Introduction

Extensive work over a long period has been carried out worldwide in the field of cultural-heritage assessment. This is reflected in international charters, conventions, and principles illustrating wide-ranging principles for cultural-heritage documentation for conservation and monitoring. As Haddad, Fakhoury, and Sakr report:

The significance and the need for CH [cultural heritage] documentation have been stressed in most of the charters and conventions starting from Athens Charter of 1931, to Venice Charter of 1964, to Principles for the Recording of Monuments, Groups of Buildings and Sites (1996) to Australian Burra Charter (1999), to ICOMOS New Zealand Charter for the Conservation of Places of Cultural Heritage Value (2010), to ICOMOS Principles for the Conservation of Heritage Sites in China (2015), as well as many other recent conventions and declarations. (Haddad et al. 2021:293)

Beyond the importance of documentation, it is widely accepted that cultural heritage plays a key role in sustainable development (Vardopoulos 2019). Nevertheless, there is still room for improvement with respect to effective heritage protection policies and practices. Target 4 of the United Nations (2023) “Sustainable Development Goal” 11 (“Sustainable Cities and Communities”) states that efforts to protect and safeguard cultural and natural heritage worldwide should be redoubled. This is especially the case for certain types of heritage, including industrial heritage. Due to its relatively short history, this has received limited social recognition so far, and protocols for its preservation have not been thoroughly established. In this context, deficiencies and cases of malpractice have been identified at various stages of the industrial architectural heritage “value chain” (Amado Reino et al. 2002).

The cultural-heritage value chain (CHVC) is a concept that is central to a specific model of integrated management that values and signifies the historical dimension of heritage. The CHVC is articulated in a series of phases that constitute the different links in the chain: identification, documentation, significance, valuation, conservation, enhancement, and reception. In each phase, different knowledge-production strategies are applied that generate an incremental effect and added value in the following phase (Blanco-Rotea 2013). This concept is not new. Described as the “interpretative chain,” it was initially developed and applied to archaeology by Felipe Criado Boado (1996a:27–30, 1996b) and developed by Matilde González Méndez (1999:17–23) in her doctoral dissertation. The change of name to “CHVC” occurred later (Amado Reino et al. 2002), considering that “the concept of value chain or valuation chain is more accurate because different strategies for knowledge production, not only interpretation, come into play in the process” (Barreiro 2009:10). This said, in practice, shortcomings are evident in the early documentation stage, which constitutes the foundation for subsequent process phases. One example that demonstrates this unfortunate reality can be found in a number of pre-Renaissance manor houses in the Basque Country (Spain) that were systematically wrongly intervened. There a lack of documentation and poor analysis of the cases involved led to the heritage value of these sites being damaged (Luengas-Carreño et al. 2020, 2021). Another noteworthy example from the field of industrial heritage is that of “Manufacturas Olaran” (Beasain, Spain). In this case, deficient documentation and analysis of the architectural complex itself led to the erroneous interpretation of its evolutionary process. Legal protection was awarded on the basis of this incorrect interpretation, and as a result half of the original building was demolished while the section that was added as a later extension was maintained (Otamendi-Irizar 2019). The above examples demonstrate that it is essential to follow an appropriate research methodology systematically.

The concept of industrial heritage dates to the beginnings of industrial archaeology in the mid-20th century and work carried out by Donald Dudley (Hudson 1979). In this context it is worth mentioning some historical sources. In Britain, the cradle of industrial archaeology, the journal Industrial Archaeology, first published in 1964, and the annual conferences first held at the University of Bath in 1966 have guided the development of industrial archaeology. In 1974 the Association for Industrial Archaeology was founded to assist regional group studies to present the picture of industrial archaeology nationally and to persist with annual meetings (Cossons 1975). In the United States, the Society for Industrial Archeology was founded in 1971 “to promote the study, appreciation, and preservation of the physical survivals of industrial and technological past” (Society for Industrial Archeology 2022). The society aims to create an interdisciplinary environment with like-minded individuals to exchange knowledge and raise public awareness with regular meetings, primarily focused on industrial heritage in the U.S. IA: The Journal of the Society for Industrial Archeology, a biannual, peer-reviewed academic journal, is published by this society.

As described above, the relatively long tradition of research on cultural heritage contrasts with the case of specifically industrial heritage, an area that has received notable attention in recent years (Zhang et al. 2020). In this context, the Nizhny Tagil Charter on industrial heritage approved by the International Committee for the Conservation of the Industrial Heritage (TICCIH) in 2003 (TICCIH 2003) was an important milestone on this path. Heritage as an idea, however, as stated by Choay (1992), has a “nomadic character.” Consequently, the concept has evolved and expanded significantly as recognized in various international documents (TICCIH 2003; ICOMOS 2011; Sobrino Simal and Sanz Carlos 2019) and multiple research projects (Alfrey and Putnam 2003; Liu 2012; Hoffsten 2013; Lu et al. 2019).

Apart from institutional recognition, as stated in the Krakow Charter (Bureau Krakow 2000), “the identification and specification of heritage is ... a process related to the choice of values.” The issue of defining values has been approached by several authors (Riegl 1903; Mason 2002; TICCIH 2003; Sánchez Mustieles 2012; Claver 2016; Kuban and Pretelli 2019). In the words of Randall Mason (2002), these systems of valuation “describe the same cake but slice it in subtly different ways.” The expansion of the concept of heritage is reflected in the existing diversity of evaluation criteria. Beyond the architecture itself, some proposals have focused on the intangible dimension of this heritage (Blake 2002) and others on the value of technological and productive assets (Claver 2016; Otamendi-Irizar 2019).

