Gründerzeit City 2.1

Central European old town centres as well as the related Gründerzeit urban expansions – firmly established structures with excellent infrastructural access – are those to which urbanity is generally ascribed, thanks to their uniqueness and diversity. These areas are emblematic of a quality city where people wish to put down roots.^[1] The quest for suitable avenues to curb the urban sprawl advancing upon our landscapes, and for a sustainable handling of increasingly scarce resources, raises various issues. There is not only the possibility of retrospectively densifying such centrally localized urban areas, but also of creating a contemporary inner-city residential living situation as an alternative to a private home in the countryside. For the more centralized and spatially concentrated urban life develops within a certain setting, the more compact and ecological a city can become. The conceptual model Gründerzeit City 2.1 builds on these considerations and, taking Graz as an example, hones in on possibilities for retrospective densification within characteristic, urban-space-fostering perimeter block developments of the nineteenth century within smaller and mid-size cities. “Gründerzeit City” here evokes not a historicizing or societal romanticism but is rather understood to be an urban building typology which rephrases a certain type of city, one that is today cited as a reference for well-functioning living quarters after having witnessed the undesirable development of modern housing development. In turn, 2.1 literally stands for an act of overwriting, for a modern-day continuation and enhancement of this urban-development typology by moving up to a building density of 2.1. The means of doing so is a purely architectural intervention that capitalizes on the characteristics of tried-and-tested urban space while bolstering existing qualities through an addition of contemporary architectural structures, and thus creating supplementary living space.

A range of factors fosters acceptance among citizens for high resident density in urban spheres. In addition to spatial proximity and compactness, relevant factors include a central location, clearly defined and invigorated public space with mixed-use, ground-level zones dedicated to local amenities, an architectural separation between public (street side) and private space (yard side), economic and cultural productivity and diversity, experience density, but also the social complexity of these districts.^[2] As a result, nineteenth-century areas of urban expansion – the so-called Gründerzeit Cities, which were originally the product of expansionist pressure, rationalization, and profit maximization – are today generally considered valuable urban residential areas within European core cities and widely deemed worthy of preservation or even emulation. The profitable commodity of the “Zinshaus”^[3] has come to once again signify competitive real-estate property, having originally served not primarily housing but rather capital-investment purposes for the middle-class in collecting as high of a profit as possible and, as such, was never tailored to the individual but instead vice versa.^[4] The layout of the rooms today, in the age of considerably lower utilization density, permits generous living space in highly diverse arrangements – a sought-after feature.

This popular reception is especially apparent in the large cities of Berlin and Vienna, which attained negative prominence at the beginning of the twentieth century, despite large-scale urban expansion, as those metropolises with the most questionable housing conditions and the highest occupancy rates.^[5] Today, the Gründerzeit districts of these two capitals^[6] in particular positively symbolize vivacity and urbanity and count among the most popular and trendiest residential areas.^[7] The high building density in terms of lot size and the narrow backyards in no way represent a detractor once occupancy rates have been reduced. In fact, these districts may be considered referential examples in terms of urbanity, density, and residential satisfaction for cities with less densified perimeter block developments.

While the Berliner Block, with its consistent eave height and its interior and exterior uniformity, follows a rather strict schematic order as far as classification goes,^[8] Vienna’s visual identity is much less homogeneous due to a lack of building-related regulation of structural alignment, building height, and number of stories.^[9] Also, public space has been shaped differently – more generously in Berlin, with wide streets and boulevards, and more narrowly in Vienna. With regard to urban-development ratios, a comparison nonetheless shows strong similarities: on a district level, in Berlin a floor area ratio of 2.46 is calculated for a typical perimeter block at a development degree of 0.48. A similar block in Vienna demonstrates slightly higher numbers (floor area ratio of 2.58, degree of development 0.59). Not taken into consideration was whether an equality of living situation existed between the front and back buildings in these two cities (see fig. 2).^[10] Here, priorities lay in the need for representation to the outside and in economic motives. Today, loft extensions exist in both cities; in Vienna, adding on up to the height of the bordering eaves is allowed, which serves to further elevate density. Further, the back side has seen less retrospective densification and more clearing.

