2.3.1. Scale

One of the most interesting characteristics of the industrial heritage, as the typology of the cultural heritage, is the variety of scales in which these assets can appear. The criteria structure of the catalogue includes five different categories for the classification by scale: chimneys and other, immovable asset, system or building set, landscape or area, and territorial infrastructure. All of these categories are easy to understand through examples, but also it is possible to give many examples in which the boundaries between categories are not so obvious. In order to help with classifying each good by this criterion, the authors defined a set of aspects that can be perceived in a different way from the perspective of each classification category [1]. Figure 4 resumes the initial guidelines.

**Figure 4.** Graphical guidelines for the classification through the scale criterion.

The category "chimney and other" is used when only the remains of some isolated parts form the original state of the asset. The most usual example of this situation is industrial chimneys, but other elements such as melting furnaces are also included in this group. These kinds of elements are not movable assets, but they are not immovable assets, either. Nevertheless, some of these elements can be really large, as in the case of blast furnaces, so they can even perceived as buildings by many people. Figure 4 identifies the habitability as the key aspect to be considered when the studied good did not

belong clearly to either of these two categories. Chimneys, furnaces, and other similar elements have been built using the same constructive systems used in the industrial buildings in which they were included, such as for example using bricks, and they can be big, too; so, effectively they can be really close to the building scale. However, they were not designed to be inhabited, and there are not real living spaces in them.

The limits between the category of "immovable asset" and "system" or "set of building" will be confusing. It is easy to distinguish between a single building and a set of them. However, there are buildings that are the result of the sum of different spaces that define various independent volumes. In these cases, it seems as if various different buildings had been joined into only one. This idea can be exposed clearer in the opposite sense. It is usual that industrial facilities, with a long enough period of activity, experiment with changes due to the adaptation of the installations to new needs. One often action in that context consists in the covering of the space between two industrial buildings in order to expand the facilities. However, this does not mean that those two separate buildings are only one, even though they can be seen in that way. When classifying an asset in that situation, its analysis will not be focused only in the constructive appearance as a single building, and its more complex nature will be detected.

Thus, the same approach can be applied to other similar situations. There are industrial buildings in which it is possible to identify enough independent elements. However, the application of this idea can be confusing, so a clear guideline must be established. An approach to the problem through reuse actions in large industrial facilities can provide the key aspect to be considered. When this type of asset is recovered for new uses, usually the whole facility is not reused, but some elements are, even for different activities, and this is a demonstration of their independence. Thus, when analyzing great buildings, which also could be understood as the result of a sum of different volumes and productive spaces, thinking about the real possibility of acting on only some of those above parts is what can help determine whether enough independence exists between them for them to be considered as different elements, or not. Figure 5 illustrates this idea graphically: on the left and right are representations for the concepts of a single asset and a set of assets, and in the middle area of the figure, intermediate situations are shown. Thus, the capability or not of acting only on particular parts is what determinates the classification as a single asset or as a set of assets.
