For the purposes of this chapter, the City of Fitchburg is hereby divided into the following districts:
181.2111. 
Residential Districts:
Rural Residential
RR
Purpose. To establish and preserve quiet rural neighborhoods of one-family homes, free from other uses except those which are both compatible with and convenient to the residents of such districts.
Residential A
RA
Purpose. To establish and preserve quiet suburban neighborhoods of one-family homes, free from other uses except those which are both compatible with and convenient to the residents of such districts.
Residential B
RB
Purpose. To establish and preserve medium density neighborhoods of one-, two- and three-family homes, multifamily uses, and other uses which are both compatible with and convenient to the residents of such districts.
Residential C
RC
Purpose. To establish and preserve medium density neighborhoods of one-, two- and three-family homes, multifamily uses, and other uses which are both compatible with and convenient to the residents of such districts.
181.2112. 
Business Districts:
Downtown Business
DB
Purpose. To establish and preserve the downtown area for retail, business services, housing, and office uses and to promote a strong pedestrian character and scale. A primary goal for the district is to provide an environment that is safe for and conducive to a high volume of pedestrian traffic, with a strong connection to retail and pedestrian accessible street level uses.
Intown Business
IB
Purpose. To establish and preserve the intown area for retail, business services, housing, and office uses and to promote a strong pedestrian character and scale. A primary goal for the district is to provide an environment that is safe for and conducive to a high volume of pedestrian traffic, with a strong connection to retail and pedestrian accessible street level uses. Intown Business District includes special flexibility to support the development of housing.
Neighborhood Business
NB
Purpose. To establish and preserve areas for small-scale retail stores, services and offices which are located in close proximity to residential areas and which have uses compatible with the surrounding residential areas.
Commercial
C
Purpose. To establish and preserve business areas bordering main thoroughfares that are attractive to a wide range of uses, including retail business and services, government, professional and medical offices, and places of amusement. While it is anticipated that most users will arrive by motor vehicle, it is intended that the area should be safe for and conducive to pedestrian traffic.
Commercial Recreation
CR
Purpose. To promote the development of facilities which support and facilitate team sports and other large-scale recreational activities, and supporting and complementary uses and activities, especially those which are suitable to attracting tourism.
181.2113. 
Industrial Districts:
Adaptive Industrial
AI
Purpose. To create a district to promote the adaptive reuse of Fitchburg's historic mills, warehouses, brownfields and previously developed properties while preserving the character of the property and nearby residential and commercial neighborhoods
Industrial
I
Purpose. To establish and preserve areas for necessary industrial and related uses of such a nature that they require isolation from other types of land uses, and to make provision for commercial uses which are necessary to service the immediate needs of establishments in these areas.
181.2114. 
Institutional Districts:
Medical Services
MS
Purpose. To establish and preserve areas primarily for medical institutions and facilities.
University District
FSU
Purpose. To establish and preserve areas primarily for university uses.
In addition, the following overlay districts are also hereby established:
Water Resource Protection District
WRPOD
Section 181.81
Planned Development District
PDD
Section 181.82
Priority Development Site Overlay District
PDS
Section 181.83
Smart Growth Zoning Districts
SGZD
Section 181.84
Floodplain Protection Overlay District
FPOD
Section 181.85
These districts are shown, defined and bounded on the map accompanying this chapter entitled "City of Fitchburg Zoning Map Adopted June 23, 2022," as amended. This map, including overlays, shall be on file in the City Clerk's office. Said Zoning Map and amendments thereto as shall be duly adopted shall be considered an integral part of this chapter.
Where uncertainties exist as to the boundaries of districts as shown on the Official Zoning Maps the following shall apply:
181.2311. 
Where the boundary lines as shown upon said Map as approximately following the street lines of public and private ways or railways, the center lines of such ways shall be the boundary lines.
181.2312. 
Where the boundary lines are shown approximately on the location of property lot lines, and the exact location of property, lot or boundary lines is not indicated by means of dimensions shown in figures, then the property or lot lines shall be the boundary lines.
181.2313. 
Boundary lines located outside of street lines and shown approximately parallel thereto shall be regarded as parallel to such street lines, and dimensions shown in figures placed upon said Map between such boundary lines and street lines are the distance in feet of such boundary lines from such street lines; such distances being measured at right angles to such street lines unless otherwise indicated.
181.2314. 
In all cases which are not covered by other provisions of this section, the location of boundary lines shall be determined by the distance in feet, if given, from other lines upon said Map, by the use of identifications as shown on the Map, or by the scale of the Map.
181.2315. 
Where the district boundary line follows a stream, lake or other body of water, said boundary line shall be constructed to be at the thread or channel of the stream or at the limit of the jurisdiction of the City unless otherwise indicated.
181.2316. 
Where physical or cultural features existing on the ground are at variance with those shown on the Official Map, or in other circumstances not covered by the above subsections, the Building Commissioner shall interpret the district boundaries.