Prefabrication experiments - 491 - From precast concrete plates to « Flying Panels »

 

Above all other systems, one embodies industrialized construction’s input on mass produced serial architecture. From the mid 1940s and throughout the decades following the second World War, the precast concrete panel manufactured to shape hives of dwellings from similar slabs and walls was deployed in Europe and in the Americas as a symbol of construction reform as well as innovation. 

 

Its plainness is at the root of its prolific and large-scale application; sheets of concrete cast in standardized thicknesses, with window openings and facing materials were produced in factories to be delivered and stacked in repetitive organisations. Either dry assembled or bonded with mortar over continuous and extending steel reinforcements knotted in a monolithic framework, the «Panelki» panel building asserted the application of centralized policy frameworks to architecture. 

 

Flying Panels, a recent exhibit, showcased the concept of this building system, lifted buoyantly into place, increasing output on a war-ravaged continent becoming synonymous with post-war prefab. Opened in 2019 at ArkDes, Sweden’s National Centre for Architecture and Design, the exhibit was accompanied by a catalogue including a variety of texts reinforcing the sheer scale achieved by concrete panels. Researched and curated by Pedro Ignacio Alonso and Hugo Palmarola, the project elegantly portrayed the globalized use of these artificial stone plates inspiring offshoots in diverse countries that faced similar challenges in the supply of affordable dwellings. Models, publications, and posters, all relate the attraction and dissemination of a controlled procedure for producing communities. The almost choreographed movement of cranes raising and setting panels horizontally and vertically multiplied identical arrangements, adapted to their contexts through a varied patchwork of facing materials or panel geometries. 

 

While reinforced concrete, in today's carbon conscious construction environment has designers searching for alternatives, the Panel Block’s role in modernity is undeniable as is its contribution to developing our current base of industrialization strategies in other materials. The case in point is mass timber (cross-laminated timber) which is being proposed in an analogous type of sheet and surface-based strategy toward affordable housing. 

An image from the exhibit

Prefabrication experiments - 490 - Looking Forward to 500

 

The first 10 blog posts (January – April, 2014) acknowledged both iconic and lesser-known prefab experiments, some productive and many flops, with the intention of elucidating promises and challenges related to offsite construction. Twelve years later, the blog will reach a milestone that seemed at the time, highly improbable: 500 posts.  Conferences, articles, publications, research endeavours, study days, and three exhibits have grown out of this ongoing exercise.

 

Looking back at 489 posts retracing the history as well as current experimentation, the challenges to industrialized construction are unchanged. The increased use of manufacturing methodologies in construction again appears inevitable considering lagging productivity, onsite wastefulness, and reduced affordability, however these methods remain marginally applied relegated to certain types of projects, as architectural singularity, outdated perceptions along with outmoded building processes remain the crux of the problem. Research - historical, creative and codeveloped - particularly within the AEC disciplines remains robust and a celebration of this fertile field of exploration will be the subject of the next 10 blog posts. 

 

Exhibits, literature, and prototypes have all been delivered to highlight how prefab would radically modify construction culture. The Dream of the Factory-Made House (Herbert, 1984), Kelly's The Prefabrication of Houses (1951), Wachsmann’s The Turning Point of Building (1961), The House as a Product (Vogler, 2016) and Refabricating Architecture (Kieran and Timberlake, 2003) all manifested and conveyed the prefab promises of their era. Curating prefab played a similar role. Architecture et industrie (Centre Pompidou, 1983)  Home Delivery (Moma, 2008), and Flying Panels (ArkDes, 2019), celebrated the diversity and influence on architectural praxis and education. 

 

Along with curating and publishing, government-endorsed exercises have disseminated knowledge aimed at enabling prefab to successfully infiltrate the market; Operation Breakthrough from the late 1960s remains the most famous. The experiments published on this blog incorporate this rich and diverse history of prefab construction specifically in their effort to reunite two fields represented by conflicting values; architectural values of singularity and the extreme production efficiency values which regard architecture's take as frivolous. These divergent views still embody the inherent complexity associated with construction’s industrialization. 

An excerpt of experiments from 1-489

Prefabrication experiments - 489 - 3D Printing - An Onsite Assembly Line

 

Considered for the designed-to-order fabrication of small complex objects in the recent history of additive manufacturing, the technology's translation to building has spawned a large amount of analogous exploration, though mostly linked to marginal prototypes. Precisely depositing a fluid concrete or clay composite layer-over-layer numerically controlled to produce an extruded form is the basic idea of these horizontally textured vertical bearing walls. 

 

Timber beams, steel purlins, or any other type of spanning element can be attached to the walls to cover interior space. Vaulting layers has also been explored and experimented with to produce compressive monomaterial structures. In all cases either a robotic arm, or a gantry type crane carrying a nozzle deposits material according to instructions contained in a 3D model, plotting in x-y directions with the z axis being developed at a relatively slow pace, which allows the material’s adequate consistency to settle and support the next layer. From bus stops to micro dwellings, and even two to three-story collective housing, 3D printing is being promoted as a low-cost alternative to conventional site cast concrete. 

