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An ordinance amending Chapters 17.04, 17.08, 17.12, 17.16, and 17.36 of the Metropolitan Code, to amend the regulations pertaining to accessory buildings, detached accessory dwelling units and the Detached Accessory Dwelling Unit Overlay District (Proposal No. 2025Z-011TX-001).
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WHEREAS, providing more opportunities for detached accessory dwelling units (DADUs) within the Urban Services District (USD) will provide diverse housing opportunities in this part of the city;
WHEREAS, providing diverse housing opportunities for DADUs within the USD and within residential districts will allow for a gentle increase in allowable housing through context-sensitive infill;
WHEREAS, revising the Metropolitan Zoning Code for Detached Accessory Dwelling Units to allow this use as a base code allowance, rather than an overlay, simplifies, clarifies and consolidates the standards so as to make it easier to administer permits for DADUs and provide parity among property entitlements in the county; and
WHEREAS, many homeowners in the General Services District (GSD), outside of the Urban Services District (USD), desire the option to have a Detached Accessory Dwelling Unit but are unable to under current rules, and since there will no longer be a need for the DADU Overlay to apply to only the Urban Zoning Overlay area of the County, revising the Metropolitan Zoning Code to permit the DADU Overlay to be applied to properties within the General Services District (GSD) outside of the Urban Services District (USD) gives these homeowners a zoning option;
BE IT ENACTED BY THE COUNCIL OF THE METROPOLITAN GOVERNMENT OF NASHVILLE AND DAVIDSON COUNTY:
Section 1. That Section 17.04.060 of the Metropolitan Code is hereby amended by deleting the definition for “Detached accessory dwelling unit” in its entirety and replacing it with the following:
"Detached accessory dwelling unit” means a detached dwelling unit separate from the principal single-family structure on any lot, or within any urban design overlay with development standards for detached accessory dwelling units. The dwelling shall be clearly subordinate in size, height, and purpose to the principal structure, it shall be located on the same lot as the principal structure and is detached from the principal structure. A detached accessory dwelling unit can be an independent structure, it can be a dwelling unit above a garage, or it can be attached to a workshop or other accessory structure on the same lot as the principal structure.
Section 2. That Section 17.08.030 of the Metropolitan Code is amended by changing the zoning district land use table as shown in Exhibit A.
Section 3. That Section 17.12.040E.1.a of the Metropolitan Code is hereby amended by deleting it in its entirety and replacing it with the following:
E. Permitted Setback Obstructions. The following structures or building components may be located within required setbacks. Except for screening walls, fences and hedges, the following features shall not be permitted within a required landscape buffer yard.
1. Accessory buildings.
a. Accessory buildings with a footprint of eight hundred fifty (850) square feet or less and located to the rear of a principal structure shall provide a minimum side setback equal to one-half of that required for the zoning district, but not less than three feet, and a minimum rear setback of at least three feet, except when garage doors or carport openings face or open directly to an alley, in which case the minimum rear setback shall be ten feet. Accessory buildings with a footprint of more than eight hundred fifty (850) square feet shall provide the full setbacks of the zoning district;
Section 4. That Section 17.12.050 of the Metropolitan Code is hereby amended by deleting the section in its entirety and replacing it with the following:
A. On all lots with a size of less than forty thousand square feet, the building coverage of an accessory structure other than a detached accessory dwelling unit located to the rear of the principal dwelling and complying with the district setbacks shall be limited to eight hundred fifty (850) square feet or fifty percent of the building coverage of the principal dwelling, whichever is greater, but in no case shall exceed two-thousand five-hundred (2,500) square feet. For regulations pertaining to detached accessory dwelling units, see section 17.16.030.G.
B. These floor area controls shall not apply to accessory structures proposed on lots where agricultural activities and domestic animals/wildlife are permitted.
Section 5. That Section 17.16.030 of the Metropolitan Code is amended by deleting Subsection G in its entirety and replacing it with the following:
G. Detached Accessory Dwelling Unit. A detached self-sufficient dwelling unit shall be allowed accessory to a principal structure subject to the following standards:
1. Applicability.
a. While the following conditions listed below apply to a detached accessory dwelling unit, they do not counteract or override the applicable life safety standards found in the code editions adopted by the Metropolitan Government of Nashville.
b. No other accessory structure shall exceed two hundred square feet when there is a detached accessory dwelling unit on the lot.
2. Lot Area. The lot area on which the detached accessory dwelling unit is to be placed shall comply with Table 17.12.020A.
