The adaptive reuse of churches has become an important heritage challenge in Western Europe. Theories, design projects, and realisations proliferate, but are often based on incomplete heritage value assessments. Especially 19^th and early-20^th-century churches are considered less valuable because too numerous and too recent. However, in Belgium, many churches from the 1830s-1940s contributed to construction innovation and resulted from passionate debates between progressives and conservatives about the use of new materials from the industrial age. However, the actual surveys of churches do not pay great attention to these innovations, in particular when they are hidden such as roof structures. Basic knowledge about roof construction technology (design, relation with vaults, assembling, etc.) and materials (timber, iron, steel, reinforced concrete) used in churches remains very limited.

Henceforth, the main goal of this research project is to add criteria to the actual heritage value assessment methodologies by studying both technical-constructive aspects and the architectural-ideological context of the construction of church roofs in Belgium. The research will focus on Antwerp, Brussels and Charleroi, three of the most industrialised towns of the country. Comprehensive onsite measurements and investigations will be complemented with literature, archival and visual sources in order to contextualise specific cases at local and international level. This research is therefore carried out in collaboration with national and international researchers, organisations and professionals in the field of construction history and restoration practice, who contribute to a better understanding of the construction heritage and adaptive reuse of churches.

This master thesis is a thorough study of the timber floors and roofs of the headquarter building of the Baron De Witte de Haelen barrack situated in Etterbeek. This 19th-century military building was designed by architect Félix Pauwels in collaboration with the Génie Militaire. This work is lying within the scope of two topics that received relatively little attention so far: 19th- century timber construction and Brussels military barracks. Indeed, 19th-century timber construction is still under-researched in comparison with iron engineering that came to the fore at that period. The military context is an enriching parameter due to the specificity of the construction typologies, organisation and the profession of the involved actors.

This work consists of three main parts. Firstly, the historical context and description of the barrack complex is addressed. The milestones that could have had an influence on the building construction are presented. Moreover, the typology of the barrack is discussed according to the influence of the historical requirements in term of functionality, discipline, hygiene and social segregation. Furthermore, the roles and impacts of the various actors, and specifically the involvement of military engineers in the project, are addressed as well.

In a second part, the focus is put on the timber frame of the headquarter building. The floors and roofs are then successively investigated according to typologies, dimensions, materials, connections, etc. As the section of the floor beams revealed to be a specific timber-iron composite section, special attention has been paid to its analysis, including bearing capacity of the floor according to 19th-century method. A reconstitution of missing roof trusses based on photogrammetry was also carried out in order to present an exhaustive analysis of the timber roof. This chapter also deals with the material quality and construction techniques via the analysis of wood species and the marks – carpenter’s mark, merchant’s mark and tools – recorded on timber elements. This part of the work aims therefore to provide clues for the understanding of the construction choices made during the design and construction of the barrack’s framework in a context driven by military knowledge and iron engineering.

In the last part of this master thesis, the preservation of the historic building is addressed. Despite the technical and social changes of the Belgian army and the World War II bombings, the building is still remarkably preserved. The original features that foster the preservation, the repairs and replacements that occurred up to the beginning of this work and the current state of the building are successively presented. The bearing capacities of the floors are also discussed by comparing the results coming from 19th-century method and today Eurocode’s regulation. Based on the overall analysis, strategies for preservation and valorisation of the building’s timber framework are presented. This master thesis therefore aims to bring historical military construction to the light and appears as a call for further research in that specific under-exploited field.