Extensive green roofs

Extensive green roofs are normally intended to be viewed from another location as visual or ecological features, and are usually not trafficked. The more prevalent types of green roof which have hardier, more drought tolerant species of plants such as sedums, mosses, and wildflowers fall within the Extensive sector.

They generally provide a visual or biodiversity interest and are considered to be less suitable as an amenity or leisure space. They are generally designed to support plants with a lower maintenance requirement, e.g. sedums, grasses, mosses and some wildflower species. These planting types are able to survive on shallower substrate depths than other types of plants, require lower nutrient levels and little or no irrigation requirement (when correctly designed and installed irrigation is generally only required in the initial establishment phase, and then very rarely afterwards).

Sedum roofs

Sedum species are well adapted to their use within extensive green roofs. They are drought tolerant, able to withstand extremes in climate and can grow on relatively shallow substrates. There are many species with a range of form and colour, and generally flower from early summer to autumn. Sedum are able to survive on shallow substrate depths, lower nutrient levels and little or no irrigation requirement (when correctly designed and installed irrigation is generally only required in the initial establishment phase, and then very rarely afterwards).

Generally planted using pre-grown mats/blankets containing mixes of sedum species and/or planted with species of young sedum plug plants and/or seeded with a mix of seed and/or sedum cuttings.

An intermediate green roof type that can include characteristics of both extensive and intensive roofs. Typically requiring a substrate depth of 100 – 200mm, a wider range of plants can be included compared to extensive green roofs, including shrubs and woody plants. Irrigation and maintenance requirements are dependent upon the plant species installed.