3. Ownership.
a. No more than one detached accessory dwelling unit shall be permitted on a single lot in conjunction with the principal structure.
b. The detached accessory dwelling unit cannot be divided from the property ownership of the principal dwelling.
c. Only one detached accessory dwelling unit shall be permitted and only when one single-family principal structure is present. When two principal structures are present, then no detached accessory dwelling unit is permitted.
d. The detached accessory dwelling unit shall be owned by the same person, or entity, as the principal structure and one of the two dwellings shall be owner-occupied.
4. Setbacks. The setbacks for a detached accessory dwelling unit shall meet the setbacks found in Section 17.12.040.E. for accessory buildings.
5. Site Requirements. A detached accessory dwelling unit may only be located behind the principal structure in the rear buildable area of the lot.
6. Driveway Access.
a. On lots with no alley access, the lot shall have no more than one curb-cut from any public street for driveway access to the principal structure as well as the detached accessory dwelling unit.
b. On lots with alley access, any additional access shall be from the alley and no new curb cuts shall be provided from public streets.
c. Parking accessed from any public street shall be limited to one driveway for the lot with a maximum width of twelve feet.
7. Bulk and Massing.
a. The footprint living space of a detached accessory dwelling unit shall not exceed eight hundred fifty (850) square feet for lots less than ten thousand square feet, or one thousand two hundred (1,200) square feet for lots ten thousand square feet or greater and shall not exceed the size of the principal structure.
b. The detached accessory dwelling unit shall maintain a proportional mass, size, and height to ensure it is not taller and/or larger than the principal structure on the lot. The detached accessory dwelling unit height shall not exceed the height of the principal structure as measured to the eave line, with a maximum eave height of ten feet for single-story and seventeen feet for two-story detached accessory dwelling units as measured from average finished grade.
c. The roof ridge line of the detached accessory dwelling unit must be less than the primary structure and shall not exceed twenty-seven feet in height as measured from average finished grade.
8. Design Standards.
a. The detached accessory dwelling unit shall be of similar style, design and material color as used for the principal structure and shall use similar architectural characteristics, including roof form and pitch, to the existing principal structure.
b. The detached accessory dwelling unit may have dormers that relate to the style and proportion of windows on the detached accessory dwelling unit and shall be subordinate to the roofslope by covering no more than fifty percent of the roof.
c. Detached accessory dwelling units may have dormers that are setback a minimum of two feet from the exterior wall.
9. Historic Properties.
a. Metro Historic Zoning Commission Action. Any existing or proposed detached accessory dwelling unit in a historic overlay district shall comply with the adopted regulations and guidelines of the applicable historic overlay.
b. Detached accessory dwelling units with a second story dwelling unit shall enclose the stairs interior to the structure and properly fire rate them per the applicable life safety standards found in the code editions adopted by the Metropolitan Government of Nashville.
10. Restrictive Covenant. Prior to the issuance of a permit, an instrument shall be prepared and recorded with the register's office covenanting that the detached accessory dwelling unit is being established accessory to a principal structure and may only be used under the conditions listed in 17.16.030.G.
11. Location. Detached accessory dwelling units shall only be permitted within the Urban Services District, within a Detached Accessory Dwelling Unit overlay district within the General Services District outside of the Urban Services District, or as otherwise permitted through a Specific Plan.
12. Short Term Rental Property (STRP). Upon enactment of this section, one STRP - owner-occupied is permitted as an accessory use to a principal structure on any single-family-zoned, Residential Neighborhood-zoned, or Residential Limited-zoned lot where a new detached accessory dwelling unit is built, or on any single-family-zoned, Residential Neighborhood-zoned, or Residential Limited-zoned lot where a new detached accessory dwelling unit is established via conversion of an existing accessory structure, short term rental property-owner occupied, is not a permitted use in the accessory dwelling unit..
13. Utilities. The detached accessory dwelling unit may be served by separate utility meter(s).
Section 6. That Section 17.36.680 (Purpose and intent.) of the Metropolitan Code is deleted in its entirety and replaced with the following language:
The Detached Accessory Dwelling Unit (DADU) overlay district provides additional housing options in the General Services District (GSD), outside of the Urban Service District (USD). Any DADU Overlays previously adopted that are located outside of the GSD may remain in effect until the Metropolitan Council adopts an ordinance canceling all or part of such DADU overlay district.
Section 7. That Section 17.36.690 (Overlay designation.) of the Metropolitan Code is deleted in its entirety and replaced with the following language:
A DADU overlay district shall only be created within the GSD, outside of the USD, according to the procedures of Chapter 17.40, Article III and depicted as a geographical area on the official zoning map. Any DADU Overlay previously adopted outside of the GSD may remain in effect until the Metropolitan Council adopts an ordinance canceling all or part of such DADU overlay district.
