Nashville allows detached accessory dwelling units on qualifying residential lots, and understanding the specific numbers, setbacks, and steps involved can save you significant time and money before breaking ground. An ADU (accessory dwelling unit) is a self-contained secondary housing unit on the same lot as a primary residence, commonly called a granny flat, in-law suite, backyard cottage, or carriage house. Landlords and homeowners build them to generate rental income, house family members, or increase property value in one of Tennessee's fastest-growing cities.
Where ADUs are allowed in Nashville
Nashville's Metro Council designates specific zoning districts where detached ADUs (DADUs) are permitted. Eligible zones generally include single-family and some mixed residential districts, but the lot must meet minimum size thresholds before a DADU application will be accepted. The Metro Codes department can confirm which zoning classification applies to your parcel before you invest in architectural drawings.
Properties in historic overlay districts face an additional review layer. The Metro Historical Commission sets design and materials guidelines to protect neighborhood character. Ordinance No. BL2011-900 expanded DADU eligibility within certain historic overlays, so a parcel that was previously ineligible may now qualify. Always verify current status directly with the Commission, since overlay boundaries and design standards are updated periodically.
Types of ADUs Nashville permits
Nashville primarily regulates detached accessory dwelling units, meaning freestanding structures built separate from the main home. Conversions of existing structures, such as detached garages or carriage houses, are also permitted. The converted structure must meet the same zoning, size, setback, and building code standards as new construction. In practice, older garages often require electrical upgrades, insulation work, and egress modifications to pass inspection, so a licensed contractor's assessment before budgeting is worthwhile.
Attached ADUs and basement conversions may also be permissible depending on lot configuration and zoning, but the DADU category is the most clearly defined pathway in Metro Code. Confirm the unit type you're planning with Metro Codes early, since permit requirements differ by structure type.
Size, height, and setback requirements
Nashville ties DADU size to the primary dwelling rather than setting a single universal square footage cap. Here are the key dimensional rules in effect:
- Floor area: The lesser of 1,000 square feet or 35% of the main home's gross floor area.
- Height: DADUs are generally limited to two stories and must remain visually subordinate to the principal structure.
- Setbacks: A minimum of 5 feet from rear and side property lines. Front-yard placement is prohibited in most zones.
- Lot coverage: The combined footprint of all structures must stay within the zone's maximum impervious surface limits.
For a 1,800-square-foot primary home, the 35% rule caps the DADU at 630 square feet, well below the 1,000-square-foot ceiling. For a 3,200-square-foot home, the 1,000-square-foot cap kicks in first. Running this calculation before hiring a designer prevents wasted plan revisions. Check the Metro Codes website for any amendments before submitting plans.
The permit process, step by step
Getting a DADU permitted in Nashville follows a predictable sequence. Skipping steps or submitting incomplete materials is the most common cause of delays.
Step 1: Confirm zoning eligibility. Verify your lot's zoning classification with Metro Codes before paying for architectural drawings. Zoning examiners can usually answer this quickly.
Step 2: Prepare a site plan and floor plan. Plans must show the proposed structure's dimensions, its location on the lot, distances from all property lines, and its relationship to the primary home. Most homeowners hire a licensed architect or designer at this stage.
Step 3: Obtain a boundary survey if required. Some applications require a current survey to confirm setback compliance. Confirm this requirement with Metro Codes before scheduling a surveyor.
Step 4: Submit through ePermits. Nashville accepts building permit applications online through the ePermits system. Plan review fees are assessed at submission and vary based on project scope and construction value.
Step 5: Historical Commission review (if applicable). If your property sits in a historic overlay, exterior design approval must come before the building permit is issued. Budget additional time for this step.
Step 6: Schedule inspections. Inspections occur at framing, rough-in mechanical/electrical/plumbing, and final completion. A certificate of occupancy is issued once the unit passes final inspection.
A straightforward application in a standard zoning district can move through plan review in several weeks when plans are complete and accurate. Projects requiring Historical Commission approval add time, often several additional weeks depending on the Commission's review calendar. Submitting clean, complete documents upfront is the single most effective way to reduce timeline.
