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Zoning is the term for rules that cities put in place to determine what kinds of buildings can be built where. It can be complex and technical, but it’s a force that shapes the places we live, and it often determines how a city grows and thrives — or doesn’t. Too-strict zoning can block the creation of sufficient housing, which leads to the skyrocketing prices we’ve seen in recent years. It can also create huge negative impacts for economic inequality, racial segregation, and the environment. That’s why Somerville YIMBY and other pro-housing groups have focused on it so closely.

Zoning and Segregation

Zoning laws can help cities guide their development in positive ways, and keep noxious industries away from homes and commerce, but the first zoning laws in the US were created to promote segregation. They achieved that mostly by keeping apartments and multifamily homes away from single-family homes. This worked because people of color were often shut out of mortgage lending, meaning that a neighborhood of owner-occupied houses was almost by definition entirely white. That segregation was reinforced by federal lending policies that gave better ratings to all-white neighborhoods and by restrictive covenants prohibiting future owners from selling to nonwhite people. To learn more about zoning’s role in creating and perpetuating segregation, read Richard Rothstein’s book The Color of Law.

Zoning and Economic Inequality

In the US, access to clean air, good schools, and good jobs is closely tied to where you live. Wealthy communities that prohibit the creation of sufficient housing and sufficient variety of housing are effectively pricing out lower-income families. Requiring big homes on big lots effectively requires building only the most-expensive housing types, and that keeps opportunities away from lower-income people.

Zoning and the Environment

Zoning that prohibits construction of dense, multifamily buildings isn’t just racist. It’s also bad for the environment: the EPA notes that sprawling development patterns create a lot of harmful emissions, and that “infill” development is a great way to reduce carbon emissions, because density is more efficient and reduces the amount of time people spend driving.

What’s Good Zoning?

A good zoning code is easy to understand, broadly permissive, and reduces the need for special permits and complex approval processes.

Keeping things simple and allowing construction without special permits (“by right”) is especially important because complex codes and requirements for special or discretionary permits also make it harder and more expensive to build anything:

  • A complex zoning code requires specialized knowledge, which means hiring insiders or expensive specialists
  • Delays and uncertainty raise prices and reduce the amount of housing created
  • A discretionary permitting process opens a door to favoritism or even outright corruption

California, especially in the San Francisco Bay Area, is emblematic of the danger of well-intentioned but counter-productive permit and process requirements, but similar issues play out in the Boston area and in many other high-cost cities.

Zoning in Somerville

In Somerville and many other places in the US, zoning got a lot stricter over the course of the 20th century, making existing buildings “nonconforming,” meaning that they couldn’t be re-built under current rules. In 2016, a group of researchers pointed out that the Somerville zoning rules prohibited the construction of nearly every home that already existed. Fortunately, the city wrote an entirely new zoning code, passed in 2019, that is easier to understand and work with. It also comes a lot closer to matching the fabric of the city that actually exists.

Somerville’s new zoning rules are called a “form-based” code: they focus on the overall shape and size of buildings in each of the various districts.

The most common districts in the city are:

  • Neighborhood Residence (NR): One and two-family residential buildings, with the occasional triple-decker.
  • Urban Residence (UR): Multifamily residential buildings such as triple-deckers, row houses, and small-to-medium apartment buildings.
  • Midrise 3, 4, 5 and 6 (MR3, MR4, MR5, MR6): 3-6 story buildings, such as large apartment buildings with retail on the ground floor.
  • Commercial Core (CC): Only business uses.
  • High Rise (HR): Tall buildings (7 or more stories).

We also have overlay districts, which modify the base rules for specific reasons. For example, the Flood Zone overlay requires additional flood control measures, and the Small Business Overlay allows corner stores and other light commercial activities in parts of NR and UR. One of our favorites is the Affordable Housing Overlay (AHO), which allows more height and faster permitting for projects where every home is subsidized affordable. For more information about the exact definition of affordability and how we achieve it in Somerville, see “What exactly do we mean by Affordable Housing?”.

You can find the complete zoning ordinance and a map at Don’t be intimidated by the length: each zone definition begins with a short description of why we have it and what’s allowed in it, so you can get a working knowledge of the rules in just a few pages. In fact, just reading pages 37, 77, and 115 will give you a general understanding of what buildings are allowed in most of the city!

Improving Somerville Zoning

Somerville YIMBY generally agrees with our city’s current zoning code, but there are some changes we’d like to see.

Neighborhood Residence

Our least-dense district is far better than the “single-family only” rules seen in other cities, but it could be better. For example, it should allow accessory dwelling units (“in-law apartments”) and three-family buildings like our iconic triple-deckers with far fewer restrictions.

Midrise Districts

We currently require special permits to build apartments in midrise districts, but should allow that use by right. The city usually grants these permits when builders request them, but there’s not a really good reason to require them at all.

Parking Requirements

Zoning codes in many other cities require too much off-street parking, which raises costs and encourages people to drive. Somerville’s code is better than most, and even sets a maximum amount of parking for construction near transit, but we’d still like to see a few adjustments to encourage less new parking construction citywide, on the general principle that space we dedicate to cars is space we can’t dedicate to people.

Map Changes

There are also a number of places we’d like to see streets or blocks moved to a denser category. In fact, we’d like to see increases in allowable density throughout the city, but in particular:

  • Davis Square: Most of the center of Davis Square is zoned for Midrise 3. Something so close to the Red Line deserves Commercial Core or Midrise 6, with surrounding residential neighborhoods zoned for Urban Residence. This is especially important as an equity issue, because the eastern parts of the city have seen far more upzoning, and Davis Square shouldn’t be exempt from development.
  • Areas surrounding Green Line Extension stops: Many areas near new Green Line stops are currently zoned for Neighborhood Residence or Urban Residence. In the spirit of the MBTA Communities Law, we should adjust the map to increase allowable density near transit.
  • Small Business Overlay: We should apply the small business overlay to more NR and UR areas along major streets to reduce the difficulty of opening a new business.