ADU (Accessory Dwelling Unit) Permit in St. Louis (2026)

A ADU (Accessory Dwelling Unit) permit is required in St. Louis, MO. The St. Louis Building Division (Community Development Administration) handles permit applications for St. Louis. Below you will find the current thresholds, fees, and process for obtaining a adu (accessory dwelling unit) permit in St. Louis.

When Is a Permit Required?

When a ADU (Accessory Dwelling Unit) Permit Is Required in St. Louis: All ADU construction

Permit Fees

ADU (Accessory Dwelling Unit) Permit Fees in St. Louis: $1,000-$4,500. Estimated timeline: 4-8 weeks.

Estimated timeline: 4-8 weeks

How to Get a ADU (Accessory Dwelling Unit) Permit in St. Louis

1. 1

   Verify whether your project meets the permit threshold in St. Louis: All ADU construction.

2. 2

   Prepare your permit application and plans. Contact the St. Louis Building Division (Community Development Administration) at https://stlouis-mo.gov/government/departments/building for required documentation.

3. 3

   Submit your application online at https://stlouis-mo.gov/government/departments/building/permits.cfm or in person at the St. Louis Building Division (Community Development Administration).

4. 4

   Pay the permit fee: $1,000-$4,500.

5. 5

   Wait for plan check approval. Estimated timeline: 4-8 weeks.

6. 6

   Schedule required inspections through https://stlouis-mo.gov/government/departments/building/inspections.cfm. All inspections must pass before project is finalized.

7. 7

   Important: St. Louis Building Division permit. Independent city status means one-stop permitting — no county approval needed. Historic district review required for ADU in designated districts.

St. Louis Building Division (Community Development Administration)

Frequently Asked Questions