ADU Setback Requirements in Somerville, MA
ADU setback rules for Somerville, Massachusetts. Front, side, and rear setback distances, plus height limits and lot coverage restrictions.
ADU Regulations in Somerville
Somerville 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. Somerville may also have additional local regulations that supplement the state baseline.
Setback Requirements
In Somerville, your ADU must be set back: 10 ft from the front property line; 3 ft from side lot lines; 3 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 Somerville 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 Somerville, 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.
Somerville ADU Rules at a Glance
Max Size
900 sq ft
% of Home
50%
Max Height
25 ft
Max Stories
2
Front Setback
10 ft
Side Setback
3 ft
Rear Setback
3 ft
Parking
None required
Approval
BY RIGHT
Owner Occupancy
Not required
Rental Allowed
Yes
Short-Term Rental
Not allowed
Somerville Building Department
Frequently Asked Questions
What are the ADU setback requirements in Somerville, MA?
In Somerville, your ADU must be set back 10 ft from the front, 3 ft from side lot lines, 3 ft from the rear. These reflect state baseline requirements — Somerville's local setbacks may differ. Check with your building department.
Can I build an ADU in my backyard in Somerville?
Yes, you can build a detached ADU in your backyard in Somerville, as long as it is at least 3 ft from the rear property line and 3 ft from side lot lines. The remaining space within setbacks determines the maximum building footprint available.
What is the height limit for ADUs in Somerville?
ADUs in Somerville 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 Somerville?
ADU setback requirements in Somerville may differ from those for the main house. ADUs often have reduced setback requirements to make them feasible on existing lots. The Affordable Homes Act sets minimum standards that Somerville must allow.
Can I get a setback variance for my ADU in Somerville?
Setback variances are possible but not guaranteed in Somerville. 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.
Where can I find all ADU regulations for Somerville?
Visit our complete ADU rules page for Somerville, 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 Somerville.