Prefabrication experiments - 433 - XL(slabs) - Streets in the Sky

 

Known for their important contribution to Team 10, an architectural collective formed from the Congrès Intérnationaux de l'architecture moderne's (CIAM) dissolution, Alison and Peter Smithson’s theories and projects were a fundamental part of nascent postwar brutalist visions and pedagogy in the UK and abroad. Mat-building previously discussed in blog article 282 envisioned urban form that rejected buildings as singular objects, exploring instead a symbiotic spatial relationship between urban geometry and building topologies. 

 

The couple married in 1949 and founded their own firm in 1950.  Their radical visions for integrating public spaces in collective housing led to imagining access walkways as «streets in the sky» redefining the slab type. The iconic Robin Hood Gardens, a social housing complex in East London, demonstrated the use of exterior access corridors at different levels large enough to support both personal and social spaces. Their design deconstructed the classic slab by placing these common voids within the structure's volume. A proposal, Terrace Housing City, took this one step further by arranging an oblique slab cross-section as a series of vertical volumetric setbacks from floor to floor flooding each floor plate's exterior skywalks with sunlight. The Streets in the sky imagery influenced many social housing proposals aiming to attribute streetscapes' spatial richness refuting the boring interior corridors synonymous with the slab. 

 

The construction of floating social spaces including roof terraces had already been proposed by modern architects, proficiently by Le Corbusier. Aerial passageways leading to flats became a symbolic component of these modernist visions and were applied most notably at Habitat 67 designed by Moshe Safdie.  Contemporary architects also reframed and refreshed the same objective of social interaction in a dense block: French architect, Jean Nouvel, designed a ship like cross-section at Nemausus in Nîmes, France, with large promenade decks. Multiple meters wide, the catwalks leading to access and exit stairwells were planned as a way of rationalizing costs by externalizing costly elements usually built within the slab. Their removal allowed for them to be built with lighter construction systems and materials redirecting these potential economies to offer larger housing units.

Sections though aerial walkways

Prefabrication experiments - 432 - XL(slabs) - ZUP at Bayonne

 

Interwar years in France intensified dwelling as well as urban hygiene crises. An estimated 5 million units lacked running water and basic services. The devastating damage to hundreds of thousands of buildings during the second world war exacerbated this need for quality housing. In response, centralized policy sanctioned new dense developments all over the country under the label, ZUP - Zones à urbaniser à prioriser (liberally translated to Priority Zones to Urbanize). Projects and their promoters which provided a minimum of 500 units in tightly packed edifices required affordable and efficient construction methods to be deployed at scale. 

 

The slab block was adopted by an industry increasingly articulated to reinforced concrete; a material the country's inventors (Hennebique, Monier, Lambot and many others) had been central in cultivating. Beyond the material's advantages in terms of fireproofing and strength, it also lent itself to all types of prefabrication strategies. Marcel Breuers' flagship ZUP design for 1100 units at Sainte-Croix/Saint-Esprit, in the small community of Bayonnne explored precast concrete construction to propose a formidable building system. Designed and built from 1963 -1967, the master plan included dwellings and several services including a school and shopping center.  

 

Using a factory cast wall panel system inspired by the Camus System (also invented in France), Bayonne buildings were arranged as a cellular hive of flats and simply covered in a precast thick panel. The basic structural strategy of walls and slabs at Bayonne was cast on site using a tunnel form system:  a moveable prismatic formwork that defines a cell with a horizontal plane supported by two vertical planes. The tunnel forms are usually made of steel. Once the concrete is cast, the steel framed-moulds slide out and are reused on subsequent floor plates. 

 

The heavy wall panels’ architectural treatment at Bayonne showcase Breurer's talent and understanding of prefabrication's potential to create dynamic façades using mass manufactured components. The panels were cast as a thick solar shading device with built-in furniture and window openings. A mirrored pattern was repeated every two stories creating a textile like façade; the project's simple renderings illustrate how architectural regularity defined a coherent material field. 

Rendering of the Bayonne master plan

Prefabrication experiments - 431 - XL(slabs) - A failed prototype ?

