Abstract: We approach, in this study the analysis of the problems of the occupation of the grounds in urban tissues of the Maghrebian cities and more particularly, in its housing units, which knew a massive importation of new urban forms and models of dwellings industrialized not adapted to the socio-economic factors, cultural and climatic; And that, through a direct analysis of the mode of occupation of the urban ground report (built/not built), urban form, use and operation of various spaces of the traditional cities in the arid areas on the one hand and the comparison of and the influence percentage occupied time of grounds (the COS-FAR: Floor area ratio-and the CES-LUI: and use intensity-) of the various types and examples of traditional dwellings on the other hand, in order to know to detect the parameters which take part in the fixing of the COS and CES optimal and thereafter, an optimal occupation of the urban ground.