ADU Pass
Saint Louis
St. Louis city portion
Also in: No County · St. Louis County
ADU Pass helps homeowners in Saint Louis, St. Louis city, Missouri navigate the permit paperwork for building an accessory dwelling unit. This area covers 18 ZIP codes.
Saint Louis City — county ADU rules and overlays
County ADU ordinance
St. Louis City, MO (293,000 residents) is an independent city - separate from St. Louis County since 1876. As an independent city it operates as both city and county for governmental purposes. The St. Louis City Zoning Code governs ADU permissibility citywide; there is no separate county ordinance because the independent city IS the county-level entity.
State-floor overlay: No MO statewide ADU preemption.
County regulatory overlays
Saint Louis City administers flood-hazard, and (where mapped) coastal, wildland-fire, historic, and airport overlays that shape ADU project feasibility. The most consistent overlay across the county is FEMA NFIP floodplain regulation; other overlays apply to specific geographies inside the county.
- FEMA NFIP Special Flood Hazard Areas in Saint Louis City — A new ADU in a mapped SFHA must be elevated to or above the Base Flood Elevation; cost impact on the project is often material.
- Historic districts and individually-listed historic resources
Missouri state — ADU law and programs
State financing programs
Missouri Housing Development Commission (MHDC), the state housing finance agency under the Department of Economic Development, does not operate an ADU-specific loan or grant product as of 2026-04-26. Construction or rehab of an ADU on a primary residence may be financed indirectly through MHDC's First Place Program (first-time-homebuyer mortgage with below-market rate) or Next Step Program (mortgage paired with a forgivable second of up to 4% of loan amount). Both are mortgage-purchase products and require the property to be the borrower's primary residence; an existing ADU on the property is permitted under standard agency guidelines. MHDC also administers Low-Income Housing Tax Credits, the Affordable Housing Assistance Program (AHAP) tax credit, and federal HOME funds — none of which is a homeowner-facing ADU instrument.
Federal (United States) — ADU-relevant rules and programs
Federal ADU law
The United States has no federal statute that directly regulates accessory dwelling unit entitlement or design. Land-use authority over ADUs resides with states and local governments under the traditional police power. Federal engagement is limited to financing (Fannie/Freddie/FHA/VA/USDA), flood insurance (FEMA/NFIP), and discretionary housing programs (HUD), which are recorded in sibling sections of this file.
Federal financing programs
Federal housing-finance agencies and GSEs set nationwide underwriting rules that govern whether an ADU can be financed, appraised, and counted toward mortgage qualifying income. The relevant actors are Fannie Mae, Freddie Mac, FHA (HUD), VA, and USDA Rural Development.
Federal tax credits
There is no ADU-specific federal tax credit. ADUs may incidentally qualify for existing federal energy-efficiency and clean-energy tax credits when the ADU construction includes qualifying measures.
Federal housing programs
HUD administers several discretionary programs that can fund ADU-related activity at the grantee's election, but none is an ADU-specific program.
ZIP Codes
- 63101
- 63102
- 63103
- 63104
- 63106
- 63107
- 63108
- 63109
- 63110
- 63111
- 63112
- 63113
- 63115
- 63116
- 63118
- 63120
- 63139
- 63147
Post Office
- 1140 Olive St, 63101
- 1409 Hamilton Ave, 63112
- 1720 Market St Rm G206, 63155
- 2920 Meramec St, 63118
- 3232 Clifton Ave, 63139
- 3415 N Kingshighway Blvd, 63115
- 4021 Laclede Ave, 63108
- 4039 Bingham Ave, 63116
- 4120 Manchester Ave, 63110
- 4455 Ridgewood Ave, 63116
- 8390 N Broadway, 63147
- 901 N Garrison Ave, 63106