Prefabrication experiments - 377 - State of the Art - 07 - Delicate Adaptive Reuse

Neglected stone dwellings, barns, and other derelict buildings have always been objects of romanticized architectural adaptations; the dream of transforming a ruin into a house for next to nothing and reviving it for a new era or use is of particular interest in an age of resource conservation.  In degrading old towns and regions, structures can be purchased for cheap by assuming the responsibility of rehabilitating the buildings, to breathe new life into demographically challenged communities. Renewing an old house requires the delicate touch of knowing what to get rid of and what to preserve that harnesses the spirit of place embedded in weathered stones. Prefabrication and industrialized building have little to do with vernacular building techniques, however, the creative interaction between old and new sometimes elevates both, providing an image of how classic building systems and modern methods of construction can complement one another in unique adaptive reuse strategies.

 

Nauman Architektur practise epitomized this idea by transforming an 18th century pigsty into a refined 21^stcentury showroom. Extensively damaged in the second world war, the building’s existing aged materials and shapes are framed beautifully by a precise timber panel system composed as a prefabricated prosthesis inserted into the existing stone structure. The planar timber structure is arranged as a type of autonomous volume, pre-assembled, lifted and slid into place. The internal form duplicates the arbitrary patterns of existing openings and serves as a background for stone bearing walls that clearly express their tectonic link to place. The plywood insert is capped off with a slick pitched roof detail amplifying the material dualities of old and new, thick and thin, light and heavy, craft and industrial production, stacked and surfaced, evident from every point of view. The prefabricated sleeve envelopes a flexible space that could be used as a multi-use living space. Turning a low road accessory farm building into an inhabitable modern space showcases the adaptability of architecture not only from a theoretical perspective but as a hands-on way of conserving and reviving history. Prefabrication in this case speaks to its potential for sensitive intervention reducing site disturbance to a minimum. 

Exploded axonometric and volume being inserted, project by Naumann Architektur

Prefabrication experiments - 376 - State of the Art - 06 - Add-on Componentization

 

Componentization is a direct consequence of industrialization. Parts, pieces, anchors, or assemblies are mass produced and include innumerable catalogued variations to create bespoke buildings. Modern buildings are all, in a way, kits composed of these manufactured parts. Design for Assembly was one of modernism's canons that conceptually defined component prefabrication’s applications. Assembling edifices from coordinated parts inspired dimensional coordination but parts remained disparate: interfaces and systemic coordination were rarely considered in parts production. Instead, romanticized harmonious detailing of diversely manufactured parts in building construction guided the architect's role in providing instructions for coherent integration. Applying Lean production principles, BIM modeling and even DfMA principles to component manufacturing is currently reforming the sometimes disjointed and entangled relationship between design, fabrication and construction.  

 

Componentization can be further enhanced by modularization, creating coherent dimensional, joining and production parameters, to produce elements designed to fit into or added-on to buildings. Premade bathroom pods, elevator frames, staircases, precast wall panels and manufactured balconies are all large sub-assemblies becoming common as offsite production is understood as an efficient and productive alternative to archaic and wasteful onsite construction.  Sapphire, a company based in the suburbs of London, produces balconies as a type of coordinated chunk devised to simply slide onto a building's structural system. The prefabricated balcony is an assembly of two main parts; the prism (deck and rails) is conceived with two framed openings that glide the floor onto extending brackets cantilevered from the building structure like the two extending forks of a forklift. These outstretched members can be bolted to steel beams or cast in concrete slabs. The two contact points reduce thermal bridging associated with continuous balcony slabs. The module is flatpacked, delivered on site and craned to be set at a specified height.  The floor «cassette» is lightweight and includes material choices for glass guardrails and decking. The company takes modern technology even further with their configurator «coach», an on-line tool deployed to customize designs from predetermined rules and dimensions. Details can then be downloaded and specified. This type of online catalogued part and process streamlines the relationship between design and fabrication through a type of preprogrammed personalization.

Sapphire balcony being lifted into place

Prefabrication experiments – 375 – State of the Art – 05 – MTP_Multi-trade Prefabrication

 

As buildings became more complex throughout the twentieth century, integrating an assortment of services, systemic entanglement came to characterize the construction industry's fragmentation. Piping, wiring, air distribution and conditioning designated a patchwork of trades competing for space, paths, and channels for distribution. Trade coordination, or lack of thereof, is at the heart of scheduling and cost overruns in building construction. Prefabrication and industrialized construction promised to reform construction by defining and manufacturing building systems streamlined for onsite assembly. Most systems have limited their scope to structure, as is the case with partial panelized and modular volumetric construction, mechanical coordination remains a challenge in harmonizing multiple stakeholders to produce a coherent network of services. 

