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

The City of Rockville Zoning Ordinance establishes maximum lot coverage standards to control density, preserve green space, and manage stormwater runoff. In the R-60 single-family zone, building coverage (the footprint of all roofed structures) is limited to approximately 35% of the total lot area. Total impervious surface coverage, which includes the building footprint plus driveways, sidewalks, patios, and other hardscaped areas, is typically capped at around 50% to 55% of the lot. The R-90 zone has lower coverage limits reflecting its larger-lot character, while the R-40 zone may allow slightly higher building coverage. Coverage calculations include the principal dwelling, attached and detached garages, covered porches, carports, sheds, and any other roofed structures. Open decks and certain permeable paving materials may be excluded from impervious surface calculations under specific conditions. The city's stormwater management requirements under Chapter 19 of the City Code impose additional controls on impervious surfaces, requiring on-site stormwater management for projects that increase impervious area beyond certain thresholds. This is particularly important in Rockville given the Chesapeake Bay watershed protection requirements. HOA communities may impose stricter lot coverage limits through their recorded covenants, particularly in newer planned developments. Contact the Department of Community Planning and Development Services at 240-314-8200 for coverage requirements and the Department of Public Works at 240-314-8500 for stormwater management questions.