4.1.1 
Applicability. Each use, building, or structure must comply with the standards described in Table 2, Schedule of Dimensional Controls,[1] except where provided otherwise by this bylaw.
4.1.2 
Lots in More Than One District. When a lot is divided by a district line and proposed to be used for a building or use that is not permitted by right in both districts (in Lexington or not), such building or use must comply with the dimensional standards of § 135-4.0, as if the district boundary line were a lot line.
4.1.3 
Lots Located in More than One Municipality. When a lot is partially in the Town of Lexington and partially in an adjacent municipality, the provisions of this bylaw are applied to the part of the lot in Lexington as if the entire lot were in Lexington.
4.1.4 
One Dwelling Per Lot. More than one dwelling on a lot is prohibited, unless specifically authorized by other provisions of this bylaw.
4.2.1 
Change in Lot That Results in Noncompliance. No conforming lot may be changed to make it nonconforming.
4.2.2 
Lot Regularity. No structure other than a solar energy system may be erected on any lot that does not have an area in which a circle, the diameter of which is 80% of the minimum lot frontage, tangent to the lot frontage and within all other lot lines, may be located.
[Amended 11-8-2021 STM by Art. 14]
4.2.3 
Lot Area.
[Amended 11-8-2021 STM by Art. 14]
1. 
Lot Area. No structure other than a solar energy system may be erected on any lot that does not have at least the minimum lot area set forth in Table 2 for the district in which the lot is located.
2. 
Developable Site Area. No dwelling may be erected on any lot that does not contain a contiguous developable site area that is at least 90% of the minimum lot area for the district in which the lot is located.
4.2.4 
Lot Frontage.
1. 
Minimum Lot Frontage Required. No structure other than a solar energy system may be erected on any lot that does not have at least the minimum frontage set forth in Table 2[1] for the district in which the lot is located on a street. Frontage on unaccepted ways in existence prior to the adoption of the Subdivision Control Law must receive a favorable determination from the Planning Board. Ways laid out, but not constructed, may not be used as frontage.
[Amended 11-8-2021 STM by Art. 14]
2. 
Designation of Frontage Street. When a lot is bounded by more than one street, any one of them, but only one, must be designated as the frontage street, provided the street meets the requirements for minimum lot frontage described in this bylaw. In the case of a lot bounded by two streets forming an interior angle of more than 135°, their combined frontage may be used to satisfy the lot frontage requirement.
3. 
Measurement of Lot Frontage. Frontage is measured in a continuous line along the sideline of the street right-of-way between the points of intersection of the side lot lines with the street right-of-way line. The measurement of lot frontage excludes jogs in the street width, backup strips and other irregularities in the street line. In the case of a corner lot, the owner may extend to the midpoint of the curve connecting street lines, instead of to their intersection.
4. 
Access. An owner must provide a means of access for vehicles from the frontage street to a principal building for emergency services, for deliveries, and for off-street parking. Alternatively, the owner may provide the access from another street provided it can be demonstrated that it is both physically and legally possible to provide access from the designated frontage street.
5. 
Frontage Reduction on Curves. Where more than half of the lot frontage is on a circular turnaround, or on a curve of less than one-hundred-foot radius, frontage may be reduced to not less than 60% of the distance required in Table 2 if the distance between the side lot lines, measured along the arc parallel to the street line at the same distance from the street line as the front yard setback required by Table 2, is not less than the minimum lot frontage required by Table 2.
6. 
Frontage on Turnaround in CRO Districts. In CRO Districts where a lot abuts on a dead-end turnaround part of a street and also abuts on such street before the turnaround, the frontage may be measured in part along the street line before the turnaround and in part along a projection of the course of such street line through and beyond the turnaround, provided that the lot has frontage of not less than 60 feet on the street, including such turnaround.
4.2.5 
Structures Below Ground. Where the upper elevation of a structure or building is below the elevation of the natural grade, and such structure is covered by earth to a depth sufficient to support vegetation, such structure may be located in a required front, side or rear yard, but no closer than five feet to a lot line. Open grates or small ventilation shafts servicing the part of the structure below ground may be located in the required yard.
