What Can You Build Without a Permit in Missouri? (2026)
The 30-second answer for Missouri
In Missouri, the projects you can usually build without a building permit are a small detached shed, a short freestanding deck, a fence under the height cap, a low retaining wall, and cosmetic interior work. The exact limits Missouri enforces are in the table below — and your city can be stricter than the state. The catch every homeowner needs to hear: even when no permit is required, the building code, zoning setbacks, and any HOA rules still apply. Permit-exempt means the paperwork is waived, not the rules.
How Missouri sets the rules
Missouri is a home-rule state with NO statewide residential building code; each city and county decides whether to adopt and enforce a code. Kansas City enforces the 2018 IBC and 2018 IRC (effective June 28, 2020); the City of St. Louis enforces the 2018 IBC/IRC family adopted by Ordinance 70794. Many of Missouri’s 114 counties never adopted any code, so building on unincorporated rural land often requires no permit at all.
Permit-exempt limits in Missouri
These are the thresholds we verified for Missouri. Treat each one as the most you can usually do without pulling a permit — a stricter city amendment always wins.
| Project | Missouri permit-exempt limit |
|---|---|
| Detached shed / accessory building | Varies by city. Kansas City follows the IRC baseline: a one-story detached accessory building (shed/playhouse/carport) is exempt from a building permit if its projected roof area does not exceed 200 sq ft. The City of St. Louis deviates sharply, exempting only 'small accessory buildings 50 square feet in area or less.' Zoning setbacks and height limits still apply, and unincorporated county land may have no requirement. |
| Deck | Varies by city. Kansas City follows the IRC baseline: platforms and decks not exceeding 30 inches above grade and not over any basement or story below are exempt. The City of St. Louis has NO deck exemption; it lists porches, decks, and retaining walls as work that requires a permit regardless of size or height. |
| Fence | Varies by city. Kansas City requires no building permit for a fence, but zoning caps height at 4 ft in a front/street-side yard (corner lots) and 6 ft in interior side and rear yards. The City of St. Louis requires a permit for all new fences of any type; only like-for-like replacement of existing fencing in a rear or side yard is exempt. |
| Retaining wall | Varies by city. Kansas City follows the IRC baseline: a retaining wall not over 4 ft is exempt unless it supports a surcharge or impounds flammable liquids. The City of St. Louis deviates hard, exempting only retaining walls 18 inches or less in height; anything taller requires a permit. |
| Patio (on grade) | At-grade paved patios generally are not a building-permit item. The City of St. Louis exempts 'paved areas for residential use on the same lot as the primary structure, without roof, covers or enclosures.' Kansas City follows the IRC (sidewalks/platforms 30 in or less and not over a basement are exempt). A roof, cover, screen enclosure, or attached structure typically triggers a permit; zoning still applies. |
Baseline: 2021 International Residential Code, Section R105.2. See the national project-by-project guide for how each threshold works.
Can you do the work yourself in Missouri?
Yes in both major cities, with limits. In Kansas City, an owner who occupies a single-family dwelling may obtain permits for any work on the premises if they perform the work themselves; hired electrical, plumbing, or mechanical work must use a licensed contractor. In the City of St. Louis a homeowner may get an electrical permit only for an owner-occupied single-family dwelling after passing a code-knowledge test, and not for service changes, rehab, or new construction.
What's different about Missouri
There is no statewide code — location decides everything
Because Missouri is home-rule with no statewide residential code, the same shed can be permit-exempt in one jurisdiction, require a permit in the next city, and require nothing at all on unincorporated county land. Never assume the IRC applies; the IRC's 200 sq ft / 30 in / 4 ft numbers govern only where your city adopted them (as Kansas City did).
The City of St. Louis is far stricter than the IRC baseline
St. Louis City exempts detached accessory buildings only up to 50 sq ft (not 200), retaining walls only up to 18 in (not 4 ft), and requires a permit for ALL decks and porches regardless of size or height. Homeowners who assume the common IRC exemptions apply here will build illegally.
Owner-occupant self-permitting is allowed but conditioned
In both Kansas City and the City of St. Louis, a person who both owns and lives in a single-family home may pull permits and do the work themselves, but hired trade work must go to licensed contractors. St. Louis City additionally makes homeowners pass a code-knowledge test to earn an electrical permit.