 

The mass-construction archetypes are produced on regular, printed foundations or over a slab on grade. Using these techniques to produce housing implies delivering material and machines on a just-in-time basis using only what is needed, reducing costly and wasteful formwork associated with reinforced concrete construction. 

 

3D printing tehniques and methods are progressing rapidly. Demonstrated for continuous printing of linear objects over a conveyor, the Blackbelt 3d printer is showing what can become an alternative to bearing structures, where beams and other types of dimensional components could be made onsite and then simply bolted together or assembled with mortar in a 3d printed kit-of-parts. Producing complex components can further optimize the technology's use by providing any shape needed to adjust to site conditions. Bringing the required digitally controlled tooling to site points to new potentials in terms of size, scope, and shape as the normal transport criteria that limits sizes and capacities need not apply.

Blackbelt 3D, printing linear objects over a conveyor

Prefabrication experiments - 488 - Modern Dry Masonry for Cleaner Sites

 

Masonry construction is commonly known as a wet construction method. The site-intensive process of laying masonry uses binders, with hydraulic lime being the most common, in which water activates a chemical reaction to harden and bond unit elements (modular or irregular) in an infinite variety of stacking arrangements. Historically, Roman opuses or opera symbolize masonry construction's durability -  some of their compressive shapes still stand thousands of years after they were built. Masonry owes its strength to both the permanent binding and the geometric stacking of elements with width and shape as indicators of performance. Bricks, blocks, and stones, are piled following modular dimensions or distributed informally to fill out walls, and more spectacularly arches, domes or vaults using temporary supports as elements are allowed to bind and cure. 

 

Masonry is associated with on-site messiness as liquid binders are mixed and troweled onsite. Dry masonry, common in contexts lacking resources and knowledge to mix robust binders, was developed as a structural alternative based not on the adhesion between units and mortar, but on how elements are fitted together, intertwined in structural resistant geometries with no binding agents except the units' form and weight. This type of clean/dry masonry construction inspires modern alternatives that relieve intensive site conditions requiring no specialized labour.

 

Three startups, Plaex™, Systeme3™ and Legioblocks^™ all share a renewed interest in simplifying masonry construction by either minimizing or even eliminating messy binders. Each system is manufactured with shapes or profiles designed to stack, interlock and snap together like toy Lego™ bricks. All three systems propose load-bearing walls that support other building elements to span horizontal spans. Systeme3™ for example showcases the use of hollow core slabs supported by precast concrete beams and posts to form an industrialized building system. The skeletal structure is infilled with the interlocking blocks which are then layered or insulated to form single- or multi-layered wall systems. Promoted on their ease of assembly, the three systems also promote new materials that include recycled content. Dry Interlocking also introduces potential disassembly and circularity to contemporary masonry construction. 

left: Plaex™, center: Systeme3™ and right: Legioblocks^™

Prefabrication experiments - 487 - The Architecture of Standardization

Since modernism pioneered new architectural possibilities based on industrial techniques and materials, architects have developed an enigmatic love-hate relationship with industrialized construction. In best cases, they have proposed prototypes ingrained with a capacity for mass production, fashioned from off-the-shelf details in the name of standardization; Iconic, well-known architects presented prefabrication as a model for mass housing. Others have been highly critical and probably one of the reasons prefab has fallen short of attaining the same large-scale successes of manufacturing in other sectors. Reaping prefab's advantages requires deep normalization. As presented in mobile home manufacturing in the United States, or in panelized precast concrete systems of the  Soviet era Gosstroys, production was tuned to economic objectives. This type of mass-produced housing was highly criticized by architects for its reduced design value.

 

Architects have espoused the narrative of standardization without the commitment to standardized design. Repeating a singular extruded curtain wall profile in a building is the type of detailing architects have come to propose as their understanding of standardization. Widespread standardization has been achieved in the building industry demonstrated by every part and piece of a building being catalogued, specified, purchased and delivered with respectable lead times; any big-box hardware retailer depicts this comprehensive normalization.

 

Using made-to-stock ready-to-use components to build a house or building is one of the reasons the fragmented building culture remains a successful albeit inefficient model of production. Contractors buy and deploy these elements without scrutinizing low-design value whereas architects will try to redefine elements arguing for the added value of singular design. This singularity associated with architecture is a complete non-standard approach leading to higher costs and increased production waste. The added value of the architectural design process is vital but must be harmonized and weighed against the required changes in production values and methods to achieve atypical designs. Standardization along with designed for manufacturing efficiencies require a grasp of production to attain scaled replicability and represents the only positive way forward for a stagnating industry. 

