How Somerville Handles Building Setbacks & Zoning: A Practical Guide

Somerville maintains 147 local ordinances across all categories, and 3 of those deal specifically with building setbacks & zoning. Here is a breakdown of what the city actually requires, what is prohibited, and where Somerville falls on the strict-to-permissive spectrum compared to other cities.

Lot Coverage Limits

Somerville's Zoning Ordinance caps lot coverage, the share of a lot covered by buildings, structures and impervious surface, on a per-building-type basis under §2.4.2.c.i. A Cottage in the Neighborhood Residential district tops out at 60%, a Semi-Detached Triple Decker in Urban Residential at 65%, and mid-rise types like the General Building can reach 90%, so the cap depends entirely on district and building type chosen.

Key details: Governing section: Zoning Ordinance §2.4.2.c.i, Lot Coverage. Cottage (NR district): 60% max lot coverage, §3.1.7. Semi-Detached Triple Decker (UR): 65% max, §3.2.7. General Building (Mid-Rise 3): 90% max, §4.1.8. Coverage measured: At ground-story exterior wall footprint.

Exceeding the Lot Coverage cap for a given building type is a zoning violation the Building Official can catch at building permit review or through a site inspection, since coverage is verified against the exterior wall footprint at the ground story. A project that comes in over the district's percentage, say above 60% for a Cottage in NR or 65% for a Triple Decker in UR, cannot obtain a building permit or certificate of occupancy without first reducing impervious area or securing the narrow egress-related waiver under §2.4.1.b, which the Building Official must document in the public record.

Setback Rules

Somerville's Zoning Ordinance sets yard setbacks for the Detached House, the city's most common residential building type, in the Neighborhood Residence district: a 10-to-20-foot front setback, a 20-foot minimum rear setback, and a minimum 5-foot side setback under Section 3.1.8.b. Corner and driveway configurations shift the side setback and require larger combined side yards.

Key details: Front setback (min/max): 10 ft / 20 ft. Rear setback (min): 20 ft. Side setback (min): 5 ft, 3 ft with front driveway. Building separation (min): 10 ft. Applies to: Detached House, NR district.

Building a Detached House closer than the 10-foot minimum front setback, inside the 20-foot rear setback, or within the 5-foot (or 3-foot driveway-adjusted) side setback violates Section 3.1.8.b and Section 2.4.3.a. The Somerville Inspectional Services Department can deny a building permit, issue a stop-work order, or require a variance from the Zoning Board of Appeals before construction proceeds.

Structure Height Limits

Somerville's Zoning Ordinance caps the city's most common house type, the Detached House, at 2.5 stories and a 12-foot maximum story height in the Neighborhood Residence district under Section 3.1.8.c. Roofs are limited to flat, gable, gambrel, hip or mansard styles, and half-story ceiling height cannot exceed 12 feet under Section 2.4.4.

Key details: Max stories (Detached House): 2.5 stories. Story height (min/max): 10 ft / 12 ft. Permitted roof types: Flat, gable, gambrel, hip, mansard. Half-story ceiling cap: 12 ft. Triple Decker max (comparison): 3 stories.

Constructing a Detached House taller than 2.5 stories, with a story height over 12 feet, or with a roof style other than flat, gable, gambrel, hip or mansard violates Section 3.1.8.c. The Somerville Inspectional Services Department can refuse a building permit, order construction halted, or require the owner to seek a variance from the Zoning Board of Appeals.

The Bottom Line

Somerville's building setbacks & zoning rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Somerville is broadly strict or permissive.

Keep in mind that Somerville can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.