18The rules for building in a city

The short version: Before anything gets built in a city, it passes through layers of rules. Zoning decides what may go where - homes, shops, factories, how tall, how dense. Building codes decide how it must be built so it does not fall down, burn or poison anyone. Permits and inspections check that the rules were followed, and before anyone digs into a street, the owners of every buried pipe and cable need to know.

What is the difference between zoning and a building code?

The two get mixed up constantly. In short:

• Zoning answers what and where. It divides a city into districts and sets what uses are allowed in each - housing, offices, industry - along with limits on height, bulk, density, parking and how far a building sits from the lot line.
• A building code answers how. It sets the technical rules for construction: structure, fire safety, exits, plumbing, electrical work and energy use.

A tower can meet every line of the building code and still be illegal because the zoning says that block is for three-story houses. A house can sit in exactly the right zone and still fail inspection because its stairs are too steep. The two systems are usually run by different offices, written by different people and changed in different ways: in the US, zoning is mostly local politics, while building codes are mostly technical documents.

In the US, when a project does not fit the zoning, the owner typically asks for permission to break the rule - a variance - from a local board.

How it changed

New York City's 1916 Zoning Resolution is generally described as the first citywide zoning code in the US.³⁷² It began as a rule on tall buildings, and other cities soon copied its provisions.³⁷³ On November 22, 1926, in Village of Euclid v. Ambler Realty Co., the US Supreme Court upheld comprehensive zoning by a 6-3 vote, giving land-use zones a constitutional footing across the country.³⁷³³⁷⁴

Our reading: zoning and building codes grew out of the same problems the sanitary reformers of the 1800s faced - crowding, fire and disease (see How cities came to need infrastructure). Zoning later took on a second role, shaping who could afford to live where. How much zoning should do is now one of the main arguments over housing, and people across the political spectrum disagree about it.

Zoning and permitting also differ a lot between countries. The US model of fixed districts set out in advance is one approach among several.

England's system, for example, is discretionary: planners and planning committees decide each proposal case by case, rather than settling most questions in a plan drawn up in advance.³⁷⁵ Japan sets zoning nationally, with about a dozen zones; a proposal that complies with the zone and the building regulations must be granted permission.³⁷⁵

Who checks the building?

Building rules are enforced in stages. The usual US sequence for a new building or a major renovation runs roughly like this:

1. Zoning review - does the use and size fit the district, or does it need a variance?
2. Plan review - do the drawings meet the building code?
3. Permits - separate permits for the building and often for plumbing, electrical and gas work.
4. Inspections - inspectors visit at set stages, often before walls are closed up so they can see the wiring and pipes.
5. Certificate of occupancy - an official document confirming the finished building meets the codes and may be used.

The people doing this work - plan examiners, building inspectors, plumbing and electrical inspectors - make judgment calls that affect both safety and how long a project takes. That is one reason the same office can be criticized both for being too slow and for being too lenient.

What happens before someone digs up a street?

A city street is a shared roof over a buried network. Under any given block there may be a water main, a sewer, a storm drain, gas, electric and telecom lines, each owned by a different organization. In Boston alone, one commission runs about 1,015 miles (1,630 km) of water main and 1,435 miles (2,310 km) of sewer and storm drain pipe.⁴⁴ A backhoe that hits a gas line or a fiber trunk can cause an explosion or knock out service to thousands of people.

The practical answer is to tell every utility before digging, so each can mark its lines on the pavement first. The painted lines and small flags on sidewalks are those marks, color-coded by the type of line. In Massachusetts, the Dig Safe Law (G.L. c. 82, ss. 40-40E) requires anyone excavating to contact Dig Safe, by dialing 811, at least 72 business hours ahead; Saturdays, Sundays and holidays do not count.³⁷⁶ The digger first outlines the planned area with white paint or stakes.³⁷⁶

In the US, the colors follow a uniform code from the American Public Works Association (APWA): red for electric, yellow for gas, oil and steam, orange for communications, blue for drinking water, green for sewers and drains, purple for reclaimed water and irrigation, pink for temporary survey marks, and white for the proposed excavation.³⁷⁷

Beyond safety marking, cities also try to coordinate digging, so that the same block is not torn up by the water body in spring, the gas company in summer and the city's repaving crew in the fall. The coordination problem follows from the patchwork of owners described in Who actually runs a city: no single owner has the full picture.

In Boston

Boston's Zoning Code was enacted in 1964 and has been revised many times since.³⁷⁸ When a project does not comply, the Inspectional Services Department (ISD) issues a zoning refusal letter, and the owner then has 45 days to appeal to the Zoning Board of Appeal (ZBA).³⁷⁸ The ZBA can grant variances and conditional use permits; a motion needs five members in favor to pass.³⁷⁸ ISD also issues the building permits - a short form for minor alterations, a long form for new buildings and major work.³⁷⁸

The building code itself is set by the state. The 10th edition of the Massachusetts State Building Code, 780 CMR, is based on modified versions of the 2021 International Codes, including the International Building Code.³⁷⁹ It first took effect on October 11, 2024, and after a concurrency period ending June 30, 2025, it became the only building code in effect.³⁷⁹

Building also feeds the city's finances. Under Proposition 2½, Boston's property tax levy can grow 2.5% a year plus "new growth" from new construction; rising values on existing property do not count.³⁶⁵ Boston already collects the maximum the law allows.³⁴² So for a Massachusetts city, new construction is one of the few ways to grow property tax revenue faster than 2.5% a year, which gives city hall a financial interest in what gets built.

The street-digging side is also tangled in Boston because the main pipe owners are not city departments. BWSC, which owns the local water and sewer mains, is a body created by state law "separate and apart from the City of Boston."⁴⁴ Its pipes connect to the state MWRA's system at 27 metered points.⁴⁴ Any street opening near one of those connections involves at least two public bodies besides the city.

What's changing now (2026)

Energy rules are the fastest-moving part of building codes in Massachusetts, as cities try to cut emissions from new buildings.

Massachusetts municipalities can opt into two state energy codes beyond the default, the "stretch" code and the "specialized" code; as of June 2025, 245 had adopted the stretch code and 55 the specialized code.³⁸⁰ Boston's specialized code took effect on January 1, 2024.³⁸⁰ It requires new buildings and major renovations to follow one of three paths - zero energy, all-electric, or mixed fuel with pre-wiring for electrification and on-site solar where feasible.³⁸¹ Separately, a 2022 state climate law created a fossil-fuel-free demonstration project for 10 municipalities: Arlington, Lexington, Brookline, Acton, Concord, Cambridge, Lincoln, Newton, West Tisbury and Aquinnah. Boston is not among them.³⁸²

Rules for existing buildings - limits on how much carbon large buildings may emit each year - are covered in How cities are adapting to a changing climate.

Report an error in this section