St. Charles County, MO Building Setbacks & Zoning: Lot Coverage Limits (2026)
Key Facts
- Max lot coverage
- 70% of site in HTCD zoning
- Governing section
- Code § 405.165(A)(5)
- Counted surfaces
- Buildings plus access, loading, parking paving
- Penalty
- Up to $500/day or 6 months jail
- Variance fee
- $250 to Board of Zoning Adjustment
- Appeal window
- 14 working days to County Council
Summary
St. Charles County caps impervious lot coverage at 70 percent in its High Technology Corridor District under Code § 405.165(A)(5), counting every building and every square foot of paving used for access, circulation, loading, or parking toward that limit. The Division of Planning and Zoning checks the cap against the required site development plan before an HTCD project breaks ground.
Lot coverage. The maximum lot coverage shall not exceed seventy percent (70%). This represents that portion of the site which is covered by impermeable surfaces, such as buildings or paving for access, circulation, loading, and parking.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4863880; v61 updated 2026-05-11; through 05-11-2026).
Full Breakdown
165(A) of the Unified Development Ordinance sets the development standards for land zoned High Technology Corridor District (HTCD), the county's business-park zone. Subsection (A)(5), titled "Lot coverage," states: "The maximum lot coverage shall not exceed seventy percent (70%). " The cap works alongside the district's other dimensional standards in the same section: a 100-foot minimum lot width (200 feet on lots of five acres or more), 30-foot front and rear yards, 20-foot side yards (30 feet on a corner lot), and a 60-foot height limit.
Before any HTCD parcel is graded or built on, the applicant must submit a preliminary site development plan and building elevations to the Planning and Zoning Commission showing every proposed paved surface, together with a preliminary subdivision plat reviewed under Chapter 410; the 70% ceiling is measured against that plan, not self-certified after construction. The Director of the Division of Planning and Zoning enforces Chapter 405 countywide. 645, the Director can inspect a site, issue a written order to remedy a violation, and require that offending construction or use stop, immediately for active building work.
650 also lets the County Counselor, the Prosecuting Attorney, or an affected neighboring owner sue in Circuit Court to enjoin the violation. 020(C)(1). 639(A), or taken directly to Circuit Court under Chapter 536, RSMo.
Violations & Fines
Building or paving beyond the 70% HTCD lot-coverage cap is a misdemeanor under Section 405.655: a fine of up to $500 per day, up to six months in the county jail, or both, with every day the excess pavement or building remains counted as a separate offense. The Director of Planning and Zoning can also issue a written stop-work order under Section 405.645, and the County or an aggrieved neighboring owner may sue in Circuit Court under Section 405.650 to force removal of the noncompliant coverage.
Frequently Asked Questions
What is the maximum lot coverage allowed in St. Charles County's HTCD zoning?
What counts toward the 70% impervious limit?
What happens if a project exceeds the lot coverage cap?
Can a property owner get relief from the 70% cap?
Sources & Official References
Other rules in St. Charles County
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