Thinking through the value chain in practical terms, one of the most effective ways for an industrial-heritage asset to survive over time is through repurposing. This issue has prompted several reflections and proposals for different strategies. Given the extensive literature in this area (Mısırlısoy and Günçe 2016; De Gregorio et al. 2020), some authors affirm that “the adaptive repurposing of industrial buildings of cultural heritage is considered to be a pervasive concept” (Vardopoulos 2019).

Vardopoulos and Theodoropoulou (2018) describe the adaptive repurposing of industrial buildings as “an industrial building conservation process, to undertake a change of use, retaining as much as possible of the original construction, while upgrading the performance to meet current standards.” In this process, however, the objective must be to facilitate adaptation to a new use through minimal intervention. It is imperative that the characteristic elements and qualities of a site are preserved. With respect to this question, the work by Pendlebury, Wang, and Law (2017) on “strategic forgetting and selective remembering” is especially valuable.

In addition to the various studies that contribute proposals to address adaptive repurposing processes (Bottero et al. 2019; Della Spina 2020), other research focuses on management modes and the importance of participation in these projects (Oevermann et al. 2016; Oevermann 2019). Especially in the case of industrial heritage, these projects tend toward complexity. Operating from an interdisciplinary perspective represents a means by which difficulties that emerge from divergent viewpoints can be overcome (Lobovikov-Katz et al. 2018).

A large proportion of existing research approaches assets and related repurposing projects through multicriteria methodologies. These can bring together a wide range of variables in a single analysis and generate methodological proposals that facilitate decision making (Bottero et al. 2019; Claver et al. 2020; Della Spina 2020; Eizaguirre-Iribar et al. 2021).

Finally, it should be mentioned that many authors have granted a progressively greater importance to the graphic dimension in the field of heritage in both the research and analysis phases (Gümüşlü Akgün et al. 2019), as well as subsequent implementation phases (Hain et al. 2016). It is also worth remarking on the proliferation of recent proposals based on emerging technologies (Bruno and Roncella 2018; Stober et al. 2018; Pavlovskis et al. 2019; Senderos Laka et al. 2019; Soonwald et al. 2019; Leon et al. 2020).

All the contributions mentioned above are relevant to the appropriate development of the value chain and thereby contribute to the safeguarding of heritage resources. As indicated, the early stages of the value chain are of the utmost importance, as they condition subsequent stages. An accurate and detailed knowledge of an asset is essential to ensure correct interpretation and appropriate intervention.

In response to this reality, this article proposes a research methodology for the documentation and analysis phase of the value chain of industrial architectural heritage. This methodology facilitates an understanding of evolutionary process and particulars of each phase. The objective is to achieve a general understanding of a given site and its particular characteristics. This represents a solid basis for a well-considered valuation. As a first step, the existing documentation is studied, with architectural elements themselves also understood as primary documents. Each document is carefully reviewed, and the information derived from different sources is contrasted. Graphic reflection, based on the systematic use of visual materials (especially plans and sketches), should be considered a tool intrinsic to this methodology. A final benefit is that the methodology also facilitates working in larger and interdisciplinary teams.

This article is structured to demonstrate the effectiveness of the methodology introduced above through its application to a case study of a particular industrial architectural complex. The complexity of this site, “Nueva Cerámica de Orio,” facilitates a detailed demonstration. First, the methodology is presented in detail, with the different phases structured chronologically. Next, the case study is described, and the sources of information detailed. The third section presents the results. These depict, first, the application of the methodology to the concrete case study and, second, they narrate the evolutionary process of the ceramic-factory complex based on the data obtained. Finally, the conclusions drawn from the research are stated.

Methodology

To evaluate cultural architectural heritage, it is essential to start from a broad knowledge of the site to be evaluated and the history of its architectural constructive evolutionary process. In this context, both the study of primary sources and a careful analysis of the building itself are essential. However, the success of the research revolves not only around the information gathered, but also in the way it is managed. The heterogeneous nature of the data involved, especially in the case of architectural heritage, can make cross-referencing a complex task. Furthermore, the fact that research is most often carried out by teams with multiple members from diverse disciplines reinforces the need for a systematic and collaborative information-management model.

Sources of information relative to a site include, on one hand, documentary materials in the archives of public administrations (local, regional, and national) as well as other institutions that may permit public access to their archives. On the other, source material is often held in private archives. The archives of the various agents that have intervened in the site under investigation, including developers, project technicians, and construction companies, are especially valuable. In the specific case of industrial architectural heritage, in addition to the above, the archives of the various companies that operated the manufacturing complex over its history are of special interest. In certain cases, documents held by supplier companies linked to technology used by the plant can also be valuable. In addition to documentary sources, oral sources can constitute a valuable avenue of investigation. In the case of industrial architectural heritage, oral testimony can play a key role. Respondents could include, in addition to the owners and other agents who intervened in the property or participated in the local context, others who participated in the factory’s activity. This covers a diversity of agents from management to shop-floor workers. As indicated above, information of a very heterogeneous nature emerges from engagement with this diversity of sources. This includes but is not limited to written, photographic, graphic, and oral material.

Finally, it should be noted that it is essential to consider the architectural complex itself as a source of firsthand information. An in-depth study of the site—treating it as a physical document—constitutes a primary avenue of investigation.