"Permit-exempt" does not mean rule-free
I spent 25 years as a firefighter before I built PermitDeck, so let me be blunt about the part that gets people hurt. "No permit" never means "no rules." When a project is exempt in Missouri, three things are still true — and now you are the one responsible for them, because no inspector is coming to check:
- Building code still applies. An exempt deck in Missouri still has to meet the structural rules of IRC R507 — real footings, a proper ledger, and guards. A shed still has to carry your local snow and wind load. The code does not care whether a permit was pulled.
- Zoning and setbacks still apply. Exempt does not mean you can put it anywhere. Setbacks from property lines, easements, lot-coverage caps, and corner-lot sight lines all still bind you — and a neighbor complaint can force you to move it.
- HOA rules are separate. Your HOA architectural review is a private contract, not a government permit. You can be fully permit-exempt with your city and still be forced by your HOA to tear something out.
The big Missouri cities
Permits are pulled locally, so your city's building department has the final word. Here are the two largest, with a link straight to their office.
Kansas City
Official City Planning & Development 'Building Permit Exempt Work' page. Follows the 2018 IRC: detached accessory buildings up to 200 sq ft roof area, decks 30 in or less above grade (not over a basement), retaining walls up to 4 ft (no surcharge), and prefab R-3 pools are exempt. Exempt work must still meet zoning/setback code.
Kansas City building departmentSt. Louis
Official Building Division 'When a Residential Building Permit is Needed' page. Exempts accessory buildings 50 sq ft or less, retaining walls 18 in or less, unroofed paved areas, and above-ground pools under 24 in water depth and under 250 sq ft. Requires a permit for all decks/porches and all new fences.
St. Louis building departmentTurns out you do need a permit? We'll match you with pros who pull it
If your project crosses one of these Missourithresholds, the cleanest path is to hire a licensed pro who pulls the permit in their own name and stands behind the inspection. Tell us the project once and we'll send it to up to three verified local pros. It's free, it's capped at three, and we never sell your information — the opposite of the lead-farm sites.
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What happens if you needed a permit and skipped it
Guessing wrong on the exemption is not a small risk. The common outcomes are a stop-work order, a fine (often double the normal permit fee), and being ordered to open finished work back up for inspection or tear it out. The expensive part usually lands later: unpermitted work routinely kills a home saleat the buyer's inspection, and an insurance claim can be denied if the damage traces back to unpermitted construction. Most jurisdictions do allow a retroactive (after-the-fact) permit — it costs more, but it clears the record.
Full detail: what happens if you build without a permit and how to get a building permit.
Missouri permit-exemption FAQs
Does Missouri have a statewide building permit requirement?
No. Missouri is a home-rule state with no statewide residential building code, so permit rules are set city by city and county by county. Many of Missouri's 114 counties never adopted a code, so building on unincorporated rural land may need no permit at all. Always confirm with your local building department before you start.
Do I need a permit to build a shed in Missouri?
It depends on your city. In Kansas City a detached shed with a roof area of 200 square feet or less needs no building permit, matching the 2018 IRC. In the City of St. Louis the exemption drops to just 50 square feet. Either way, zoning setbacks and height limits still apply, and unincorporated areas may have no rule.
Can I build a deck without a permit in the City of St. Louis?
No. Unlike the IRC baseline that exempts small ground-level decks, the City of St. Louis requires a permit for all decks and porches regardless of size or height. Kansas City is more lenient, exempting platforms and decks 30 inches or less above grade that are not over a basement. Always confirm with your own city building department.
Can a homeowner pull their own building permit in Missouri?
Generally yes, if you both own and occupy a single-family home and do the work yourself. Kansas City and the City of St. Louis both allow this, but hired trade work must use licensed contractors. St. Louis City also requires homeowners to pass a code-knowledge test for an electrical permit and bars owner permits on new construction.
Sources we verified against
Every threshold on this page is anchored to Missouri's building code or the sources listed above. Where a number varies by city and we could not verify it, we say "verify locally" rather than guess — a permit page you cannot trust is worse than no page at all.
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