No building shall be erected to a height in excess of the allowed maximum number of stories or the maximum height as indicated, whichever is less, except as provided in Section 4.217; provided, however, that all accessory buildings and detached garages shall be at least 10 feet from the principal building.

The percentage of lot coverage shall include all principal and accessory buildings on any lot.

Side yard width shall be 10 feet where a building does not exceed two and one-half (2 1/2) stories in height; in all other cases it shall be not less than one-fourth (1/4) the height of the building.

An open or lattice-enclosed fire escape may project not more than five feet into a rear yard.

Buildings shall be not less than 150 feet from any street line and 100 feet from any property line. They shall be so grouped that each building shall face for the full length of its front facade either upon an existing street or upon an open space which in its least dimension shall not be less than 70 feet. Where the rear elevations of the principal buildings are built parallel to each other or within 30° of parallel, the distance between their long dimensions shall not be less than 50 feet. Each building, whether principal or accessory, shall be at least 50 feet distant from any other buildings in the group, which distance shall be measured in a straight line between the points of the building which are nearest to each other.

No part of any minimum landscaped area shall be used for parking purposes. Also, any additional landscaped area as required by special permit up to 40% of total parcel area shall be measured from the twenty-five-percent minimum landscape requirement.

Where a lot is located entirely in a Commercial District or where a lot is located partly in a Commercial District and partly in another nonresidential district and where such a lot does not exceed 25,000 square feet in total area and has a frontage of less than 100 feet and where such a lot does not abut residential districts, the rear setback requirement shall not apply and the side yard requirement shall apply to only one side. In all other instances, the application of the front, side and rear setbacks shall be as follows:

Where a lot is located entirely in an Industrial District or where a lot is located partly in an Industrial District and partly in another nonresidential district and where such a lot does not exceed 25,000 square feet in total area and has a frontage of less than 100 feet and where such a lot does not abut residential districts, the rear setback requirement shall not apply and the side yard requirement shall apply to only one side. In all other instances, the application of the front, side and rear setbacks shall be as follows:

See Section 3.737 for the definition of minimum open space and the open space criteria for all developments seeking a special permit for increased development intensity above the FAR allowed as of right.

The minimum lot frontage shall be maintained on all lots as a minimum lot width to a point equivalent to the rear facade of the principal building or 50% of the depth of the lot, whichever is greater. However, lots laid out on approved cul-de-sacs may reduce the minimum frontage by 1/3. Further, lots in the Limited Commercial District shall be permitted to maintain their minimum required lot frontage along the front lot line only. The provisions for culs-de-sac and lots in the Limited Commercial District shall only apply to existing lots as of June 13, 2005.

Public or private educational institutions which are fully accredited by recognized private, state or federal organizations shall be allowed to exceed the height limitations of the RA-2 and RA-3 Districts given the following building setback criteria from residential or public open space property lines as specifically noted below:

Consistent with the higher floor area ratios allowed by special permit, the City Council, when issuing a special permit for intensity of use, may allow for an increased number of units per acre up to the following maximums:

In the Business C District, no new structure may be constructed within 10 feet of a public pedestrian way of at least five feet in width if said public way is used for access to a parking area, public open space or public building.

For parcels that abut the Charles River, a setback from the Charles River to any portion of any structure shall be at least 50 feet if the lot has a depth of at least 200 feet. In the instance where the lot depth is less than 200 feet, the setback shall be at least 25 feet.

For side yard and rear yard requirements where a lot abuts a Conservation/Recreation or Residence District, see Sections 4.234 and 4.241.

In Business A Districts, the maximum floor area ratio (FAR) allowable by right shall not exceed .20 for retail use. In Business B Districts, the maximum floor area ratio (FAR) allowable by right shall not exceed .24 for retail use. In Commercial Districts, the maximum floor area ratio (FAR) allowable by right shall not exceed .28 for retail use. In Industrial Districts, the maximum floor area ratio (FAR) allowable by right shall not exceed .28 for retail use.

See Section 4.214 for changes to FAR and open space caused by dividing lots with two or more principal buildings.