This article details a methodological proposal (Fig. 1) that addresses the reality described above. It is divided into four phases. These include the initial collection of data in situ, a documentary-research phase, data interpretation, and finally a verification of hypotheses through carrying out samplings in the architectural complex being investigated.

Fig. 1
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The different phases of the methodological proposal. (Figure by authors, 2022.)

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Phase 1: Data Collection In Situ

The first phase includes data collection on the architectural complex under investigation. A base planimetry is essential to this process and may be either existent or created by the research team. Information characterizing the current state of the complex is compiled in this planimetry. In the case of industrial heritage, both technological (Aguilar Civera 1998; Claver 2016) and structural elements are characteristic. Neutral or open spaces—which are adaptable to a variety of uses and are defined by the structure itself—are relatively common (Aguilar Civera 1998).

This said, the structure of buildings should be characterized, identifying each structural element and its characteristics, including type of structure, materials, and dimensions. Data should also be collected on the general dimensions of different spaces. This information, entered in the base planimetry, facilitates an understanding of the general constructive and spatial logics, as well as the identification of unique elements that can assist with understanding the different evolutionary stages of the site. The coexistence of materials should be addressed, as well as dimensional diversity within elements of the same material. These can be indicators of different construction periods in the evolutionary process of the complex.

The site’s productive assets should also be identified and described, including their distribution and general dimensions. Any traces of productive assets no longer physically evident in the complex should also be documented. The objective of this phase is to help understand the various stages of production and identify the productive-spatial logic of the factory through a study of the spatial distribution of the productive elements. It is advisable that, preparatory to this phase, some research is done into the general characteristics of the production process linked to the industrial activity of the site being researched.

The whole site should also be documented photographically, including the general state of the site as well as the different specific features identified with respect to structural and productive elements. Oral testimonies can make important contributions to understanding, corroborating, completing, and clarifying the information obtained from the physical site in this first phase.

Phase 2: Documentary Research

The second research phase includes revising the documentary sources obtained. This process demands a customized digital database. Specific fields should allow for a basic description of the various documents identified, including their source (archive, background, original document code, title, etc.). A dedicated field should be included for the coding to be used in the research. Other descriptive fields can be used to record the type of document, date, scale, description, and other information as necessary.

The remarkable diversity of sources, heterogeneity of the data to be collected, and the involvement of multiple researchers demands effective systems for methodical information processing and management.

To this end, this methodology argues for a systematic reading of each document, extracting the most relevant objective information, and entering this data as a data sheet in the project’s global database. Each data sheet (hereafter “document data sheet”) should include the information of interest derived from the study of each document. Thus, data sheets should include fields for general information (title, code, date, linked files, etc.) and other fields dedicated to the main content. Here, the objective textual information (transcribed or consisting of descriptive annotations), interpretations on the objective data, and possible related hypotheses deduced are gathered together. In the main content, a field for graphic information accompanying the reading of the textual information is included. Hence, a similar task is done graphically, including information from each document (if possible) in the base planimetry from phase 1.

The creation of document data sheets establishes initial hypotheses, but normally these cannot be corroborated at this stage, as information is lacking or there may be contradictions among the information collected from different sources.

Phase 3: Data Interpretation

In the third phase, a process of reflection is carried out through cross-referencing the data collected and analyzed in earlier stages. The aim is to corroborate or refute hypotheses generated in previous phases and to draw up new hypotheses with respect to understanding evolutionary process in the architectural ensemble being researched. Defining specific units of study and/or representative elements of the given architectural complex, according to such characteristics as size, typology, and other key points, is essential in this process. A unit could be a building in a complex containing differentiated constructions or a characteristic area in a compact complex or in cases where a single building is being researched. Research based on these units allows researchers to understand the complex in accordance with the logic of the site itself. The architectural and productive assets characteristic of a factory complex (facade, structure, machinery, etc.) can also constitute differentiated units of study. In some cases it becomes necessary to define subunits. One example might be differentiating particular elements within a unit of study encompassing an area or a building.

In order to facilitate cross-referencing, the methodology proposes the establishment of a second standard data sheet (hereafter “unit data sheet”) (Fig. 2) for each unit of study. This file systematizes the information compiled in the different document data sheets created in the previous phase with respect to each unit. Hence, it is necessary to assign the information compiled in phase 2 to the identified units. In all cases, the origin of the data entered is identified through the assigned coding, and the information is then ordered chronologically. Additionally, these data sheets should be filled in with data from other sources, including oral testimony and documentary sources. The structure and method for filling out these data sheets is similar to that described above in phase 2. Accordingly, the creation of these data sheets facilitates a global vision of the information (textual and/or graphic) with respect to each unit of study. This in turn facilitates a comprehensive analysis and, therefore, the construction of unified hypotheses. The cross-referencing of the graphical information is carried out using different computer-assisted design layers for each of the documents studied, overlaying the information obtained from each document. This makes it easier to identify overlaps, complementarities, or conflicts among diverse information.

Fig. 2
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Sample unit data sheet. (Figure by authors, 2018.)

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Phase 4: Defining Conclusions

The fourth and final phase involves defining a matrix that includes all the information in an integrated and systematized format. This facilitates a global understanding of the evolutionary process of the architectural complex and the characteristics of each evolutionary stage. This matrix is structured along two axes: a chronological axis, characterized by the evolutionary stages of a given site, and a spatial axis, including the different units—and subunits—of study. This step facilitates a global reading of a site’s history. It also makes it possible to identify gaps in knowledge and hypotheses deserving of further, specific investigation.