In contrast to Berlin and Vienna, the perimeter-block sites in Graz from the Historicism period display strongly deviating features to the backyard side, though they remain similar on the street side. As compared to the examples cited from the capital cities, in Graz the average district floor area ratio is 1.3 at a development degree of 0.4, therefore low for inner-city conditions. Today this has a negative effect on lived urbanity in the case of less densely occupied apartments, thus providing the main argument in favour of retrospective densification for the future. In this provincial, bourgeois city – where growth pressure did exist but, thanks to a lack of significant industry, not as explosively as had been the case in other cities – it was possible to proceed with more considerate planning by observing international developments and making circumspect decisions for action.^[11] Moreover, building activity was indeed determined by the bourgeoisie, with buildings also being erected to cover one’s own housing requirements and other standards being used for orientation than those of a miscreant speculator. This resulted in an affirmation of the principles of the Biedermeier period with its gardens^[12] and concomitant willingness to forego maximal lot utilization to the benefit of enhancing quality of life. Along the street front, the established design conventions of the time were adhered to. By rowing together differently styled façades with their dominating cornices circling the structures at almost the same height, it was possible to simulate exterior uniformity and size, even if this monumental habitus ultimately remained packaging and format attitude.^[13] The liberalist theory that trees do not actually belong in the city^[14] was not greeted with enthusiasm in Graz. As such, the courtyards of Graz perimeter-block housing have for the most part remained undeveloped, and most still today contain private gardens. Yet these refuges may be actively used by but a few residents, who have been careful to protect their privilege with fences and hedges. The fundamental circuitousness of these courtyards, paired with a moderate height of the buildings, fosters a potential that even makes continued building in an appropriate form conceivable. The related conception is rooted not only in the assumption that retrospective urban densification is fundamentally necessary from an ecological and economical perspective, but also in numerous other objectives. In addition to an augmentation and diversification of housing supply, actual improvement of the district represents a main focus, with the specific aim of honing the special qualities already present. For when urbanity appears on the street to a not insignificant degree, then a deficit may be localized here. Although, spatially speaking, a city is both seen and felt, actual urban life seems to play out only conditionally. While over the first half century and longer the ground-level zone indeed offered public and authentic urbanity, attributable to a much higher number of residents,^[15] this state is no longer apparent one hundred years later. Today’s public space is predominately occupied by parked vehicles. True business and street life with diversified local-amenity and gastronomy functions are concentrated at only a few select spots. Animated ground-level zones facilitate urban life and vice versa, but they cannot be forced into existence; in fact, they cannot take form until certain density parameters have been met, which does not appear to be the case in the Graz districts. Population density, personnel density, and a balance of the two surely play a weightier role here than structural density,^[16] which primarily targets quantitative spatial utilization, yet without actually giving an indication of when people are actively present day or night. All the same, Dietmar Eberle – after having extensively compared urban quarters – specifies a value of 1.5 to 1.6 as the minimum structural density for well-performing intermingling and pedestrian approachability.^[17] As per Eberle, this must first be a given before urbanity can develop. When the value of 1.3 is taken, as has been determined to represent an average section of Graz (see fig. 2), then no more than a minimum value for spatial development of public and private open spaces has been reached. And public space, in spite of comparatively low building height, can actually still be perceived as being clearly defined. Now doubts may certainly arise about the validity of defining of urban qualities through simple compliance with density values, but within the explorative question at hand these number games verify that which is obvious: a lack of liveliness. An elevation of population numbers through an expansion of housing supply represents an effective means of improving this situation. Due to building-policy-related limitations, previous attempts at affecting an increase in living space have been concentrated on spatially exhausting existing structures, meaning the expansion of basement apartments and the enlargement of attics, which tends to impair protected roofscapes. These approaches go hand in hand with familiar spatial and structural weaknesses. If we disregard the current policy situation, then quantitatively noteworthy spaces for retrospective densification can certainly be found in the well-preserved Gründerzeit districts: for one, the mostly empty yard areas, and also the space above the eaves. However, erecting structures within the courtyards where greenery is cultivated would not only destroy the special quality of Graz perimeter-block developments and also foster an air of confinement within the yards; it would also entail large, concentrated construction mass. For an average block, while assuming the smallest amount of distance between the buildings, such horizontal densification would call for a height of ten stories^[18] in order to attain the increase in area necessary for a two-story addition of highest living quality (see fig. 2).^[19] From a qualitative perspective, the preference clearly lies in favour of vertical densification, for the encroachment of the surroundings that would be induced by developing the yards in a way that inevitably generates a sense of confinement cannot be deemed acceptable. By contrast, the annexing of a circumferential addition – as a rim that surrounds the entire perimeter block as a unique architectural structure – harbours, next to several basic prerequisites, a variety of advantages as compared to the parcelled attic extensions practiced up to now.