Where a lot having irregular topographical characteristics is located entirely in a Limited Commercial District and contains in excess of 10 acres of land, the maximum building height shall be 45 feet (but not to exceed three stories) if:

Swimming pools in the Conservation/Recreation District must comply with the front, side and rear setback requirements of the Conservation/Recreation District as set forth in Section 4.11.

Any conflict between the FAR by Right and the FAR by Special Permit in Section 4.11 and Section 3.721 shall be governed by Section 4.11, Table of Dimensional Requirements, however, all exemptions stated in 3.721 shall be applicable to Section 4.11.

Where a lot having irregular topographical characteristics is located entirely in a Residence D District and contains in excess of 10 acres of land, or is adjacent to one or more additional lots, held in common ownership, with a total area in excess of 10 acres, the City Council may grant a Special Permit for a maximum building height up to 60 feet (but not to exceed four stories) if:

Any application for a special permit for intensity of use for new multifamily dwellings to be constructed in the Residence D District shall include provision for the construction of age-restricted housing with the effect that the number of age-restricted housing units to be provided shall be at least 30% of the number of housing units proposed to be constructed pursuant to such special permit. At the discretion of the City Council, the age-restricted housing may be located on a lot located in a Residence D District and adjacent to the lot on which the non-age-restricted housing units are to be located. Nothing herein shall negate the requirement that the applicant for such a special permit shall comply with the affordable housing requirements of Section 9.1 except that the number of dwelling units required by Section 9.141 shall equal 12.5%; the dwelling units required by Section 9.142 shall equal 20%; the "fee" required by Sections 9.143 and 9.144 shall be 20% of the total development cost (TDC). In lieu of the increased requirements of Section 9.141, 9.142, 9.143 and 9.144 provided for in the previous sentence, the applicant may reduce said requirements to no less than the requirements provided for in Sections 9.141, 9.142, 9.143 and 9.144 by City Council approval of a petition by the applicant for a conservation set-aside. In lieu of each affordable housing unit not provided, the applicant shall set aside 10,000 square feet of land with conservation value or in lieu of the fee required in Sections 9.143 and 9.144 an equivalent square footage of land with conservation value equal in assessed value to the fee not provided, but in no case less than 54,450 square feet, such set-aside to be accomplished through:

Subject to the requirements of Sections 8.65 and 8.66, the City Council may by special permit, and within the limitations imposed by said Sections 8.65 and 8.66, alter the dimensional requirements for a project within the Limited Commercial Revitalization Area Overlay District.

Subject to the requirements of Sections 8.75, 8.76 and 8.77, the City Council may, by Limited Commercial Residential Area Protection Overlay District special permit, and within the limitations imposed by said Sections 8.75, 8.76 and 8.77, alter the dimensional requirements for a project within the Limited Commercial Revitalization Area Overlay District as set forth in Section 8.7 et seq.

Minimum building setback(s) requirements shall not apply to any pedestrian bridges or overpasses existing in the HR-2 District on January 1, 2018.

A detached garage and/or an accessory building in the HR2 District that is not associated with multifamily or assisted living use may be erected up to a maximum of four stories, but no more than 55 feet maximum building height, provided that such detached garage or accessory building is located no closer than 425 feet from the nearest point of any public way in existence as of January 1, 2018, excluding Hope Avenue. In addition to the exception to height restrictions set forth in Section 4.217, in the HR2 District the height restriction shall not apply to elevator vestibules and associated facilities, stair enclosures, ventilation, mechanical equipment, lighting and other necessary appurtenances on the top level of any such detached garage or accessory building.

Rounding up prohibition. When calculating the number of residential units allowed on any given lot, it is prohibited to round-up on any fraction of the total.

Use, height and area provisions. No building or other structure nor any land shall be used nor shall any building or structure be erected or altered except in conformity with those provisions of this chapter that regulate the use, height and area of land and buildings, including amendments thereof, which apply to the district in which the building, structure or premises shall be located.