In these cases, targeted sampling can be carried out to obtain material evidence clarifying hypotheses. The locations selected for taking samples should be determined by the specific material evidence needed to shed light on pending unknowns. Sampling should take into account the constructive and architectural characteristics of the site. This process involves decision making in situ based on the material evidence found. Given that gathering samples involves material destruction, it is important to document the process and to integrate sampling with relevant testimony from different historical periods. The methodology for sampling involves the creation of a data sheet for each sample (hereafter “sample data sheets”). These data sheets should include the initial hypothesis, the objective of the sampling, a description of the process and the results achieved, conclusions, and, finally, photographic documentation of both the process and the results of the sampling.

At this point it becomes necessary to finalize the conclusions matrix by integrating findings derived from samples. Thus, this matrix includes all essential data related to the evolutionary process of the complex being investigated, and so constitutes a summary of the research.

Case Study and Data: The “Nueva Cerámica de Orio” Factory

The methodology detailed above was applied to a modern industrial architectural complex in Gipuzkoa (northern Spain). Although this site has been awarded official heritage status, it had not been studied in detail prior to this research. Protection was granted because of its architectural style and the renown of Luis Tolosa, who was the main actor involved in the architectural design of the complex. However, the interior of the building was undocumented, as access was not possible in the initial evaluation process. As a result, several important gaps in knowledge of the site remained.

The “Nueva Cerámica de Orio” factory is located at the mouth of the Oria River in the municipality of Orio. It is south of the urban nucleus on a plot delimited by the estuary to the south and the road to the north. It is currently made up of three buildings: the main industrial facility in the southeast of the plot, an office building in the southwest, and a laboratory and truck weighbridge building in the northwest. Four principal historical stages were identified (Fig. 3).

Fig. 3
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Principal historical stages of the “Nueva Cerámica de Orio”: (a) pre-1919, (b) 1925, (c) 1940s, and (d) 1960s. (Figure by authors, 2018.)

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The complex visible at present was consolidated in the 1940s. The origins of the plant, however, date from the end of the 19th century. In 1888 the factory occupied at least one smaller building and another larger one housing kilns and chimneys at the northern end of the plot. By 1910 there was also a pavilion made up of seven parallel three-story warehouses with wooden structures and gabled roofs. These were constructed in the southern area. These buildings constituted the site in the first stage (Figs. 3a, 4a). In 1925 the factory expanded through the addition of a drying room in the southeastern area of the plot. This building was based on a reinforced concrete structure. Designed by Luis Astiazaran, it was based compositionally and structurally on the preexisting three-story pavilion. This intervention, which represented an important innovation for the complex, defines the second evolutionary stage (Fig. 3b). In the 1940s a major operation was undertaken to redevelop the image of the preexisting complex based on the grouping together of various factory buildings, constituting the third stage of evolution (Figs. 3c, 4b). A large-scale factory building was built to fit in with the preexisting elements, bringing together many productive assets and existing structures and creating a unified image of the complex. Luis Tolosa proposed a building that extended from the north to the south of the plot, creating an architecture that presented a modern image achieved through the horizontality of the facade and a flooded flat roof that finished off the whole (Azpiri Albistegui 2012). Although the present appearance of the complex is in line with the image conceived by Tolosa, further interventions were carried out on this building as part of a fourth evolutionary stage (Fig. 3d). The unified and apparently simple aesthetic of the complex hides a very complex reality. This is true to the point that the first issue confronted was to understand how the execution of this project was approached, that is, how the preexisting elements were integrated with the new ones and the productive features with the architectural. This research was therefore focused on clarifying this issue and concentrated on the third evolutionary stage corresponding to the project designed by Tolosa.

Fig. 4
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View of the factory from the southwest: (a) 1919 (OPA 1919), (b) 1939 (LTA 1940).

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Access to documentation is essential in heritage studies, with private archives being of special interest in the case of industrial architectural heritage. Diverse sources and types of documents relevant to both the architecture and technology were consulted, including, among others, photographs, planimetry, and correspondence. The sources consulted are detailed in Table 1. As well as naming sources, this table clarifies their ownership and the information obtained. Additional information was obtained directly by gathering data in situ and through sampling carried out in the buildings.

Table 1 Documentary sources for the research
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Results

The results section below explains how the methodology described above was applied in the case of the “Nueva Cerámica de Orio” factory. Subsequently, the specific results obtained by focusing on the evolution of the manufacturing complex—centering on Tolosa’s project—are detailed, specifying the origin of the data that justified the decisions taken and solutions proposed.

Application of the Methodology to the Case of the “Nueva Cerámica de Orio” Factory

The methodology was applied in the following four phases: data collection in situ, documentary research, data interpretation, and the write up of conclusions.

Phase 1: Data Collection in Situ

In the first phase, the factory complex itself was treated as a physical document from which to extract essential information. The first step in this process was an initial survey of the complex to identify structural elements, including columns, beams, joists, and construction joints. Each of these elements was measured, and the different existing systems, materials, and construction features documented (Fig. 5). A basic digital planimetry for the structural description of the factory was generated from these data.

Fig. 5
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Structural data-collection sketches of the western area of the “Nueva Cerámica de Orio” (left) and furnace drawings (right). (Drawings by Irati Otamendi-Irizar, 2018.)

