ADU Regulations in Missouri (MO)
Missouri is rated Moderate for ADU construction with an ADU-friendliness score of 30/100 (Restrictive). Missouri does not have a statewide ADU law — regulations are set entirely by local jurisdictions. Owner must reside on the property. Additional parking may be required. Missouri has no statewide ADU law. Kansas City, MO adopted a permissive ADU ordinance in 2022, allowing ADUs by right on most residential lots. St. Louis has more limited ADU provisions. Other cities vary.
Full ADU Regulations Summary for Missouri
| ADUs Allowed | Yes |
| Statewide ADU Law | No |
| Maximum ADU Size | Set locally |
| Owner Occupancy Required | Yes |
| Parking Required | Yes |
| Minimum Setback | Set locally |
| Permitting Timeline | Varies by jurisdiction |
| Impact Fees | Varies by jurisdiction |
| Long-Term Rental Allowed | Yes |
| Short-Term Rental (Airbnb) Allowed | Yes |
| Ease of Building | Moderate |
ADU Regulations by City in Missouri
ADU rules can vary by city even within the same state. Without a statewide ADU law, Missouri cities set their own rules, and policies can differ significantly. Below are ADU details for 3 cities in Missouri.
Kansas City
ADUs allowed by right on single-family lots since 2022. No owner-occupancy requirement. Maximum 900 sq ft. One of the most permissive ADU ordinances in the Midwest.
St. Louis
ADUs permitted in some zones. St. Louis City allows ADUs with zoning approval. County regulations vary.
Columbia
ADUs allowed in certain residential zones with conditional use permit.
How Missouri Compares to Other States
Below is a comparison of Missouri with five states that have similar ADU-friendliness scores. This comparison helps illustrate where Missouri stands nationally.
| State | Score | Statewide Law | Parking Req? | Owner Occ? | Ease |
|---|---|---|---|---|---|
| Missouri (MO) | 30 | No | Yes | Yes | Moderate |
| Alabama (AL) | 30 | No | Yes | Yes | Difficult |
| Arkansas (AR) | 30 | No | Yes | Yes | Difficult |
| Delaware (DE) | 30 | No | Yes | Yes | Moderate |
| Georgia (GA) | 30 | No | Yes | Yes | Moderate |
| Idaho (ID) | 30 | No | Yes | Yes | Moderate |
Frequently Asked Questions About ADUs in Missouri
Can I build an ADU in Missouri?
Yes, ADUs are allowed in Missouri. However, Missouri does not have a statewide ADU law, so the specific rules depend on your city or county's zoning code. Some cities are more permissive than others. The ease of building is rated "Moderate" with a friendliness score of 30/100.
Do I need to live on the property to have an ADU in Missouri?
Yes, Missouri generally requires owner occupancy — the property owner must live either in the main house or the ADU. This means you cannot rent out both units simultaneously. Note: individual cities may have their own owner-occupancy rules, so check your local zoning.
How big can an ADU be in Missouri?
Missouri does not set a statewide maximum ADU size — this is determined by your local jurisdiction. Common local limits range from 600 to 1,200 square feet. Check your city's zoning code for the specific maximum.
Do I need extra parking for an ADU in Missouri?
Missouri may require additional off-street parking for ADUs. The specific number of spaces depends on your local jurisdiction. This can be a significant barrier if your lot has limited space for parking.
Can I rent out my ADU in Missouri?
Yes, long-term rentals of ADUs are allowed in Missouri. Short-term rentals (like Airbnb) are also generally permitted, though your city may have separate short-term rental regulations.
How long does it take to get an ADU permit in Missouri?
The permitting timeline in Missouri is: Varies by jurisdiction. Without a statewide mandate, permitting timelines depend entirely on your local jurisdiction's review process. Actual timelines can be affected by plan review backlogs, inspection scheduling, and the complexity of your project. Pre-approved ADU plans, where available, can significantly speed up the process.
Check ADU Rules for Your City
Use our ADU regulations lookup tool to find the specific rules for your city in Missouri, or browse all 50 states to compare ADU regulations across the country. Remember that local rules may be more specific than state-level regulations.