Belmont Cleared the Way for Accessory Apartments. Four Homeowners Have Used It.

Since February 2025, any homeowner on a single-family lot in Belmont has had the legal right to add a small second home to their property. A basement apartment, a converted garage, a cottage tucked into the backyard. No special permit. No zoning board hearing. No neighbors testifying against it at Town Meeting.

As of April 2026, four people had tried.

That number comes directly from Christopher Ryan, Belmont's director of Planning and Building, who told the Belmont Citizens Forum that the town had received four ADU applications since the by-right rule took effect fourteen months earlier. Two were approved and are under construction. None have been completed. Two more were explored and then dropped. Ryan's own reaction, on the record, was that he is "surprised that it's as light as it has been." He attributes the slow pace to construction costs and interest rates, not to the bylaw itself.

That distinction matters more than it sounds like it should, because it tells you where the real friction sits for anyone in Belmont weighing whether an accessory unit is worth pursuing right now.

What the old rule actually blocked

Before February 2, 2025, Belmont allowed accessory dwelling units only by special permit, and only inside historic accessory buildings such as old carriage houses. Planning Board member Carol Berberian described the restriction bluntly at a late 2024 meeting: the town's structure was too limiting to work for most properties, since there were very few cases where a unit could fit inside the envelope of an existing historic outbuilding.

That was the barrier the Affordable Homes Act was designed to remove. Governor Maura Healey signed the act in August 2024, and the accompanying state regulation, which allows accessory dwelling units up to 900 square feet by right in single-family zoning districts, took effect that following February. Belmont brought its own zoning into line with a bylaw amendment approved at the March 2025 Town Meeting, and in doing so did more than the state strictly required. The town added a 5 percent bonus to maximum lot coverage for properties adding an ADU and relaxed its open-space requirement to match, specifically because Belmont's existing residential districts already carry tight lot-coverage rules that would otherwise make a unit hard to fit on a typical lot.

On paper, that is a real accommodation. In practice, four applications is not a rush.

The math the town already ran

The gap becomes sharper when you look at Belmont's own estimate of how many properties actually qualify. A FAQ document published by the town's Planning and Building office puts the number at 1,439 lots eligible for a detached ADU and 3,991 eligible for an internal one. That is a combined pool of roughly 5,400 properties where a homeowner could, today, build a legal accessory unit without a discretionary hearing.

The same document cites outside data suggesting that in regions where ADU laws have loosened, fewer than 2 percent of qualifying lots typically build one in a given year. Applied to Belmont's own eligible pool, that low-end rate would predict somewhere north of 100 applications annually.

Four applications against a base case of a hundred or more is not a town slow-walking a popular program. It is a town where almost nobody who is legally eligible has decided the project makes sense yet.

Belmont isn't unusually strict. It's unusually slow.

If Belmont's bylaw were the bottleneck, you would expect comparably sized Massachusetts towns to be moving at a similar pace. They aren't. Milton, a town with a population close to Belmont's own (28,630 versus Belmont's 27,295), had already permitted 25 ADUs by June 30, 2025, according to state tracking data cited in the same Belmont Citizens Forum reporting. Statewide, at least 1,229 ADUs had been approved by the end of 2025, based on data from 293 of the state's 351 municipalities.

Belmont also isn't starting from a worse regulatory position than its neighbors. Arlington had already built out a clearer ADU framework before the state law arrived. Lexington and Waltham are working through more complicated, special-permit-heavy legacy rules that now have to be reconciled with the by-right standard. Belmont, by contrast, adopted a comparatively simple structure that largely mirrors the state's own requirements, with local adjustments limited to lot coverage and open space.

None of that explains four applications. What Ryan pointed to instead, construction costs and interest rates, is the more honest answer, and it lines up with what the town's underlying zoning tells you about who this actually works for.

Why the zoning stopped being the obstacle

Belmont's own Planning Board chair, Taylor Yates, has noted that the majority of properties in town are already nonconforming under the current bylaw, typically for lot size. That fact used to work against ADU applicants. Under the state law, it no longer can. If a lot's only nonconformity is failing to meet the minimum lot size, the town cannot use that alone to deny an ADU.

Combined with the lot-coverage bonus, this means the properties most people assumed would be hardest to work with, older, tightly built lots with irregular footprints, are frequently the ones now cleared to proceed. The zoning fight in Belmont is largely over. What's left is the technical and financial review, and that is precisely where Belmont's four applicants have been sitting.

What this actually means if you're considering one

Belmont's median home sale price sat at $1.4 million over the three months ending June 2026, down 7.2 percent from the same period a year earlier, with homes selling in an average of 17 days. That price level is exactly why an accessory unit is worth serious consideration for the right property. A basement apartment or converted garage can offset a mortgage, or it can solve a genuinely different problem: housing an aging parent without asking them to leave the community, or giving an adult child a place to land while they save for their own down payment. Planning Board member Berberian raised the first case directly, noting that Belmont's Age Friendly Action Committee sees ADUs as a viable option for seniors who want to stay in their homes. Yates raised the second and third, describing ADUs as a way for homeowners to generate rental income or give young professionals a foothold in town.

The reason so few Belmont homeowners have acted on that opportunity isn't that the path is blocked. It's that running the actual numbers on a specific lot, current construction costs against realistic rental income or the value of keeping a parent close, takes more than reading the bylaw. It takes someone who can look at your particular footprint, your particular nonconformities, and your particular budget and tell you honestly whether this is one of the properties where it works or one of the many where it currently doesn't.

A few questions worth asking before you call a contractor

Do I have to live in the main house or the ADU myself? No. The state law removed owner-occupancy requirements, and Belmont's local rules follow that standard. Both the main house and the accessory unit can be rented out.

Can Belmont deny my project because my lot is smaller than the zoning minimum? Not on that basis alone. If lot size is the only nonconformity, the town cannot use it to reject an otherwise qualifying ADU.

Can I rent the unit on a short-term basis? No. Belmont's bylaw, like the state framework it's built on, prohibits using an ADU or the primary residence for short-term rentals under 30 days.

Four applications in the first fourteen months tells you the door is open and almost nobody has walked through it yet. Whether your particular lot is one of the ones where the math works is a different question, and it's not one a bylaw page can answer for you. If you're weighing an accessory unit against a move, a renovation, or simply the numbers on your current mortgage, Kelly Kovacs can walk your specific property against Belmont's actual rules and help you figure out which side of that math you're on. Schedule a free consultation to start.