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This planimetry identified productive assets, including kilns (Fig. 5), chimneys, presses, and mills, and recorded their distribution, basic function, and general dimensions. In the case of machinery, basic data, including model, brand, engine data, and year, were also documented. In this phase, the visible remains of productive assets that had been used in earlier periods of operation were also identified, as well as the signs of interventions carried out for the installation of these elements. Perforations in slabs executed to make it possible to use chains to transfer machinery were one example of this. Another was the presence of reinforced concrete slabs that marked where earlier generations of machinery had been installed.

Throughout this process, the oral testimonies of both the owner and a factory-floor worker proved enlightening with respect to the operation of the factory and some modifications made over time. The oral testimony complemented the information obtained via data collection in situ. This procedure allowed the team to acquire a broad knowledge of the complex before proceeding to the study of the documentation that would form the basis of the investigation.

Parallel to the information-gathering process, other researchers on the team proceeded to graphically survey the factory using photogrammetric techniques and laser scanning, combined with traditional techniques (Senderos Laka et al. 2019). The photographic documentation of the rest of the site and the productive elements it contained was carried out by the same means.

Phase 2: Documentary Research

To engage with the diversity of the documentation handled as part of this research, a custom database was generated as described in the above section on methodology. In the case of the documentation from the “Nueva Cerámica de Orio” Company Archive (NCOCA), documentation was digitized as a necessary prior step to subsequent cataloguing.

The systematic study of the documentation resulted in the generation of 25 document data sheets. This phase, added to the information gathered through data collection in situ, made it possible to identify the four fundamental stages in the evolutionary process of the complex. It also provided some indicators with which to identify the particularities of the stage corresponding to the intervention by Luis Tolosa, which was the most significant transformation of the factory over its time in operation.

Phase 3: Data Interpretation

In order to carry out the interpretive phase, the existing factory complex was divided into six study units. Four of these units correspond to the different zones identifiable through construction joints in the main factory building: Zone A-B, Zone C, Zone D, and Zone X (Fig. 6). The two smaller buildings in the complex (a laboratory and office building) constituted another unit. Finally, the factory envelope was categorized as a separate unit of study due to its importance in the Tolosa project. The names allocated to the four zones of the factory were based on the denomination used by Tolosa himself when designing the project.

Fig. 6
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Different zones of the main factory building. (Figure by authors, 2018.)

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Zones C and D, originally dedicated to the firing phase of the material produced, are characterized by the existence of various kilns and chimneys, as well as vestiges of older iterations that have disappeared from the site. For this reason, three study subunits were defined with respect to the productive assets in both zones.

For the cross-referencing of data from the document data sheets, six unit data sheets were generated. These made it possible to establish the main hypotheses for each unit and the links between them. The hypotheses addressed such issues as the factory prior to the Tolosa project and the identification of the preexisting elements or parts located in each study unit, the influence of these preexisting features on Tolosa’s decision making and the solutions he adopted, the phases of implementation of the Tolosa project, and subsequent interventions (Fig. 7).

Fig. 7
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The foundations plan of Zone C based on the textual data obtained from several written documents (top) and plan of foundations of Zone D (bottom) (LTA 1940) that allowed researchers to corroborate hypotheses about subsequent construction in this zone. The rectangle with a dashed line indicates the joint between Zones C and D. (Figure by authors, 2018.)

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Phase 4: Defining Conclusions

As proposed in the methodology section, a matrix was generated with the information from the previous phases. The organization of the chronological axis was based on the different evolutionary stages of the architectural complex. These have been detailed above. The spatial axis included the six units of investigation and the corresponding subunits already mentioned. For systematization, each piece of information was identified by the code of the document from which it was drawn. These codes were determined in the archival research phase.

This operation facilitated a global understanding of the evolutionary process of the complex and the corroboration of most of the hypotheses drawn up. In addition, researchers were able to understand the origin of the zoning defined by Tolosa. On the one hand, the different zones coincide with the areas in which different stages of the project were executed. These phases were determined by the indispensable condition that they would not result in a shutdown of industrial production. On the other hand, the zoning is consistent with the various conditions to which Tolosa had to adapt both the design and the construction process. Tolosa’s transformation of the complex from a group of heterogeneous constructions to a new unitary configuration while maintaining several elements and minimizing disruption to production compelled him to implement different solutions in different parts of the factory.

In the case of hypotheses that could not be corroborated through archival sources and in the case of questions that deserved further verification with material evidence, researchers proceeded to onsite sampling. Two samples were taken to clarify the possible existence of material remains of two kilns of types that are no longer in evidence at the complex. A third sample confirmed a hypothesis about the solution adopted by Tolosa to reuse a preexisting structure in the new factory. In addition, two samples confirmed that the existing spatial configuration in one of the areas corresponds to an intervention posterior to the Tolosa project.

From Data to Understanding: Reconstructing the “Nueva Cerámica de Orio” Factory

Among the archival material employed in the research, a project draft from the 1940s (NCOCA 1940–1942) illustrates the general organization of the reinforced-concrete factory designed by Tolosa. The objective of the project was to create a unitary factory body with an updated and unified aesthetic. The envelope of this architectural volume exhibits a dual character: closed toward the road and open toward the estuary (Fig. 4b).

The unitary exterior of the industrial complex conceals a much more complex internal organization. On the one hand, the open/closed duality was a response to technical imperatives of production that are reflected inside the building. On the other hand, the need to include several preexisting elements without stopping production led to a staged process of construction. Different areas were acted on in different phases.