Required yards or open spaces. No part of a yard or other open space required for any building for the purpose of complying with the provisions of this chapter shall be included as a part of a yard or other open space similarly required for another building.

Lots in two districts. Where a district boundary line divides a lot in single or joint ownership of record into two different districts at the time such line is adopted, the regulations for the less restricted portion of such lot shall extend not more than 30 feet into the more restrictive portion, provided that the lot is still owned by the owner of record of such lot when such line was established; that the lot has frontage in the less restricted district; and that access to said lot is from the frontage located in the less restricted district. Notwithstanding the foregoing, the regulations for a less restricted district shall not extend under any circumstances into a conservation/recreation district.

Reduction of lot areas. Except as provided in this section, no lot on which a building is located in any district shall be reduced or changed in area, shape or frontage so that the building or lot fails to comply with the provisions of this chapter. No lot on which a building is situated shall be reduced in area or frontage if such lot is smaller than is herein prescribed. This provision, however, shall not apply when a portion of a lot is taken or conveyed for a public purpose.

It shall not be a violation of this chapter to divide a lot that contains two or more principal buildings which contain a use set forth in Section 3.4 under Commercial, Industrial and Institutional, as well as Hotels/Motels as set forth in Residential, that are either lawful nonconforming structures or are protected under provisions limiting actions, suits or proceedings contained in MGL c. 40A, Section 7, with respect to FAR and minimum open space requirements, provided that each resulting lot contains at least one principal building; and such nonconforming or protected status shall be deemed to continue notwithstanding such division. This paragraph shall not apply to residential uses except as set forth above.

Notwithstanding anything to the contrary in this section or in Section 3.511, in the case of any lot resulting from a division described in the preceding paragraph, whether or not such lot has an FAR that is less than the FAR by right in the zoning district in which the lot is located, any subsequent increase in intensity of use shall require a special permit in the same manner as is provided in Sections 3.5 and 7.5 for increases in intensity of use above the FAR by right.

More than one principal building on a lot. Only one principal building designed or available for use for dwelling purposes shall be erected, placed or converted to residential use on any lot without the approval of the Board of Survey and Planning in accordance with MGL c. 41, Section 81Q and Section 1.0 of its rules and regulations; further provided that, if a residential principal building is located to the rear of another residential principal building on the same lot, the open space between such buildings shall be at least 50% greater than the rear yard requirement for the district. The rear building shall be subject to the side yard requirement for the district. The rear building shall be subject to side and rear yard requirements of the district in which it is located. More than one nonresidential principal building may be allowed on one lot under certain circumstances. Every nonresidential principal building shall have frontage on a street, public or private, or a clear unobstructed passageway to such street at least 20 feet wide for its entire length over the lot on which it is located. If a nonresidential principal building is located to the rear of another nonresidential principal building on the same lot, the open space between such buildings shall be at least 50% greater than the rear yard requirement for the district. The rear building shall be subject to side and rear yard requirements of the district in which it is located. When such nonresidential buildings are built on a single lot, they shall be sited in a conformance with all front, side and rear yard requirements of this chapter and the rules and regulations of the Board of Survey and Planning.

Minimum area for dwellings. With the exception of single-family residential buildings, any building used for human occupancy in any district shall provide a habitable ground floor area of not less than 600 square feet.

Height exceptions. The provisions of this chapter governing the height of buildings shall not apply to chimneys, cooling towers, elevator bulkheads, skylights, ventilators and other necessary appurtenances usually carried above roofs; nor to domes, towers, stacks or spires, if not used for human occupancy and if they do not occupy more than 25% of the ground floor area of the building; nor to ornamental towers, observation towers, windmills, radio broadcasting towers, television and radio antennas and other like structures which do not occupy more than 25% of the lot area. (See Section 3.87.)