 

Generated from industrialization and its new construction materials, specifically, reinforced concrete, the slab building was forged by assembly line production and its accompanying design theories. Thin, linear, rigorous grid organizations simplified structural design and service distribution, making these replicable arrangements ideal candidates for scaled serial production. The linear apartment blocks repeat floor plans and extrude sweeping vertical sections that sometimes seem to go on infinitely. This regularity is what made the slab a formidable affordable housing strategy but what also ultimately embodied the downfall of this expressly modern type.

 

Inaugurated in 1954 in St. Louis, Missouri, Pruitt-Igoe's 33 high density buildings underwritten by federal policy heralded the post war enthusiasm and urban planning doctrines associated with the slab block. The experiment like so many other modernist developments was rife with economic and social challenges.  Its symbolic demolition only years after its construction refuted modernist ideologies of mass housing.

 

Still, the slab endures as an iconic composition of flats designed to optimize collective and social cohesiveness. These buildings offer a rational way of using the same principles that gave us terraced housing but scaling them to taller structures. Recent proposals deploy the same underlying ideas to produce buildings from a generic aggregation of flats contextualized in mixed-use settings to counterbalance flawed modernist functional segregation. 

 

A contemporary example of a contextualized slab designed by Arrhov Frick Arkitektkontor in Sweden, is composed of a dual-oriented adaptable loft inspired units.  The typical floor plate of the Hmmarby Gård project is a multiplied sequence of two flats articulated to a shared vertical circulation core and arranged around a service hub surrounded by flexible living spaces.  13,6 meters wide, flats include large balconies on their north eastern façade and operable curtain wall façades on the opposite connecting the see through building to its surroundings. The repetitive plan makes a case for modern industrialized principles, repetition, modularity, standardization. This reproducible sameness that was decried more than half a century ago is valued as fashionable and mass customizable, elevating the slab from a once promising but failed prototype into a dynamic way of breathing new life into a city.  

Hmmarby Gård typical floor plan

Prefabrication experiments - 430 - XL(slabs) - Linear dwelling hives

 

Known simply in architecture as slab blocks, these densely packed, multi-unit edifices are arguably the most iconic template for arranging dwellings articulated to modernism and its sustaining doctrines linked to industrialization: standardization, modularity, repetition. They are symbolized by a sweeping aggregation of flats stacked to form linear, sinuous, and seemingly endless patterns. Characterized by slim double-loaded corridors and the liberated ground plane surrounding them, these monuments shaped a mass-void proportion that completely disrupted classic city planning. Narrow floorplates, associated with slabs, were sometimes also fed by elevated catwalks giving access to single-sided flats. 

 

A normalized floor plan supported by some type of open large-spanning skeletal structural system made it possible to alternate lodging typologies and organizational patterns within the same structural grid. The post and beam, post and slab, or the panel and slab are the most common. Prefabrication and industrialized construction relate to these slabs as design was condensed to expressing an axis onto which dwellings were connected as if conveyed by an assembly line into their permanent position. Modular volumetric, panel systems or a combination of both strategies were used to relate affordability through duplicating regulated types for both dwelling units and normalized components for all other building systems, particularly for elevations.   Le Corbusier’s Unité d’habitation at Marseille (1952) or Marcel Breuer’s ZUP de Sainte-Croix at Bayonne (1968) typify the unit to whole relationship of theses territorial edges standing vertically as monolithic hives dominating extended landscapes.

 

Providing flats at a mass scale attached to common services or amenities communicated the long-standing analogy between large cruise ships of the early twentieth century and the modern slab block buoyantly touching ground, its body filled with ergonomic cells and its rooftops imagined as gardens for leisure. Defined by some modernist architects as open racks onto which manufactured units would simply be inserted foreshadowed megastructures, Japanese modernism’s answer to postwar rebuilds.  Slabs come in a myriad of scopes and scales but all feature an extruded or sweeping shape creating a hedge of dwellings. Alvar Aalto’s Baker House (1949) or even Ralph Erskine’s inhabitable wall proposal for Resolute Bay (1973) demonstrate the vast social and environmental possibilities of these straight or sinuous lines defining urban form. 

