DC zoning caps lot occupancy (not impervious surface) at percentages ranging from 40% in R-1 detached zones to 100% in downtown commercial zones. R-4 row house zones cap at 60%. The 2016 zoning also introduced FAR (floor area ratio) and pervious surface requirements. Green Area Ratio applies in many zones to maintain ecological function.
DC uses 'lot occupancy' — the share of lot area covered by building footprint — rather than a total impervious coverage metric for most zoning control. Under 11 DCMR Subtitle D, residential lot occupancy limits are: R-1-A 40%, R-1-B 40%, R-2 40%, R-3 60%, R-4 60%, R-5/RA apartment zones 60-75%. Commercial and mixed-use zones go up to 80-100%. Floor Area Ratio (FAR) limits stack on top: R-1 typically 0.4, R-4 typically 1.8, MU zones 2.5-6.0. A separate concept, the Green Area Ratio (GAR), applies in many zones and requires a weighted score of landscape, tree canopy, green roofs, and permeable pavement to meet ecological targets — residential GAR scores range from 0.3 to 0.4 depending on zone. Impervious surface rules also derive from the DC stormwater regulations (DOEE 21 DCMR 5) that trigger retention requirements at 5,000 square feet of disturbance or 50% of land area. Permeable pavers and green roofs can be credited. The Zoning Administrator calculates lot occupancy at the time of building permit review. Variances require BZA action, and historic districts frequently impose practical lower limits.
Exceeding lot occupancy: DOB denial of permit. Retroactive construction: stop-work order, $1,000-$5,000 fine, demolition order for excess footprint. Green Area Ratio non-compliance: Certificate of Occupancy withheld until compliance. Stormwater violations: DOEE fines $500-$10,000.
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See how District of Columbia's lot coverage limits rules stack up against other locations.
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