Charles County, MD Building Setbacks & Zoning: Lot Coverage Limits (2026)

Section 297-300 of the Charles County Zoning Ordinance defines impervious surface broadly: any surface that does not absorb rainwater, expressly including buildings, roads, sidewalks, patios, parking areas, and any other area paved in concrete or asphalt. The section ties the actual numeric ceiling to the impervious surface ratio (ISR) published in the Schedule of Zone Regulations found in Articles VI through VIII of the ordinance, so the allowable percentage differs by zoning district rather than being a single countywide figure. A homeowner in a low-density agricultural or rural zone has a much lower ISR than a lot in a mixed-use activity center or commercial zone.

The Zoning Officer checks proposed impervious coverage at site plan and building permit review, comparing the total paved and roofed area on the plan against the ISR assigned to that parcel's zone. Section 297-29B(3), governing accessory structures, reinforces the cap by separately barring any accessory use or structure from pushing impervious surface area beyond the maximum already permitted on the lot, closing off sheds and detached garages as a workaround. The code also states a policy preference, directing that efforts to minimize impervious surfaces shall be encouraged, which the Planning and Growth Management Department can weigh when reviewing stormwater and site design alternatives such as pervious pavers or reduced parking counts.