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/

Prefabrication experiments - 481 - Off and On Site Challenges

The opposition between one-off building processes - bringing together disparate actors as a fragmented team for a singular project, and the harmonization of stakeholders under one roof for the scaled production of building subassemblies off site - endures. Beyond the successes of the mobile home, factory-made buildings have failed to achieve any generalized use even though the assembly line was touted as a disruptive force capable of reforming conventional construction modes. The current design and construction culture is one of the biggest obstacles to off-site.

 

The potential advantages of industrialized construction are multiple and well documented: preassembly in a controlled manufacturing environment, precise design for fabrication, bulk material procurement, iterative optimizations, waste reduction, standardized repeating details from project to project, rigorous quality control methods and efficient task overlapping - producing elements in a factory while other work proceeds on site compresses schedules, reducing costs linked to project duration and site management (winter conditions, equipment rentals, etc.).

 

While these important factors argue for greater use of offsite construction methodologies, beyond the negative connotations, industrialization implies some particularities and drawbacks that must be managed. Greater upfront planning, collaboration and required stakeholder engagement from design phases are needed to reform the highly discordant processes ingrained in conventional onsite construction. The necessary collaborative process can be facilitated by contemporary virtual design and construction tools to achieve the information and detailing required to plan for streamlined manufacturing, delivery of components and onsite assembly. Reduced onsite flexibility is also discussed as an obstacle, however it should be noted that the onsite bricolage may be flexible, but, it is also intensely wasteful. 

 

Architectural customization, singularity and cultural expressivity are also often cited as being unachievable with prefabricated systems. Buildings are anchored in settings that require civil, earthworks and groundwork adjustments that are not only difficult to repeat, but that characterize an edifice’s link to place. The interface between these informalities and the rigorous systemic repetition required for successful industrialized systems like modular volumetric construction should lead to new innovative systems and exploration aimed at marrying the cultural richness of individual sites with the efficiencies of offsite manufacturing. 

Setting Offsite produced house on site

Prefabrication experiments - 480 - Construction industry’s capacity to self-regulate

Conventional construction backers have generally shown resistance to embracing offsite construction. Further, the sector’s capacity to control what is and what is not adopted is an interesting case study in its autoregulation. The successful application of industrialization principles to produce buildings requires a special set of circumstances that balance supply, demand with simple building systems. Mass-deployed light-timber platform framing for single family dwellings, precast reinforced concrete panel blocks for collective housing in postwar Europe and box construction for mobile homes have all displayed the required perfect storm to harmonize supply and demand. Previous housing crises have provided these systems with the required equilibrium and impetus for adopting offsite construction systems at scale.

 

Current interest and vigorous policy are driving a renewed willingness to shake up the industry toward comprehensive manufacturing methodologies. This optimism is fueled by increasing demand for urbanized and affordable dwellings. However, market integration remains marginal. On-the-ground production capacity to respond to present needs continues to stagnate. The construction industry with its peculiar way of getting things done and archaic methods is self-regulated by this equilibrium of influences. A cultural transformation, even with massive investments and education to reorganize logistics would take years to induce wide-spread change.

 

Wide-ranging industrialization like the complete fabrication of buildings is not likely to take shape, at least not soon, and will remain marginal for several reasons, including the lack of stable demand and centralized purchasing agents. However, the autoregulating nature of the construction industry has already demonstrated the types of offsite construction that will further integrate the industry; panelized systems for walls, roofs, and floors, while less factory intensive than modular volumetric, bring a type of customizable prefab to the building site with the added value of partial systemic integration without the logistical challenges of more comprehensive systems. Panelized timber has already been massively adopted to reduce pressures on framers. Alleviating labour shortages with simple preassembly is showcasing how prefab can be part of the industry's capacity to self-regulate.

Timber framing offsite is now an integral part of onsite construction

 

Prefabrication experiments - 479 - Circularity and offsite construction

 

Designing for material circularity to avoid the «take-make-waste» approach common since mass industrialization implies a far more interconnected conceptual strategy including end-of-life considerations from the onset of both the design and construction planning processes. Buildings erected conventionally and according to modern standards are in a sense a heap of raw materials put together with all manner of durable connections, glues, weatherproofing membranes, plastics and wet joint compounds to perform in line with fireproofing, weatherproofing or other technical criteria and to maintain these conditions over a building's lifespan - durability has always denoted long-lasting. 

 

End of life scenarios in relation to materials and systems have rarely been considered and resources often end up in landfills as renovations are required, repeating the same wasteful processes.  Adaptive reuse, functional renovations, and energy retrofits are all ways of giving the integrated energy flows required to erect a building a second or even a third lifecycle moving away from linear processes. Keeping materials in buildings retains the carbon initially spent in service, while reducing the amount of extraction and production energies required for new construction. 

 

Offsite construction and prefabrication are often identified as facilitating circularity. Components are designed, produced and delivered to streamline onsite assembly and potentially their disassembly. This is theoretically possible, however, conventional building with all its regulatorily imposed seamlessness along with modern building culture's fascination with a minimalist aesthetic impede systemic disassembly: Removing plasterboard or ceramic tile, or continuous foam insulation, just to name these, implies destructive demolition making recycling and reusing of embedded components difficult - nearly impossible. 

