Extensive roof gardens

Extensive green roofs are primarily installed to give visual appeal, to reduce the environmental impact of the building, to create a habitat for flora and fauna and to enhance building performance. They are not usually installed for recreation purposes although extensive planting can be included in intensive schemes.

Extensive design

Normally inaccessible but provide greater biodiversity than intensive roofs

Self-sustaining vegetation - succulents, mosses, herbs, grasses, wild flowers

Thin soil substrate, water retaining reservoir

Minimal maintenance

Flat or sloping roofs

Soils or substrates are usually of a low nutrient type thus suppressing the growth of invasive weed species and of minimal thickness. Plants are selected on their attributes for thriving in such conditions and planting styles are usually naturalistic with the object of establishing a self-sustaining plant community on the roof. Sedum and wildflower mats, pre grown trays or plug plants can all be incorporated into an extensive design. Recent developments have seen the creation of conditions similar to "brown field sites" as these are known to support a wide selection of plant, animal and invertebrate communities to the enhancement of city centre environment.

Roofs are harsh environments for plants and although Axter advises the use of reservoir boards, to conserve and control water, flow beneath the soil, the inclusion of a 'leaky pipe' in the design will help keep the plants alive in dry periods.
Axter offers a number of extensive green roof designs for installation on either a warm (ALPAFLORE) or inverted (WILOTEKT-PLUS) roof design:-