Prefabrication experiments - 515 - What is Modular?

 

The diverse vocabulary associated with offsite construction can sometimes fog what is meant by «modular». Today, Offsite construction has been popularized, but the term is often used interchangeably with modern methods of construction, manufactured housing, prefabrication, industrialized building or modular, all refer to similar yet distinct concepts. Modular as a generic term should always be specified in relation to what is produced, a 2D panel, a 3D volume or a linear element can all be modular in the sense that their dimensions inform how they are either transported or how they contribute to shaping a larger whole.

 

In this sense modular volumetric construction would be the correct term for building with large boxes produced in a factory determined by transport criteria, then lifted and stacked into place. Modular volumetric can be deployed for a whole building composed of many megablocks, or to prefabricate complex parts; service cores or pods can be manufactured and inserted into an open framework.

 

With much of the work completed in the factory - up to 90% in certain cases - this formidable building strategy can go up quickly to reduce project timelines and when part of a scalable mass-production strategy could contribute to reducing construction costs. 

 

While the advantages are clear, building large chunks of a building in a factory requires a shift in planning as all project parameters must be determined and harmonized for the factory long before it’s required for a conventional onsite build. The traditional onsite process is linear with all building systems added onsite as required. Modular volumetric building begins either before or concurrently to site work and once elements are produced and brought to site, there is little room (no room) for change - or in the worst case, adapting to new site conditions interrupts factory production. Upfront planning can be seen as an advantage but is often identified as a barrier. Modular volumetric units are planned down to their most seemingly insignificant details with harmonized supply chains epitomizing manufacturing methodologies applied to building, thereby upsetting traditional paradigms. 

Modular components and subassemblies

Prefabrication experiments - 514 - Cooperation - advantage or inconvenience

 

The advantages of offsite construction are chiefly articulated to preparing components in advance of their use in a controlled setting for their subsequent delivery and assembly on site. Preparing sub-assemblies in a factory leads to potential gains in quality as acknowledged impediments to conventional construction are mitigated: climate, health and safety hazards, supply chain tuning and greater collaboration between designers and producers. This last aspect is often cited as a challenge to increased uptake in offsite construction, which relates to how comfortable the construction sector has become with the entangled mess that is onsite building. 

 

Cooperation between trades, design professionals, general contractors and manufacturers generally leads to better projects whether on or offsite built. However, when it comes to producing elements in a factory this close cooperation is necessary to ensure a streamlined chain of decisions that overlaps with conditions that are proceeding onsite. These conditions become difficult to adapt to with a manufacturing process if site situations change from those initially planned.

  

Integrated project teams or even design-build teams are more conducive to onsite/offsite cooperation as they provide the upfront planning and collaboration required to ensure that all technical aspects are precisely coordinated before the project begins. Mistakes and errors in factory production arise but can be corrected in the factory before sending parts out to the field; however discrepancies between field conditions and production are extremely costly to repair onsite and can lead to long work stoppages and cost overruns. 

 

While the intensive planning and collaboration phase can be time consuming when evaluated against the conventional design-bid-build process, it should not be seen as a challenge but as an opportunity to achieve much higher quality reducing wasteful onsite adaptations.

 

Generally, the type of necessary cooperation can be maintained by keeping lines of communication open between all parties and sharing proper documentation and shop drawings that detail elements that will be delivered to the field along with their required stitching details. Digital virtual modelling can certainly facilitate this process but it’s not a panacea and must be accompanied by adequate and continuous communication between all parties involved.

 

Off-site and On-site logistics from Zhang, C., Jiang, J., Xia, C. et al. Dual-objective optimization of prefabricated component logistics based on JIT strategy. Sci Rep 14, 31267 (2024). 

