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

Chapter 24's per-zone dimensional tables set two separate coverage ceilings for every residential district: an impervious lot coverage maximum (covering driveways, patios and roofs together) and a building lot coverage maximum (the building footprint alone). 2-1 caps the R-A zone, the city's low-density single-family and institutional district, at 50% impervious and 35% building coverage, with front-yard impervious coverage separately capped at 35% for single-family detached and duplex lots. 3-1 for the R-90 zone, built primarily around single-family detached homes on smaller 7,500-square-foot lots, allows more coverage: 70% impervious and 50% building coverage, again with a 35% front-yard impervious cap.

The pattern continues up the density scale: R-6 allows 60% impervious and 50% building coverage, R-20 allows 80% impervious with building coverage split by housing type (60% for detached/duplex, 80% for townhouse and multifamily forms), and the RP-T zone caps overall impervious coverage at 75% while leaving building coverage unset. Each table note limits the impervious cap to specific housing types, generally single-family detached and duplex dwellings, so multifamily and non-residential lots in the same zone can be governed by a different standard or none at all. 2.