Lot area. Substandard lots may be combined for the purposes of meeting zoning regulations. Further, lot area as required by Sections 4.211 through 4.214 shall not apply to lots for single- and two-family residential use which, prior to the adoption of this chapter, were shown as separate parcels on subdivision plans approved by the Board of Survey and Planning or were assessed as separate parcels or were shown on plans or deeds duly recorded with the County Registry of Deeds. With respect to such lots in residential areas, the following provisions shall apply:

Yard exceptions and projections. Projecting eaves, chimneys, and cornices shall not project more than three feet into required open spaces nor more than 1/4 of the width of the required open spaces within the lot over which they project, whichever is less, but may project one foot in any case. Belt courses and other ornamental features shall not project more than 12 inches into such required open spaces. On single-family and two-family homes unenclosed steps, unroofed porches and the like which do not project more than 10 feet beyond the line of the foundation wall may extend into a required yard area; provided, however, that at no point shall be actual yard area setback be less than 1/2 of the minimum yard area setback otherwise required for the district in which the structure is built.

Location and area of accessory buildings. A detached accessory building may be located in the rear yard area, provided that not more than 25% of the required rear yard area shall be so occupied. An accessory building shall be at least 10 feet from the principal building and five feet from the side lot line and the rear lot line.

Swimming pools. One swimming pool may be constructed on a lot. The pool shall have the minimum setback requirements for the district and shall be at least 10 feet from the side lot line and rear lot line. In the event that such a pool would not provide the minimum setback and rear yard requirements of the district, the Board of Appeals may grant a special permit for such construction after a finding that such action will not be injurious to the neighborhood. For the purpose of this section, the term "swimming pool" shall include all accessory buildings, decks and appurtenant structures. If swimming pools and appurtenances of a portable type comprise a total area of 100 square feet or less, the requirement of the Building Code for a certification for the correct pool location by a registered land surveyor shall be waived.

Height of accessory buildings. When an accessory building shall exceed 15 feet in height, the height shall not be greater than 125% of its least horizontal dimension, but not greater than 20 feet in height. No accessory building shall exceed one story in height.

Corner clearance. On corner lots there shall be a clear, unobstructed space seven feet high beginning 30 inches above the grade of the curve connecting two street lines within the area formed by the street lines and an are formed by a radius curve of 25 feet meeting the street lines as tangents to the area.

Access and parking for business, commercial and industrial uses in adjacent residential zones. Except on adjacent land in the same ownership on the same side of the street and extending for a distance not greater than 60 feet, no land located in a residential district which abuts a Business A, Business B, Commercial or Industrial District shall be used as a parking area (space) of any business use which may be permitted in a Business A, Business B, Commercial or Industrial District. Where parking is permitted under the provisions of this section, the use of such parking area shall be restricted to customers and employees of a business operating in a building immediately adjacent to the abutting residential district and in no event shall such parking area be used for the parking of an automobile, truck, tractor-trailer or any other kind of motor vehicle which is for sale or for rent; and, provided further, that parking in such an area shall only be allowed on the ground level and no parking structure which is more than one story in height shall be permitted.

Private garages for single- and two-family dwellings. Except as otherwise provided herein, one private garage with storage space for not more than three motor vehicles, either detached or forming part of the principal building, is permitted on each lot on which a dwelling is located. In the case of a garage forming part of the principal dwelling, the minimum setback, side yard and rear yard requirements of the district shall be provided. In the case of a detached garage, the minimum setback requirement of the district shall be provided and the garage shall be at least three feet from the side and rear lot lines and at least 10 feet from the principal building. Not more than one commercial vehicle may be kept on a lot or on a parcel consisting of more than one lot in the same ownership; and provided, further, that the gross vehicle weight of such commercial vehicle shall not exceed 9,900 pounds. Farm properties shall not be subject to the provision of this section.

Private garages for multifamily dwellings. In the case of multifamily or group dwellings, individual garage storage space for each dwelling unit accommodated on the lot may be provided either as an integral part of the building or in an accessory building or buildings, but such an accessory building for more than three motor vehicles shall not be located nearer than six feet to any side or rear lot line. Space for the storage of a commercial vehicle shall not be leased or let in any such garage, except that a resident tenant of the premises may be permitted to store a commercial vehicle of not more than three-fourths (3/4) of a ton in rated capacity.

