Thinking about turning your garage into a guest suite or building a backyard cottage in Franklin? You are not alone. Many homeowners want flexible space for family or rental income, but the rules can feel confusing. This guide breaks down Franklin’s ADU rules in plain English so you know what you can build, how to permit it, and what to expect with rentals. Let’s dive in.
What counts as an ADU
In Franklin, an accessory dwelling unit can be detached, attached to your home, or built over a garage. It is a secondary home on the same lot as your main house. Above-garage apartments are specifically contemplated in the ordinance. You can confirm these forms in Franklin’s ADU definitions.
Key rules at a glance
Before you sketch plans, get familiar with the essentials in Franklin’s ADU standards:
- One per lot. Each property can have only one ADU.
- Owner occupancy on single-family lots. The lot owner must be a permanent occupant of the premises.
- Size cap. The ADU footprint cannot exceed 50% of your main home’s footprint.
- Height and design. The ADU cannot be taller than the main home and must be visually compatible in materials and style.
- Parking required. You must meet the city’s minimum parking standards.
Design, size, and parking
Franklin focuses on compatibility. Materials, colors, roof style, and window placement should align with your home and face inward when possible to reduce impacts on neighbors. Dormers and exterior stairs may be allowed, but they must respect setbacks and orientation guidelines. For parking counts and dimensions, check the city’s Minimum Parking rules (Section 10.2).
Permits and inspections
ADUs require building permits with electronic plan submittal. You will also need separate trade permits if you add or modify electrical, plumbing, or mechanical systems. Review timelines and fees vary by scope, and residential reviews often move faster. Start with the city’s permit applications and information, then schedule required inspections using the online inspection portal. For fee tables, see the Unified Development Ordinance fee references.
Sewer and septic basics
Utility capacity matters. If your home connects to public sewer and water, your ADU will typically tie into those services under city standards. If your property uses an onsite septic system, you must confirm capacity and get county approvals, which can add time and cost. Review the city’s subdivision and utility coordination standards in the infrastructure regulations.
Historic districts and HOAs
If your property is inside Franklin’s Historic Preservation Overlay, exterior changes will likely need a Certificate of Appropriateness. The Historic Zoning Commission reviews materials, massing, roofs, dormers, and visibility from the street. Learn about process and expectations through the Historic Zoning Commission. Also check any private neighborhood covenants, which can be stricter than the city’s rules; see the ordinance note on private covenants.
Short-term rentals and ADUs
Short-term rental rules are separate from ADU rules. Franklin allows only one short-term rental per lot and often requires owner occupancy. If you have both a main home and an ADU, you may live in one and rent the other short term if you follow the permit process. Where only the main home exists, whole-house nightly rentals are capped at a set number of nights per year. Review the specifics in the city’s short-term rental rules.
Your homeowner checklist
- Verify your zoning and whether you are in a historic overlay.
- Confirm sewer availability or request a septic evaluation if applicable.
- Draft a simple site plan and elevations to check footprint, height, and parking.
- Ask the city about parking counts, review timelines, and required submittals.
- Prepare building and trade permit packages for electronic submittal.
- If in a historic district, apply for a Certificate of Appropriateness.
- Schedule inspections and keep final approvals for your records.
- Review HOA covenants and confirm any lender or insurer documentation needs.
How we help
An ADU can add flexibility and long-term value, but the path works best with a clear plan. Our team pairs local market knowledge with builder-side experience to help you evaluate feasibility, navigate review, and understand resale impacts. If you are weighing multigenerational use versus rental, we can also help you model options and position your property for the future.
If you want to explore an ADU or garage apartment in Franklin, reach out to Susan Gregory. We will help you move forward with confidence.
FAQs
Can you build an apartment over a garage in Franklin?
- Yes. Franklin allows accessory dwellings in detached structures or above a garage, subject to one-per-lot limits, owner occupancy on single-family lots, size, height, design, permits, and parking.
How big can a Franklin ADU be?
- The ADU footprint cannot exceed 50% of your main home’s footprint, and it cannot be taller than the principal dwelling.
What permits do you need for an ADU?
- You need a building permit with electronic plan submittal and trade permits for electrical, plumbing, or mechanical work, plus inspections at key stages.
Do historic districts change the process?
- Yes. Properties in Franklin’s Historic Preservation Overlay typically need a Certificate of Appropriateness for exterior work, which adds a design review step.
Can you Airbnb an ADU in Franklin?
- Possibly. Franklin limits short-term rentals to one per lot and often requires owner occupancy. If you have an ADU, you may live in one unit and rent the other if you follow the city’s STR permit rules.
