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The Zoning Guide:
A User Guide to the City of Cambridge Zoning Ordinance
Index
Please note that the Zoning Guide does not in any way replace the Cambridge Zoning Ordinance. The Zoning Guide provides an overview of the Ordinance and seeks to explain some of the more technical concepts in language accessible to the layman.
II. Zoning Regulations: What, Where and How Much
The Zoning Ordinance defines what people may and may not do with their property. There are two parts to the Ordinance, the map and the text.
The Zoning Map divides the city into zoning districts. It shows district boundaries which have been described in legally precise terms when an area is zoned or rezoned.
The Zoning Ordinance Text spells out the regulations for each class of district. Each regulation usually applies to all locations within a given district classification. Four principal types of regulations may be found in the text of the ordinance: use, dimensional, parking and special regulations. The text also contains the procedures for enforcing and administering those regulations.
Use Regulations specify which types of land use (e.g. apartment building, store, restaurant, warehouse) may be located in each zoning district. The Ordinance contains a Table of Use Regulations listing over one hundred different land use types. For each type, in each class of district, the table specifies whether that use is allowed as-of-right, prohibited or conditionally permitted. A conditionally allowed use will be permitted only if granted a special permit, as described in the fourth part of this booklet.
Dimensional Regulations limit the intensity of activity and the size and location of buildings on a piece of land. These regulations specify maximum gross floor area, density, height and minimum yards and open space.
- Floor area ratio (FAR) limits how intensively a lot may be built upon. Indirectly it controls building volume. FAR is the gross floor area of the building divided by the area of the lot. Areas devoted to parking, to building mechanical systems and certain other areas are not counted when calculating gross floor area, Business districts such as Harvard Square and Central Square have much larger FAR limits than most residential neighborhoods. Diagram 1. shows how floor area ratio allowances are applied.
- Density regulations limit the number of dwelling units which may be built on a piece of land by requiring a minimum number of square feet of lot area per dwelling unit. A dwelling unit is a portion of a building containing the living space for one family or household. A 6,000 square foot lot in an apartment district with a 1200 square foot minimum lot area could contain a five unit (6000/1200) apartment building. It is often useful to convert the minimum required lot area for one dwelling unit to units per acre. This provides a measure of how many new units exist or are allowed on a city block or other larger tract of land.
- Height regulations limit how tall buildings may be. This is expressed as a maximum number of feet. As a rule of thumb, a single story of a building is about 10 feet high. Some districts have different height limits at the edge of the district than at other locations within the district. Diagram 2 shows how height regulations are applied.
- Setback regulations control the distance between the building and street and lot lines. These distances define the yards on a lot. The Zoning Ordinance specifies minimum front, side and rear yard setbacks for residential and office districts and for some business and industrial districts. Diagram 2 shows how setback regulations are applied.
- Open space regulations require that a specified minimum portion of a lot remain open and usable. Several dimensional regulations are illustrated in the accompanying diagram.
Go to Diagram 1
Go to Diagram
2
Parking Regulations specify the amount of off-street parking required for each type of land use. These are usually expressed as one space per some unit of measure (e.g. dwelling unit, gross floor area, or number of seats). Parking regulations also control the location of the parking, and layout and landscaping of parking facilities.
Special Regulations in the Ordinance provide special controls for activities and land uses which have characteristics not sufficiently regulated by the three classes of general regulations. There are special regulations for accessory uses, and fast food restaurants, for example.
Townhouse Zoning is an option which developers may exercise in the Residence B and C, Office, Business and Industry A-1 districts enabling the construction of one and two family row houses. This zoning allows more flexible dimensional requirements permitting the creation of lots without side yards. In addition, the townhouse regulations provide for a floor area bonus and height bonus. However, the overall density of a townhouse development (number of units per acre) is the same as other dwellings in the district in which it is located. Larger townhouse projects in Residence B and C districts require a special permit from the Planning Board.
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