Corner lot side yards. On a corner lot, the side yard adjacent to the intersecting street shall be subject to the same provisions as the front yards of buildings on such intersecting streets, except that in no case shall any building, including a detached accessory building, be nearer than 10 feet to the side street line, and in all cases the provisions set forth in Section 4.241 shall be observed.

Front yards as affected by existing buildings. No building need be set back from the street line of any street more than the average setback of existing buildings on either side of it within a distance of 200 feet on the same side of the street or no more than the zone requirement in the zone in which it is located, whichever is less, except that in no case shall any part of a building be nearer than 10 feet to the street line of any street. For lots for single- and two-family residential use which do not meet current lot area requirements, but which are eligible for small lot status under Section 4.218, Subsection 4.2181, or Subsection 4.2182, the following provision shall apply: No building need be set back from the street line of any street more than the setback of existing buildings on either side of it within a distance of 200 feet on the same side of the street or no more than the zone requirement in the zone in which it is located, whichever is less, except that in no case shall any part of a building be nearer than 10 feet to the street line of any street.

Location of public garages, automobile service facilities and alcoholic beverage establishments. No public garage, storage battery service station, gasoline filling station nor any of their appurtenances or accessory uses and no commercial establishments for the sale or dispensing of alcoholic beverages shall hereafter be erected or placed so that any entrance or exit at the street line thereto shall be within a radius of 200 feet from any entrance or exit at the street line (such as a door, walk or driveway) of any public or private school, public library, church, playground or institution for the sick, dependent or for children under 16 years of age if such entrances or exits are on the same street or on an intersecting street; nor within 25 feet of any residential district. No motor fuel dispensing pump or device located at a service station or filling station shall be situated within 75 feet of a residential dwelling unit. Not withstanding the foregoing provisions of this subsection, structured parking, as defined in Section 2.3432, may be allowed in the Business C District, regardless of the location of any entrance or exit thereto, when approved as part of an intensity of use special permit.

Location of accessory buildings. A detached building may be erected in the side yard or rear yard area but shall not be located nearer than 10 feet to the principal building, and it shall be subject to all applicable front, side and rear yard requirements. An accessory building attached to the principal building shall be considered as an integral part thereof and shall be subject to front, side and rear yard requirements applicable to the principal building.

Rear yard under certain conditions. The rear yard in the case of a lot running through a block from street to street, when improved by a single nonresidential principal building, shall be at least equal to the required rear yard depth of the adjacent lots.

Rear yard requirements where district abuts Conservation-Recreation or Residence Districts. Where the rear yard of a lot in a Business, Commercial or Industrial District abuts a Conservation-Recreation or Residence District, there shall be provided on such lot a rear yard of 1/2 the height of the building or 25 feet, whichever dimension is greater.

Side yard requirements where district abuts Conservation-Recreation or Residence District. Where the side of a lot in a business, Commercial or Industrial District abuts Conservation-Recreation or Residence Districts, there shall be provided on such lot in the less restricted district a side yard of one-half (1/2) the height of the building or 25 feet, whichever dimension is greater.

[1] Location of accessory buildings. A detached building may be erected in the side yard or rear yard area but shall not be located nearer than 10 feet to the principal building, and it shall be subject to the same front, side and rear yard requirements as the principal building. An accessory building attached to the principal building shall be considered as an integral part thereof and shall be subject to the front, side and rear yard requirements applicable to the principal building.

Calculation of height. Owing to the irregular topographical characteristics within the Hope Avenue Redevelopment Districts, the owners of lots within such districts shall have the option to determine building heights in accordance with either:

More than one principal building on a lot. Notwithstanding the provisions of Section 4.215, more than one residential and/or nonresidential principal building shall be allowed on one lot so long as:

Location of exterior doors for multifamily townhouses and multifamily rowhouses. In all multifamily townhouses and multifamily rowhouses, the unit closest to the street on which the lot frontage is measured shall be required to have a first floor door, leading directly from the individual unit to the outside of the building, on the side of the building which faces the street on which the lot frontage is measured.