Do I Need a Permit to Build a Deck in Missouri?

Missouri's unusual code landscape

Missouri stands out from most states in a significant way: it does not enforce a statewide building code for residential construction. There is no state agency that sets minimum deck construction standards, no statewide permit system, and no uniform set of rules that applies everywhere.

Instead, every city and county in Missouri adopts and enforces its own building codes — or, in some cases, no codes at all. Major cities like Kansas City, St. Louis, Springfield, and Columbia have adopted versions of the International Residential Code (IRC) with local amendments. Suburban counties have done the same. But smaller municipalities and rural unincorporated areas may have minimal or no building code requirements.

The Missouri Department of Public Safety has some oversight role, but it does not function as a statewide building code authority the way equivalent agencies do in states like New York or Maryland. Legislative efforts to establish statewide building codes have been introduced — most recently Senate Bill 743 and House Bill 2870 — but as of 2026, none have passed.

For modular construction, Missouri does reference the 2021 IRC and IBC. And the state uses the 2021 IBC as an evaluation standard for professional conduct of licensed architects and engineers when no local code has been adopted. But for your backyard deck, the rules are set locally.

This creates a situation where the permit requirements can change by crossing a municipal boundary. A deck that's exempt in one city might need a full permit in the next town over. If your property sits in an unincorporated area, you may fall under county jurisdiction — or, in rare cases, face no building code requirements at all.

Deck permit requirements vary significantly across the country — see our national deck permit guide for how Missouri compares to other states.

When you need a permit

Since there's no statewide standard, the answer depends on your jurisdiction. However, most Missouri cities and counties that have adopted building codes follow a common pattern based on the IRC. Permits are typically required when a deck:

• Is more than 30 inches above finished grade
• Is attached to the dwelling
• Is larger than 200 square feet (in some jurisdictions)
• Serves as a required exit from the building
• Includes any electrical, plumbing, or gas components

Some jurisdictions are stricter. The City of Gladstone (in the Kansas City metro area) requires a building permit for any deck or porch construction regardless of size — the only exception being structures where no portion exceeds 18 inches above adjacent grade. St. Charles County requires a permit for any deck construction and uses the 2009 IRC as its code basis.

At the other end of the spectrum, some unincorporated rural areas of Missouri have no building permit requirement at all. If you're building in an unincorporated area, check with your county government to determine whether any codes apply.

Kansas City and the western metro

Kansas City is Missouri's largest city and has a well-established building code based on the IRC with local amendments. The city's Development Services department handles residential permits, including deck construction.

Kansas City requires a building permit for most deck construction. The application process involves submitting construction plans and a site plan through the city's online permitting system. The city enforces standard IRC deck requirements, including guardrails at 30 inches above grade, proper ledger attachment, and frost-depth footings.

Frost depth in the Kansas City area is approximately 30–36 inches. Footing piers must be at least 12 inches in diameter and extend below the frost line. The Kansas City metro area includes multiple jurisdictions — Independence, Lee's Summit, Blue Springs, and O'Fallon each have their own building departments and may have slightly different fee schedules and review timelines.

St. Louis: city and county are separate

St. Louis presents a unique jurisdictional situation. The City of St. Louis is an independent city — it's not part of any county. St. Louis County surrounds the city and contains dozens of smaller municipalities, each with its own building department.

The City of St. Louis requires building permits for deck construction and processes applications through its Division of Building and Inspection within the Department of Public Safety. The city has adopted the IRC with local amendments. A building permit is required when any structural change or new construction is undertaken. Smaller residential projects generally don't require professionally prepared plans — a clear drawing showing dimensions, materials, and structural details is typically acceptable.

St. Louis County municipalities each run their own permitting. St. Charles County, directly west of St. Louis, requires permits for all deck construction and provides detailed deck construction guidelines on its website. The county uses the 2009 IRC and specifies a 30-inch minimum frost depth for footings. Plan review in St. Charles County typically takes about 10 working days.