Prefabrication experiments - 513 - Junior Trelement industrialized building system

 

The endless battle of standardization versus customization, a longstanding obstacle stinting the uptake of industrialized construction, has often guided the conception and promotion of open systems capable of bridging the conceptual gap between a cost-effective required seriality and ingrained configurational agility. Design flexibility becomes an advantage and a selling point for the commercialization of these industrialized construction systems as demonstrated by Alco Germany's Junior Trelement kit of aluminum pieces, patterned on adaptable grids implemented in one-story facilities, first in Germany and then throughout Europe. 

 

Advertisements and the published product catalogue describe the early-1970s platform as a solution for personalized affordable manufactured architecture for everything from schools to office buildings and to single-family dwellings. The system's aluminum frame was regulated by a triangular grid, with connecting beams forming a hexagon geometry of roof joists attached to a six-pronged plate; this configuration shaped the basic polygonal composition. Available in rectangular as well as the triangular arrangement described above, the Junior Trelement structure spanned approximately 5 meters. In the triangular version - each equilateral module had a segment length of 2,3 or 2,5 meters. The intersection plate at maximum spans sat on an aluminum column or post whose cross section mirrored the connector's star shape.

 

Ideally suited to single-storey buildings, the Trelement horizontal plane roof could be tessellated to create coverings of any shape and size. Still marketed today, the company also promotes an after-sales service for existing buildings constructed with the system - foregrounding the advantage of repairability and replacement of existing parts. 

 

This type of systemic circularity is embedded in Trelement's DNA as well as its aluminum parts. Marginally applied in buildings due to fire constraints, aluminum's malleability specifically its capacity to be extruded in very precise shapes or profiles - makes it an ideal material for this type of time-based adaptability as elements can be put together and disassembled multiple times without fatiguing. Further each piece is theoretically interchangeable with those of any other building made of the same components, establishing a potential trading network of Trelement parts harvested from disused, disassembled buildings. 

Alco's Junior Trelement System

Prefabrication experiments - 512 - A prefab «sweet spot»

 

Growing global interest in prefab raises interesting questions for its future development: do systems define an era, or do eras inform a need that breeds a particular system? Light timber framing for low-density residential construction, heavy centralized panelized precast concrete to rebuild Europe, and integrated modular volumetric systems, known as MIC (modular integrated construction) in various contexts recount and symbolize a period's dominant framework for streamlining building construction with manufacturing. Mobile homes or steel skeletons for industrial hangars have somewhat less generalized histories but are equally emblematic. Today, comprehensive factory production remains elusive, but building culture is overwhelmingly mass-produced and standardized, attuned to materials and methods that are aligned with an onsite/offsite sweet spot. 

 

The mechanized sawmill in the US which led to balloon framing, required fireproofing for dense urban architecture in Europe generated patents for the reinforced concrete flat slab system, and panelization in particular illustrate success stories of Industrialized building systems balancing strategies with project functions, scales and socio-economic criteria: timber panels have been massively adopted to accelerate construction. Integrated (closed) panels or structural frames (open panels), for walls, floors, and roofs reduce sitework and waste without the predetermined architectural language associated with modular volumetric or comprehensive proprietary factory production. Their variability is an asset; architects can design any configuration that is translated as «panelized», produced as flat-packed building surfaces, delivered just-in-time, and assembled in an orchestrated sequence to facilitate construction management.

 

The adoption of this type of prefab for single family as well as multi-unit residential construction up to a regulated maximum of six stories (in Canada) showcases the industry's capacity to auto-regulate and adjust to technologies that can be introduced into construction's fragmented process without substantially altering it. Kitchen cabinetry, modular roof truss frames, prefabricated cladding systems, precast architectural panels, and curtainwalls all represent a similar manufacturing «sweet spot» suited to a traditional construction process: a seemingly seamless coordinated  on and off site production process applying rigorous manufacturing criteria, assembly details, and principles – examples of DfMA applied to buildings. 

