Last updated: October 10, 2026 — rows marked "confirm" are ones we couldn't settle from the published code text.
Often — and in unincorporated St. Charles County, always. The county's residential code exempts small detached accessory structures from building permits "other than storm shelters" — so every storm shelter there needs a permit, whatever its size. Elsewhere the answer depends on who governs your address: the City of St. Louis builds under the 2018 International Residential Code; unincorporated St. Louis County under the 2015 codes; and St. Louis County's 88 municipalities either run their own permitting or contract it to the county. Even where a small shelter might slip through an exemption, structural work — cutting a slab, building a reinforced room, anchoring a steel unit — usually brings a permit with it.
Why permits matter for a shelter
A permit means someone checks that the shelter is on a foundation and anchors that match its design, that it's located legally on the lot, and that electrical work is done right. For a building meant to hold up in a tornado, that check is worth having. A permit record also documents the shelter for a future buyer.
Jurisdiction table
| Jurisdiction | Code basis | What we found | Status |
|---|---|---|---|
| St. Charles County (unincorporated) | 2021 St. Charles County Residential Code (§500.150; latest amendment Dec. 2025) | R105.2 exempts "Other than storm shelters, one-story detached accessory structures" up to 200 sq ft — so storm shelters always need a permit | Verified Oct 10, 2026 |
| City of St. Louis | 2018 International Residential Code (Ord. 70795) | Building Division Permit Section handles residential permits; storm-shelter-specific guidance not found | Code verified; shelter guidance: confirm |
| St. Louis County (unincorporated) | 2015 International Building and Residential Codes as amended (Ord. 27,654, effective April 1, 2020) | The amended building code exempts sheds and playhouses up to 120 sq ft; that language doesn't describe storm shelters, and we couldn't read the county's residential-code amendments | Confirm with the county |
| St. Louis County municipalities | Varies — about 50 have their own building codebooks; others adopt the county's (St. Louis REALTORS, 2021) | Some contract permits to St. Louis County (Oakland, for example); others issue their own (Florissant through Public Works). Chesterfield issues zoning approval, then the county issues the building permit | Confirm by city |
| Clarkson Valley | 2024 IBC and IRC, adopted July 7, 2026 (city permit-process page) | Newer code than most of the county | Shelter rules: confirm |
| Jefferson County (unincorporated) | 2015 IRC as amended (Nov. 2023) | Exempts accessory structures of 200 sq ft or less from building permits; whether that covers a storm shelter isn't stated | Confirm with Code Enforcement |
| Franklin, Lincoln and Warren counties | Not verified | — | Confirm |
| Madison, St. Clair and Monroe counties, IL | Not verified | — | Confirm |
"Confirm" means we read what we could and didn't find a clear answer. Every quote we send names, in writing, the permits your address requires, based on the code in force at the time.
What the residential code says about shelters
Model residential codes reference the ICC 500 standard for storm shelters. That sets the standard a shelter must meet if you build one; we're not aware of any code here that requires a home to have one. St. Charles County's exemption language — "other than storm shelters" — shows the county wants every shelter reviewed.
What a permit reviewer usually asks for
- Site plan showing where the shelter goes, especially for detached or outdoor units (setbacks apply).
- Manufacturer's documentation: model, the standard it's tested to, test reports, door labels.
- Foundation and anchoring details: slab thickness and strength, anchor type, spacing and edge distances — the manufacturer's installation instructions usually cover this.
- For built-in or reinforced rooms: construction drawings, often stamped by an engineer.
- Electrical permit if you add lighting or outlets.
Rebuilding after the 2025 tornado?
In the City of St. Louis, Executive Order 90 (August 25, 2025) directs the Building Commissioner and Cultural Resources Office to expedite permits for tornado-damaged property, with one year of flexibility in historic districts and three-year extensions for permits and approvals. A safe room designed into a rebuild goes on the same permit. Our 2025 tornado guide covers the City's recovery orders.
Who pulls the permit?
Our quotes say who applies for each permit. Watch for out-of-state sellers who ship a unit and leave the permit to you. Ask before you buy. Our quote comparison guide lists this as a line.
How to check your own address
- Find your jurisdiction on your county's property records — municipality or unincorporated.
- Call or email the building department with the shelter type, size and location.
- Ask: Is a building permit required? An electrical permit? Are there setbacks for a detached or outdoor shelter? What documents do you need?
- If you're in an HOA, check covenants for outdoor or detached structures.
Related guides
- FEMA P-361 and ICC 500 explained — what the documentation should show
- Installing in an existing garage slab — the anchoring details reviewers ask about
- The complete St. Louis storm shelter guide
Frequently asked questions
Is a permit required for a storm shelter in St. Charles County? In unincorporated areas, yes: the county's residential code excludes storm shelters from the small-structure exemption. Cities in the county, such as O'Fallon and St. Peters, run their own permit offices — check with yours.
Is a permit required for a steel safe room in a St. Louis County garage? Likely, but it depends on your municipality. Check with the city or the county before installation.
Does a permit slow down installation? It adds review time. Simple above-ground installs often move quickly; built-in rooms take longer.
What if a seller says no permit is needed? Ask them to show you the code section. In unincorporated St. Charles County, that answer is wrong.
Sources
- St. Charles County Code §500.150 — 2021 Residential Code, R105.2 — Ord. 25-085 (2025-12-15); accessed 2026-10-10
- City of St. Louis — building codes; permits page — upd. 2025-08-11; accessed 2026-10-10
- St. Louis County — 2015 codes "user friendly" (Ord. 27,654) — approved 2019-12-18, eff. 2020-04-01; accessed 2026-10-10
- Jefferson County Code §500.400 — Ord. 23-0465 (2023-11-16); accessed 2026-10-10
- St. Louis REALTORS — Inconsistent Regulations white paper — Oct 2021; accessed 2026-10-10
- City of Florissant — Permits — current; accessed 2026-10-10
- City of Oakland — Forms and permits — current; accessed 2026-10-10
- Clarkson Valley permit processes — current; accessed 2026-10-10
- Chesterfield building permits — current; accessed 2026-10-10
- St. Charles County cities 2021 IRC adoptions — current; accessed 2026-10-10
- FEMA — Residential Tornado Safe Room Doors fact sheet — Nov/Dec 2024; accessed 2026-10-10
- FEMA — Safe rooms — current; accessed 2026-10-10
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