 

A revolution in design is necessary. Design for disassembly, too marginally applied, should be integrated into construction standards, codes and regulatory frameworks to engrain buildings with a capacity for change. Offsite manufacturing in this respect can be conducive to circularity as assembly details are already designed to facilitate onsite connections and coordination. Managing resources throughout their lifecycle and planning for their reuse can also be facilitated through the data management required in manufacturing.

Façade components in the circular economy - TU Delft - by Christina Michael (2016) Master's Thesis

 

Prefabrication experiments - 478 - From Citroën to Citrohan

 

Inspired by principles ingrained in a mass production business model fostered by Henry Ford in the early 20th century, motorized vehicle production was centralized around single corporations. Automobile producers set their sights on domestic internal markets before endeavoring to expand internationally and long before partnering with the competition to share knowledge and platforms became the norm. Ford, FIAT, Mercedez-Benz, Skoda, and Peugeot all began producing cars nationally and inspired a revolution in the marketing of consumer goods. 

 

Car production was equally fundamental in pushing toward revolutionary changes in building construction and in architectural design. Seriality, flow production, piece or modular standardization, and mass-produced components all became underlying principles of modern architecture. Citroën in France began producing automobiles in 1919 in the same era that Le Corbusier was quickly becoming an iconic figure arguing for new mechanization methods to facilitate the serial fabrication of quality housing. 

 

His prototype for the Citrohan house employed his Five Points of a New Architecture as the basis of democratizing innovatively designed and produced dwellings. These three-floor prismatic units included a double-height living space that would become synonymous with some of the architect's famous proposals and was inspired by the architect’s fascination with painters' studios.

 

The whitewashed exteriors covered a traditional masonry unit construction system supported by the flat slab DOMINOpresented as an open construction platform. Based on François Hennebique's patents, reinforced concrete made it possible to build fireproof structures with open plans and non-bearing façades by replacing them with slender columns and thin slabs spanning 5-6 meters. 

 

Initiating a flexible approach to architectural planning, DOMINO could be infilled with any layout in plan and with large expanses of glass in elevation, replacing common openings. Le Corbusier's vision of brand equity with Citroën sustained and propelled the theoretical relationship between car manufacturing and building production. While this comparison is still evoked to showcase prefab’s potential, Citrohan succeeded in integrating architectural folklore but only marginally succeeded in mass producing architecture.

Citrohan House representation (1920)

Prefabrication experiments - 477 - Prefab as policy

 

Catalogued designs, uniform platforms, replicable buildings, preapproved prefab micro dwellings - governments are scrambling to test many of these ideas to supplement affordable housing supply faced with a stagnating construction sector. Offsite construction complements these approaches by applying manufacturing methodologies to increase efficiencies and capacity. While some see current crises as prefab's heyday, the possible links between manufacturing, architecture and housing construction already sustained modernism a century ago. 

 

Modern architects explored and elevated prefab to a type of language spawned through material innovation, redirecting architectural production from the onsite fashioning of materials to the streamlined assembly of factory-made components. From relationships with military industrial complexes, governments also underwrote prefabrication as a way forward toward stimulating inventive systems. Prefab’s time came and went in the 1940s, 50s and 60s with each generation explaining why their era was the right time for a robust turn toward industrializing construction.

 

Going from architecture and construction as a cultural phenomenon based on centuries of onsite informalities and peculiarities to industrial production tainted by mass production connotations is a transformation that requires more than simple reforms - it requires a complete conversion of business models for builders that are ingrained in business-as-usual and apprehensive about the expanded economic risks that go along with mass production. These changes are even more tenuous as demand for and successful application of offsite construction as a product-based pattern is constrained to certain relevant building types with repeating organisations. 

 

Iconic experiments like the Lustron House, designed by Carl Strandlund, convey the rich heritage of government support along with ambitious inventors looking to produce coordinated components for easy-to-assemble low-cost housing. Their application was largely obstructed by onsite principles promoted by tract housing developers like William J. Levitt who took simple to build platform or balloon framing and democratized onsite mass production processes that were ingrained with complete flexibility.  Lessons from both production methods tell the tale of prefab's marginal uptake and consumers' enduring need to feel that their home is a one-off process, even though all its components and properties are mass-produced.

Onsite construction using mass production principles

Prefabrication experiments - 476 - Carbon emissions onsite versus offsite

 

Prefabrication, industrialized building systems and offsite construction are valued for their potential to reduce costs, condense timelines and to bolster quality standards. As tasks are transferred into factory and manufacturing settings, the effective harmonized workflows that are applied in other industries bring added value to the preassembly of large building fragments to facilitate on site coordination. Still marginally applied when compared to conventional construction methods, the climate crisis along with housing and labour shortages have put prefabrication on policy makers' radar to address many current challenges. 

