Patio Drainage Slope Calculator for UK Homes

The standard recommended slope is between 1:80 and 1:60, which means a fall of 12–17 mm per metre. This ensures water runs off efficiently without being noticeable underfoot.

Impermeable surfaces like concrete and porcelain need steeper slopes because water can't pass through. Permeable materials like gravel or resin allow better drainage and require less fall.

Yes. A taut string line with a spirit level is a simple way to mark your slope. Measure the drop from one end to the other, then calculate the percentage based on your patio width.

Yes. Even with a soakaway or drainage system, you still need a slight slope to guide water toward it. Flat patios are prone to puddling and freeze damage in winter.

In most UK cases, patios don’t need building regulations unless they're affecting surface water run-off to public drains. However, good drainage design is essential to avoid future issues.