Side by side · Tennessee
Compare ADU rules across Tennessee
Flexible on where you build? The same backyard cottage can be routine in one city and impossible next door. This table puts 4 Tennessee cities side by side so you can shortlist the friendly ones before reading a single ordinance, or narrow it to just the cities you are deciding between. Every value is summarized from the city's own code; open a city's page for the full notes, citations, and fine print.
The short answers
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| City | Detached ADU | Attached / internal | Max size | Owner occupancy | Extra parking | Approval |
|---|---|---|---|---|---|---|
| Chattanooga | Allowed | Allowed | 800 sq ft gross (detached and attached alike), measured by exterior dimensions; conditioned sleeping lofts and interior stairwells count toward the cap. Conversions of existing space must also meet the 800 sq ft standard. | Not required | No. There is no minimum on-site parking requirement for ADUs; existing required parking for the principal dwelling must be maintained or replaced on-site if it is lost when the ADU is created. | Permitted use |
| Knoxville | Allowed | Allowed | 40% of the primary dwelling's floor area, maximum 2 bedrooms; detached ADUs in accessory structures are also bound by the accessory-structure coverage chart (750 sq ft on lots of 15,000 sq ft or less, 900 sq ft up to one acre, 1,100 sq ft over one acre, or the primary structure's building coverage if less) | Required | 1 off-street space required for the ADU | Permitted use |
| Memphis | Allowed | Not allowed | Lot under 7,000 sq ft: no ADU. 7,000 sq ft up to 1.5 acres: 700 sq ft or 1/3 of the principal dwelling's gross floor area, whichever is smaller. 1.5 acres or more: up to 50% of the principal dwelling's gross floor area. Never larger than the principal structure's living area; Zoning Administrator may grant an administrative deviation of up to 10% more. | Not required | Only if the ADU displaces existing parking below what the underlying zoning requires; then one additional on-site space, located in the side or rear yard or on the ground floor of the ADU structure. | Permitted use |
| Nashville | Detached ADUs (DADUs) are a 'Permitted with Conditions' (PC) use in AG/AR2a, RS, R, RM, RN1/RN2, RL1-RL3, OR20-OR40, and ORI districts per the 17.08.030 land use table, but only on lots inside the Urban Services District, inside a council-adopted DADU overlay in the General Services District, or where allowed by a Specific Plan; one DADU per lot and only with a single single-family principal structure. Code of Ordinances 17.16.030.G (esp. G.3, G.11); 17.08.030; 17.36.680-17.36.730Full rules for Nashville Ordinance read July 2026 | Attached/internal ADUs exist only as 'accessory apartments': the home must be owner-occupied, the unit is capped at 25 percent of gross floor area, must connect internally (no street-facing entrance added for it), may not have separate utility meters, and the second unit must be occupied by a listed family member, so it cannot be rented to the general public. Ordinance read July 2026 | DADU living space: 700 sq ft on lots under 10,000 sq ft; 850 sq ft on lots 10,000 sq ft or larger; never larger than the principal structure. Accessory apartment (attached): max 25 percent of gross floor area excluding garage and utility space. | Required | 1 space for a detached accessory dwelling unit (no maximum limit in the Urban Zoning Overlay); 1 space for an accessory apartment. | Permitted use |
Summarized from each city's ordinance text, most recently read July 2026. Tap a value marked with an info icon to see exactly what it depends on, straight from the ordinance. Nearly every value has zone, lot-size, or process caveats beyond that; the per-city pages carry the full notes and code citations. Treat this as orientation, not a permit determination.
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Reading the table
- Detached ADU is the make-or-break column for backyard cottages: minimum lot sizes (often 8,000 to 14,500 sq ft) hide behind many of the "Allowed" values, so check your lot before celebrating.
- Attached / internal (basement apartments, additions) is legal almost everywhere and is usually the path of least resistance.
- Approval: "Permitted use" means staff-level sign-off; "Conditional use" means a public hearing, which adds time, cost, and uncertainty.
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