Unité d'habitation (top left); ZUP de Sainte-Croix (top right); Baker House (bottom left); Resolute Bay proposal (bottom right)

Prefabrication experiments - 429 - SML(urban blocks) - Wohnregal precast concrete components

 

Providing affordable housing solutions is a deepening problem for contemporary cities. Construction costs are soaring, dense urban form engenders logistic challenges, conventional construction is wasteful and traditional project delivery methods are organizationally messy. Considering these obstacles, it’s increasingly difficult to grasp why offsite construction hasn’t earned a larger portion of new housing starts. Although building construction employs wide-ranging mass-produced components, high levels of integrated systemic design and manufacturing remain elusive. Current crises are potentially inflecting interest in offsite methodologies with all stakeholders understanding the enduring web of nuisances that prefabrication has the potential to address. From efficiency to quality, architects are also rediscovering industrialization concepts for increased performance and to ensure higher quality projects.

 

Historically, architects have generally critiqued prefabrication as either too prescriptive or too rigid. Architectural studio FAR recently designed a six-floor urban block using a kit of precast reinforced concrete components. Wohnregal in Berlin, Germany built in 2019 celebrates a tectonic arrangement of columns, beams and slabs to assemble a warehouse/loft type edifice with large spans conducive to flexible layouts and dwelling patterns; 13-meter spans provide plenty of room for occupants to accommodate their needs. Floor to ceiling glass walls reveal the structure’s manifestly modern roots and the open spans devoid of load-bearing obstacles make it possible for the interior spaces to evolve over time.   The components were dry assembled in six weeks requiring less on-site management and wasteful shuttering that would normally be required for an onsite traditionally cast equivalent structural system. Dry assembly also increases possibilities for long term circularity. 

 

FAR’s proposal aimed to showcase a bridge between customization and industrialization, a subject that continues to be the crux of many architectural and industrial prototypes. Mechanical cores were also used to rationalize systemic distribution and increase flexibility as all adjacent spaces can be subdivided without affecting the overall structural or mechanical layouts. The urban multi-story warehouse archetype has long been associated with flexibility, changing occupants, and even mutating according to evolving functions. While Wohnregal maintains this type of structural openness, its prefab components highlight a symbiotic relationship between architectural form, rationalized structure, reducing costs, quicker construction and potential adaptability, all fundamental elements of any robust housing strategy. 

Wohnregal dry-assembled precast components

Prefabrication experiments - 428 - ML(urban blocks) - Modernist principles and the Yerba Buena Lofts

 

The urban block comprised of different apartment types and shapes organized in a coherent aggregation influences social diversity within collective housing projects. Arranging differentiated relations also presents opportunities to enrich an edifice's appearance by particularizing façades that celebrate or camouflage the tensions between typological organization and their external affirmation. Modern prototypes like Le Corbusier’s Unité d’Habitation mezzanine unit or Mies Van de Rohe’s Lafayette Parks interlocking flats, and even Alvar Aalto’s Hansaviertal Apartments provide iconic examples of intertwining spaces to create dynamic housing patterns. While the three prototypes were not factory produced, their repetitive grids and composing spatial elements feigned an industrialized posture which played into modernism’s serial production narrative. 

 

Contemporary architects still combine and relate these ideas and disciplinary subplots to showcase innovative urban housing strategies. The Yerba Buena Loft units designed by Stanley Saitowitz and Natoma architects in San Fransicso  (2002) employ a mezzanine loft typical flat section along with a thick façade holding loggias or winter garden balconies to shape a crenellated streetscape pattern of masses and voids within a concrete superstructure, betraying their modernist roots. The apartment building’s section bridges front and back streets with double height commercial spaces establishing a pedestrian scale and a central portion of the deep section containing a four-story parking structure. Above this fourth floor, the building is divided into 2 parts: deeper mezzanine units on the south and half depth mezzanine units on the north. Both north and south units use the same principles to organize flexible loft units. The double height loggia spaces relating to Folsom Street side are directly linked to a corresponding interior space where a spiral stair leads to a bedroom open to the lower level. The mezzanine unit sections, and exterior loggias are repeated throughout the block. 

