502. RULES OF MEASUREMENT FOR PERVIOUS SURFACES

RULES OF MEASUREMENT FOR PERVIOUS SURFACES Only the following shall be considered pervious surfaces for the purposes of calculating the pervious surface area: Grass, mulched groundcover, all areas of a vegetated roof planted with a growing medium, and other planted areas; Permeable or pervious pavers or paving that facilitate the infiltration of water into the soil; and Decks or porches constructed above the surface of the lot that are erected on pier foundations, and that maintain a permeable surface underneath that can facilitate the infiltration of water into the soil or are located directly above a surface defined in Subtitle C § 502.1. Pervious surfaces on a lot shall not include: On-grade surface treatments used for purposes of recreation (e.g. patios), outdoor stairways, walking, driving and parking areas made of concrete, brick, asphalt, decorative pavers, compacted gravel or other material that does not facilitate the infiltration of water directly into the subsurface of the lot; The building footprint based on its foundation perimeter, whether located below grade or at grade; Where a building does not have a foundation, the area of the roof; and The area dedicated to a below or above grade swimming pool. The percent of pervious surface area shall be calculated by dividing the total area of pervious surfaces on the lot by the total area of the lot. SOURCE: Final Rulemaking published at 63 DCR 2447, 2712 (March 4, 2016 – Part 2); as amended by Final Rulemaking published at 73 DCR 009999 (July 10, 2026). District of Columbia Municipal Regulations Zoning Regulations of 2016: General Rules 11-C DCMR § 502