Missouri · Penalties if you skip one

What you can build without a permit in Missouri

By Mario Bailey Last checked · 15 official sources

Quick answer

Across the 2 Missouri jurisdictions we have verified, 1 of 20 project rules need no permit at all, 17 turn on a size or scope condition the jurisdiction publishes, and 2 require a permit regardless. Deck work is where the answer most often comes with a published condition rather than a flat yes: 2 of the 2 jurisdictions that answer publish one. The numbers are not statewide: deck thresholds alone run from 12 to 30 inches depending on the jurisdiction.

How to read this page

"No permit" means the jurisdiction publishes that the work needs no building permit. "Depends" means it publishes a size, height, depth, cost or scope condition that decides the answer, quoted in its own words in the last column; the number beside it is the figure that condition turns on, and which side of the number is exempt is stated by the condition, not by us. Exempt from a building permit is not exempt from zoning, setbacks, height limits, flood rules, an HOA, or a separate electrical, plumbing or mechanical permit, and several of the conditions below say exactly that.

Deck

All 2 make the deck answer turn on a size or scope condition the jurisdiction publishes, and the 2 that state a number publish figures from 12 to 30 inches.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends 30 inches height of a platform or deck above grade at any point, where it is also not located over any basement or story below.
St. Louis Depends 12 inches inches above adjacent grade for an uncovered wood deck or patio resting directly on the ground or a rock base with no permanent foundation.

Electrical

All 2 make the electrical answer turn on a size or scope condition the jurisdiction publishes.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends Electrical work is permitted work in Kansas City, with a genuinely useful homeowner carve-out that people get wrong.
St. Louis Depends The City Electrical Code requires a permit before any electrical work begins, with a narrow minor-repairs exemption: swapping a convenience outlet of the same current rating (unless an ungrounded outlet is being replaced with a grounding type that needs new wiring), a like-rated light switch, a light socket and holder, a single light fixture on the same outlet box, and, inside a dwelling unit, a like-for-like fractional horsepower fan, blower or pump motor limited to 240 volts.

Fence

Kansas City requires no fence permit at all. 1 of 2 makes the fence answer turn on a size or scope condition the jurisdiction publishes.

Jurisdiction Permit Published figure What the rule says
Kansas City No permit Kansas City is one of the few large cities that requires no permit at all for a residential fence: Sec. 18-16(b)(1)e of the Building and Rehabilitation Code exempts fences outright from the building permit requirement, and Chapter 27, the city's separate fence and wall code, sets height and location rules but never requires an application.
St. Louis Depends The City of St.

HVAC

All 2 make the HVAC answer turn on a size or scope condition the jurisdiction publishes.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends Mechanical work needs a permit in Kansas City, and the city says so at the top of its own trade permit page.
St. Louis Depends Mechanical permits in St.

Patio

All 2 make the patio answer turn on a size or scope condition the jurisdiction publishes.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends Kansas City names patios directly in its exemption list, which is unusual and makes the answer clean at one end: Sec. 18-16(b)(1)w exempts walks, patios and driveways constructed on existing grade from a building permit.
St. Louis Depends An at-grade paved patio is exempt in the City of St.

Plumbing

All 2 make the plumbing answer turn on a size or scope condition the jurisdiction publishes.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends Plumbing needs a permit in Kansas City, and the more useful thing to know is which department issues it.
St. Louis Depends The City Plumbing Code requires a permit before plumbing, drainlaying or process drainage work, before any connection to a sewer, and before installing, replacing or permanently removing a backflow prevention device, with minor repairs carved out.

Pool

All 2 make the pool answer turn on a size or scope condition the jurisdiction publishes.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends 5,000 gallons water capacity of a prefabricated above ground pool accessory to a one- or two-family dwelling that is also less than 24 inches deep with its walls entirely above the adjacent grade.
St. Louis Depends 24 inches inches of water depth, applied together with a 250 square foot surface area test.

Roof Replacement

All 2 make the roof replacement answer turn on a size or scope condition the jurisdiction publishes.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends Kansas City does not require a permit for the ordinary residential reroof.
St. Louis Depends 25 percent percent of roof sheathing removed and replaced during a like-material roof covering replacement.

Shed

All 2 make the shed answer turn on a size or scope condition the jurisdiction publishes, and the 2 that state a number publish figures from 50 to 200 sq ft.

Jurisdiction Permit Published figure What the rule says
Kansas City Depends 200 sq ft projected roof area of a one-story detached accessory building used as a tool or storage shed, playhouse, garage, carport or similar use.
St. Louis Depends 50 sq ft square feet of floor area for a detached accessory building, which must also keep the setbacks required by the Zoning Ordinance.

If the work is already built

Missouri has no statewide residential building code and no state crime of building without a permit, so both the permit requirement and its penalty come from city or county ordinance. Where a municipality enforces under its zoning enabling act, RSMo 89.120.2 makes it a misdemeanor to erect, construct, reconstruct, alter or convert a building in violation, punishable by not less than $10 and not more than $250 for each and every day the violation continues, or imprisonment for 10 days for each day it continues, or both, rising to $100 to $500 per day for a second or subsequent offense at the same building; in a city with more than 300,000 inhabitants the range is $10 to $500 per day and $250 to $1,000 per day for repeat offenses.

Missouri penalties, the after-the-fact path, and what the statute actually says

The 20 answered rules come from 15 official sources, each linked from the permit page behind every jurisdiction name. See the full picture for the state on the Missouri permit requirements page, or the national view of which projects need a permit at all on Do you need a building permit?

This page compiles what each Missouri jurisdiction publishes, with a last checked date. It is not legal advice, and a project that is exempt from a building permit can still need zoning approval or a trade permit. Confirm with the office linked from the jurisdiction's page before you build.