Springfield, Columbia, and outstate Missouri

Springfield is Missouri's third-largest city and enforces its own building code based on the IRC. The city requires contractor licensing for jobs exceeding $500 in value — a local requirement that doesn't apply statewide. Springfield's Building Development Services department handles residential permits.

Columbia, home to the University of Missouri, has adopted building codes through its Building and Site Development division. The city requires permits for deck construction and enforces setback, height, and structural requirements.

Outside these major population centers, the regulatory picture gets thinner. Many of Missouri's smaller cities have adopted some form of the IRC, but enforcement capacity varies. In rural unincorporated areas, building code enforcement may be minimal or nonexistent. This doesn't mean you should skip good construction practices — the IRC exists to keep structures safe, and a deck built to code will last longer and cause fewer problems regardless of whether an inspector checks the work.

Missouri's climate and construction factors

Missouri's climate creates several construction considerations for deck builders.

Frost depth ranges from about 24 inches in the southern Ozarks to 36 inches in the northern part of the state. The Kansas City and St. Louis metro areas generally specify 30–36 inches. As with all frost-depth requirements, footings that don't reach below the frost line will eventually heave, cracking the footing and destabilizing the deck.

Termites are a concern throughout Missouri. The state falls within an area of moderate to heavy subterranean termite activity, and the IRC requires termite protection measures. All structural wood in contact with or near the ground must be pressure-treated with an approved preservative or be naturally decay-resistant.

Humidity and storms also factor in. Missouri's humid summers accelerate wood decay, and the state sees frequent severe thunderstorms with high winds. Proper connection hardware — post-to-footing brackets, joist hangers, ledger attachment bolts — provides resistance against both gravity loads and wind uplift. Corrosion-resistant fasteners (hot-dipped galvanized or stainless steel) are required in most jurisdictions that have adopted the IRC.

Tornado risk is real across Missouri, though the building code doesn't typically require tornado-specific design for residential decks. Safe rooms are increasingly common in new home construction but aren't mandated statewide.

Applying for a deck permit in Missouri

Because there's no statewide system, the process depends on your jurisdiction. In most cities that require permits, you'll need:

• A completed building permit application (many cities offer online submission)
• A plot plan or site plan showing your property, existing structures, and the proposed deck location with distances to property lines and easements
• Construction plans showing deck dimensions, framing layout, materials, footing details, and railing specifications
• Contractor information (if applicable — licensing requirements vary by city)

St. Charles County's process is representative of well-organized suburban jurisdictions: submit plans (PDF preferred) showing size, spacing, spans, lateral bracket locations, and lumber types, along with a plot plan. The county reviews plans within about 10 working days, notifies you by email when the permit is ready, and calculates the fee based on construction cost.

Inspections in St. Charles County include a footing/pier inspection (after excavation, before concrete), a framing inspection (checking lateral brackets and structural connections), and a final inspection. The approved inspection sheet serves as a certificate of occupancy.

Review timelines in major cities run from one to three weeks for straightforward residential deck projects. Smaller jurisdictions may process permits faster. Fees typically range from $50 to $500 depending on project size and the jurisdiction's fee schedule.

What happens if you skip the permit

The consequences of unpermitted construction depend on your jurisdiction. In cities with active code enforcement — Kansas City, St. Louis, Springfield, Columbia, and their suburbs — building without a permit can result in fines, stop-work orders, and mandatory retroactive permitting.

In jurisdictions with less enforcement capacity, unpermitted work may go unnoticed — until you try to sell the house. Real estate transactions increasingly involve permit record checks, and an unpermitted deck can delay or complicate a sale. Buyer's inspectors may flag the structure, and title companies may require resolution before closing.

Insurance is the other risk. If someone is injured on an unpermitted deck that doesn't meet code, your homeowner's insurance may deny the claim. The cost of a permit is trivial compared to the liability exposure of an uninsured structural failure.

For an overview of all building permit requirements in Missouri — including sheds, fences, pools, and more — see our complete Missouri building permit guide.

If you're also planning a fence or patio alongside your deck, note that Missouri cities have separate permit requirements for each — see our guides to fence permits in Missouri and patio permits in Missouri.