ADU Size Limits in Quincy, MA
The maximum ADU size in Quincy is 900 sq ft, or 50% of your home.
Find the maximum ADU size allowed in Quincy, Massachusetts. Includes square footage limits, height restrictions, lot coverage, and bedroom count.
ADU Regulations in Quincy
Quincy follows the Massachusetts state baseline under the Affordable Homes Act. This means all Massachusetts state-level ADU rights apply — including by-right approval, no owner occupancy requirement, and standardized size limits. Quincy may also have additional local regulations that supplement the state baseline.
Size Limits: Room for a Full Cottage
At 900 sq ft, Quincy allows enough space for a complete 2-bedroom accessory dwelling unit. This is well above the minimum needed for a comfortable living space and provides flexibility for a kitchen, bathroom, living area, and dedicated bedrooms.
Height and Stories
ADUs in Quincy are limited to 35 feet in height and 2 stories. This allows for a two-story design, which maximizes living space on a smaller building footprint — useful if your lot has tight setbacks.
Percentage-Based Size Limit
In addition to the absolute square footage limit, Quincy allows ADUs up to 50% of the principal dwelling's living area. For homeowners with larger homes, this percentage rule may allow a bigger ADU than the flat square footage cap.
Quincy ADU Rules at a Glance
Max Size
900 sq ft
% of Home
50%
Max Height
35 ft
Max Stories
2
Front Setback
25 ft
Side Setback
10 ft
Rear Setback
13 ft
Parking
1 space(s)
Approval
BY RIGHT
Owner Occupancy
Not required
Rental Allowed
Yes
Short-Term Rental
Not allowed
Quincy Building Department
Frequently Asked Questions
What is the maximum ADU size in Quincy, MA?
In Quincy, you can build an ADU up to 900 square feet or 50% of your home's living area, whichever is larger. With 900 sq ft, you have enough room for a full 2-bedroom cottage with a kitchen, bathroom, and living area. This is guaranteed by the Affordable Homes Act.
How tall can an ADU be in Quincy?
ADUs in Quincy can be up to 35 feet tall (2 stories maximum). This allows for a two-story design, which is useful for maximizing living space on a small footprint.
Is ADU size based on my home's size in Quincy?
Yes. In Quincy, your ADU can be up to 50% of your main home's living area or 900 sq ft, whichever is larger. This means larger homes can support larger ADUs.
Is there a minimum lot size for ADUs in Quincy?
Quincy requires a minimum lot size of 7,650 square feet to build an ADU. If your lot is smaller, you may still qualify for an interior conversion or attached ADU, which typically have less restrictive lot requirements.
What types of ADUs are allowed in Quincy?
Quincy allows detached, attached, conversion ADUs. With up to 900 sq ft allowed, a detached ADU gives you the most flexibility — enough for a full 2-bedroom cottage.
Can I add a bedroom to my ADU in Quincy?
With 900 sq ft allowed in Quincy, you can comfortably fit 2 bedrooms plus a kitchen, bathroom, and living area. All bedrooms must meet building code requirements for egress windows and minimum dimensions.
Where can I find all ADU regulations for Quincy?
Visit our complete ADU rules page for Quincy, MA for a full overview of zoning, permits, size limits, setbacks, parking, and costs. We cover all Massachusetts municipalities with data sourced from local ordinances and state law.
Check Your Address
See exactly what ADU rules apply to your specific property in Quincy.