 

The construction industry evolves slowly, with ingrained challenges related to productivity, transparency, and trade entanglement. However, panelization shows the sector’s ability to integrate nimble strategies that hit a sweet spot where advantages for design and fabrication become obvious to all stakeholders.

open (left) versus closed (right) panels

Prefabrication experiments - 511 - Design for Disassembly Before its Time - Jean Prouvé's Maisons démontables

 The confluence of military rigour applied to construction management, design methodologies and generational investments in housing encouraged inventivity in building systems. Manufacturing advances outpaced onsite construction producing a myriad of components for the rapid erection of diverse building types. This spirit of production for assembly spawned new experiments and their foundational industrious professional practises. Further, materials as well as methods associated with war efforts and their subsequent transfer to civilian use supported an integrated industrial design process applied to architecture, foreshadowing DfMA approaches promoted today.

 

Metalworker and self-taught industrial designer/architect Jean Prouvé’s work personified this generative triad of crisis, industrialization and the impulse for manufacturing in architecture. Responding to postwar government mandates, Prouvé developed a series of service core houses «for better days». His vision for the serial production of houses steered Prouvé to design and fabricate building kits with dimensionally coordinated metal parts for structural frames infilled with glass and timber panels in a type of multifunctional curtain wall system.

 

Included in a highly productive career, Prouvé explored the theory of demountable buildings arguing for an open-source architecture that could be mass produced. Articulated to his 1-meter grid, the demountable building kits integrated a mature approach for scalability linked to part interchangeability; with pieces, details, assemblies and repetitive patterns for overall systems harmonized for simple arrangements. From his 4x4-meter military shelter designed first as an armed forces or emergency dwelling and then as a leisure unit for a budding post-war prosperity to examples designed for their disassembly developed for specific functions, the reversible elements could feasibly be used, reused or repurposed for the repair and replacement of parts. 

 

These early discussions around flexibility and adaptability evolved into contemporary strategies for circularity, component standardisation, and optimizations for interoperability. The simplicity of Prouvé’s demountable structures would not be as straightforward in today’s performative and normative building culture, however the underlying ideas are certainly being revived as our contemporary crises call for action to reform how the built environment is produced, managed and repurposed. 

An example of the Demountable Houses

Prefabrication experiments - 510 - Modern Industrialized and Practical Kitchens - a modular success story

 

As the practicality of gas and electricity replaced wood and coal as fuels for cooking and heating in homes, kitchens were transformed into multifunctional and cleaner areas, becoming the locus of social life. Further, these conveniences reduced spaces for wood storage, made cooking consistent and increased time for leisure. The kitchen also benefitted from advances in technology and mass-produced appliances. The Bauhaus Kitchen of Haus am Horn (1923) and The Frankfurt Kitchen (1926) designed by Grete Schütte-Lihotsky and built-into many of Ernst May's mass housing projects improved ergonomics and foreshadowed postwar comforts. 

 

In 1933 Bruynzeel Kitchens founded in the Netherlands, drawing on a longstanding experience in furniture manufacturing, reformed kitchen design with their prefabricated coffers. The modular cabinets could be juxtaposed to create various cabinet configurations, introducing early mass customization that would become the predominant business model in kitchen design. 

 

Post-World War II technological dissemination simplified hardware, made electrical appliances the norm, introduced cheaper materials and production methods, and defined what would become the mid-century modern kitchen, conceived to facilitate everything from storage to preparation. USDA (the United States Department of Agriculture) idealized these facilities and packed them into a 1949 film: The Step Saving Kitchen. Linked below the film pitched to middle-class homemakers, spawned fantasies about the latest design features, commodifying the kitchen as home’s powerful engine requiring spinning shelves, hide-away compartments, and integrated garbage disposals.

 

Democratization initiated in the 1920s laboratory work-kitchen and promotion of consumerism like the 1949 film still underline most kitchen designs. In the 1980s, Ikea took Bruynzeel’s model and perfected it with their own DIY culture articulating kitchen design to their prefab caissons manipulated on digital configurators empowering anyone to predetermine their own kitchens equipped with enumerable cabinet types, fixtures and utensils. Today, the variable assembly of modular caissons remains the accepted model for producing personalized kitchens. Many companies offer similar approaches or preconceived models that can be either panelized, modularized or packed, protected and delivered to be plugged into any coordinated space; making the kitchen probably the most successful offsite-built system in the history of prefabrication.