Construction in existing contexts as a strategy for promoting sustainability can only ever be successful when it takes existing factors into consideration, yet without favouring traditional design or romanticisms over conventional lifestyles and societal forms. Therefore, considering this prerequisite, the addition of stories to perimeter-block developments where the entire block as a whole is encompassed by no means implies the destruction of the buildings at hand. Instead, this reflects the more efficient utilization of existing resources as well as a respectful guarantee that the structure will stay standing. The existent building will be preserved in that it forms an abiding plinth for something new. The monumentality of the established ensemble is then further underlined by a uniform construction, whereas individual attic enlargements or parcelled additions instead engender inhomogeneity.

Only reflection on the perimeter block that takes the lot situation as a whole into account allows for a disengagement from the constraints imposed by the compartmentalized nature of the individual buildings. This approach generates a freedom of planning and design but also, at the same time, manifold economic and ecological synergies that are not present when taking a parcel-bound vantage point. Individual structural sections with just a few apartments turn into building projects of interesting economic and spatial-development scope. The well-established public infrastructure is more intensively used, making additional planar expansion into surrounding regions unnecessary as well as maintenance and repair more economical. To the inside of the building, there is the synergetic possibility of a large-scale elimination of investment gaps and of bringing the buildings up to date ecologically, which would represent a valuable contribution to cleaner air for the whole city. By integrating the highest ecological and energy-related standards in the new structural section, the act of retrospective vertical densification moreover offers an opportunity to improve the buildings’ total energy balance even without a thermal rehabilitation of the historical façades.

Liberation from the right structural corset between fire walls and stairwells facilitates a true richness of apartment types in the new attic zone and thereby a sensible answer to the issue of needing alternatives ranging from a diversified inner-city residential living situation to a replacement for the one-family house surrounded by private open space. The fact that not every existing stairwell must be continued on up to access the upper addition or retrofitted with an elevator – instead, fire regulations specify the maximum clearance for vertical access – makes this flexibility in designing layout attainable while also yielding much higher floor space. The gardens located in the inner yards would then be united and opened for all residents of adjacent buildings to use, for higher levels of density necessitate more open space,^[20] not only as buffer greenery but also for contemplative use. Thus, hardly accessible, fenced-in private gardens become collectively used parks, playgrounds, sports facilities, ponds, and vegetable gardens – opportunities for leisure-time activity that are otherwise very difficult to find close-by within a city.

By exchanging steep gabled roofs for flat ones, it becomes possible to create, in addition to the courtyards, terraces and roof gardens, the utilization of which is conceivable both for individuals and for the collective. With all parcels consolidated, such premium zones for leisure and movement provoke not only a repositioning of the block at a new usage level, but also a subsequent and completely new way of looking at perimeter-block developments and their surroundings. The worn corrugations of the brick-red pitched roofing are replaced by a new, sophisticated roofscape that leaves a mark on the cityscape from above while also proving to be accessible and thus experienceable.

