The Somerville zoning ordinance explained: a plain-English guide for homeowners

If you own a house in Somerville, the Somerville zoning ordinance decides what you can add, raise or build on your lot. I read it every week for my clients' projects, so here's the plain-English version: where to find it, what your district means, and when you'll need a public hearing.

The quick answer: look up your district on the city's Zoning Atlas, find your building type in the ordinance, and check whether your project fits its standards. If it fits, it's by right. If it doesn't, you're asking a board for permission.

Where to find the Somerville zoning ordinance and zoning map

The city links both from its zoning page:

• The ordinance text is on enCode Plus. It has 15 articles. Homeowners mostly need Article 3 (Residence Districts), Article 14 (Nonconformance) and Article 15 (Administration).
• The zoning map is the interactive Somerville Zoning Atlas, which the city calls the official set of maps for every district boundary.
• Questions go to the Inspectional Services zoning team at [email protected], per the same city page.

The main residential districts: Neighborhood Residence and Urban Residence

Article 3 of the zoning code sets up two residence districts:

In NR, you get one principal building and one accessory building per lot. Beyond these two, the map also has Mid-Rise, High-Rise, Commercial and Special districts.

By right, Special Permit or Hardship Variance?

1. By right: your project meets every standard for your building type. The Building Official does a zoning compliance review, then the building permit moves forward (Article 15).
2. Special Permit: a discretionary approval after a public hearing. A common one: adding a permitted building component, like a porch, to a building that doesn't match today's rules. A Special Permit stays valid for three years from when the decision is filed with the City Clerk.
3. Hardship Variance: for development that doesn't comply. The ZBA must find all three: special circumstances about the lot's soil, shape or topography or an unusual existing structure; substantial hardship from literal enforcement; and no substantial harm to the public good. Use variances aren't allowed.

A public hearing must be held within 65 days of a complete application.

Somerville Zoning Board of Appeals vs. Planning Board

• Zoning Board of Appeals: decides Site Plan Approval and Special Permits in NR, UR and a few other districts, hears all Hardship Variances and administrative appeals, and generally meets on the first and third Wednesday of each month (City of Somerville).
• Planning Board: the decision maker for Site Plan Approval and Special Permits in the Mid-Rise districts, and it advises the City Council on zoning amendments.
• Applying: zoning applications go through CitizenServe. A neighborhood meeting or design review may be required first.

How zoning affects additions, dormers, ADUs and triple-deckers

• Dormers: gable and shed dormers are permitted on Cottages, Detached and Semi-Detached Houses and Duplexes. They can't stick out past the exterior wall or rise above the ridge, and they can break the eave only if the half-story floor is at least 2 feet below it.
• Rear additions: permitted on those same four building types.
• Triple-deckers: the Detached Triple Decker is allowed by right in NR, with up to 3 stacked units, 3 stories and a flat roof. The ordinance's table doesn't permit dormers or rear additions on that type. Many older triple-deckers don't match today's standards; see my triple-decker zoning guide.
• ADUs: NR allows one Backyard Cottage by right. It needs a 3-foot paved walkway, buried utilities, and sprinklers unless the lot is a corner lot, has a driveway to the cottage, or abuts an alley. State law also allows one ADU up to 900 square feet (or half the main house, if smaller) without a special permit in single-family zoning (Mass.gov). Check your lot on my backyard ADU map.

Older houses and nonconformity

Most Somerville homes went up between 1900 and 1930, long before today's rules. Under Article 14, normal maintenance is always fine, but changes can't create a new nonconformity or make an existing one worse without relief.

Need a hand?

Planning a dormer, addition or ADU in Somerville, Cambridge or Medford? Book a free walkthrough. I'll check your district and building type, tell you whether it's by right or needs a hearing, and send a written line-item budget, usually within 48 hours.

About the author

Mateus Magno is the founder of Magno & Co — a licensed Massachusetts Construction Supervisor (CS-123658), registered Home Improvement Contractor (HIC #220484) and certified Lead-Safe Renovator Supervisor who has renovated and managed over $3 million in projects across Greater Boston.

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