Walter Gropius and Konrad Wachsmann's Packaged House

Prefabrication experiments - 486 - The Patterns of Timber Framing for Teaching Robots

 

Envisioning the streamlined fabrication of customized pieces, panels, or chunks delivered just-in-time, for the quick, and easy assembly of a house or building has been the ambitious value proposition of many industrial protagonists. Some have succeeded in harmonizing their business model with a localized specific demand; however, the more generalized industrialization of construction required to increase productivity and respond to the growing challenges of onsite construction is still elusive. The required reform toward production in construction, is all-encompassing from the small onsite contractor to the large developer. The industry is too bogged down by old habits; manufacturing requires upfront investments that make it difficult to compete in terms of costs and agility with conventional builders. 

 

A startup based in Alberta, Canada, is striving to reform the prefab producer’s business model based on a completely integrated Factory Operating System that deploys lean robotic production to streamline the framing of house panels for floors and roofs. Promise Robotics is looking at prefab in a new way by understanding how robots can be taught to assemble project specific and industry standardized framing patterns, in a just-in-time factory-to-site delivery process. A relatively small production bay is controlled by the file-to-machine data-driven process. The robotic arms can switch from lifting, cutting, placing, aligning, nailing, seamlessly executing machine learned patterns orchestrated to produce a 40-foot wall framed panel in 8 minutes. 

 

Two robotic arms working in conjunction, borrowed from the automotive industry, were set up to learn from a local manufacturer's production process and endeavor to reproduce timber framing in idealized AI-driven conditions. From this research and development, the company is proposing to market agile «flying factories» all over the country to help increase supply and encourage the adoption of new prefab ideas. Recognizing that housing construction is not only a production problem but includes material management, supply chain harmonization, and factory to site logistics, their value proposition includes an operating system that outlines and manages every part of the process, including the choreographed robotic assembly of wall components. 

See article in  https://www.canadianmanufacturing.com/manufacturing/promise-robotics-opens-new-homebuilding-facility-in-alta-312995/

 

Prefabrication experiments - 485 - On- and Offsite management

Dealing with difficult climate conditions, labour shortages, or even health and safety issues on building sites seems to point toward greater offsite uptake as an obvious solution for improving construction's productivity and efficacy. The enduring fragmentation of the sector made up of many small contractors and trades managing their projects on a one-by-one survival-of-the-fittest model has led to a construction industry that is not only conservative but is refractory to any type of change or innovation. Buildings in general still go up inefficiently the same way they have been for the past hundred years and industrialization, while promising an integrated model for producing other commodities, has led to a disjointed process isolating designers from fabricators and builders.

 

Construction has become about managing disparate subtrades and coordinating an onsite entanglement of systems or tasks, that,  at best is ordered by a proficient general contractor or at worst a convoluted mess of discordant contractual relationships. While the building industry’s fragmented culture is difficult to shift on a dime toward harmonized practices, one of the current drivers for reform is the impetus to efficiently respond to the environmental crisis, by reducing waste and gaining any competitive advantages linked to streamlining potential efficiencies.

 

This potential swing toward reducing waste is where construction management and offsite fabrication can be tuned to operate in a just-in-time symbiotic relationship to deliver value added subcomponents. The pre-assembly model is different from basic modular volumetric or panelized systems as it is based on what makes sense to prefabricate and can yield greatest results in terms of time management. The overlap of onsite and offsite tasks is an untapped opportunity to apply manufacturing principles to construction. The constructor-manufacturer integration model also presents challenges, as traditionally companies have specialized in one or the other. However, the benefits of managing tasks ideally suited to their off- or on-site conditions can create a different type of prefabrication company based on managing project processes rather than completely separating construction and manufacturing, which only leads to further entanglement of stakeholders.

Just-in-time delivery of a preassembled chunk

Prefabrication experiments - 484 - Competitiveness and Timesavings

 

Advanced manufacturing, big data optimizations along with precise resource management are all combining to generate all manner of efficient fabrication and labour-saving production processes. This is the case in nearly all sectors. Why haven’t these translated to a competitive edge for prefabrication deployed toward building construction? This simple question relates to offsite construction and manufacturing requiring different cost structures, an enduring obstacle to a sustainable uptake. Most agree, prefab reduces timelines; if time is money, prefab should be much cheaper when compared to onsite conventional construction. Time savings have not necessarily translated to economies on one-off projects. Higher upfront planning costs, greater factory overhead, entanglements caused by on- and off-site coordination and steep learning curves for inexperienced stakeholders can increase overall expenditures.

 

When compared to other manufacturing sectors where industrialization has optimized quality, while reducing time and costs per unit, architecture remains bogged down in singular prototypes. Each building includes far too many contextual specificities to justify the mass production flows required to consistently lower costs. Replicating details, components, processes over multiple projects can present opportunities for bulk purchasing and regulating supply chains, however, varying loads, soil conditions, environmental constraints, management requirements in dense urban areas, ever-changing stakeholders, and code obligations all differ from one site to another occluding stable demand for normalized designs that would induce important savings.