Permit costs and fees
Nashville calculates building permit fees based on the estimated construction value of the project. A DADU built for $150,000 will carry higher permit fees than a simple garage conversion. Beyond the base building permit fee, expect separate charges for plan review, mechanical permits (HVAC), electrical permits, and plumbing permits. Total permit costs for a mid-size DADU typically range from a few hundred to over a thousand dollars depending on scope. Confirm the current fee schedule with Metro Codes or through the ePermits portal before budgeting, since fee schedules are updated periodically.
Owner-occupancy and rental rules
Nashville's ADU regulations have historically included an owner-occupancy requirement: the property owner must reside in either the primary home or the DADU. This rule is intended to prevent single-family lots from converting entirely into absentee-owned rentals and to preserve residential neighborhood character.
Short-term rentals through platforms like Airbnb are governed by separate Metro licensing rules. Nashville distinguishes between owner-occupied short-term rentals and non-owner-occupied rentals, and each carries different licensing requirements and zoning restrictions. If you're planning to rent the DADU short-term, verify that use is permitted in your zone and obtain the appropriate Metro permit before listing the unit.
HOA and deed restriction considerations
Metro zoning approval doesn't override private deed restrictions or homeowners association rules. If your property is subject to an HOA, review the CC&Rs before investing in plans. Some Nashville-area associations prohibit detached accessory structures outright or restrict rentals to non-family members. Deed restrictions recorded with Davidson County can also limit ADU construction regardless of what Metro Code permits. Check with a real estate attorney or title company if you're unsure whether private restrictions apply to your lot.
Utility connections
DADUs can share the primary home's existing utility connections or be set up with separate meters. Separate water, sewer, and electrical meters simplify cost allocation when renting the unit, but adding meters involves coordination with Metro Water Services and Nashville Electric Service and carries upfront costs that vary by connection complexity. Confirm requirements with both providers early in the planning process, before permit submission, to avoid surprises that delay your timeline.
Financial impact: value, taxes, and insurance
A well-built DADU can increase a Nashville property's market value by an estimated 10 to 20 percent, depending on location, finish quality, and local rental demand. That increase also raises your property tax assessment. Contact the Davidson County Assessor of Property to understand how adding a DADU will affect your assessed value and annual tax bill before you finalize your budget.
Rental income from an ADU changes your insurance needs as well. A standard homeowners policy typically won't cover a tenant-occupied unit, leaving you exposed to liability and property damage claims. If you're renting the DADU, review your coverage with a landlord insurance provider. Tennessee landlord insurance policies are structured to cover rental properties and the liability that comes with tenants, and getting the right policy in place before the first tenant moves in is worth the effort.
Frequently asked questions
What is the maximum size for a DADU in Nashville?
Generally, the lesser of 1,000 square feet or 35% of the primary home's gross floor area. A 2,000-square-foot home would cap the DADU at 700 square feet under the 35% rule. Confirm the exact figure for your lot with Metro Codes before finalizing plans.
Can I build a DADU in a historic overlay district?
Yes, in many cases. Ordinance No. BL2011-900 expanded DADU eligibility in certain historic overlays, but the Metro Historical Commission must approve exterior design before the building permit is issued. Review the Commission's guidelines for your specific overlay before proceeding.
Do I have to live on the property if I build an ADU?
Nashville's regulations have historically required owner-occupancy in either the primary home or the ADU. Verify the current requirement with Metro Codes, since ordinances are updated and your specific situation may be subject to recent changes.
How long does the permit process take?
A complete application in a standard zoning district can clear plan review in a few weeks. Projects that require Metro Historical Commission approval typically take longer, sometimes several additional weeks. Submitting accurate, complete plans the first time is the most reliable way to avoid back-and-forth delays.
Will an ADU affect my property taxes?
Yes. Adding a DADU increases your assessed value, which typically raises your annual tax bill. Contact the Davidson County Assessor of Property for a specific estimate based on your project scope and current comparable values in your neighborhood.
Does my homeowners insurance cover a rented ADU?
Standard homeowners policies generally exclude tenant-occupied structures. You'll likely need a landlord or dwelling fire policy to cover a rented DADU properly. Talk to an insurance provider before the unit is occupied to avoid gaps in coverage.
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