Slopes & Ramps

Slopes Chart

Find information on how to read the values below the chart.

See above chart with common slopes and examples.

Exterior surfaces should always have positive drainage and be free of undrained depressions since these may cause water stagnation. Using a minimum slope of 1.5% allows for deviations or construction tolerance that may result in the slope being less than designed.
Unpaved slopes do not drain well; Slopes less than 1% should not be designed as there will inevitably be undrained depressions and water stagnation. Per the note above, this also relies too heavily on precise construction tolerances that may not be realistic to achieve.
25-50% : In order to help stabilize soil, plant ground cover that won’t need to be mowed. This slope only works if the soil is stable.

2.0 to 10% - Drainage ditches
0.5 to 1.5% - Sanitary sewers (depending on diameter)
- The larger the pipe, the less pitch is needed to drain.
2.0 to 3.0% - Grassy areas for recreation

Pitch is the ratio of Rise to Run. Pitch is also considered the Slope Ratio.