Link to the film 

 

 

Prefabrication experiments - 509 - Loft-Liner, the split-level mobile home

 

The mobile home has come up regularly in this blog, and while it’s certainly not a model of building industrialization most pursue today, we have tried to objectively portray its successes as well as its failures, and sometimes even its follies. Mobile homes have a somewhat complex relationship with prefabrication, as they are often blamed for a generalized lack of uptake. In the manufactured home sector, negative connotations led to evolving vocabulary to relinquish links to assembly-line lightweight timber boxes produced at a time when regulatory frameworks were nascent and normalization not sufficiently developed.

 

The history of mobile home construction is filled with all manner of peculiar ideas to bring affordable dwellings to the masses. Elmer Frey of Milwaukee's Marshfield Homes, a well-known pioneer in the industry, even stacked mobile homes to showcase their evolving potentials (see blog no. 211). Frey is also credited with advocating for reform in transport bylaws and permitting for wider models. Rather than stacking or making wider models, another mobile home forerunner chose to integrate a second floor to increase flexibility of these houses on wheels. Founder and model designer, Myron Poole of the Holan Engineering Company explored 2-storey split-level-inspired designs and applied for the Loft-Liner trademark in 1954.

 

Holan Engineering Co and then its subsequent subsidiary Ventoura Homes marketed these trailers as packing the same amount of livable space and amenities as was possible in a much longer and difficult to tow 50-foot mobile homes. With a standard single-wide width the Loft-Liner evoked affordable suburban living and was sold in three lengths: 38, 40 and 46 feet, each with options for one bedroom on the first floor and a second on the upper floor adjacent to extra storage space. The company sold thousands of Loft-liners with an upper level which would prove difficult to tug around with today's height restrictions, but the 1950s allowed these behemoths to travel freely to mobile home parks and displaced according to a family’s needs and economic conditions.

Loft-Liner advertisement

Prefabrication experiments - 508 - Natural Pavilion

Associated with authors and researchers N. John Habraken (Supports and Infill) and Stewart Brand (How Buildings Learn), adaptability includes strategies that facilitate a building's evolution and its functional changes over time; converted to new needs, uses or simply to be renewed with replacement parts as needed. Material circularity principles take this one step further as architecture is conceived and produced to be completely dismantled into its constituent components and potentially delivered as a kit to a new site and toward multiple service lives.  

 

From individualized fit-out (Habraken) and systemic autonomous layering (Brand), both proposed design solutions framed by their permanence: long-term durability for infrastructure and at the other end of the spectrum easy to replace and redesign elements for short-lived banalities. These strategies outline «open building» theories that have been and continue to be explored most proficiently in the Netherlands. 

 

The 1000-square-meter Natural Pavilion test structure assembled in 2022, designed by dp6 architectuurstudio in the city of Almere, well-known for its architectural prototypes, combines an «open» modular timber framework with bio-sourced and recycled materials. The structural platform frame is completed with CLT floor plates. Wall panels and other flexible infill elements include bio-based or recycled materials along with reused plate glass elements harvested from buildings that no longer required them; all elements are dimensionally coordinated to create many possible configurations.  

 

The structural frame is based on an analogous principle to shipping containers where standardized connectors facilitate stacking 3x3x3m cubes composed of similarly profiled posts and beams. Three-faced heavy-duty moment connector plates fixed to the end of each timber member constitute the vertices of the off-site or on-site prefabricated modular volumes. The built-up perimeters of these open box frames are then simply bolted together at the plates' extending intersections. Steel bars are placed diagonally as needed to brace certain faces against lateral loads.The steel connectors have a furniture-scale quality, like those used in standard modular shelving.  

 

In opposition to the seamless continuity, we have come to expect from our modern building interiors, this pavilion shows the cultural leap required for the design-for-disassembly approach to be more than just another pipe dream in the history of adaptable prefabrication.

