The problem of post-disaster reconstruction goes unavoidably through the phase of transitional living. To build for temporariness is first of all a cultural issue and today can be interpreted according to two prevailing needs: (i) to comply with the requirements of minimizing the impact on the land, protecting the resources and maintaining environmental balance; (ii) to stress the temporariness of the building itself, in order to realize the highest degree of reversibility once its use has been fulfilled. The concept of reversibility of the construction needs to be operated as a process innovation rather than as a product innovation, through systematic actions of planning, design, construction and de-construction, and re-introduction of the technical resources in a further productive cycle that adheres as much as possible to the realities of industry and to the rules of the productive system. The transitional house becomes a built object which is dis-integrable in two senses: (i) as a system of components which can be easily disassembled and (ii) using a biological metaphor, as a construction that is dissolved without leaving waste, since the material resources from which it is made can be reused. This paper illustrates the results of research aiming at defining the design requirements of the transitional living phase after an emergency and to show the technical feasibility of the reversibility of the building process.