Green roofs also known as garden roofs must be weather proofed. Single ply, built up felt, liquid membranes and asphalt are all suitable. Green roofs are described generally as either intensive or extensive. Intensive roofs consist generally of conventional plants, grasses, shrubs and even trees grown in soil. Subject to the type of plants the weight of intensive roofs can be considerable because of the amount of soil required to sustain plant growth. Extensive roofs are much lighter, they tend to be planted using succulent Sedum plants that require little care or maintenance. Controlled water runoff and the stabilising of external temperature fluctuations are major benefits.