Driveway Slope and Drainage: Minimum Codes and Best Practice
Proper slope and drainage are essential for driveway longevity. Water causes erosion, cracking, and foundation damage.
Why Slope and Drainage Matter
Proper slope and drainage are essential for driveway longevity and home protection. Water is one of the most destructive forces—causing erosion, cracking, and foundation damage.
Driveway grade directs water off the surface. Minimum 1% (1/8 in per ft), recommended 2% (1/4 in per ft). Water must flow away from your home's foundation.
The most critical rule: water must flow away from your foundation. A driveway sloping toward the house causes basement flooding, soil erosion, and structural damage.
Key Requirements
- Minimum slope: 1% (1/8 inch per foot)
- Recommended: 1.5-2% for better water removal
- Maximum for accessibility: 5%
- Direction: Away from structures, toward street or drainage
Slope Requirements
Grade is the angle at which your driveway inclines or declines. 1% = 1 foot rise/fall per 100 feet. Minimum 1%, ideal 1.5-2%, max for accessibility 5%. Direction: away from house toward street or drainage.
Drainage Patterns
To street (most common), to swales, French drains, or rain gardens. Never onto neighboring properties. Cross-slope minimum 1%; crowned driveways: center highest, 2% to each edge.
Drainage Solutions
Channel Drains
Trench drains collect water across surfaces. $50-150/linear ft. Best for driveway entrances, low spots.
French Drains
Subsurface collection: 12-18 in deep, perforated pipe, geotextile, gravel. $20-50/linear ft. For high water table, springs.
Swales
Shallow vegetated channels. 2-4 ft wide, 1-2% slope. $5-15/linear ft. Natural-looking.
Permeable Surfaces
Permeable pavers, porous asphalt, pervious concrete allow water to pass through, reducing runoff.
Frequently Asked Questions
1-2% (1/8 to 1/4 inch per foot). Provides adequate drainage without steep grades.
Add channel drains, resurface for proper grade, install French drains, create swales, use permeable materials.
Most codes limit to 15%. Slopes over 8% challenging in winter.
Grade % = (Rise ÷ Run) × 100. Example: 2 ft drop over 100 ft = 2%.
Prevents foundation damage, basement flooding, soil erosion, structural settlement.
Trench drains that collect water across surfaces. $50-150/linear ft. Best for entrance areas.
Side-to-side grade. Minimum 1%. Crowned driveways: center highest, 2% to each edge.
New installations typically require permits. drainage plan may be required. Check local building department.