The documentation studied made it possible to identify and understand the details of the execution of the work by stage and zone. Documentation relating to the execution of the Tolosa project from the NCOCA dates both the start of the works and the calendar of execution of work in each zone. The footing calculation document prepared by the builder (NCOCA 1940–1942) reveals that by January 1941 works had already begun, since the results of load tests carried out are mentioned. Similarly, a note from the construction manager (NCOCA 1940–1942) reports that in November of the same year the construction of Zone C was being finished and the construction of the foundations of Zone D had begun.

Comparison of a structure-measurement document (Luis Tolosa’s Archive [LTA] 1941) with the plan of Zone C (LTA 1940) revealed the existence of multiple foundation columns in the footings of the joints between different zones. This is shown in Figure 7 at the junction of Zones C and D, marked by the rectangle drawn with a dashed line. Hence, it follows that the two adjacent zones (A-B and D) were built later. Similarly, in the measurements of Zone D (LTA 1941), the footings of the joint with Zone C are not mentioned, thus verifying that Zone C was constructed earlier. In this last document, however, the footings of the joint between Zones D and A-B are mentioned, and therefore it can be deduced that Zone D was built before Zone A-B. Additionally, invoices and project reports from November 1942 (LTA 1941) confirm that, at this stage, Zone C had been completely executed and Zone D partially finished, with the structure having been built up to the second floor. By contrast, no measurements or end-of-project documentation were found with respect to Zones A-B or X.

Thus, researchers determined the following sequence for the execution of the Tolosa project: Zone C, Zone D, Zone A-B. The dates of execution of works in Zone X were not able to be established. It was confirmed that Tolosa faced a complex onsite situation. The preexisting complex was made up of various grouped buildings and, therefore, the original conditions in each of these areas were very different.

Action in the Northern Part of the Factory: Zones C and D

Historical photographs (Orio Photo Album [OPA] 1910, 1919) allowed researchers to see that, in the 1910s, the complex that occupied Zones C and D consisted of a three-story building with a two-sided roof arranged parallel to the road and a smaller building perpendicular to the road. This building was two stories tall with a three-sided roof. Similarly, a dated photograph (Deschamps 1939) clarified that, at least as late as 1939, the largest building parallel to the road was still standing. Thus, it can be inferred that Tolosa’s project replaced the preexisting buildings with reinforced concrete structures on the same site. Design documents dating from 1940 (LTA 1940) (Fig. 8) provided details of the general plan of the project, as well as information on the structural layout of beams, joists, and columns. In addition, these documents allowed researchers to identify different areas in which the plan was adapted to work around preexisting productive assets.

Fig. 8
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Site plan, 1940. The red line marks the area to be occupied by the new building, housing preexisting elements in its interior (LTA 1940).

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Five structures that represented kilns of various sizes and geometries were identified (LTA 1940). Researchers were also able to locate six openings around which the building’s structural framework was adapted, four of which still house two separate kilns. On the site map, a small circle marked with the word “kiln” at the western end of Zone C deserves special attention. This circle represents one of the small kilns that, according to an industrial registration document dating from the beginning of the 20th century, existed prior to the construction executed in the 1940s (Municipal Archive of Orio [MAO] 1906–1943). While there is no kiln at this location at present, the need to house it did call for an opening in the first-floor slab. This opening is still in evidence. Samples confirmed this hypothesis by identifying material evidence of what was the ceramic base of the kiln.

In addition to this kiln, two circular kilns marked on the site map in Zone D correspond to those existing today. These kilns were connected to a frustoconical chimney with a square section. This chimney is featured in a photograph from 1919 (OPA 1919), which confirms the existence of the aforementioned kilns before they were documented on a site map from 1925 (MAO 1925).

The same area contained a square kiln that appears on the abovementioned site map from 1940 (NCOCA 1940–1942). The earliest documentary evidence found corresponds to a site map from 1925 on which this kiln also appears. This kiln no longer exists, but the gap in the slab needed to house it is still in evidence. Additionally, the structural design of the second-floor slab—executed by means of a header beam—enabled researchers to identify the hole that once existed for the chimney. This evidence confirms that Tolosa included these productive elements as part of his project. Elevations drawn by Tolosa (NCOCA 1940–1942) also show the existence of the aforementioned truncated cone-shaped chimney and a slender chimney connected to the square kiln. In the research carried out, samples were taken to corroborate this hypothesis, with the aim of identifying material evidence of the base of a kiln at this location. Analysis of the samples taken did not provide this confirmation, most probably because the area has undergone major alterations to accommodate heavy machinery.

Finally, in contrast to the two kilns and the chimney currently existing in Zone C, on the 1940 site map (NCOCA 1940–1942) a circular kiln is depicted with a discontinuous line. This indicates that it was, at that stage, a planned addition to be executed at a later phase. This idea is corroborated by the arrangement of the footings for the structure around the kilns. In Zone D, the footings were built off center and concentric to the kilns. This was due to a need to work around the already existing kilns and surrounding area. In Zone C (NCOCA 1940–1942), foundations were laid with greater liberty, following the orthogonal logic of the structure in general without deviating in response to preexisting elements. In addition, in Zone D the slabs for the first and second floors feature extensions—by means of eaves formed by the slab—adapted to the perimeter of the kilns at each floor. This made it possible to avoid leaving a gap between the slab and the kiln (Fig. 9). However, in Zone C these extensions were not present. This indicates that the building was adapted to the anticipated future installation of a kiln, and enough space was left for its installation.

Fig. 9
figure 9

The structural plan of Zones C and D. In the zoomed-in image, the two circles show the extension of the first- and second-floor slab adapted to the perimeter of the kiln (NCOCA 1940–1942).

