ADU Pass
Franklin
Williamson County portion
Also in: No County
ADU Pass helps homeowners in Franklin, Williamson County, Tennessee navigate the permit paperwork for building an accessory dwelling unit. This area covers 3 ZIP codes.
Map
ADU details
ADU legality: yes
ADUs are allowed by-right in Franklin's single-family residential districts when the Section 5.2.7.A six-element checklist is satisfied. The 50% footprint cap and owner-occupancy are the binding constraints in practice.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 400 | $850 | $124,000 | $124,850 |
| midpoint | 700 | $1,500 | $217,000 | $218,500 |
| 1000 | 1,000 | $2,300 | $310,000 | $312,300 |
Fee breakdown
Viability (permitted uses)
- Long-term rental: yes 30+day rental of ADU permitted under Section 5.2.7.A so long as the owner-occupancy of one of the two dwellings is maintained.
- Short-term rental: with-restrictions Section 5.2.7.A.2 requires the owner to be a permanent occupant of one of the two dwellings. Owner-occupied STR (e.g., owner lives in principal home and STRs the ADU) is workable; non-owner-occupied STR is not.
- Office rental: no Section 5.2.7 defines accessory dwelling as a self-contained dwelling; commercial-office tenancy is not a permitted use.
- Home office: yes Home occupation permit available under Franklin residential districts.
- Studio / workshop: yes Personal artist/workshop use is a permitted accessory residential use.
- Agriculture: with-restrictions Limited residential gardening/keeping permitted; livestock varies by district.
- Relative support: yes Multigenerational ADU explicitly permitted; Section 5.2.7.A's owner-occupancy condition aligns with this use.
Incentives
- TN Tax Relief / Tax Freeze for Elderly Homeowners (Williamson County participates) — Income-qualified seniors may freeze property tax base; ADU added to a frozen-base property does not unfreeze the underlying principal-residence freeze.
Utilities
- Water: City of Franklin Water Management Department (Harpeth River source) · 21d connect · $4,200
- Sewer: City of Franklin Water Reclamation Facility · 28d connect · $5,400
- Electric: Middle Tennessee Electric Membership Corporation (MTEMC) - TVA wholesale · 21d connect · $1,800
- Gas: Atmos Energy · 21d connect · $1,500
Property values & taxes
Construction timeline
Realistic total: best 9mo · typical 14mo · worst 22mo
Financing
Insurance impact
HOA prevalence & preemption
Franklin's affluent New-Urbanist masterplans (Westhaven, McKay's Mill, Cool Springs East/West, Berry Farms) are HOA-governed. TN has no statute voiding HOA ADU bans. Westhaven's pattern book DOES contemplate accessory dwellings consistent with traditional-neighborhood-development form; other HOAs vary - read the declaration.
Regulatory overlays (3)
- historic-district — Franklin Historic Preservation Overlay (downtown core, NRHP-listed) plus surrounding NRHP residential districts; multiple Civil War battlefield/preservation overlays (Carter House / Carnton / Battle of Franklin Trust) · +35d · +12% cost
Section 5.2.7.A.4 design-standards rule (materials/color/roof matching principal structure) is tightly enforced inside the overlay; Historic Zoning Commission Certificate of Appropriateness required. (map) - flood-zone — Harpeth River SFHA Zone AE through downtown / River Park; tributary AE on Spencer Creek; FEMA Map 47187C · +14d · +7% cost
Lowest-finished-floor elevation requirements apply along the Harpeth River and tributaries. (map) - other — Battle of Franklin (1864) battlefield protection - several blocks of central Franklin sit on NRHP-eligible battle ground · +7d · +3% cost
Subsurface archaeology may be triggered for excavation within the battlefield boundary. (map)
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
Legal history (timeline)
Current ordinance: City of Franklin Zoning Ordinance, adopted 2025-12-01, last amended 2026-01-13
- 2013-01-01 — Williamson County Zoning Ordinance effective date (city-ordinance)
Williamson County's countywide zoning ordinance (adopted May 14, 2012) becomes operative.
Effect: Establishes the unincorporated baseline; does not create an ADU regime. - 2026-01-13 — City of Franklin Zoning Ordinance, Ord. 2025-25 effective date (city-ordinance)
Comprehensive zoning ordinance update adopted by the Franklin Board of Mayor and Aldermen in late 2025.
Effect: Replaced the 2023 ordinance edition; Section 5.2.7.A Accessory Dwellings carries forward the 50% footprint cap and owner-occupancy condition.
Known issues (1)
- ordinance-transition (since 2026-01) — Older online references may cite Section 5.6 or other prior numbering; staff have transitioned to the 2025-25 numbering. Confirm citation with current ordinance text. (source)
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.
ZIP Codes
- 37064
- 37067
- 37069
Post Office
- 810 Oak Meadow Dr, 37064