## 5 Results  
Deconstruction needs to be separated into two categories, depending on the relation to structural or non-structural elements [80]. \"_Structural deconstruction_\" involves the dismantling of the structural building components that are an integral part of the building and contribute to its stability, such as beams and pillars for rigid frames and walls made by bricks for load-bearing systems. It needs a range of tools and equipment, heightened safety considerations, and a time frame of days or weeks to be realized. It is not always possible, depending on the construction technique whether it allows the connection between the elements in a reversible way or not [36]. \"_Non-structural deconstruction_\" consists in the recovery of non-structural components whose removal is not dependent on the structural integrity of the building and that are usually easy to dismount, such as doors, windows, and finishing materials. In general, non-structural deconstruction can be accomplished relatively easy and with few tools, limited labor, and typical job-site safety considerations, usually lasting hours or days. The building components can be removed without destructive approaches and additional structural support, such as bracing is usually not needed during the deconstruction operation [36]. Furthermore, the reuse of these elements is today considered a solid market [81]. Practical considerations and common sense suggest deconstructing the non-structural elements first, dismounting all the components such as appliances, windows, doors, and other finishing materials, which if removed do not cause the building to collapse. After the non-structural deconstruction, the structural one is the next step, and it is usually realized from top to bottom, starting from the removal of the roof to get to the foundations to avoid the collapse of the building. The following Table 4 describes the main characteristics of these two deconstruction approaches, making a comparison between them and the related criteria for demolition. The categorization in Figure 8 defines the different layers that make up the building and the related consecutive phases in which these must be deconstructed, regardless of the chosen building construction system. The first two layers consist of all the technical installations, such as wiring, plumbing, fire extinguishing systems, air conditioning, heating and ventilation systems, as well as and finishes such as fences, suspended ceilings and floor tiles. Many buildings are demolished early if their outdated systems are too entrenched to be easily replaced; therefore, a very flexible strategy is needed from the building's design stage in order to allow deconstruction at the building end of life. For example, the use of suspended ceilings, ensuring high spaces and that all installations are mounted in a visible way, allows both an easy inspection in homes, installations that need to be repaired or renewed, and an easy deconstruction of both the systems and the false ceilings. The third layer consists of all the partitions, the interior layout that includes partition walls, and internal doors. These building components can be also realized with dry connections, which make deconstruction activities easier and allow good results in terms of reuse of the building components. Sometimes, the connections are realized with binders, but their deconstruction can be quite easily accomplished, maybe not for reuse but for downcycling or recycling. The fourth layer consists of the enclosures, the building envelope--namely the facades and roofs of the building. As previously pointed out, the building shell can have a structural or non-structural function, depending on the building constructive system. However, there are parts, such as windows and doors, that are non-structural elements regardless of the type of building, and once deconstructed, they are easily reusable or recyclable. The fifth and sixth layers consist of the structural elements, in elevation and in foundation.