4.2.6 
Accessory Buildings in Setbacks. One accessory building, including tool or storage sheds for household equipment or other similar accessory use, but, for the purposes of this section, not including garages or chicken coops, may be located in a side or rear yard, but no closer than five feet to a lot line, provided that the accessory building covers less than 150 square feet and that neither the height nor the length of such accessory building is greater than 12 feet.
[Added 3-31-2021 ATM by Art. 41]
4.3.1 
Structures Other than Buildings.
[Amended 11-19-2020 STM by Art. 13; 11-8-2021 STM by Art. 12]
1. 
The maximum height, in feet, for structures other than buildings may not exceed the maximum height for buildings as set forth in Table 2.[1]
2. 
Structures other than buildings may be located in a minimum required front, rear or side yard, provided the height of the structure is not greater than its horizontal distance from the lot line, except that:
a. 
Structures of any height which are required to enable access for disabled persons may be located anywhere on a lot;
b. 
A fence not greater than six feet in height may be located on or closer to a side or rear lot line;
c. 
A fence or retaining wall not greater than four feet in height may be located on or closer to a front lot line; and
d. 
Supporting posts for a fence may extend six inches higher than the top of a fence.
3. 
A solar energy system may be located over any paved parking lot.
[Added 3-28-2022 ATM by Art. 37[2]]
[2]
Editor's Note: This article also renumbered former Subsections 3 through 6 as Subsections 4 through 7, respectively.
4. 
Structures shall not interfere with safe stopping sight distance on a street.
5. 
Where two or more fences or retaining walls are separated by a distance that is less than the height of the highest such structure, all such structures shall be considered a single structure and their height shall be equal to the combined height of the structures.
6. 
A sign, permitted under § 5.2, may be located in a front yard.
7. 
A solar energy system may be located over any paved parking lot.
4.3.2 
Structures on a Building. Structures erected on a building and not used for human occupancy may exceed the maximum height of a building in feet provided no part of the structure is more than 20 feet higher than the upper elevation of the building and the total horizontal coverage of such structures on the building other than solar energy systems does not exceed 25%.
[Amended 11-19-2020 STM by Art. 13]
4.3.3 
Calculating Height for Segmented Buildings. Where a building is on a sloping site or has some stories that do not extend for the full building coverage, the height in feet and number of stories of the several elements of the building may be computed separately provided that neither the maximum height in feet nor the number of stories in any one element exceeds that permitted by Table 2.
4.3.4 
Special Permit. The SPGA may grant a special permit for structures, but not buildings, to exceed the maximum height in feet otherwise allowed by § 4.3, or the percentage of horizontal coverage of structures erected on a building specified above, provided it makes a determination that the structure is compatible with the scale of the neighborhood and does not intrude on the solar access of any adjoining lot.
4.3.5 
Height of Dwellings Near Lot Lines. The height of a one-family or two-family dwelling may not exceed the maximum height from Table 2 or 20 feet plus 4/3 times the smallest distance from the dwelling to a lot line, whichever is less.
[Added 3-30-2016 ATM by Art. 39]
[Added 3-30-2016 ATM by Art. 41]
4.4.1 
Purpose. Lexington seeks to have a socially and economically diverse community, both over the whole of the community and within its neighborhoods. In support of that fundamental social goal, a basic housing goal is to provide housing opportunities supportive of the population diversity we seek. The Town encourages small- and medium-sized housing stock, in the interest of providing diverse housing sizes throughout the Town, § 4.4 limits the massing of buildings, which may impact owners of abutting properties, the streetscape, landscape, and the character of the neighborhood and Town.
4.4.2 
Maximum Allowable Residential Gross Floor Area Tables. The total gross floor area of all buildings on a lot containing a one-family or two-family dwelling may not exceed the amount listed in Table 4.4.2.2 based on lot area, except that:
[Amended 4-24-2023 ATM by Art. 40[1]]
a. 
Buildings for which a building permit application has been submitted before January 1, 2024, may be extended, altered, reconstructed or structurally changed so long as the total gross floor does not exceed that in Table 4.4.2.1 below based on lot area. For the purposes of this § 4.4.2, extension, alteration, reconstruction, and structural change shall not include any construction which involves demolition of more than 50% of the primary building's shell exclusive of demolition of a single-story attached garage. For purposes of calculating the percentages of any demolition under this subsection, all demolition shall be taken into account which commenced, or could have commenced, pursuant to an issued permit within two years prior to the date of any request for any permit to construct, reconstruct, alter, add, extend or otherwise structurally change any structure.
b. 