Section 8. That Section 17.36.710 (Permitted Land uses) of the Metropolitan Code is deleted in its entirety and replaced with the following language:
The range of land uses permitted within a DADU overlay district shall be those permitted by the underlying zoning district(s) as established by the zoning district land use table of Section 17.08.030 and detached accessory dwelling unit. On any lot where a new detached accessory dwelling unit is built, or on any lot where a new detached accessory dwelling unit is established via conversion of an existing accessory structure, short term rental property-owner occupied, is not a permitted use in the accessory dwelling unit.
Section 9. That Section 17.36.730.A.1 (Detached Accessory Dwelling Unit Overlay District) of the Metropolitan Code is deleted in its entirety and replaced with the following language:
A. Application of a DADU overlay.
1. A DADU overlay may be applied to properties zoned AR2a, AG, R/R-A, RS/RS-A or properties where a DADU is a legally permitted use prior to the establishment of the overlay.
Section 10. The Metropolitan Clerk is directed to publish a notice announcing such change in a newspaper of general circulation within five days following final passage.
Section 11. This Ordinance shall take effect upon publication of above said notice announcing such change in a newspaper of general circulation, the welfare of The Metropolitan Government of Nashville and Davidson County requiring it.
Agenda Analysis
Analysis
This ordinance, as substituted, amends Title 17 of the Metropolitan Code of Laws to change the regulations for detached accessory dwelling units (DADU), increase the coverage allowance for accessory structures, and amend the existing DADU overlay provisions. The ordinance proposes to make multiple changes throughout Title 17 to permit DADUs with conditions within the RS zoning districts throughout the Urban Services District (USD). Currently, only RS zoning districts within a DADU Overlay are permitted to have DADUs. Additionally, the ordinance proposes to remove the requirement that lots must be 15,000 square feet in size, abut an improved alley, or be within a historic overlay or urban design overlay that permits DADUs. The ordinance also proposes to increase the permitted living space size of DADUs to 850 square feet on lots smaller than 10,000 square feet and 1,200 square feet on lots larger than 10,000 square feet. Currently, the living space of DADUs are restricted to 700 square feet on all lots. Any DADU will still have to be subordinate in size and scale to the principal structure on the property, and the height restrictions remain unchanged. As substituted, a DADU’s maximum eave height and roof ridge line shall be measured from the average finished grade.
The ordinance also proposes to increase the allowed lot coverage of accessory structures to 850 square feet or 50 percent of the building coverage of the main house (whichever is greater), with a maximum of 2,500 square feet of building coverage. Currently, accessory structures are limited to 750 square feet or 50 percent of the building coverage of the main house (whichever is greater), with a maximum of 2,500 square feet of building coverage. This increase in building coverage also extends to the reduced setback provision for accessory structures, permitting accessory structures with a building coverage of 850 square feet to only provide side setbacks equal to half that required by the zoning district, but not less than 3 feet. Minimum rear setbacks can be 3 feet except when garage doors or carport openings face an alley directly-in that case, the rear setback must be 10 feet. If the accessory building has a building coverage more than 850 square feet, then it must provide the full setbacks of the zoning district. Currently, the reduction in setbacks is limited to accessory structures with a building coverage of 750 square feet or smaller.
Finally, the ordinance proposes to augment the existing DADU overlay to permit and/or regulate DADUs on AR2a, AG, R, and RS zoned lots within the General Services District (GSD), outside the USD, while maintaining the existing regulations of the DADU overlay provisions. Currently, the DADU overlay can only be applied to R and RS lots within the urban zoning overlay (UZO) or the Highland Heights Study Area. Currently within the GSD, DADUs can only be constructed on lots zoned R or OR that meet the size and alley requirement within the existing DADU definition or be located within a historic zoning overlay or urban design overlay that permit them. Existing DADU overlays within the UZO and Highland Heights Study area will remain until the Metropolitan Council passes a rezoning ordinance removing the overlay.
As substituted, owner-occupied short term rentals would not be allowed on any single-family-zoned, Residential Neighborhood-zoned, or Residential Limited-zoned lot where a new DADU is built, or on any single-family-zoned, Residential Neighborhood-zoned, or Residential Limited-zoned lot where a new DADU is converted from an existing accessory structure.
This item was approved with a substitute by the Planning Commission (7-0-1) at their October 23, 2025 meeting.