O'Fallon, MO Building Setbacks & Zoning: Lot Coverage Limits (2026)

Section 400.080(D)(3), governing the 'R-1' Single-Family Residential District, states: 'Lot Coverage. The maximum lot coverage shall not exceed thirty-five percent (35%).' That 35% cap sits alongside the district's other Section 400.080 standards, including a 10,000-square-foot minimum lot area, an 80-foot minimum lot width, and 25-foot front and rear yards with 6-foot side yards. The adjoining 'R-1A' Single-Family Suburban Residential District is more permissive on lot size but stricter on coverage: Section 400.085(D)(3) caps lot coverage there at 'twenty-five percent (25%) of the lot area,' on lots with a 22,000-square-foot minimum area.

The 'R-2' Two-Family Residential District, by contrast, allows a maximum lot coverage of 'forty-five percent (45%)' under its own regulations, and other residential districts range as high as 50%. Section 400.265(A), titled 'Maximum Lot Coverage Calculation,' defines what counts toward the percentage: coverage 'shall include the total area of all principal and accessory buildings as measured along the outside wall at ground level or above as viewed from above and includes all projections other than open porches, fire escapes, canopies or the first three (3) feet of a roof over-hang,' while 'roads, driveways, parking lots and swimming pools shall not be included in determining the maximum lot coverage requirements.' The same section confirms the caps apply 'to all property platted either before or after the effective date of this Section,' so older, previously platted lots are not grandfathered out of the current percentage limits.