Quincy · Norfolk County

Can you build an ADU in Quincy?

Quincy publishes its own ADU guidance through Inspectional Services, and it is more specific than most. There is a minimum size, a transit-linked parking rule, and a list of districts where an ADU is not allowed at all.

What the state guarantees you

Since 2 February 2025 this applies in every Massachusetts community. A town may be more generous than this. It may not be less.

Rule	What it means
Allowed by right	One ADU in single-family zoning districts, statewideNo special permit and no public hearing for a protected-use ADU
Maximum size	900 sq ft, or 50% of the principal dwelling, whichever is smallerA town may allow larger. It cannot allow smaller
Owner occupancy	A town cannot require itSo you may rent both units, or live in the ADU and rent out the house
Parking	One space at most, and none at all within half a mile of transitA town cannot ask for more than this
Short-term rental	The state leaves this to each townAll six towns documented here ban it, and two of them ban it for the main house too
In force since	2 February 2025Any conflicting local zoning became unenforceable that day

What Quincy adds on top

Rule	In Quincy
Where allowed	Single-family zoning districts
Where not allowed	Bus C, Ind A and Ind B districts, and lots holding a variance
Maximum size	50% of the principal dwelling's gross floor area, or 900 sq ft, whichever is less
Minimum size	320 sq ft for a detached ADU
Parking	One extra off-street space, unless the lot is within a half mile of a transit station
Short-term rental	Prohibited
Ownership	The ADU cannot be separately owned or sold
What you file	Site plan covering drainage, utilities, architectural drawings and parking

The 320 sq ft floor on a detached unit is the one to notice. It rules out the smallest backyard studios, so a Quincy detached ADU has to be a real small dwelling rather than a converted shed. The transit exemption is worth real money here, because Quincy has four Red Line stations and a great many lots fall inside a half mile of one.

Questions people ask

Can I build an ADU in Quincy without a public hearing?

A protected-use ADU is allowed by right in single-family districts, so no special permit or public hearing is required. You still file a site plan with drainage, utilities, architectural drawings and parking, and it is reviewed administratively.

How big can a Quincy ADU be?

Up to 50% of the principal dwelling's gross floor area or 900 square feet, whichever is less. A detached ADU must be at least 320 square feet.

Do I need an extra parking space for an ADU in Quincy?

One additional off-street space is required unless any part of the lot sits within a half mile of a transit station, in which case none is required.

Can I rent a Quincy ADU on Airbnb?

No. Quincy prohibits using an ADU as a short-term rental.