Mechanical and physical properties of earthen material for construction can be modified by stabilisation in order to meet current requirements. Although cement stabilisation is generally used, gypsum is the subject of stabilisation in studies conducted by Istanbul Technical University. New composite is called Alker. In case of new material and technologies, ageing of the material and structure is important due to safety and maintenance concerns. Though gypsum has been used in historical architecture, gypsum stabilisation of earth as construction material is not much known. The aim of this study is to gain experience on Alker as construction material. A case-study building out of Alker was constructed in 1983 after the basic laboratory studies having started in 1978. Production process and properties of the material, construction techniques, design criteria and life-cycle performance of the building will be proved for answering the question on ageing.