ADU laws in Tennessee

In plain words

Tennessee has no statewide ADU law. An ADU, or accessory dwelling unit, is a small second home on the same lot as a house. It might be a backyard cottage, a garage apartment, or a suite inside the house. Each county and city decides through its zoning. Zoning is the local rulebook for what can be built where. So the answer depends on exactly where your property is. Some cities allow ADUs widely. Chattanooga allows one ADU up to 800 square feet wherever single-family homes are allowed. The owner does not have to live there. Nashville allows backyard ADUs only in certain areas. There, the owner must live in the house or the ADU. That rule is called owner occupancy. Nashville also caps size at 700 or 850 square feet, depending on lot size. Rules outside the big cities can be very different. In the country, septic approval is often the biggest hurdle. A septic system treats wastewater on your own land. A 2025 law lets the state grant septic exceptions. They cannot be used on lots that already hold more than one home. In 2026, lawmakers looked at a bill that would have made every town allow ADUs. It would have stopped towns from capping ADUs below 850 square feet or making the owner live on site. That bill died in committee, so local control stays in place. Before you plan, check your city or county code and your HOA rules. You may be able to build only if local rules and your property allow it.

The rules at a glance

What to do next

1. Find out whether your property is inside city limits or in unincorporated county land; this decides which zoning code applies.
2. Look up your zoning district and read the local ADU or accessory-dwelling rules, or call the planning or codes office and ask what is allowed on your lot.
3. If you are on septic, contact the state or county septic permitting office early to learn whether your soil and system can serve a second unit.
4. Read your deed and any HOA covenants; private restrictions can ban a second unit even where zoning allows one.
5. Ask about owner-occupancy rules, size caps, parking and short-term rental limits before you design, since these vary the most across Tennessee.
6. Get zoning and building permits before construction starts.

What your town still decides

No Tennessee statute makes counties or cities allow ADUs. Zoning powers come from Tennessee Code Annotated Title 13, Chapter 7, and each county, city and metropolitan government decides whether ADUs are allowed, where, how big, and whether the owner must live on site. Rules often change at the city line, so whether land is inside a city or in the county matters. Septic approval is often the real limit in rural areas; a 2025 law lets the state grant septic variances over stricter local rules, but not for lots already holding more than one home with accessory buildings. A 2026 law (Public Chapter 1037, HB 2509) created a workforce-housing loan pilot run by the Tennessee Housing Development Agency that counts local flexibility such as 'accessory units' as a plus; its loans go to public-private partnerships, not to individual homeowners. Private deed restrictions and HOA rules can also ban ADUs, and the failed 2026 statewide bill would have left those in place.

Examples of local rules

• Nashville (Metro Nashville-Davidson County): Detached ADUs (DADUs) are allowed only where the zoning lists them: the Urban Services District, DADU overlays in the General Services District, and some overlay or specific-plan areas. One DADU per parcel with one single-family house; both must have the same owner and one must be owner-occupied. Living space is capped at 700 sq ft on lots under 10,000 sq ft and 850 sq ft on larger lots, with a 27-foot ridge height limit. New DADUs in single-family and similar zones cannot be used as short-term rentals. Source
• Knoxville: The 2019 zoning code (Sec. 10.3.B) allows one ADU inside, attached to, or detached from a single-family home on lots of at least 5,000 sq ft, with size tied to lot area (600 to 1,200 sq ft, never over 40% of the house or two bedrooms) and one off-street parking space. Detached units need 5-foot side and 10-foot rear setbacks. In December 2023 the planning commission recommended dropping the owner-occupancy rule citywide and easing setbacks and size limits, and City Council took up the change in February-March 2024. Source
• Chattanooga: Ordinance 13839, in effect since June 14, 2022, makes ADUs a permitted use in zones that allow single-family detached homes. One ADU per property, from 200 to 800 sq ft, with no owner-occupancy requirement; units over 700 sq ft need two exits. Short-term rental use needs a permit, and a property where the owner does not live may need a rezoning first. The city adopted follow-up amendments in 2024. Source
• Memphis and unincorporated Shelby County: The joint Unified Development Code (Sec. 2.7.3) ties ADU rules to lot size. A county guide says new ADUs are not allowed on lots under 10,000 sq ft; on lots from 10,000 sq ft to 1.5 acres an ADU may be the smaller of 700 sq ft or one-third of the house's ground floor, and on larger lots up to half of it. A rewrite of the code was in draft in 2026, so check the current text. Source

What we’re still confirming

• Knoxville amended its ADU rules in 2024; confirm current owner-occupancy, size and distance-from-lot-line rules with the city.
• Sources disagree on the minimum lot size for an ADU in Memphis and Shelby County (10,000 or 7,000 sq ft); confirm with the planning office.

Laws, bills and citations

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.