Modular open frame boxes designed for disassembly

 

Prefabrication experiments - 507 - ...in passing, again

Providing high-quality, creative as well as comfortable, affordable and resilient housing is a contemporary challenge, with demand not seen since early industrialization, urbanization, and world wars drove population displacements, shortages and massive rebuilds. The impetus to supply housing productively has renewed discussions around factory production and its potentials to improve conventional construction's degrading productivity. 

 

Policies pushing for greater uptake include road maps, building type catalogues, centralized building designs, all pushing the idea that efficiency is related to normalized patterns outlined for quicker and cheaper production. However, the standardization that succeeded in other industrial sectors is difficult to reproduce in construction where local traditions, regulatory frameworks, civil infrastructures, and climate conditions particularize project criteria and characteristics limiting architectural or systemic repeatability. 

 

Regularity in design is the basis for mass production's capacity to reduce costs while increasing quality and output. From mass customization to platform approaches promoting design families for different residential assets, these methodologies have garnered interest, but remain marginal, as both fields architecture and manufacturing remain mired in their anchored values. 

 

A fundamental cultural shift is required for architects and designers to understand industrial processes and their application; at the same time manufacturers in the building sector need to be educated in what constitutes quality architecture. The automobile, ship, aircraft, and mobile phone industries along with many others integrate design criteria values from the start of product development. All too often, industrialized production of architecture is seen as just another sub-trade in the construction process which makes it extremely difficult to become cost and design effective on a project-by-project basis. 

 

Systemic change is difficult to replicate within a construction culture ingrained in its artisanal fragmentation. Still, the change is necessary and could eventually provide outlets for a new type of industrialized architecture defined by some form of content standardization that supports innovation. The argument of singularity is moot, as architecture already repeats many processes; it is time to harness greater collaborative efforts between fields to achieve design productiveness. If the discussion continues to oppose unique design to cookie-cutter repetition, no advancement is possible. 

Resolution 4 architecture's take on normalization and singularity

 

Prefabrication experiments - 506 - Jean Barets' Near-site Prefabrication

 

The number of building systems invented to quell housing shortages in the wake of the Second World War is impressive. Lightweight experimental building kits in steel, timber and aluminum, plastic composite shell prototypes and most prolifically heavy panelized systems in reinforced precast concrete were deployed to rebuild and affordably house the masses. Most benefited from some form of government sponsorship using policies to initiate large-scale building underscored by the need to reform a stagnating construction industry. Factory production had been a determining factor in advancing wartime technologies and the optimism linked to new technologies propelled the following thirty years of building programs. 

 

As systems were designed and tested the tension between individuality and serial production became a central focus - some remained anchored to the mass production of elements scaled for a myriad of repeating buildings, while others projected variable near-site production and assembly as a bridge between productivity and customization. These different approaches were embodied by two French heavy precast systems with iconic names, Camus and Barets; both achieved success, with thousands of flats produced all over Europe and abroad. 

 

Most large panel blocks seem to have been cut from the same cloth, but they contain some important differences. Camus - see blog posts 131 and 311 -  relied on greater initial production investments and factory-intensive processes, while the Jean Barets system proposed near site assembly lines for frames, panels and floor slabs assembled monolithically with site-cast concrete or mortar filled joints. 

 

The near-site agility made it possible to bring fabrication to any context and reasonably sized projects without relying on the vital upfront project pipeline as was the case for the Camus panel blocks. Project specific finishes and profiles could be determined by architects and designers with an open system nimble enough to adapt to any residential building type as was shown in a beautiful example by architect Marcel Breuer at the Z.U.P. project in Bayonne (1964-68) using the panel production process which when all told would be used to develop 16 000 flats of different sizes and scales. The project specific panels, modulated as thick architectural envelopes, were nuanced to develop rich textures and profiles from tweaked repeating moulds. 

Section through panels in the Bayonne project