Rooftop rain / LondonA sample collection study

What the
roofs caught.

446 Lcollected across seven sample roofs

One patch of sky. Seven different ways to catch it.
Each cylinder shows the runoff from a 5 m² roof sample.

Scroll the seven collection cylinders horizontally.

81 L
Slate pitchStoke Newington
84.6 L
Standing zincHackney Wick
27 L
Sedum bedIslington
75.6 L
Clay tilePeckham
55.8 L
Loose gravelBermondsey
85.5 L
Glazed sawtoothBethnal Green
36 L
Meadow roofCamden

18 mm event. 445.5 litres collected; 184.5 litres retained or otherwise lost.

Water has a memory

The green-roof difference

In this model, planted surfaces hold back more of the rainfall before it reaches the collection vessel.

Read the sculpture

Cylinder height represents volume, on a shared 0–160 litre scale. The seven locations and collection values are illustrative, not observed measurements.

How it is calculated

Rainfall in millimetres × 5 square metres × a fixed runoff coefficient. Real retention varies with saturation, materials and storm duration.