State Guide · Verified 2026
Deck Construction Permits in Missouri
There is no single statewide building code, so the rule is set by your local jurisdiction; most still require a permit for any deck attached to the house or more than 30 inches above grade.
The Building Code in Missouri
No statewide code, major cities independently adopt their own IRC-based ordinances; SB 743 and HB 2870 proposed a statewide standard but had not passed as of 2026
Missouri leaves building code adoption entirely to individual cities and counties, with no state agency functioning as a statewide building code authority for residential construction. Kansas City, St. Louis, Springfield, and Columbia each maintain their own IRC-based codes with local amendments. Legislative efforts to establish a statewide building code, most recently Senate Bill 743 and House Bill 2870, had not passed as of 2026. Where cities enforce codes, deck permits generally follow the standard IRC pattern, over 30 inches above grade or attached to the house, but Gladstone requires a permit to add or replace a deck or porch regardless of size, with the sole exception of a structure where no portion exceeds 18 inches in height from adjacent grade. St. Louis County separately applies a "50% rule": replacing more than half of a deck's finish decking, guard components, or structural elements requires bringing the entire structure up to current code.
Quick Facts
Who Sets the Rules
One of the few large states with no statewide code at all
Missouri has no state agency setting minimum deck construction standards, and legislative attempts to change that, most recently Senate Bill 743 and House Bill 2870, had not passed as of 2026, leaving the patchwork fully intact.
Gladstone shows just how far a city can diverge
Where most Missouri cities follow something close to the standard 30-inch IRC threshold, Gladstone requires a permit to add or replace a deck or porch regardless of size, with only one exception: a structure where no portion exceeds 18 inches above adjacent grade.
St. Louis County's real rule for replacement work
Replacing more than 50% of a deck's finish decking, or more than 50% of the guard components or the entire linear length of the guard, triggers a requirement to bring the entire structure, not just the replaced portion, up to current code, a real and specific administrative threshold.
Older housing stock adds real structural questions
St. Louis's brick four-flat and rowhouse buildings often have rear deck additions where the age of the original structure makes a structural assessment particularly important before adding or replacing a deck.
Kansas City draws a clean line for ground-level work
Kansas City explicitly exempts walks, patios, and driveways built on existing grade from permit requirements, a clear carve-out that doesn't extend to any raised deck structure.
What people get wrong
The most common mistake is assuming a Kansas City or St. Louis pattern applies broadly across Missouri. Gladstone's near-universal permit requirement, with its narrow 18-inch exception, shows how far a specific city can depart from the more common 30-inch figure.
Counties With Their Own Rules
These Missouri counties have verified, county-specific deck construction rules that differ from the state baseline:
Check Your County
Select your county for the local rule, fees, and your building department's contact details:
Building It Yourself? Here's What You'll Need
Popular tools and materials homeowners use for a deck construction project:
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Official Sources
Rules change and cities within a county may differ. This guide is general information, not legal advice — always confirm with your local building department. Reviewed by the StateDataIndex Editorial Team · Updated September 2026.