Mankind’s most-used materials, construction materials pose major environmental challenges, mainly related to the increasing scarcity of certain primary resources. Using secondary resources, i.e. materials extracted from buildings and networks,is one response to these challenges. However, powerful constraints confront this kind of use. Paris region is studied as an example of an urban area in which secondary resources for construction offer strong potential. Possible courses of action to meet these challenges are outlined in the conclusion.Keywords–construction materials, construction and demolition waste, circular economy, materials flowsand stocks analysis, secondary resources