The building green movement is not new, nor is the practice of using natural resources responsibly to sustain life and encourage the regeneration of natural resources. In recent, many European municipalities have mandated the incorporation of green roof systems as standard building practice. Green roof systems are usually built as stormwater management systems and as comfortable, accessible, open spaces over structure. And also it is very useful to reduce building thermal energy, so they are adopted in many buildings. Artificial soils have been developed and used in developed countries and light soils are commonly used for green roof system, however, they are imported and constructed from foreign countries in Korea. The light soils have some problems of weight, maintenance, and durability. In this study, concrete blocks made of bottom ashes are designed and evaluated as environmentally friendly materials. The blocks are very chief, light and have high moisture contents. The specific gravity is 1.11~1.14 which are lower than normal ground soil and the compressive strength of cement block shows up to 3.03 MPa which is more suitable than normal soil for resisting plant roots.