 

Combining the advantages of prefabrication, primarily a controlled work environment, concurrent onsite and offsite progress, with the one-off architectural designs, Multi-Trade prefabrication mandates trades to collaborate, in a factory, to assemble chunks or parts of a building that will subsequently be delivered and completed on site. The multi-trade component is an co-creative/constructive process outlined by contractual documents that identify methods, materials, place of production, tools and responsibilities for each trade brought together to construct optimized sub-assemblies. This process rationalization increases efficiencies, reduces waste, and most notably has the potential to eliminate costly coordination errors. The idea has been deployed on complex projects by industry leaders like Skanska and has even inspired a segment of production: Multi-Trade Rack Prefabrication is specifically linked to mechanical distribution chunks that are fabricated offsite in modular formats to facilitate both design and construction. 

 

BIM (building information modeling) is the main driver and facilitator for this type of prefabrication. Digital twins provide fundamental documentation and information sharing tools to organize spatial and functional criteria, specify, design, and identify coherent routes for trade interaction. Virtually designing and assembling mechanical systems before they are built makes it possible to apply both rigorous organizing principles and a high level of standardization by modularizing mechanical racks. The success of MTP hinges on an integrated process and contractual clarity imposing a comprehensive overhaul of traditional procurement methods.

Base4 Modular prefabricated MEP racks

Prefabrication experiments - 374 - State-of-the-Art - 04 - Collins House kit-of-parts assembly

 

Skyscrapers are contemporary marvels of engineering symbolizing wealth and power, just as gothic cathedrals or tower-houses were in middle-age cities and towns.  Industrialization of steel and reinforced concrete along with advances in structural computations inspired verticality to showcase modernity.  Building tall frames requires imaginative ways of buttressing these thin cantilevered beams sprouting from the ground, reaching for the sky, and anchored by increasingly small floor plates. Stacked small floor areas also require novel building methods in dense urban environments constraining traditional construction methods. 

 

Bates Smart Architects, 4D Workshop structural engineers and Hickory, general contractor, designed and erected the Collins House in Melbourne Australia in 2002 based on an innovative interpretation of an age-old idea – the box beam: a hollowed out structural section braced by its perimeter surfaces. With a height to width ratio of 16:1, the 58-floor building's structural strategy employs 4 shear walls:  2 lateral walls and 2 cross walls that form an overall H-shape braced in both directions. The service core portion of the H shape includes large vertical openings for an egress scissor stair and three elevators. The building's first 14 storeys are outlined by urban property lines, while floors above the 14th gain a 4,5 m cantilever on purchased aerial rights over an adjacent heritage building. This 44-floor cantilevered appendage is post-tensioned to its supporting lateral shear wall. 

 

The building is a manifest of current offsite construction methods applied to unique one-off edifices. Shear walls, exit stairs, cantilevered volumetric sub-assemblies were all produced offsite, delivered, set, and stitched on site.  Precast sections of post tensioned bearing walls were stacked along with complete floor sections; elements were then joined with structural mortar connections. A notable example of multi-trade prefabrication, systems are fully factory coordinated by multiple trades working together as they would onsite, but in a factory setting. Hickory group distributed contractual roles and responsibilities among trades and manufacturers. The unitized curtain walls, and temporary floor jack-posts were also installed in the factory reducing onsite work to a minimum. Modularization is applied to all building subsystems making this tall structure a giant Meccano kit-of-parts designed for precise assembly in a tightly woven urban context.  

Elevation and structural strategy

Prefabrication experiments - 373 - State of the Art - 03 - From the mobile home to the CrossMod®

 

According to the U.S.A.-based Manufactured Housing Institute's Industry Overview for 2021, the average construction cost of a manufactured home is 57$ per square foot compared to 119$ per square foot for an onsite built home - 50% less. This affordability is evidence of the successful application of industrial principles developed throughout the 20th century. From the earliest trailer coaches in the 1920s, to single and double-wide’s evolution in the aftermath of World War II, mobile homes influenced single family home production in the United States; even referred to as American vernacular by modern architect Paul Rudolf. Negative undertones associated with subpar construction forced United States Congress to adopt the National Manufactured Housing Construction and Safety Act in 1974. This increased and imposed national standards for quality to stabilize the industry's credibility. The term manufactured home also conveyed manufacturing potentials and dissociated the industry from the entrenched idea of impermanence.

 

Still representing 9% of all single-family housing starts, the dream of the industrialized house is alive and supported by dynamic forward-thinking producers envisioning greater demand coming from the current lack of housing supply and a dearth of traditional construction trades. Redefining the industry and promoting design and efficiency also led to a new term: CrossMod®. An industry initiative in 2016 highlighted the renewed need to elevate industry standards and more importantly to reach a new generation of consumers still inhibited by enduring connotations of less than par products. Linked to the crossover that has become an immensely popular breeding of cars with SUVs in the automobile industry, the CrossMod® presents some of the features of a site-built home, most notably a permanent foundation. Modular sections can also be combined and stacked to construct homes that are difficult to distinguish from their site-built counterparts and that come with the advantages of constantly improving manufacturing processes. 

 

Short some 5.4 million single family dwellings according to recent studies (USA), the market potential is clear. It remains to be seen if this most recent change in terminology will reform the industry and increase market share: 9% of all new housing starts represents a figure that is strangely unchanged from the 9% of housing starts in 1954.

Evolution from the Mobile home to the CrossMod®