St. Louis County, MO Building Safety: Building Permits (2026)

Section 105.1 of the Building Code of St. Louis County, enacted through County Code § 1115.101, puts the duty on the owner or the owner's authorized agent: apply to the building official and hold the permit before work starts. The trigger list covers constructing, enlarging, altering, repairing, moving or demolishing a building, changing its occupancy, installing or altering a ground level paved parking lot (other than one serving a single-family dwelling), and establishing a new or relocated lot line that affects an existing structure. Electrical, gas, mechanical and plumbing work is covered too.

Section 105.2 lists the exemptions, and none of them excuses a code violation. One-story detached sheds and playhouses need no permit up to 120 square feet of floor area. New or replacement fencing up to 7 feet high in rear or side yards is exempt, but fences around pools, spas or hot tubs, and any fence using electrified components, barbed wire or razor ribbon, are not. Retaining walls up to 3 feet high are exempt (2 feet if they support a surcharge or impound Class I, II or III-A liquids), yet a permit is required when the wall sits within its own height of the property line or when wall plus guard or fence passes 6 feet. Prefabricated above-ground pools are exempt only at a maximum depth of 24 inches and 5,000 gallons. Awnings projecting no more than 54 inches and finish work like painting and carpeting also need no permit.

Reroofing needs a permit on roofs sloped under 4:12, and any change in roof covering system needs a permit, plans and specifications at any slope. Temporary buildings need a temporary structures permit under Section 3103 of the International Building Code. Disaster repairs need a Disaster Damage Repair Permit, discounted or free at the building official's discretion if issued within 90 days after the disaster ends, and the work must finish within one year.

An application is abandoned 180 days after filing unless pursued in good faith, with extensions of up to 90 days each. An issued permit expires if work does not begin within 180 days or stops for 180 days, with extensions of up to 180 days each. Demolition permits expire if work does not start within 30 days or finish within 90 days. A permit is not valid until the Chapter 1100 fees are paid.