Washington, DC Fence Regulations: Retaining Walls (2026)

Title 11 DCMR Subtitle C, Chapter 14 governs retaining walls built in any R (Residential House) or RF (Residential Flats) zone (§ 1400.1); it does not reach commercial or other zone categories. Height is measured vertically from the natural grade at the wall's base to its top, taken at the highest point if the wall varies, and berms or similar terrain mounding cannot be counted toward the measurement (§ 1401.1). The baseline maximum is 6 feet (§ 1401.2), but that drops to 4 feet along any street frontage, property line, or within a required side setback, and within 25 feet of the rear property line in the R-1-A and R-1-B zones, or within 20 feet of the rear line in the R-2, R-3, and RF zones (§ 1401.3).

A wall along a street frontage on a block where adjacent walls already exist cannot exceed the tallest neighboring wall, capped at 4 feet regardless (§ 1401.4). Anywhere between the property line and the building line, the cap tightens further to 42 inches (§ 1401.5), while a wall abutting an improved alley in the R-3 or RF zones may rise to 12 feet (§ 1401.6). Owners can stack height by tiering or terracing walls, but the flat area between each tier must be at least twice the height of the lower wall and must stay pervious, not paved or otherwise covered with impervious material (§ 1401.7).

A wall that cannot meet these limits is not automatically prohibited: the owner may apply to the Board of Zoning Adjustment for a special exception under Subtitle X, but must show the building, terrain, or surrounding conditions make full compliance unduly restrictive, prohibitively costly, or unreasonable (§ 1402.1).