Grading

Slope gradient

Slope gradients are expressed as Y:X where Y is a single unit of rise and X is the corresponding run. It can be calculated by dividing the rise by the run: e.g.:${\frac {rise}{run}}={\frac {4\ m}{12\ m}}={\frac {1}{3}};we\ say\ the\ slope\ =1:3\ or\ 1\ in\ 3$

Slope percentage

Slope percentage is calculated similarly by dividing rise by run, but then multiplying by 100 to get a percentage: e.g.:$slope=\left({\frac {rise}{run}}\right)\times 100=\left({\frac {4\ m}{12\ m}}\right)\times 100=33\%$

Slope in degrees

$\tan \theta =\left({\frac {4\ m}{12\ m}}\right);\theta =\tan ^{-1}\left(0.33\right)=18.3^{\circ }$

Grading Standards and Critical Gradients

Use	Extreme range (%)	Desirable range (%)
Public Streets	0.5 - 10	1 - 8
Private streets	0.5 - 20	1 - 12
Service lanes	0.5 - 15	1 - 10
Parking areas	0.5 - 8	1 - 5
Parking ramps	up to 20	up to 15
Collector walks	0.5 - 12	1 - 8
Entrance walks	0.5 - 8	1 - 4
Pedestrian ramps	up to 12	up to 8
Stairs	25 - 50	33 - 50
Game courts	0.5 - 2	0.5 - 1.5
Paved gutters	0.25 - 100	1 - 50
Grassed swales	0.5 - 15	2 - 10
Terraces and sitting areas	0.5 - 3	1 - 2
Grassed banks	up to 50	up to 33
Planted banks	up to 100	up to 50