Direct Answer
In St. Louis, retaining wall construction work generally requires a permit when the project exceeds $10,000 or involves system replacements. Your licensed contractor should pull the permit — if they ask you to pull it yourself, that's a red flag. Unpermitted work can cause problems when selling your home.
Full Explanation
St. Louis follows MO state building codes administered by the local building department. Permit fees vary by project value. All inspections must be scheduled through the St. Louis building department. Keep all permit documentation — required for home resale disclosure.
Local Factors in St. Louis
📍MO permit threshold: $10,000
📍St. Louis building department issues local permits
📍Sales tax on materials: 8.5-10.5%
📍Permit records are public and transfer with the home