What is falls and gradients in drainage?
A fall is the slight downward slope incorporated into a paved surface to allow rainwater and surface moisture to drain away rather than pool or sit.
When a paving contractor lays a driveway, patio, or other hard surface, they build in a fall, or gradient, to shed water. This means the surface is not perfectly flat but slopes gently downhill in one or more directions, channelling water away from the structure and preventing puddles from forming.
The gradient is typically expressed as a ratio. Common falls for driveways and patios in Cheltenham range from 1 in 40 to 1 in 60, meaning the surface drops 1 metre in height for every 40 to 60 metres of horizontal distance. This slope is so gentle that it is barely noticeable to the eye or underfoot, yet it is effective at moving water towards drainage channels, soakaways, or edges.
Proper fall is essential because standing water accelerates decay of both the paving material and the base beneath it. On concrete and block paving, water pooling will cause frost damage in winter, weeds to establish in joints, and surface algae growth. On tarmac, poor drainage leads to weakening of the binder and faster deterioration.
A competent paving contractor will calculate and set the fall during the base preparation stage using levels and string lines. The fall direction depends on site layout, boundary positions, and where runoff can safely discharge. Falls must also comply with building regulations and local planning conditions, particularly where drainage affects neighbours or public land.