The soil is a basic natural resource, not renewable, and this implies it must be assessed in all urban extension actions, the occupation of the land by urbanization, its necessity, suitability and opportunity, because of principles of irreversibility and uncertainty.
It is shown in this work the need to include a selection of determinants for sustainability, among which are found as fundamental those indicated in the text: density, diversity of uses, open public space and treatment of free of building surface. The debate should result in the agreement of internationally accepted basic standards as has happened with the standard of green zones set by the WHO. At the same time, flexible standards through the fixing of forks or minimum/maximum, so that they are applicable to the social, geographical and economic characteristics of the different territories.
In addition, it is observed that some of the indicators used are more decisive than others, as is treated in the case of density, and for that reason a weight should be considered in an aggregated index of sustainability.