Three case studies have been chosen to discuss the adaptation process of converted buildings and demonstrate a novel mapping method. They have been chosen for their different scale, function and qualities as architectural spaces. Moreover, they date from different periods of the twentieth century. Therefore, even though they are all skeleton buildings, they show subtle differences in the scale of the components and the complexity of the construction. It is no coincidence that most of today's large-scale conversions are originally industrial buildings, which in their generosity and robustness allow for many potential reuses, but even in their possibly modernist expression have qualities all their own. Unfortunately, many such buildings are nevertheless demolished, and the following discussion is intended to reveal decisive characteristics of good adaptability.
Belgrade building, Brussels, 1972/2022
The first case already has a dense history of reuse within its 50 years of existence. Built in 1972 by Brussels architecture firm AUSIA, the building was conceived as a compact Cinzano factory. It was then turned into a warehouse with offices in 1995. Embedded in a residential area, the building stands out from its surroundings, mainly because of its brutalist façade. It has a very regular concrete structure consisting of a wide span skeleton and superimposed slabs spanning in both directions. The spans are consistently 8 m with cantilevers varying between 0.5 m and 1.5 m with clear room heights between 3.61 and 4.50 m. Next to the main loadbearing skeleton structure stands a structural core providing stability to the building and allowing vertical circulation of people and services (stairs, elevators, technical shafts). Thanks to the core, the building featured vast open space for the warehouse and offices (Figs. 2 and 3a).
The municipality decided to develop the empty building as social housing in 2020 (https://www.bogdanvanbroeck.com/projects/belgrade). The architects Bogdan & van Broeck won the design competition, and construction works started in early 2021. They left most of the existing structure but opened the slab at two locations, a larger part of roughly an entire span to create an open garden in the back and a smaller part to create a patio and introduce daylight in the heart of the building. All storeys are used for apartments. Each of them is split up into three or four living units. They are organized around the existing circulation shaft and a corridor and distribution area varying from floor to floor (Fig. 3b).
Mapping the structural porosity diagram, we can see the very regular structure of the building. The façade is not part of the load-bearing structure and can thus be adjusted independently. The skeleton has a generous spacing and allows for a flexible interior space free of any inner columns. The regular beam pattern allowed the partial removal of the slabs. However, as the spans between them are relatively long (8 m), the slabs feature a much greater thickness than the traditional Hennebique system, resulting in beam depths between 45 and 76 cm and the slab between 27 and 47 cm. Opening the ceiling creates large openings because of the beam spacing; therefore, the ceiling has a large porosity that is technically enabled through its thickness and less through the beams.
The generous room height from 3.61 to 4.50 m allows acceptable light conditions for all possible use scenarios of the building’s depth of 17.50 m. As the old use was almost monofunctional, the circulation concept is highly pragmatic by providing access through a core connected to the side of the building leaving all storeys intact as large, uniform and undisturbed spaces. For the new functional scenario of monofunctional housing, the existing circulation system determines the configuration of possible units. There had to be corridors in front of the core from which access to the units is provided. However, the length of the units is then given and cannot be easily varied. Also, technical services, which might be added later, can connect to the units (arriving through the core). However, the primarily small corridors, which remain on the side of the core, allow one large PoU for one tenant.
Although the room height and the floor areas allow for various functions, a mix of them within the same storey is complicated as users of different functions would have to take the same access route. In addition, the circulation area would have to increase (along the building axis) to allow for smaller units of use. However, this relatively long-term arrangement would be in conflict with the flexible space plan and the possible rearrangement of uses. Therefore, a second vertical circulation route would be very valuable, ideally placed on the opposite side of the building, to allow for a more extensive diversity of circulation.
Figure 4 gives an overview of the key figures of the building structure regarding its porosity and usability. While the small corridor on the two upper floors creates a continuous useable area, the largest PoU in the entire building, the access areas on the two lower floors separate the useable area into small PoU. The Belgrade building has a rough porosity of its structure, providing wide open spaces and equally wide-open areas within the slab. However, the low hierarchy of the slab, together with its massive thickness, renders it relatively rigid for changes.
Building Anton, Eindhoven, 1929/2014
Designed as a factory building for Philips, Building Anton was constructed in 1927 by de Broekert (architect) and Bouten (engineer). The seven-story building has a regular reinforced concrete skeleton structure with a grid of 7,5 by 7,5 m, featuring two internal rows of columns and creating long wide and open construction halls (Fig. 5a). At the backside of the building, three cores organize the vertical circulation of people and services and provide stability to the building. Next to the most outer cores, technical areas were set up on each floor (Fig. 6a). However, in 1990 the industrial activities in the factory stopped, and the building became vacant.
In 2014 Dutch architecture firm Diederendirrix converted the building with a broad mix of functions creating an internal metropolitan area. Since the building is protected as a volume with its outside appearance, changes were limited to the inner part. Five large elliptical voids were introduced to connect the new program vertically and add some daylight, penetrating the original floors but leaving the beams intact. These voids form the new main vertical circulation and are connected by a central corridor on each floor (Fig. 6b). The new apartment areas only consist of loft units inviting the users to use the large room height with built-in mezzanines (Fig. 5b). The entire structural skeleton remained untouched, and future changes could make use of it again. Diederendirrix strengthened the structure of the building to allow for a later addition of two extra top floors in the future (https://www.diederendirrix.nl/nl/projecten/gebouw-anton).
