Paver Patio on Negative Slope: Drainage Engineering for Row House Backyard

A 16x30 DC row house backyard slopes 2% toward the house (negative slope), causing kitchen water intrusion. Contractors disagree on full vs. partial paving. Here's the engineering reality.

Core Principle

Any area can be paved IF drainage capacity matches inflow. The slope direction doesn't prohibit paving—it demands engineered drainage.

Required Drainage System

• Perimeter French drain (gravel trench + perforated pipe) around entire patio
• Cross-slope French drains feeding perimeter drain
• Discharge point: Alley, storm sewer, rain tank, or rock-filled soakaway
• Gravel trenches planted with iris/sedum for aesthetics

Contractor Evaluation

• "Half patio only" contractor: Conservative, avoids liability
• "Full patio OK" contractors: Must specify drainage design—ask for details
• "French drain won't work" claim: False—works anywhere with slope and discharge

Professional Help Needed

This requires a landscape architect or civil engineer for:

• Hydraulic calculations (pipe sizing, slope, capacity)
• Grading plan with drainage integration
• Permit coordination (DC likely requires)

Decision Framework

Don't choose based on contractor opinions. Commission a drainage design first, then bid the specified system.