Sufficient parking for the motor vehicles now filling public space can be created under the courtyards as jointly used underground parking lots.^[21] This results in a redefinition of public street space, with some smaller streets even showing potential for becoming completely car-free. Public space would accordingly offer more room for people, who in turn could move about and interact more freely, again fostering new opportunities for utilization and design.

The creation of an upper addition to perimeter-block developments spanning all parcels demonstrates how nature and city are indeed reconcilable within confined spatial conditions. The generous open yards, private open areas, and the new roofscapes offer close proximity to nature and a chance to freely shape this nature. Tending to a varied need for interaction is an advantageous equilibrium between privately and collectively used areas as well as the preservation of clear spatial separation between private and public spaces, higher population numbers and social diversification; and, thanks to the involved diversity, these factors also foster chances both for cultivating sociable activities and for sustaining privacy and anonymity. The larger floor area ratio leads to invigorated public spaces and ground-level zones – in terms of spatial-visual perceptions but also thanks to higher population density with all its consequences – and hence to enhanced urbanity. Local amenities are likewise bolstered, allowing the much-conjured city of short distances – enabling manageability of daily life without motorized individual traffic – to become a reality.

Residential value – which “is equally comprised of the quality of the apartment itself and that of the living environment,” whereby living environment is everything “that goes beyond the pure utility of the accommodations, though not as luxury but rather as satisfaction of elementary needs”^[22] – is elevated through these retrospective densification measures.

Each addition must be tailored to the possibilities and vertical scaling of each locale, which means that the solution to this endeavour cannot lie in one unique typology. Unavoidable encroachment on existing conditions, such as an increase in street-side shading of the ground level, can be compensated by the reorganization of utilization structures. What may also be clearly noted is that not all street breadths permit flexibility in building height. Yet according to present calculations, a realistic district-wide floor area ratio for the yardless Graz Gründerzeit perimeter block, with such vertical retrospective densification possibilities, would be 2.0-2.1. This translates to additional living space for approximately 500 residents over 21,000 m² net floor area in a district befitting this example, or to circa 145 residents more per hectare^[23] (see fig. 2), thus offering all the vitalization effects expected within this urban interaction setting. If this model were extended to include all eligible city districts in Graz, then there would be potential for thousands of new apartments, thus quantitatively moving into the sphere of true urban expansion without ever needing to tap into greenery reserves or to develop new infrastructure.

From a design perspective, the concept of vertically adding on to the entire perimeter block offers one possibility for doing justice, in terms of form, to the closed perimeter-block development from the Historicism period. The block ensemble, in all its monumentality, is considered and treated as one architectural unit. Instead of lending emphasis to compartmentalization and inhomogeneity through individual loft conversions or penthouse additions, this concept allows the buildings to be encircled by the cornice, which heightens their monumental effect. We are thus adhering, via a contemporary interpretation, to the basic intentions of early Historicism, which sought a uniform appearance.^[24] The victim of the already vitiating roofscape is posited vis-à-vis a new roofscape – green, accessible, usable. The block’s appearance on the lower levels, however, sees little change, for the existing structure remains effectively untouched up to the eave level. What amounts to a two-story addition on average is limited heightwise to about the level of the present roofing, meaning between eave level and ridge, yet it yields substantially more utilizable volume and use options than a conventional loft conversion.

Though this purposeful block-spanning increase in quantitative density – concrete floor area ratio and thus also related resident density – it is possible not only to create additional premium living space but also to enhance the urban qualities of the districts as a whole. This should not be carried out along the lines of laissez-faire principles, but rather only according to clear quality criteria and building policy that have been specifically tailored to the local situation. Under these conditions, Gründerzeit City 2.1 – which embodies the principle of vertical densification – may be applied to any kind of perimeter-block development so long as the courtyards remain open spaces. In this way, the concept can move from a local vision to an interim stage on the journey to the compact Green City. Hence, small and mid-size cities with expansionist pressure, which are often ignored within ongoing discourse on density, can – through noteworthy retrospective densification of central city areas by means of purely architectural devices – grow within their existing borders, can help to avert further urban sprawl, and can thus become more sustainable as real and true “dense cities.”