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Tolosa’s preliminary draft plans did not include the chimney associated with the abovementioned kilns. Furthermore, the opening that currently allows passage of the chimney is not finely finished. It is evident that a preexisting slab had to be drilled for its installation. This constitutes evidence that, when Tolosa rebuilt the factory, the construction of these ovens and their chimney was not undertaken. Researchers were able to support this hypothesis through archival material, specifically a site map from a project dating from 1952 (NCOCA 1952) that depicts the constructive and formal characteristics of one of the currently existing kilns (NCOCA 1940–1942).

Action in the Southern Part of the Factory: Zones A-B and X

According to an historical photograph from the late 1910s, the southern part of the factory—including Zones A-B and X—incorporated a pavilion made up of seven three-story warehouses, each with a gabled roof per nave, and a smaller body. The first was in Zone B and the second in part of Zone X, while Zone A did not contain any structures (NCOCA 1940–1942). Photos from two decades later demonstrate changes in Zone X (Deschamps 1939). The preexisting smaller structures have been replaced by a pavilion, also with a gabled roof, equal in height to the preexisting pavilion but aligned toward the estuary. These changes were a result of a project to create a drying area signed by Luis Astiazaran in 1925 (MAO 1925) (Fig. 10). The newer building had a reinforced-concrete structure and a roof based on wooden trusses for each bay. Although the reinforced-concrete structure is still present, a flat reinforced-concrete roof substituted for the original as part of the subsequent Tolosa project. Tolosa inherited the complete reinforced-concrete structure designed by Astiazaran and built new structures in the rest of the area (Zones A-B, C, and D). In order to create a unified image for the factory, in addition to acting on the roof of Zone X, Tolosa added eaves to each of the slabs running along the entire southern section of the building envelope.

Fig. 10
figure 10

A plan of the drying area project, designed by Luis Astiazaran in 1925. The structure depicted from the middle of the image down toward the bottom corresponds to that designed by Astiazaran. The rest was already present on the site (MAO 1925).

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This conclusion is based on data from various sources. On the one hand, on the 1940 site map (NCOCA 1940–1942) there is a notable difference in the way the structure in Zone X is represented as compared to other structures. This could indicate that this structure was designed by Astiazaran. Likewise, the volume calculations for the metallic part of the structure in Zone X—sourced from documentation specific to the execution of the Tolosa project (NCOCA 1940–1942)—refer only to the construction of the flat roof and the eaves in reinforced concrete. In this regard, observation of the structure confirmed that the columns and beams of the portico corresponding to the envelope differ from the rest. This was most likely due to their role in the construction of eaves on a preexisting structure. Sampling carried out on one of the facade pillars allowed researchers to understand the constructive solution used. The structural elements of the original portico were found to be embedded within the currently visible newer elements, which have a thicker cross section.

The southern part of the complex housed the initial phases of raw-material preparation (crushing, grinding, etc.) as well as the shaping and drying of pieces. For this reason, it contained large open surfaces for drying. The productive assets that were in this area at different times were smaller machines installed for use in the preparation and shaping phases. The 1940 site map indicates that Tolosa took the productive assets in Zone B into account. Researchers were able to identify several structural adaptations, including the elimination of some pillars in locations where they would have interfered with production. Additionally, the plans detailing the reconstruction of the factory (NCOCA 1940–1942) illustrate construction solutions that specifically responded to these exceptions. Some of these are currently visible in the factory.

This said, while some of the structures described above are still recognizable, a large proportion of the interior of Zone A-B has been significantly modified. This zone is currently characterized by the existence of a diaphanous double-height atrium space. The generation of this open space was executed through structures that differ significantly in dimension in respect to those proposed by Tolosa. The preexisting structure is maintained in a perimeter bay on the first and second floors (except for the side of the joint with Zone D and X). The slab has been modified on the second floor and completely replaced on the third. These changes were corroborated through samples taken at the edge of the first-floor slab that forms the perimeter of this two-story atrium. Specifically, the end point of a rough truss that was bent during construction to close out the slab that was partially demolished in order to create the open space was identified.

The first documentary evidence of this two-story atrium corresponds to a technological project (NCOCA 1940–1942) (Fig. 11) that included the installation of two new presses and a mixer, as seen in the lower left part of the picture. For dimensional reasons, it was necessary to remove the first-floor slab and create a double-height atrium to accommodate the new machinery. This matches the machinery currently installed in this space. However, the structure in the proposal differs from what was eventually constructed. It seems that the planning documents represent an initial idea that was principally focused on the technological upgrade. On the basis of the documentation referring to the machinery installed in this space (NCOCA 1952–1970), researchers were able to ascertain that the purchase process for the first machine began in 1961. By 1965 the largest machine had already been installed. As this installation would not have been possible prior to the creation of the open space, researchers were able to confirm that the execution of this two-story atrium occurred prior to 1965. The appearance of this new space coincides with the abandonment of a project to build a new large-scale storage warehouse on the adjoining plot (NCOCA 1953). This suggests that the atrium project to house new machinery represented an alternative solution to the needs of the moment. Instead of increasing storage space for larger reserves of stock, production capacity was increased.

Fig. 11
figure 11

A plan of the technological project for the atrium, depicting the double-height space created on the ground floor to house the large machines (NCOCA 1952–1970).

