If you’ve ever wanted to build an extra apartment in your basement or above your garage, you’re not alone. Louisville has some specific rules + regulations when it comes to putting up an Accessory Dwelling Unit, aka ADU. So here’s what you need to know before you a-d-d an A-D-U.
What is an ADU?
Any smaller, secondary residential unit located on the same lot as a main residence qualifies as an ADU. They can be attached to the main dwelling, like a “mother-in-law” suite or a garden apartment, or detached, like a carriage house or a renovated garage. Either way, ADUs have to follow some rules:
- ADUs can’t exceed the height of the main dwelling.
- The maximum square footage is 800 sqft or 30% of the main dwelling, whichever is greater.
- ADUs cannot be used as short term rentals — no AirBnB or VRBOs.
- You can rent out your ADU, but the owner of the property must reside in the main dwelling.
Bonus: If you’re looking to build an ADU to rent out, there may be funding available through the Louisville Affordable Housing Trust Fund.

Studio MAYO is a pre-approved plan for a customizable ADU that can include up to two full bedrooms and a covered porch.
Photo via Louisville Metro.
Let’s build it
You’ll need to follow these steps if you want to built an ADU on your property:
- Check how your property is zoned. ADUs are allowed in most residential zoning districts.
- Contact an architect to discuss a plan — the city offers three free pre-approved plans to get you started.
- Submit your plan and application, even if you’re using a pre-approved plan.