For the purposes of § 6.12.3.7(a), Table 4.4.2.1 shall be used to determine the gross floor area permitted based on a proof plan.
Table 4.4.2.1
Lot Area
(in square feet)
Maximum Gross Floor Area
(in square feet)
0 to 5,000
0.8 * lot area
5,000 to 7,500
4,000 + 0.55 * (lot area - 5,000)
7,500 to 10,000
5,375 + 0.23 * (lot area - 7,500)
10,000 to 15,000
5,950 + 0.2 * (lot area - 10,000)
15,000 to 30,000
6,950 + 0.16 * (lot area - 15,000)
More than 30,000
9,350 + 0.16 * (lot area - 30,000)
Table 4.4.2.2
Lot Area
(in square feet)
Maximum Gross Floor Area
(in square feet)
0 to 5,000
0.76* Lot Area
5,000 to 7,500
3,800 + 0.42 * (lot area - 5,000)
7,500 to 10,000
4,850 + 0.12 * (lot area - 7,500)
10,000 to 15,000
5,150 + 0.11 * (lot area - 10,000)
15,000 to 30,000
5,700 + 0.1 * (lot area - 15,000)
More than 30,000
7,200 + 0.1 * (lot area - 30,000)
[1]
Editor's Note: This article also stated that the amendments adopted to this section shall take effect on 1-1-2024.
4.4.3 
Special Permit. Pursuant to § 9.4, the SPGA may grant a special permit for a building to exceed the maximum gross floor area otherwise allowed by § 4.4 provided that the SPGA finds that the desired relief may be granted without substantial detriment to the neighborhood and without derogating from the intent and purpose of this bylaw including Town policy documents that define housing goals. In addition to the criteria in § 9.4.2, the SPGA shall find that:
a. 
The project is compatible with the scale of the neighborhood;
b. 
The massing of the project does not adversely impact the solar access of adjoining lots;
c. 
Noise generated by fixed plant equipment, such as, but not limited to, air conditioners, pumps, fans, and furnaces, does not adversely impact adjoining lots; and
d. 
The project design addresses specific neighborhood and Town concerns.
[Added 10-14-2020 STM by Art. 9]
4.5.1 
Purpose. The purposes of this section are to preserve and protect groundwater; to maintain and enhance the public safety, environment, health, and general welfare by establishing minimum requirements; and to establish procedures to control the adverse effects of building basement floors nearer than two feet from the estimated seasonal high groundwater table (ESHGWT), including basement flooding, pumping and discharge of groundwater to neighboring properties, discharging groundwater to the public way, and illicit connections to the Town's sewer and stormwater connections.
4.5.2 
Definitions.
ESTIMATED SEASONAL HIGH GROUNDWATER TABLE (ESHGWT)
The estimated highest level to a zone of saturation in the soil in most years under normal wet season, as determined by a registered professional engineer, a qualified soil scientist or licensed soil evaluator.
4.5.3 
Applicability. The requirement of this § 4.5 shall apply to:
1. 
A new dwelling; or
2. 
Additions to an existing dwelling that increases a building footprint by more than 1,000 square feet.
4.5.4 
Conditions and Requirements. The vertical distance between the finished basement floor of any dwelling shall not be less than two feet above the ESHGWT. Permission for a vertical distance less than two feet above the ESHGWT may be granted if the applicant provides sufficient evidence that a proposed lesser vertical distance will not impact the structure being proposed in a manner contrary to the purposes of this § 4.5, any other structures or constructed facilities, or the functions of the natural groundwater system (such as base flow maintenance) and if all of the following conditions are met:
1. 
Detailed engineering plans, certified by a registered professional engineer showing a foundation and perimeter drain management system and roof stormwater management system(s) that will mitigate and control groundwater discharge and stormwater runoff, are provided;
2. 
The provided foundation and perimeter drain discharge management system and roof stormwater management system plans have been reviewed by the Building, Conservation, Health and Engineering Departments and comments adequately addressed;
3. 
Roof drains and downspouts connect to a stormwater management system designed by a registered professional engineer; and
4. 
The applicant has agreed to pay the fee for consulting services to perform engineering review pursuant to the provisions of MGL c. 44, § 53G.