St. Louis Permit Guide · 2026

Home Addition Permits
in St. Louis, MO

Permit fees for a home addition in St. Louis typically run $425–$1,700. Here's exactly which permits you need, what they cost, and how long MO review takes.

Do you need a permit for a home addition in St. Louis?

Always — an addition is new structure. Expect full plan review, zoning checks, and multiple inspections in St. Louis. Permit fees for a typical $85,620 home addition run about $425–$1,700 (valuation-based fee plus plan review), and MO plan review typically takes 2–4 weeks.

Permits you'll likely need

Building

full permit with stamped plans and plan review

Zoning

setback, lot-coverage, and height review

Trade permits

electrical, plumbing, and mechanical rough-ins

Site/grading

excavation and drainage in many jurisdictions

Usually exempt

Nothing meaningful — every part of a home addition runs through permitting. Budget for it up front.

How to get home addition permits in St. Louis

1
Confirm what triggers a permit
Building, Zoning, Trade permits, Site/grading permits apply when the scope includes full permit with stamped plans and plan review. Cosmetic-only scopes may be exempt.
2
Budget the fee
Plan for $425–$1,700 in St. Louis — a valuation-based fee on a typical $85,620 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.

Home Addition permits in St. Louis: FAQ

Do I need a permit for a home addition in St. Louis?

Always — an addition is new structure. Expect full plan review, zoning checks, and multiple inspections 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 home addition permits cost in St. Louis?

Expect roughly $425–$1,700 in St. Louis for a typical $85,620 home addition. 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 home addition 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 home addition, 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

Home Addition permits in other MO metros

Is your home addition bid fair?

A typical St. Louis home addition runs $85,620. Check your contractor's bid — permits included — against live 2026 local data, free.

St. Louis home addition 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.

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Home Addition Permits in St. Louis, MO