What does 3F zoning mean in Boston?

Boston's 3F district allows the classic three-family 'triple-decker' building type, permitting up to three dwelling units on a single lot. Exact lot size, height, and setback minimums vary depending on which neighborhood zoning article governs the parcel.

How do I find the zoning for an address in Boston?

Use the BPDA's online zoning viewer, which overlays parcel-level district boundaries plus the applicable neighborhood article and any overlay districts. Because Boston's code is organized by neighborhood article rather than one uniform citywide map, always confirm which article governs the specific parcel.

Boston, Massachusetts · city zoning districts · 9 districts

Boston, MA zoning map & districts

Boston's zoning is unusual among major U.S. cities: instead of one uniform citywide map, the Boston Zoning Code is built from a citywide base code layered with dozens of neighborhood-specific zoning articles, each mapping its own district boundaries and sometimes its own variants of the standard district types. The Boston Planning & Development Agency (BPDA) administers the code and staffs the Zoning Board of Appeal, which handles variances and conditional-use appeals.

The code Boston Zoning Code

Boston zoning map

The BPDA's online interactive zoning viewer shows parcel-level district and overlay boundaries; the underlying legal text is the neighborhood-specific articles of the Boston Zoning Code, published by the Boston Planning & Development Agency, with variances and appeals routed through the Zoning Board of Appeal.

There is no link to the official map here yet — confirm current district boundaries directly with the Boston planning or zoning department.

A published summary is never the authority. The adopted ordinance and the city's official zoning map govern, and both change — verify the district and every standard on your parcel before you rely on it.

How zoning works in Boston

Any project that crosses defined size or height thresholds — generally 20,000 square feet of gross floor area or more, among other triggers — is also subject to Article 80 large-project review, a design and community-impact process layered on top of base zoning. That means zoning compliance alone does not guarantee a building permit for larger developments; large projects need a separate BPDA sign-off before permitting.

Boston zoning districts by family

The 9 district codes below are the ones that decide most projects in Boston, grouped by what they are for rather than by the order the ordinance prints them.

Key districts in the Boston Zoning Code — a curated reference, not the exhaustive list. Confirm against the current adopted code.
Code	District	What it is for
Residential 4 districts
1F	One-Family Residential	Detached single-family homes; minimum lot size and dimensional standards vary by neighborhood article.
2F	Two-Family Residential	Two-unit buildings, common across Dorchester, Roslindale, and similar neighborhoods.
3F	Three-Family Residential	Boston's classic 'triple-decker' district, permitting up to three units on a lot.
MFR	Multi-Family Residential	Apartment and condominium buildings above three units; height and density are set per neighborhood article.
Commercial 3 districts
L-1	Local Business	Small-scale, neighborhood-serving retail and services with limited height; mapped across a graduated series (L-.5, L-1, L-2) with tighter districts allowing less floor area.
CC	Community Commercial	Larger-format retail and commercial corridors serving multiple neighborhoods.
B-2	General Business	The broadest commercial use mix, typically mapped along higher-intensity corridors; graduated across a B-1/B-2/B-4/B-8/B-10 series, with higher numbers allowing greater height and floor area.
Industrial 2 districts
LI	Local Industrial	Light industrial and flex/production uses compatible near residential areas.
I-2	General Industrial	Heavier industrial and manufacturing uses.

Boston zoning — common questions

What does 3F zoning mean in Boston?: Boston's 3F district allows the classic three-family 'triple-decker' building type, permitting up to three dwelling units on a single lot. Exact lot size, height, and setback minimums vary depending on which neighborhood zoning article governs the parcel.
How do I find the zoning for an address in Boston?: Use the BPDA's online zoning viewer, which overlays parcel-level district boundaries plus the applicable neighborhood article and any overlay districts. Because Boston's code is organized by neighborhood article rather than one uniform citywide map, always confirm which article governs the specific parcel.
Does zoning approval guarantee a building permit in Boston?: Not for larger projects. Developments that trigger Article 80 large-project review — generally around 20,000 square feet of gross floor area or more, among other triggers — need BPDA design and impact review in addition to base zoning compliance before a permit can issue.

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The parcel layer lands in the order demand does. Illinois went first because that's where the deals were; the next state is decided by who tells us what they're trying to underwrite. Tell us where you're building and what you wanted to run — you'll hear from us when Massachusetts opens, and sooner if we need a test parcel.

Keep reading

← Massachusetts zoning — who holds the zoning power in Massachusetts, under which enabling statute, and the reforms that override local rules.

Other Massachusetts cities

The zoning reference → — every state, plus city-level district guides like this one.

Boston zoning summaries on this page are provided for information, not legal advice. Confirm every project against the current adopted code for the jurisdiction.