Infill development—Applicability and requirements.
Metropolitan Code of Nashville and Davidson County § 15.64.131
in effect15.64.131 - Infill development—Applicability and requirements.
A. No project shall add impervious area without meeting the requirements of this section, unless otherwise specifically exempt from regulation pursuant to this section.
B. There shall be three tiers of infill development for projects that are subject to infill regulation by this section:
1. Tier I - Projects creating between eight hundred and two thousand five hundred square feet of net additional IA and with the total lot IA exceeding 30.0% must treat, by means of capture of the first inch of rainfall runoff, an IA equal to the net increase of IA.
2. Tier II - Projects creating between two thousand five hundred and eight thousand square feet of net additional IA, without regard to total lot IA percent must treat, by means of capture of the first inch of rainfall runoff, an IA equal to the net increase of IA.
3. Tier III - Projects creating between eight thousand and fifteen thousand square feet of net added IA, without regard to total lot IA percent, must treat, by means of capture of the first inch of rainfall runoff an IA equal to the net increase of IA. Additionally, the project design must insure there is not an increase in the 10-year storm peak flow from the site, and be certified by a professional engineer.
C. Construction projects that meet the definition of regulated residential infill shall include provisions for the management of the first inch of rainfall runoff from an impervious area equal to the net added impervious area; and shall not be exempt from the provisions of Section 15.64.120 concerning prohibition of increase in the degree of flooding.
D. Prior to the net addition of at least eight hundred square feet of impervious area or issuance of a building permit, a sufficient development plan prepared and stamped by a licensed land surveyor or professional engineer and supporting information required by the latest version of the regulated residential infill guidance document shall be submitted to and approved by the metropolitan department of water and sewerage services.
E. The net added impervious area shall be calculated by subtracting the IA present in the aerial photography data obtained by metro in March 2014 from the proposed post-development IA and maintaining the original property boundary as the regulated project boundary, regardless of subdivision, re-plat, horizontal property regime, or any other modification of property boundaries by deed or plat.
F. The owner/developer of a project meeting the definition of regulated residential infill shall endeavor to treat the first inch of rainfall runoff from net added impervious area using methods from the regulated residential infill guidance document. If this treatment proves impractical, analysis of the downstream management system to identify adequate drainage per the regulated residential infill guidance document or improving downstream drainage to mitigate a known flooding problem with assistance from a professional engineer may be considered for all or part of the one inch treatment requirement.
G. The metropolitan department of water and sewerage services shall have the authority to offer additional runoff volume reduction measures and incentives. Refer to the latest version of the regulated residential infill guidance document for details.
H. Notwithstanding other provisions of this section to the contrary, excluded from infill regulation are projects that:
1. Add less than eight hundred square feet of net new IA,
2. Add more than fifteen thousand square feet of net new IA,
3. Are on lots larger than forty thousand square feet, or
4. Are on lots with a grading permit previously filed with the metropolitan department of water and sewerage services, as long as the post-construction IA conforms to the original grading plan.
I. Projects on lots larger than forty thousand square feet may seek infill classification on a case-by-case basis.
(Ord. BL2025-897 § 4, 2025; Ord. BL2014-910 § 3, 2014)
Source: Metropolitan Government of Nashville and Davidson County, Metropolitan Code and Charter (Municode Library, library.municode.com)URL: https://library.municode.com/tn/metro_government_of_nashville_and_davidson_county/codes/code_of_ordinances?nodeId=CD_TIT15WASEOTPUSE_DIVIGERE_CH15.64STMA_15.64.131INDEPPREFetched: 10/28/2026