St. Louis Accessory Dwelling Unit Guide
Data version: Q2 2026 · Last updated 2026-05-13
TL;DR. Find out if your St. Louis property qualifies for an accessory dwelling unit. Buildability™ checks the local ADU ordinance, Missouri state law, your zoning district, lot size, setbacks, parking requirements, and owner-occupancy rules in about 20 seconds. Free for your first check.
St. Louis ADU rules at a glance
St. Louis follows local ordinances layered on top of Missouri state ADU law. Typical restrictions cover maximum size (often 800–1,200 sqft), height (16–25 feet), side setbacks (4 feet minimum in most jurisdictions), parking (often waived near transit), and owner-occupancy. Buildability™ reads St. Louis's specific code against your exact lot.
Why this matters
Most St. Louis homeowners don't discover their ADU is infeasible until they've spent $3,000+ on preliminary design. Buildability™ catches the blockers first — easements, overlays, wetland proximity, utility extension costs — so you don't waste soft costs on a dead-end project.
How Buildability™ checks your St. Louis property
Enter any St. Louis address. Buildability™ pulls zoning, lot dimensions, easements, environmental overlays, utility access, and current Missouri state ADU law. Results include your Buildability Score™, setback envelope, maximum ADU size, parking waiver eligibility, and an estimated permit timeline — in about 20 seconds. Free for your first check.
Help us keep this accurate
Buildability™ translates St. Louis's ADU rules in plain language. Rules change and overlays are sometimes missed — if you spot an error on this page, email team@buildability.us with the URL and what's off. We verify with the St. Louis planning department and update within 48 hours of a confirmed correction. St. Louis planning staff: the same email works if you'd like to flag corrections or set up a direct verification channel.
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