 

Flexibility principles are evident in the ordering of served and service spaces: Wet rooms, kitchens and baths, are concentrated on corridor and demising walls freeing adjacent spaces to varied organizations. The rigorous grid-based concrete structure presents an industrial discourse conveying a dynamic interplay between skin, structure, and interior planning. 

 

Yerba Buena Lofts

Prefabrication experiments - 427 - ML(urban block) - Modular reconstruction with Speedstac

 

The serial urban block symbolized 20th century prefabrication and industrialized construction. Framed by normalized government intervention using panelized or modular volumetric construction, planning logistics, zoning, arrangements, materials, and systems were all optimally coordinated from procurement to site installation. In the USSR in particular, the pattern buildings’ production was centralized; factories were set up and neighborhoods were completely built by national and local Gosstroys (state committees for construction) deploying similar design and construction methodologies geared toward efficient production. 

 

Since these buildings shared details, dimensions, performance criteria and components, they have also aged analogously and are susceptible to similar degradations. Sixty to seventy years after their initial commissioning some have either been demolished or most are in dire need of functional updates, repair, maintenance and in some cases, new conflicts that have destroyed parts of the structures. As the buildings share similar characteristics, their upkeep, renovation, or even restoration can lead to a form of standardized formula applied to their composing parts. 

 

The Speedstac^tm, an offsite manufactured retrofit unit made up of Integrated Structural Panels designed by architectural firm WZMH architects, proposes an industrialized building system for refurbishing or reconstructing parts of K buildings damaged by the Ukraine Russia conflict. The K acknowledges the Krushchyovka, nine story buildings produced by the USSR during the cold war. Arranged in the form of containers, the strategy could prove to be an efficient platform geared for adaptive reuse and recommissioning the typical prefab block. Contrary to the original systems, Speedstac uses high performance construction for both thermal and acoustic comfort.  The modular units’ panels include all necessary amenities, systems and function like a plug-in prosthesis for either parts of a building or for complete rebuilds. Planned in the context of the current crisis, the boxes could feasibly be used in any flat slab concrete structure stripped of its outdated services and envelopes to act as a support framework. The factory completed containers would simply slide into the structure.  

 

Produced for quick installation this type of functional unit could also be used for adapting existing commercial buildings as an affordable housing solution in cities with an aging building stock. 

Prefabrication experiments - 426 - SML(urban blocks) - Tenements and industrialization

 

Planning dwellings vertically around a common circulation core is symbolic of 19th century urbanization.  The urban block of flats is a fundamental component of the modern city. Characterized by repeating flats stacked 4-6 stories high, this type evolved and guided the development of emblematic localized patterns: tenements, in New York rose out the rapid urbanization of the city. Their organizations were based on a centralized stair well and sometimes a series of lifts giving access to each floor plate. The New York tenements built on 25 foot by 100 feet parcels divided for high density, allocated industrialized city form. Urban blocks have remained consistent and are both an affordable and sustainable strategies for housing provision. 

 

Offsite construction can be leveraged toward the urban block as dense housing has an engrained repeatability in spatial organizations, systems, amenities and interior functional elements such as rooms, baths and kitchens. Independent of any industrialized building strategy, rationality and frugality were the keys to the speculation that spawned these housing solutions. The typical floor plate layout is an example of standardization applied to housing design. Each unit could then be constructed from similar potentially mass-produced components.

 

Today’s affordable housing crises and the continuing urbanization of populations tends to both reviving the collective housing block and industrialized building strategies. From stacking reinforced concrete modules at Habitat 67 to the precast panelized blocks built throughout Europe in the aftermath of World War 2, prefabrication was used to invent and develop the collective housing typologies of the 20th century harnessing principles of bulk procurement and centralized logistics. Still, while stacking similar flats and floorplates lends itself to prefabrication, it has been marginally applied as each edifice in a series is usually built as a prototype. The postwar Eastern European socialist model deploying the pattern urban block repeating the same building systems and designs from context to context spearheaded a vision of industrialization underwritten by political choices; this model seems to be the only way of achieving the mass-scale application of offsite construction in collective housing supply.   