 

Among present drivers for innovation in prefabrication is the need to decarbonize the built environment, reducing embodied carbon of materials and methods along with infrastructures' operational carbon. Offsite manufacturing has the potential to reduce waste at every step of the fabrication process; this argues for its systematic use even though comprehensive studies demonstrating relative reduction in embodied carbon are lacking and offer contradicting viewpoints. Component fabrication reduces embodied carbon by optimizing material use, however in some cases, as in modular volumetric construction, embodied carbon can be slightly higher due to material redundancy.

 

Holistic, whole building studies are complex and require methodologies that account for the immense variety of materials, components, contexts, seasonal variables, climate conditions and processes involved in building construction. It can be simple enough to calculate embodied carbon of site cast concrete versus offsite cast panels; however they only account for a specific element within the building’s overall footprint.

 

All seem to agree that offsite construction’s shorter schedules, in part due to task overlapping logically lead to lower carbon emissions; if the construction of a building is reduced by 3 months over a 12-month schedule, time savings translate to less travel to and from sites for everything from workers, tooling and machinery. Further, projects that are built in extreme conditions require heating. Propane or any other type of energy is squandered as buildings' temporary enclosures offer little climate performance. Onsite's wastefulness is well-documented which can easily be mitigated with offsite construction. 

Carbon emissions from buildings - diagram by lmnarchitects.com 

 

Prefabrication experiments - 475 - Modular evolutions in mass timber

From forest to sawmill, to artisans and finally to the construction site, timber buildings evoke a modesty linked to generations of builders. Dry joinery, steel anchors, bolts and a plethora of other fasteners, including the earliest iron cut nail, have made it possible to create both grand and vernacular structures. Recent advantages in engineered timber products complement enduring principles to elevate timber's advantages without some of the dimensional nuisances, distortions and changes associated with sawn lumber.

 

Glulam and cross laminated timber (CLT) in particular have become synonymous with a type of precise kit-of-parts construction where elements are shaped to sizes as well as complex profiles and assembled to generate variable forms with the robust technical characteristics generally associated with steel or reinforced concrete, but without the carbon footprint of these energy intensive materials.

The kit-of-parts approach to timber construction based on digital manufacturing of detailed building components reduces waste by optimizing offsite methodologies and delivering only necessary elements to site. Further, mass manufacturable and scalable with a high strength to weight ratio, cross laminated timber is being deployed in projects as a potential alternative to concrete flat slab systems common to fireproof multistory buildings. 

 

Staging the mass customization and adaptability potentials of CLT, Nordic Structures, a Canadian producer and supplier recently produced modular volumetric CLT boxes in the Northern community of Chibougamau, Québec located approximately 500 km north of Montréal. Les Pavillons du 49° designed by Montreal-based studio Perch architects was fostered by Nordic's local vertical supply chain, from forest to panel to module to delivery, to erect this first example of modular volumetric CLT in the company's portfolio. It only took four days to stack the 47 factory produced modules. A total of 20 rental units, each organized from at least two CLT mega chunks delivered with exterior cladding, leaving weatherproofing and stitching to be finalized on site. Large balconies along with dynamic window placement were used strategically as arrangements to avoid the modular box type architecture sometimes associated with modular volumetric. 

Nordic Structures, Les pavillons du 49° during module setting and construction

Prefabrication experiments - 474 - Organized offsite pre-assembly with Consolidation Centres

 

Building construction dictates logistic challenges: closing streets off to traffic, delivering materials and oversized machinery to sites, and disposing unused or hazardous materials are just a few elements that underscore the intricacies associated with even the most accessible sites. These complications are exponentially augmented in remote locations with extreme climate conditions where construction is limited to certain seasons. 

 

Beyond the habitual obstacles faced in accessible communities, the housing supply crisis in remote areas like the Far North is compounded by sociodemographic barriers including years of underfunding, a tenuous grasp of local housing demand and building culture, sizeable distances between communities, and rapidly changing climatic conditions accelerated by global warming.  Further, construction’s highly fragmented design to delivery process is aggravated by difficult to reach sites impeding the normative, quick, effective and sustainable supply of housing. Prefabricated houses have been proposed to solve some of these issues, however the logistical challenges of onsite delivery and completion along with low social acceptability of shipping less than adapted housing exacerbates the already problematic context. 

 

An issue that should be addressed is the convoluted delocalized supply chains disconnected from local settings and onsite assembly in communities without existing production infrastructure.  Construction Consolidation Centres (CCCs) are increasingly researched and explored to harmonize the just-in-time delivery of components to complex building contexts. A combination of management, logistical and distribution facilities receive orders for components and materials which can be assembled into large modular building chunks or optimally packaged as kits-of-parts to reduce onsite time or waste and ensure efficient resource management. 

 

Governance of these CCCs for remote construction would have the potential to link multiple communities, achieve economies of scale, and prepare optimal housing bundles into ready-to-deliver loads.  A co-op CCC operated by neighbouring communities enables coordination of diverse physical and social needs. Beyond the grounded harmonization of actors, CCCs require a political will combined with policy tuning supply with delivery, along with pertinent design, inspection and operation criteria for quality products.  The CCC model combined with offsite preassembly can be a way forward for reducing the entanglement of actors, methods, materials and components associated with conventional supply models. 

Construction Consolidation Centre imagined by CSB Logistics - https://www.csblogistics.com/