PERCH · ADU LEGALITY INDEX · UPDATED 2026-07-17

ADU Laws in Missouri — 2026 Guide

Statute summary, size caps, owner-occupancy rules, permit timelines, and a 4-question eligibility quiz. Part of the PERCH ADU Legality Index — one page per state, verified against real statute references and updated as laws change.

4-question eligibility quiz

Q1 · State
What state are you building in?
Q2 · Lot size
How big is the lot?
Q3 · Zoning
What zoning district is the lot in?
Q4 · Property type
Which best describes the build?
Result

Key rules · Missouri

Statute summaryMissouri HB 1737 (2024) preempted municipal ADU bans in cities over 75,000. Kansas City permits ADUs by-right; St. Louis expanding.
ADU allowedConditional — depends on jurisdiction
Size cap (sqft)800
Owner-occupancy requiredNo
Permit timeline (days)25-80
Statute citationHB 1737 (2024)
Last verified2026-07-17

Frequently Asked Questions

Are ADUs legal in Missouri?
Yes, conditionally — Missouri permits ADUs on qualifying lots per HB 1737 (2024). Larger cities generally lead adoption; smaller municipalities may apply variance or conditional-use permit requirements.
What are the size limits on an ADU in Missouri?
Missouri permits ADUs up to approximately 800 square feet per HB 1737 (2024). Individual municipalities may set lower caps; verify with your city or county planning department before ordering.
Do I need a permit for an ADU in Missouri?
Yes — every ADU in Missouri requires a building permit issued by the city or county. The permit process typically runs 25-80 days depending on jurisdiction, complexity, and whether discretionary review is triggered.
Can I rent out my ADU in Missouri?
Long-term rental is generally permitted in Missouri where the ADU itself is legal. Short-term rental (under 30 days) is subject to municipal registration and may require additional permits; check with your local planning department.
Does Missouri require owner-occupancy on the primary residence when I have an ADU?
No — Missouri does not require owner-occupancy under state statute per HB 1737 (2024). Local ordinances may still add owner-occupancy requirements in specific cities.
What zoning districts allow ADUs in Missouri?
Most Missouri municipalities permit ADUs in single-family residential zones (R-1, R-2 equivalent). Missouri HB 1737 (2024) preempted municipal ADU bans in cities over 75,000. Kansas City permits ADUs by-right; St. Louis expanding. Consult your city zoning code for the specific district table.
How long does an ADU permit take in Missouri?
Typical ADU permit timelines in Missouri run 25-80 days from application to approval. Fast-permitting counties can move in under 30 days; metro-core jurisdictions with discretionary review can extend to 150+ days.
Are there setback requirements for an ADU in Missouri?
Yes — most Missouri municipalities apply the same setback requirements to ADUs that apply to the primary structure (typically 5-10 feet rear and side, 15-25 feet front). Some cities apply reduced setbacks specifically for detached ADUs. Verify with your city zoning code.
Can I finance an ADU purchase in Missouri?
Yes — several financing pathways cover ADU purchases in Missouri: Fannie Mae HomeStyle Renovation, FHA 203(k), construction-to-perm loans, HELOC on the primary residence, and cash. Check with modular-friendly lenders like 21st Mortgage, Cascade Financial, and Triad Financial for the Missouri-specific product.
What's the difference between an ADU and a JADU in Missouri?
The JADU (Junior ADU) category originated in California and is not a distinct legal category in Missouri. Most Missouri municipalities regulate internal conversions and detached units under a single ADU/accessory apartment definition.

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