Constant changes occur to the family requirements of housing with the flowing of time, and these changes are due to the number of its members, their needs , the standard of living the economic conditions , or as a result of increasing technical developments. This implies facing house requirements and applying changes in the number of the house rooms, or the functions of these rooms. So the family either tends to change its house to fit its needs, and that exhausts it socially and financially. They made adapt their house with the family constant needs, and here comes the importance of achieving flexibility as the best economic solution that reduces the value of the house, of it, by providing the efficiency of the best use of the whole spaces. In addition, the role of flexibility is to respond to the social stability of families by the best use of the whole time age of their houses. This research handles the concept of design flexibility as one of the most economic housing standards in the thesis of the most important architects , and goes through steps of applying it in the house functionally and structurally in the designing phase by effective interaction between the designer and the user side by side.