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SetbackIQ

Steep slopes and problem soils in Washington, DC

DC has no steep-slope zoning for houses. SetbackIQ flags lots the DC soil survey puts in the 15 to 40 percent slope class. On those lots, expect DOEE erosion controls (any work moving more than 50 sq ft of soil) and engineered walls: retaining walls over 4 ft need a DC-licensed design professional, and DOB may ask for a soil report.

A person last checked these rules on October 20, 2026. This is guidance only, so confirm with Washington before you build.

The details

  • Soil survey classes: B 0 to 8%, C 8 to 15%, D 15 to 40%. SetbackIQ treats class D as steep.High confidence
  • Any excavation over 50 sq ft needs an erosion and sediment control plan.High confidence
  • Retaining walls over 48 in need a plat and a sealed design, with a safety factor of 1.5 against sliding and overturning.High confidence

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SetbackIQ reads the zoning, flood zone, historic district, and environmental maps for your lot. Then it applies these rules.

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Common questions

Do steep slopes or soils like marine clay change what I can build in Washington?
DC has no steep-slope zoning for houses. SetbackIQ flags lots the DC soil survey puts in the 15 to 40 percent slope class. On those lots, expect DOEE erosion controls (any work moving more than 50 sq ft of soil) and engineered walls: retaining walls over 4 ft need a DC-licensed design professional, and DOB may ask for a soil report.

Sources

  1. DC GIS, Soil Type by Slope (USDA NRCS soil survey), slope classes. Checked 2026-10-21
    [SLOPE classes] B: 0 to 8 percent slopes; C: 8 to 15 percent slopes; D: 15 to 40 percent slopes.
  2. DC Department of Energy and Environment, Erosion and Sediment Control. Checked 2026-10-21
    An ESC plan is required for building construction and redevelopment projects that disturb or move more than 50 square feet of land... [The minor track covers projects that disturb] less than 5,000 square feet of land [and don't require stormwater management…
  3. DC DOB, Building Code Interpretation, Retaining Wall. Checked 2026-10-21
    Plat required for erection of retaining walls higher than 48inches... Retaining walls greater than 4ft require seal and stamp of a District licensed Design Professional... Minimum factor of safety for global stability sliding and overturning is 1.5... Soil …

Disclaimer: This is general information, not legal or professional advice for any one property. Codes change. SetbackIQ is not a zoning determination, a permit, or a survey, and it does not replace an architect, engineer, or lawyer. Confirm with your building and zoning offices before you build, buy, or sign a contract.