Mapping the structural porosity diagram for the converted building, the repetitive structure of the building becomes clear (Fig. 6). Here, the façade is part of the load-bearing structure and protected, so it is a given outer boundary. The columns have a generous spacing of 7.5 m allowing for a flexible interior space. In the Anton building, the skeletal structure is even more hierarchical. There are large main beams in the longitudinal direction of the building with 1 m in depth and above them, transversely, smaller beams of 40 cm depth, contributing to the ribbed slab. Therefore, the slab itself is only 8 cm. This, together with the regular beam pattern, allowed the partial removal of the slabs. These openings are limited to the vertical circulation areas. The architects left all existing beams intact so that those changes could be turned back or adapted differently.
In relation to the depth of the building, but in particular to the column grid that indicates a use layer, the clear room height is very generous and allows good lighting for all uses. Like the Belgrade building, the maximum continuous, usable space is made possible by placing the circulation cores to the side. No special corridors were provided in the old factory use as people went from the access zone directly into the production rooms. Now, the cores are preceded by distribution areas, and a narrow corridor connects them longitudinally through the entire building, slightly off-centre so that two usage zones of different widths are created. This cutting of the large usable area is necessary to make the entire building accessible, as an exterior corridor is not possible due to the protected façade. This division creates two smaller PoU between the distribution zones in front of the cores and a very large one on the opposite side. By linking all vertical accesses through the longitudinal corridor, there are always several access options for all parts of the building. The newly inserted internal vertical shafts further strengthen the high DoC. In this way, it is possible to allow a large mix of uses, even within one floor. Service installations can also be inserted and replaced at any time along with the cores and corridors.
Figure 7 shows the key figures of Anton building’s structure regarding its porosity. On each floor, two small and a large PoU make a moderate DPoU, but the redundant access to the areas allows excellent usability in differently sized units. In addition, the room heights, different use depths and sizes, and a high DoC allow for excellent mixability of uses in the building. With the generous column grid and the room height, the SSP is very good, and due to the lack of load-bearing interior walls and the fine gradations of the beams and the thin slab, the PSP is also very good.
Lamot brewery, Mechelen,1922/2005
Founded in 1855, the Lamot Brewery has a long history of adaptations. The brewery is located in the historic centre of Mechelen, next to the river Dijle. In 1922 two main brew towers and a warehouse were added. All three structures have a reinforced concrete skeleton, with a load-bearing firebrick façade which also stabilises the building. The structural skeleton of the brew towers features small spans and a layout particular to their function. The warehouse has larger spans, creating wide open areas (Figs. 8 and 9a). The brewery was extensively adapted during the following seventy years, with three significant interventions, each adding and subtracting new structures.
After being vacant for ten years, the building was converted in 2005 by 51N4E architects collaborating with Architektenkoöperatief. A new program was introduced with a combination of cultural and commercial activities. Some smaller structures were demolished and gave way to a new central circulation area, connecting the different volumes and spaces. The first floor of this new part functions as a large foyer, separating the commercial and cultural functions. To visually open up this floor of the building towards the city, the firebrick façade was demolished and replaced by large glass panels exposing the building's interior. The brew towers host smaller functional spaces, such as a café, a restaurant and offices, while the warehouse contains larger auditoria and exhibition spaces. To accommodate these larger functions, the three top floors were demolished and replaced by two new levels, introducing column-free spaces and greater room heights (Fig. 9b).
As this research mainly focuses on adapting the long-lasting existing structure, the new part with the auditoria is left out in the following analysis and the diagrams (indicated with a dashed volume in Fig. 9b at the front right). Figure 9 shows the change in structure, circulation and use. The skeleton in each part of the building corresponds to its load-intensive use and space requirements. The spans of the dense grid in the towers are only 5 m, while it is between 6 and 18 m in the warehouse. In the dense grid, there are deep beams (43 cm) above each column and regular smaller beams (23 cm) above those as part of a ribbed slab. Thanks to the massive beams and the dense column-beam arrangement, the slab is only 14 cm deep. The slabs have not been removed in these parts, but they could, similar to the Anton building. In the upper storeys of the towers, the structure features wider spans with columns standing on the structure below and holding slabs above without beams whatsoever.
The original buildings provided a linear circulation system. Between the various sub-buildings, all adjacent floors were reached via the vertical circulation. From there, one passed through all areas of the storeys. This corresponded to the mono-functional use of each building and floor. In the converted building, additional corridors were inserted between the old sub-buildings and the new auditorium building, which run along its entire depth. In this way, the usable areas of the respective floors can be divided and made accessible individually. Similarly, the technical supply ducts can also run through the corridors and can be accessed at any time. This circulation method is therefore very good for mediating between sub-buildings and making them accessible effectively. The SPoU and LPoU then always correspond to the entire floor areas of the respective sub-building. Because of the central vertical circulation, the route to and from the areas of use is always predetermined, i.e., the DoC is low. Thus, within the floors of a partial building, uses cannot be highly mixed, as they are always connected via the same corridor. An additional vertical circulation point would be beneficial to increase the DoC.
Figure 10 summarizes the essential porosity figures of the converted Lamot brewery. With the various sub-buildings, a moderate DPoU is provided. However, the variety of clear room heights is extraordinary, but because the structural configuration varies significantly in the sub-buildings, so does the SSP. It is very good in the old warehouse and the new storeys, as they allow flexible use and changes, e.g., partly additional mezzanines can be included. The ceilings of the new floors have a poor PSP as flat slabs, while in the old floors below, it is not good because of the massive and densely arranged beams in the slab.