St. Louis Permit Guide · 2026

ADU / Garage Conversion Permits
in St. Louis, MO

Permit fees for a ADU or garage conversion in St. Louis typically run $775–$3,125. Here's exactly which permits you need, what they cost, and how long MO review takes.

Do you need a permit for a ADU or garage conversion in St. Louis?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in St. Louis. Permit fees for a typical $155,673 ADU or garage conversion run about $775–$3,125 (valuation-based fee plus plan review), and MO plan review typically takes 2–4 weeks.

Permits you'll likely need

Building

full plan review for the dwelling conversion

Zoning / occupancy

ADU ordinance compliance and occupancy approval

Utilities

sewer, water, and electrical service connections

Fire / egress

separate egress and smoke/CO requirements

Usually exempt

Nothing meaningful — every part of a ADU or garage conversion runs through permitting. Budget for it up front.

How to get ADU or garage conversion permits in St. Louis

1
Confirm what triggers a permit
Building, Zoning / occupancy, Utilities, Fire / egress permits apply when the scope includes full plan review for the dwelling conversion. Cosmetic-only scopes may be exempt.
2
Budget the fee
Plan for $775–$3,125 in St. Louis — a valuation-based fee on a typical $155,673 project plus plan review.
3
Apply with complete documents
Submit scope, drawings, and contractor license info to the St. Louis building department. MO plan review typically takes 2–4 weeks.
4
Verify it in the bid
A complete St. Louis bid lists permit fees as a line item. If a bid omits permits — or suggests skipping them — analyze it before signing.

ADU / Garage Conversion permits in St. Louis: FAQ

Do I need a permit for a ADU or garage conversion in St. Louis?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in St. Louis, MO. When in doubt, call the St. Louis building department before work starts — unpermitted work can block a future sale.

How much do ADU or garage conversion permits cost in St. Louis?

Expect roughly $775–$3,125 in St. Louis for a typical $155,673 ADU or garage conversion. Most jurisdictions charge a valuation-based fee of about 0.5–2% of project value, plus plan review and per-trade permit minimums.

How long does a ADU or garage conversion permit take in St. Louis?

Simple trade permits are often issued over the counter in St. Louis. Where plan review applies, MO turnaround typically runs 2–4 weeks. Submit complete drawings the first time — resubmittals are the most common cause of delay.

Who pulls the permit — me or my contractor?

Usually your contractor pulls permits for a ADU or garage conversion, and their license is attached to the work. A contractor who asks you to pull an owner's permit for contractor-performed work is shifting liability onto you — treat that as a red flag when reviewing bids.

More St. Louis permit guides

ADU / Garage Conversion permits in other MO metros

Is your ADU or garage conversion bid fair?

A typical St. Louis ADU or garage conversion runs $155,673. Check your contractor's bid — permits included — against live 2026 local data, free.

St. Louis ADU or garage conversion costs AUDIT MY BID

Data sources: Zonda Cost vs Value 2025; Houzz 2024 Cost Guides; BLS OEWS 2023; FRED regional price indices; Reddit homeowner & contractor reports.

Our Goal

Build Your Confidence

Ready to Score Your Bid?

Upload your contractor's estimate and get instant, data-backed analysis.

Analyze Your Bid

ADU / Garage Conversion Permits in St. Louis, MO