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The two most significant changes to the industrial complex that occurred subsequent to the transformation executed by Tolosa therefore include the aforementioned two-story atrium and the modifications in the building envelope executed in the southern and western areas. The latter compromised the open and luminous character of the original building. The western facade appears closed and follows the formal and constructive logic of the envelope on the north face. On the southern face of the factory, the light metal railing designed by Tolosa has been replaced by a parapet formed by cylindrical elements made of reinforced concrete. Although these two interventions have not been dated precisely, a photograph shows that the facade of the west face had already adopted its current appearance in 1961 (OPA 1961).

Conclusions

In recent years, proposals based on new technologies and multicriteria methodologies for the recognition and repurposing of industrial architectural heritage have emerged. In this context, this research has identified deficiencies in the initial stages of the value chain. Given this reality, systematic documentary research is an essential part of any research into architectural heritage. For these reasons, this article argues for a careful and detailed study of a heritage asset, taking into account all the documentation compiled from different sources. This includes understanding the asset itself as a document and, therefore, as an important source of information. A specific methodology created to address the gap identified in the field is described in this article.

This methodology is based on the cross-referencing of data from different sources in order to formulate and corroborate hypotheses. To achieve this, on the one hand, documentary information is graphically dumped onto a planimetry, creating a superimposition of information from different documents that is key to understanding various specific aspects of a site. On the other hand, the cross-referencing of data with textual information is carried out by means of sheets and tables created specifically for each phase of the research (document data sheet, unit data sheet, matrix, sample data sheet). This procedure, organized in a systematized set of data sheets, made it possible to corroborate the majority of the hypotheses generated over the course of the research.

In contrast to the latest research trends based on new technologies, which demand a high degree of research specialization, the methodology proposed herein allows for greater flexibility. This increases its usefulness for multidisciplinary teams and/or in the case of research with limited economic resources, using basic tools. Nevertheless, the manual creation of data sheets could impose limits with respect to the organization and processing of larger volumes of data. Were this the case, the application of methodology might demand the use of information technology (IT) systems, including automated databases. For this reason, a future evolution in the methodology could occur through the systematization of the processes based on IT tools, where downloading of information from document data sheets to unit data sheets could be automated. Hence, the integration of latest-generation technological tools could complement and enrich the research process, if this did not represent a dramatic departure from the basic premises of the methodology. Going further, the use of “Heritage Building Information Modeling” as a digital tool for the study and management of heritage should be mentioned. However, the level of technological sophistication changes considerably, resulting in the extension of heritage research projects over time or the expansion of the research teams.

The methodology proposed herein is particularly applicable for research into industrial heritage, taking into account the type of sources analyzed. However, it can also be used for other architectural-heritage assets, taking into account typology, period, and geographical location. It should be added that it is especially valuable when researching more complex sites, including complexity in terms of chronology, dimensions, or spatial factors, and in cases in which a site or complex has undergone alterations as part of its development and evolution.

In this regard, the methodology can add value across all the different phases of heritage research that make up the CHVC, since further deepening in the documentation phase of the CHVC enhances all subsequent phases. Without a thorough knowledge of the asset in question, considering not only the final architectural outcome but also construction processes, evolution, spatial organization, and historical context, agents involved in heritage management will not be able to make the most appropriate decisions or convey all the values that a heritage asset may have. In this regard, the methodology proposed herein for documentation and analysis enables a comprehensive understanding of heritage assets that facilitates a prioritization of repurposing actions and, hence, decision making during the design phase or even in site management. The more knowledge, the more tools become available for decision making.

This article described the application of the methodology to the “Nueva Cerámica de Orio” factory heritage complex. By following the research procedure, researchers were able to identify the different evolutionary phases, different areas and units that made up the industrial building, and alterations made over time. In general, the research confirmed that, in the case of industrial heritage, the study of the production processes is of special interest. As occurred in the case study, this facilitates an understanding of the constructive and architectural elements. To this end, the study of the evolution of the production process in the factory—especially the demands this made on space and spatial distribution—and the specific documentation referring to the machinery used in the factory was essential. With regard to documentary research, the case study of the “Nueva Cerámica de Orio” factory confirmed that indirect information from a document can be as important as direct information. Documents about projects that were not executed can provide information about projects that were executed without leaving a documentary trace, for example. Individual sketches and different forms of representation found in planning documents can also provide strategic information. Dashed or shaded lines may refer, for example, to elements that are anticipated rather than actually in existence at the time of drawing. Finally, some very specific documents, such as the end-of-project paperwork and photographs, can be essential to corroborate the execution of different phases or construction elements, since they refer to the reality existing at a particular time.

Hence, the methodology proposed herein allowed researchers to generate a better understanding of a particular heritage asset. In the case of the “Nueva Cerámica de Orio” factory, it was concluded that the heritage value of the site was considerably higher than had been previously assumed, as initial heritage recognition was granted based primarily on the architectural style of the building envelope. In fact, the work of Luis Tolosa must also be recognized as a remarkable technical and creative achievement, encompassing as it did a complex and heterogeneous existing reality, including machinery, kilns, and even an existing building within its unitary envelope, while also being executed in such a way as to minimize interruption in production. Moreover, it was observed that the technological value of the asset is noteworthy.

Finally, certain limitations were encountered over the course of the research. On the one hand, although a variety of information relevant to the case study was identified, it was ultimately insufficient to produce a detailed understanding of actions complementary to the main works and to changes that were planned or initiated but never completed. With respect to sampling, preservation was prioritized. More extensive sampling might have led to confirmation of further hypotheses, but at the cost of the destruction of valuable parts of the complex.