ADU Setback Requirements in Boston, MA
ADU setback rules for Boston, Massachusetts. Front, side, and rear setback distances, plus height limits and lot coverage restrictions.
Boston's Local ADU Ordinance
Unlike most Massachusetts municipalities, Boston operates under its own zoning charter with ADU-specific rules that may differ from the state baseline. This means some state-level rights may not apply in the same way. Check the specific rules below for Boston's requirements.
Setback Requirements
In Boston, your ADU must be set back: 25 ft from the front property line; 5 ft from side lot lines; 5 ft from the rear property line. These setbacks determine the buildable area on your lot — the larger your lot, the more room you have after accounting for required setbacks.
Height Limits
ADUs in Boston can be up to 25 feet tall (2 stories maximum). Height is measured from the average finished grade to the highest point of the roof. Consider that taller ADUs may require greater setbacks in some jurisdictions.
Planning Your ADU Placement
When planning your ADU in Boston, start by mapping your property boundaries and subtracting the required setbacks on each side. The remaining area is your buildable envelope. Consider the location of existing structures, utility connections, access paths, and landscaping when choosing the best spot for your ADU.
Important: State Baseline Data
The information on this page reflects Massachusetts state baseline rules. Boston may have additional local requirements. We recommend confirming with your local building department before starting your project.
Boston ADU Rules at a Glance
Max Size
1250 sq ft
% of Home
75%
Max Height
25 ft
Max Stories
2
Front Setback
25 ft
Side Setback
5 ft
Rear Setback
5 ft
Parking
1 space(s)
Approval
BY RIGHT
Owner Occupancy
Required
Rental Allowed
Yes
Short-Term Rental
Not allowed
Boston Building Department
Boston Inspectional Services Department
1010 Massachusetts Ave # 5, Boston, MA 02118, USA
Phone: (617) 635-5300
Frequently Asked Questions
What are the ADU setback requirements in Boston, MA?
In Boston, your ADU must be set back 25 ft from the front, 5 ft from side lot lines, 5 ft from the rear. These reflect state baseline requirements — Boston's local setbacks may differ. Check with your building department.
Can I build an ADU in my backyard in Boston?
Yes, you can build a detached ADU in your backyard in Boston, as long as it is at least 5 ft from the rear property line and 5 ft from side lot lines. The remaining space within setbacks determines the maximum building footprint available.
What is the height limit for ADUs in Boston?
ADUs in Boston are limited to 25 feet in height, with a maximum of 2 stories. Height is typically measured from average finished grade to the peak of the roof.
Do ADU setbacks differ from the main house in Boston?
ADU setback requirements in Boston may differ from those for the main house. ADUs often have reduced setback requirements to make them feasible on existing lots. Check Boston's local zoning ordinance for specific ADU setbacks versus primary dwelling setbacks.
Can I get a setback variance for my ADU in Boston?
Setback variances are possible but not guaranteed in Boston. You would need to apply to the zoning board of appeals and demonstrate a hardship — such as an unusually shaped lot or topographic constraints. Before pursuing a variance, verify your exact property dimensions against the setback requirements.
How accurate is the ADU data for Boston?
The information on this page reflects Massachusetts state baseline rules under the Affordable Homes Act. Boston may have additional local requirements that differ from the state baseline. We recommend confirming with your local building department before starting your project.
Where can I find all ADU regulations for Boston?
Visit our complete ADU rules page for Boston, 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 Boston.