 

Notwithstanding the one-off contextual intricacies, reduced timelines should still translate to savings in overall project costs. A condensed schedule of even a modest 10-15% on a standard timeline can minimize interest payments on loans, site management costs like heating for winter conditions, equipment rentals and even deliver earlier earning potentials, an important advantage in housing or production facilities. A structured global cost analysis and comparisons should be applied to offsite construction by including some type of time equivalent factorization. The archaic nature of onsite construction is still mired in analysing construction costs in terms of management, labor and materials. Reforming costing methodologies is one of the important cultural shifts required to increase offsite construction’s potential market penetration.

Extracted from https://www.ellismodular.com/why-modular/ 

Prefabrication experiments - 483 - Constant, stable purchase order pipelines

 

One of the most important differences between the on-site subtrade or contractor and the off-site manufacturer is the need for consistent purchase orders with similar characteristics; A constant portfolio (often referred to as a pipeline) is required to cover important investments in everything from marketing to tooling, all essential for high quality and quantity fabrication. 

 

On-site contractors benefit from logistics that are defined and managed according to a single project. Specifically in a conventional design-bid-build process contractors estimate and then purchase all specified elements to build a building and their risk is limited to these purchases. Risk is also mitigated by the fact that any cost overruns that are incurred because of omissions or unforeseen conditions will, in the end, be assumed by the client. 

 

Along with all the same functional, technical and economic criteria of an onsite project, off-site fabricators need to amortize costs over repeated productions. This creates conditions that constantly challenge the economics of high-value-added prefabrication. The bipolar objective of responding to a client’s one-off prototype criteria while managing large overhead costs of manufacturing is completely foreign to onsite builders and thus defines the lack of competitiveness of offsite versus onsite at least when it comes to delivery of one-off projects. 

 

Offsite manufacturing can only be economically feasible if project pipelines permit advanced planning and resource management to justify just-in-time flows that balance sales with bulk purchases. When comparing the bidders' supply chain between two competing companies, one onsite and one offsite, the overhead required to sustain the prefabricator’s advantages, compared with the jobsite contractor who assumes lower overhead linked to project specific tools and materials, is difficult to overcome. Further, materials for the onsite contractor are paid for as claims progress on site. 

 

Unstable demand that does not sufficiently replicate certain elements will never be a viable avenue for off-site construction, if the objective is to reduce costs. The crux of the problem is that ingrained architectural singularity occludes the potential for large-scale project pipelines - this simple but hard to crack polarity has spelled the end for many promising prefab experiments.

Similar characteristics in manufacturing of modular volumetric

Prefabrication experiments - 482 - Aligning Stakeholders for prefab's success.

 

Repeatable, iterative processes, gaining value from each outcome, and replicable designs are the basis of off-site construction's potential successes. The factory production of complete houses, of large modular volumetric chunks or panelized building segments require a harmonized supply chain contingent to purchasing and investing. Capitalizing includes everything from infrastructure and machinery to software and skilled labour, all optimally managed to gain sufficient efficiencies to outperform on-site construction. 

 

While these expenditures have been the basis of making products since the beginning of the Industrial Revolution, building construction is complicated by the number of parts and systems that need to be synchronized. Certain tasks simply can’t be accomplished in a factory setting: civil services, foundations, and site work. A building will therefore always require two types of construction stakeholders: the offsite manufacturer and the onsite contractor. Maximizing upfront planning and carefully pinpointing exclusive and shared responsibilities for both is not an easy task, especially in a conflicting building culture. 

 

The offsite manufacturer is often responsible for supplying an assembly of materials that is systemically incomplete. Its on-site completion involves other contractors, sometimes multiple subtrades and this is where prefab can lose some of its advantages due to wasteful overlapping that is not meticulously rooted out. Further, investing in a factory, production machinery, marketing departments, lifting and moving equipment also imposes greater costs to the prefabricator when objectively compared to a contractor with a small team that receives their materials as needed and paid for them earlier, as materials are considered installed once they are delivered to the construction site. 

 

These challenges for manufacturers drive the requirement for a portfolio/pipeline of similar types with replicable characteristics to spread planning and operational costs over multiple projects. Design modularity, task repeatability, and component interoperability are ways to achieve success in prefabrication. Unfortunately, an irrational quest for singularity is entrenched in architecture, even for repeating types like housing. Buildings already repeat a certain number of elements and details that can be outlined, described, and regulated; however, the fragmented nature of construction has been shaped to repeat the same wastefulness repeatedly. 

Idealized process - published by Canadian Homebuilders Association
https://www.chba.ca/factory-process/