ADU Pass
Saint Louis
No County portion
Also in: St. Louis city · St. Louis County
ADU Pass helps homeowners in Saint Louis, No County, Missouri navigate the permit paperwork for building an accessory dwelling unit. This area covers 12 ZIP codes.
Map
ADU details
ADU legality: unclear
Missouri leaves ADU regulation to local municipalities under home-rule or Dillon-rule authority. Saint Louis permits ADUs subject to local conditions per its zoning ordinance.
Cost scenarios
| Scenario | Sq ft | Permit | Build | Total |
|---|---|---|---|---|
| minimum | 150 | $1,700 | $35,250 | $36,950 |
| 600 | 600 | $1,700 | $141,000 | $142,700 |
| midpoint | 525 | $1,700 | $123,375 | $125,075 |
| maximum | 900 | $1,700 | $211,500 | $213,200 |
Fee breakdown
Viability (permitted uses)
- Long-term rental: yes Long-term rental of ADU generally permitted; landlord-tenant law and any city rental-registration ordinance apply.
- Short-term rental: with-restrictions STR rules vary by city. Saint Louis regulates STRs separately from ADU permitting; check local STR ordinance and HOA covenants.
- Office rental: with-restrictions Detached office rental requires home occupation permit or rezoning.
- Home office: yes Home occupation permitted with restrictions on signage and customer traffic.
- Studio / workshop: yes Personal artist studio is a permitted accessory use.
- Agriculture: with-restrictions Limited urban agriculture permitted in residential zones; livestock varies by district.
- Relative support: yes Family-occupancy ADU explicitly permitted in single-family zones.
Utilities
- Water: Saint Louis Water Utility · 30d connect · $4,500
- Sewer: Saint Louis Sewer / Wastewater · 30d connect · $5,500
- Electric: Saint Louis Electric Utility · 21d connect · $1,800
- Gas: Saint Louis Gas Utility · 30d connect · $1,500
Property values & taxes
Construction timeline
Realistic total: best 7mo · typical 10mo · worst 16mo
Financing
State ADU loans:
Insurance impact
HOA prevalence & preemption
Missouri has no HOA-ADU preemption; HOA covenants restricting ADUs are enforceable.
Regulatory overlays (1)
- historic-district
Saint Louis historic districts trigger Architectural Review Board / Historic Preservation Commission review for ADUs in historic boundaries.
Technical envelope (climate & building code)
Climate & energy code
Building code
Amendments:
- Amendment
- Amendment
Legal history (timeline)
Current ordinance: City of Saint Louis Municipal Code — Accessory Dwelling Units, adopted 2020-01-01, last amended 2024-04-01
- 2024-01-01 — City of Saint Louis ADU code refresh (city-ordinance)
Conforming local-code amendments aligning with current Missouri accessory-dwelling framework.
Effect: Codified permissive ADU standards consistent with state law and local zoning.
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
- 63145
- 63151
- 63156
- 63157
- 63158
- 63163
- 63166
- 63169
- 63177
- 63178
- 63179
- 63188
Post Office
- 10701 Lambert International Blvd, 63145
- 1140 Olive St, 63101
- 1720 Market St Lbby, 63155
- 1720 Market St Rm 3025, 63155
- 2318 Woodson Rd, 63114
- 2700 S Jefferson Ave, 63104
- 3198 S Grand Blvd, 63118
- 375a S County Center Way, 63129
- 4021 Laclede Ave, 63108
- 5636 Telegraph Rd, 63129