apartments, are small, independent homes located on the same lot as another home. They may be created within an existing home, built as an addition or constructed as a separate structure. ADUs can provide space for aging parents, adult children, caregivers or people with disabilities. They can also provide homeowners with supplemental rental income and add new rental opportunities within existing neighborhoods.
Before the Affordable Homes Act, Massachusetts had no consistent statewide standard for ADU zoning and permitting. A patchwork of requirements, including owner-occupancy restrictions, restrictive size limits, subjective design reviews and discretionary approvals, often made ADUs difficult or impossible to build.
The Affordable Homes Act created a consistent statewide standard allowing one ADU up to 900 square feet (or no larger than half the gross floor area of the principal dwelling) to be built by right on lots located in single-family zoning districts, subject to reasonable local requirements. Boston has separate zoning authority and its own ADU rules.
New Resources for Homeowners
To help more homeowners move from initial interest to construction, the Healey-Driscoll Administration has launched new programs addressing three common barriers to building an ADU: design, early project planning and financing. All resources can be found in one location at Mass.gov/ADU.
Free designs through the ADU Design Challenge
Homeowners can now browse and download free designs selected through the administration’s ADU Design Challenge. The designs include a range of sizes, layouts and construction approaches that homeowners can use as a starting point when planning an ADU.
ADU feasibility support through MHP
The Massachusetts Housing Partnership’s ADU Incentive Program helps property owners take the first step in determining whether they can build an ADU on their property. The program connects homeowners with professionals who can assess factors such as site conditions, zoning, utility needs, preliminary design considerations and potential construction costs.
Affordable construction financing through MassHousing
The MassHousing ADU Loan Program provides fixed-rate second mortgage financing of up to $250,000 for detached ADUs and up to $150,000 for attached ADUs. The program serves eligible homeowners who have completed design and permitting and are ready to begin construction.
Online interactive ADU tools
The Massachusetts Clean Energy Center (MassCEC) also launched a Massachusetts ADU Resource Center at MyMassADU.org in May. Homeowners that are interested in building an ADU on their property can read through a step-by-step guide, enter their address into the ADU Wizard tool to drop a design of an ADU on their property, then enter info like property value and home equity into a calculator to see what financing they might be eligible for.
Homeowners in the Pioneer Valley can then take advantage of the Pioneer Valley ADU Accelerator Pilot program, also run by the MassCEC, to obtain technical support for building detached, modular, all-electric ADUs in Hampden, Hampshire and Franklin counties.
Residents interested in building an ADU should contact their city or town’s building or inspectional services department to learn about local permitting requirements. Additional information about the statewide law and resources for homeowners and municipalities is available at mass.gov/ADU.