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Agencies, City: (which may be involved with zoning)

Inspectional Services Department (ISD) Issues building permits, inspects construction sites. Professional staff.
Community Development Department (CDD) Professional staff doing planning studies and administering grant programs
Planning Board –
Volunteer board appointed by the City Manager. Reviews major projects and zoning law change proposals
City Council
– Elected body. Makes changes to zoning law
Board of Zoning Appeals (BZA) – Volunteer Board which reviews requests for zoning variances and special permits

As-of-Right Development - Most development or use of unimproved land need meet only the provisions of the Zoning Law to be granted a building permit. This means that a developer may build a structure as-of-right if the structure complies with zoning laws and the building code. The developer simply files architectural plans with Inspectional Services and can begin construction upon issuance of a building permit.

Building Size - The maximum size (or bulk) of a building on a lot is determined by the floor area ratio (FAR) assigned to each zoning district. It controls the physical volume of buildings. (See Floor Area Ratio below)


Commercial Districts - A Commercial District is designated by the letter O (office), B (business), and I (industrial)

Overlay Zoning Districts (PUD) impose additional regulations or restrictions on uses. Overlay districts have different boundaries than the base zoning districts

Residential Zoning Districts refer to land which may be developed with some type of housing. They are indicated by the code "Res" followed by letter further describing the zoning requirement, and a number following the letter, for example "Res C1". A residence is a building or part of a building containing dwelling units, including one-family or two-family houses, multiple dwellings, boarding or rooming houses, hotels, educational uses, health care, community centers, schools and colleges, or apartment buildings. The Residence C3 district mostly applies to institutional land.

PUD – Planned Unit Development districts allow for greater intensity of development when there is extensive review of proposals. PUD districts are generally used in areas of the city where redevelopment is desired.

Density - Density refers to the maximum number of dwelling units or floor area permitted on a site. It is regulated by the minimum number of square feet of lot area required for each dwelling unit or building square foot.

Development - A development includes: a) the construction of a new building or other structure on a zoning lot; b) the relocation of an existing building to another lot; or c) the use of a tract of land for a new use.

FAR (floor area ratio): the gross floor area of the building relative to the area of the lot on which it's built. Each zoning district classification contains an FAR limit A building can contain floor area equal to the lot area multiplied by the floor area ratio (FAR) of the district in which the lot is located. In a zone where the permitted FAR is a maximum of 1.0, a 40,000 sq foot lot (approximately an acre) could have a 40,000 sq ft building. Staying within the FAR limit, a developer might build a 4-story building at 10,000 sq ft per floor, or a 2-story building at 20,000 sq ft per floor. Height rules permitting, it could also be a 10-story building at 4,000 sq feet per floor. If the FAR is 4.0 (the greatest FAR currently permitted in Cambridge), the same lot could hold a 160,000 sq ft building. Parking areas, cellar space, floor space in open balconies, elevator or stair-bulkheads, and other non-habitable space within the building do not count as part of the FAR.

Height and Setback - Height and setback provisions also provide for light and a sense of openness in the streets and yards. In most medium and higher density districts, the height of a building's front wall at the street line will be generally limited to 55' or 4 stories. Above that height, a building is required to set back behind a theoretical inclined plane -- the sky exposure plane -- which cannot be penetrated by the building wall. In certain districts, a rear sky exposure plane provides greater light and air to the rear yards. In most lower density districts, there are specific maximum building heights, which include sloping roofs. In general, space must be provided between certain types of residential buildings on the same zoning lot according to a special formula. In addition, there are also requirements for the amount of space which must be provided in front of legally required windows.

Non-Compliance - A legal non-complying building is any building that was legal when it was built which no longer complies with one or more of the present district bulk height, or use regulations.

Open Space. Open space is the part of a zoning lot including courts or yards, which is open and unobstructed from its lowest level to the sky, and is accessible to and usable by all persons occupying dwelling units on the zoning lot. In all residence districts, residential development must provide open space on the zoning lot. The amount of open space required is determined by the open space ratio (OSR), which expresses the percentage of total lotarea that must be provided as open space on a development parcel.In addition to open space, there are regulations for minimum size of front, rear, and side yards.

Parking - Zoning laws also require the provision of off-street parking for most new developments. Parking on the site of a new development helps eliminate congestion on nearby streets. In areas where additional parking would generate more traffic than desirable, and where mass transit is available, the requirement for on-site parking is reduced or eliminated. Off-street loading berths for commercial and manufacturing uses may be required.

Sky Exposure Plane (proposed) - A sky exposure plane is a theoretical 45-degree inclined plane, through which the height of a building may not penetrate when it is taller than certain standards, that is designed to provide light and air for adjacent properties, or develop a consistant streetscape, where low density zones abut high density zones. It rises over the zoning lot at 45-degrees, extending from the lot line or zoning district line through the subject property.

Special Permit - Some uses in certain zoning districts require findings by the Board of Zoning Appeals or the Planning Board (certain special permits are assigned to each Board) of compatibility with existing or planned development in the area and compliance with specified standards. There are two types of special permits: modifications of the use regulations and modifications of the dimensional or parking regulations.

Variance - A request to vary the regulations of the Zoning Ordinance, such as the minimum lot size or yard requirements. Variances are subject to approval by the Board of Zoning Appeals. Although certain strict standards are supposed to apply, by tradition, the board grants most variances when there is little opposition to a proposal.

Zoning Amendments - There are two types of zoning amendments: amendments to the zoning text and amendments to the zoning map. A change to the zoning text or map may be reasonable in a situation where the zoning regulations would result in an awkward site plan or prevent useful development of an area. this is what variances are all about, and the amendment process is not used this way in Cambridge. In other cases, a change to the text or map may be necessary to preserve an area from unwarranted or destructive change. Amendments frequently set out detailed rules for districts in which change is desired.

Zoning Maps Zoning maps are maps that are included in the provisions of the Zoning Resolution to indicate the location and boundaries of zoning districts. Zoning maps are available for a fee from the Community Development Department, 57 Inman St, 3rd floor.