St. Louis, MO Fence Regulations: Retaining Walls (2026)
Key Facts
- Permit-exempt height
- 18 inches or less above grade
- Permit required above
- Any wall over 18 inches
- Permit fee basis
- Estimated construction cost (§ 109.2.3)
- Issuing agency
- Division of Building and Inspection
- Enforcement
- Daily fines under § 25.01.030
Summary
St. Louis exempts retaining walls of 18 inches or less above the lowest adjacent grade from a building permit; any taller wall needs a Division of Building and Inspection permit and construction documents.
Permits shall not be required for the following: ... 6.Replacement of existing fencing of the same height, material, and location except when enclosing swimming pools, hot tubs, or spas;7.Retaining walls eighteen inches or less in height above lowest adjacent grade;8.Tents smaller than 1,000 square feet, or those used for private family events on the same lot as the owner's residence;
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 11).
Full Breakdown
Section 105.2 of the Building Code, adopted at Revised Code § 25.01.020, lists retaining walls eighteen inches or less in height above the lowest adjacent grade among the work exempt from permit: the same threshold applies regardless of whether the wall sits in a front, side, or rear yard. Anything taller triggers Section 105.1: the owner or an authorized agent must file a permit application, including construction documents, with the building official before starting work. Permit fees for retaining walls and other miscellaneous site structures are charged under Section 109.2.3, based on the estimated cost of construction per the fee table in Section 109.3.1.
Violations & Fines
Building a retaining wall over 18 inches without a permit is a Section 114 violation: the building official can post a notice of violation and issue a stop-work order, and the owner can be fined under § 25.01.030, with each day of continued violation a separate offense.
Frequently Asked Questions
Do I need a permit for a short retaining wall in St. Louis?
What happens if I build a tall retaining wall without a permit?
Sources & Official References
Other rules in St. Louis
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