Happy Tuesday, and welcome to another edition of Rent Free. This week, we’re going to jump right into it with a philosophical question: What is an accessory dwelling unit anyway?
It’s a question that officials in Somerville, Massachusetts, are realizing they didn’t know the answer to after learning that a state law allowing ADUs in single-family neighborhoods could also require them to approve three-story backyard mini-apartments.
As the Boston Globe reported on Sunday, Somerville’s “deep ethos in favor of new housing” is being tested by the extent of the state law. Elected officials are describing the potential for three-story ADUs as a “joke,” and the area’s state lawmakers, including one who voted for the state law, are demanding reforms to stop them.
The law in question was a statewide accessory dwelling unit (ADU) legalization tucked inside a major housing package of mostly new spending programs that passed in 2024.
The bill required municipalities to allow ADUs of either 900 square feet or half the size of the primary dwelling (whichever is smaller) anywhere single-family homes are allowed. A subsequent rule issued by state regulators also forbade localities from imposing height and bulk limits on ADUs that are stricter than the limits imposed on primary dwellings.
That latter rule is what’s causing Somerville’s freakout.
Because the town allows triple-decker apartments (a three-story triplex common in New England) in all its single-family zones, the state rule means that it must also allow ADUs to be three stories tall.
https://reason.com/2026/10/20/adu-nihilism/
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