Extensive Green Roofs in London

Glossary

Expanded clay aggregate

A lightweight building material made by kiln-heating clay. The process is also used to make expanded shale and slate, which, along with clay, were patented in 1918 as Haydite.

Extensive Green Roof

A low-management type of green roof that has soil depths ranging from three to seven inches. Due to the shallow soils and the extreme environment on many roofs, plants are typically low-growing groundcover species that are extremely sun and drought tolerant.

Intensive Green Roof

A mid- to high- management type of green roof that requires a reasonable depth of soil to grow trees, large plants, or conventional lawns and is labor-intensive, requiring irrigation, feeding, and other maintenance.