Prefabrication experiments - 425 - SMLXL(row-houses) - Interlocking modular dwellings

 

Industrialized housing solutions can display imaginative assemblies projecting homes in many variations. Stacked, aligned, interlocked or juxtaposed modular volumetric dwelling proposals employ densely packed or clustered organizations to rationalize building footprint, infrastructure provision and service distribution. Aggregating spaces and volumes in hive-like structures and arrangements using container-like prisms is the most common strategy. The manufactured units are completed before delivery and setting, a streamlined supply chain from planning to factory to site includes overwhelming advantages in terms of project timelines. Architectural singularity is perhaps the biggest challenge for modular volumetric’s rational stacking. 

 

A recent project for student accommodations by Dyson Industries displays a unique silhouette with normalized factory finished boxes. Each Cross laminated timber box is connected to supporting or adjacent units to shape a 6-unit agglomeration. Designed by WilkinsonEyre architects, a London based firm, the «modular village» is based on rigorously dimensioned and designed giant building blocks structured in CLT and clad in Aluminum. The boxes are massed in a unique volume with each recognizable box cantilevered or setback to achieve differentiated form from simple prisms. 

 

Even more complex organizations of interlocking modules have been explored leveraging geometries toward extreme compactness. Architect Liu Lubin's proposal for adaptable micro houses develops a modular composition from functional ergonomic sections, representing human postures and activities, resting, standing, sitting etc. The cross-shaped modular blocks can be matched and linked into micro-dwellings or larger mat-like collective housing blocks. Each cross-shaped unit is planned on a 600 mm grid within an overall dimension of 2,4m wide by 2,1 m deep. The stackable, enclosed, scalable, rotatable object envisions domesticity and its forms as changeable. A fibre-reinforced foam core composite makes it possible to easily lift and move the modules while achieving a smooth white ascetic surface inside and out. A comprehensively manufacturable product including factory finished doors and windows along with built-ins meticulously drawn-up to provide interior functionality, Lubin's vision deploys similar concepts used by Japanese Metabolists plugging dwellings together to establish novel forms of urbanity; shaping intense living environments that are determined by human form - a type of anthropomorphic collectivity.

Liu Lubin's cross-shaped modular volumetric proposal

Prefabrication experiments - 424 - ML(mat-building) - Fredenborg Houses

 

A proliferation of row-houses in multiple directions, the mat-building concept has been applied to low-rise, hi-density housing in varied types, scopes and scales; all share fundamental principles including compact rational plans, shared party walls, grid configurations, standardized constellations and common building methods. Some twentieth century prototypes also explored an ideal of adaptability or even expandability; modular arrangements could be composed in response to varying landscapes, evolving functional requirements determined by an entrenched systemic capacity to add units, organically breeding neighborhood fields.

 

System building, adaptability and modularity seem to go hand in hand, and their underlying approaches were posited by three generations of modernist architects from Walter Gropius’ expandable house system to Cedric Price’s steel houses and as seen in the last post, Steven Holl’s Dense Pack Dwellings. The creative association of building elements with harmonized volumes to achieve uniquely industrializable forms, at least in narrative, informed flexible carpets of territorial expanses. Their adaptability also pointed to enabling users to interact, design and construct their own environments. 

 

Danish architect Jørn Utzon, best known for the Sydeny Opera house, also explored affordable housing through modular, adaptable organizational systems. His proposal for the Expansiva Byg A/S building kit system was sold by local timber builders and marketed as flexible, adaptable and expandable. The modular components were standardized for repetitive detailing and for maximum user involvement in their assembly.  The basic post and beam structure with a shed roof was completed with panels for walls, roofs and normalized openings regulated for the overall modular scheme. Employed for Utzon’s Fredensborg Houses (1959–1963) described as flowers on the branch of a cherry tree, the archetype outlined a clustered planning of housing units surrounding collective courtyards accessible from public walkways inserted in the spaces between units all leading to a centralized public square. The link between modern grid principles and classical urban concepts were united to shape a field of dynamic dwelling spaces. Built as individualized patio houses anchored to site topography, each unit was placed according to ideal conditions for views, daylighting and shelter from prevailing winds. 

Expansive Byg A/S building system by Jørn Utzon