Prefabrication experiments - 465 - Factory building and Buildings

Currently, making building chunks in a factory deploys all manner of numerically controlled cutters, routers, cranes, panel bridge nailers, butterfly tables, and conveyors to increase offsite construction's capacities and value. Uptake in all sectors of construction’s industrialization is being stimulated and directed by these digital tools and techniques along with their underlying data. The principles of factory production applied to architecture can reduce waste at all levels of the building process functioning in a climate and quality-controlled environment. The invisible hand supporting factory production is standardization. Replicable elements and processes increase scalable efficiencies. Cutting, organizing, assembling, and packing in a covered space stresses how Fordisms and Toyota-isms (lean construction) can be arranged for producing edifices. 

 

While the tools have been updated with the objective of increasing productivity, the primary elements of a factory remain the same.  The Ford Motor Company factories as designed by Albert Kahn at the end of the 19th and beginning of the 20th centuries promoted an open system, with spanning elements supported by small and vastly spaced vertical bearing elements. Reinforced concrete, steel and timber examples all traced a similar path; the roof or covering plays a fundamental role in orchestrating a malleable choreography of materials, machines and people to achieve a streamlined process from receiving components to the delivery of value-added assemblies. Logistics are comprehensively protected from climate and other contextual difficulties imposed by conventional job sites. 

 

The factory can be permanent or temporary (flying factories) structured by the posture of protection and an ideal of adaptability. While the interior arrangement of equipment can change, the building system itself is a generic support structure where a robust slab supports floor equipment and robust beams or girts suspend tools, creating ideal horizontal planes delineating a secure manufacturing environment. The architecture produced in these environments is normalized and of greater quality than projects built onsite as systems, details, assemblies are perfected gaining knowledge from product to projects. Cleanliness, organization, process geared spaces of production are an important part of construction culture, whether prefabricated or site built; iconic temples of mass production hangars protect and generate efficiencies for better buildings.

Ford Motor Company Long Beach Assembly Plant, Assembly Building, 700 Henry Ford Avenue, 

Long Beach, Los Angeles County, CA

Library of Congress Prints and Photographs Division Washington, D.C. 20540 USA

 

Prefabrication experiments - 464 - Catalogues and pattern buildings

 

As housing demand increases and supply festers because of aggravating construction challenges, policy makers are surveying offsite construction as a quick fix to a systemic problem. Housing provision is not only related to productivity but should also address changing lifestyles, demographic fluctuations, and affordability which require comprehensive governance beyond design and production. The catalogue of housing types and the pre-approved pattern building have been proposed as potential avenues for boosting supply. 

 

The catalogue was explored by Canadian housing authority (CMHC) in the 50s and 60s and led to the construction of many homes responding to the post war baby-boom. Architects were given an opportunity to contribute archetypes for the nuclear family in a suburban setting. Articulated to house similarities private industry developed high levels of standardized designs and construction strategies. While not prefabricated, the catalogue certainly pushed low value-added industrialized components in every suburban tract; the timber platform frame was abundantly used. 

 

Similar normalization and socialist policies in post-war Europe deployed reinforced concrete precast panels as the system of choice for replicable collective blocks. The «pattern» large panel edifice was an exercise in standardization akin to the single-family dwelling but with the added value of serializing a kit-of-panel elements to be used en-masse. Both systems, lightweight timber and reinforced concrete, were made affordable by their large-scale use. The catalogue and the typical block directed straightforward solutions to housing supply - repeatable designs that could be patterned and predetermined to harmonize supply chains economically federating all required materials and methods. 

 

Critiqued over and over, today this regularity, while not a comprehensive solution to the current housing crisis is being promoted once again arguing that housing provision is slowed by design and approvals; remove architects from the planning process, simplify permitting, its associated delays, offer model buildings, and housing will go up quicker. This type of short-sighted planning is partially what killed prefab’s potentials through enduring prejudices.  Supporting creative initiatives toward innovative and affordable solutions for contemporary needs, may take more time to develop, but the current crisis requires a holistic approach to avoid offsite bearing blamed once again for systemic challenges. 

Left: CMHC catalogue design by R.T. Affleck ; Right: Pattern large panel blocks for a new town (USSR)

Prefabrication experiments - 463 - Lessons from the mobile home sector

Critiques of the mobile home industry range from suspect construct quality to cookie cutter inferior design and to trailer parks denoting less than ideal living conditions. While these assessments have been debated, the production of these untethered shelters on an assembly line can certainly relate expertise about dwelling affordability. 

 

The self-built inhabitable trailer and the manufactured house, a progression of the mobile home, share the chronicles of building a whole or half of a house on a mobile steel chassis. The chassis, a movable foundation platform onto which the home's structure is attached, also facilitates rolling the structure in the factory from one production station to another. The mobile home differs from modular volumetric building chunks which are usually produced without the steel wheeled base, installed on a permanent foundation, carried on a truck and stacked multiple stories high. Both share the benefits of completing most building tasks in a climate-controlled setting.

 

For a typical onsite built house, labour can represent up to 50% of total costs; factory workers' reduced wages, automated manufacturing, assorted aids such as hoists, jigs, automated machinery and gantry cranes can reduce labour costs by as much as 30%. The repeating patterns of mobile homes also make it possible to make bulk purchases for everything from wall board to kitchen cabinetry and plumbing fixtures. With all these cost rationalizing measures, the mobile home industry still represents a successful segment of home production accounting for roughly 9% of all homes built in the US. 

 

One of the important lessons of the inhabitable trailer is the in-factory optimization integrating experience from home to home reducing task times and waste at every step of the process. When compared to onsite construction, quality control in the factory and inspecting recurring designs and organizations is simpler - fostering clear procedural practises. Founded on the strengths of mass production, most companies offer predetermined designs with some options for customization, however product seriality whether based on linear or cellular manufacturing lines is the formidable lesson that can be learned from mobile homes. 

Star Mobile Homes advertisement

Prefabrication experiments - 462 - Panelization principles

 

Panelization, assembling buildings with wall or floor factory produced panels, has succeeded more than other industrialized building strategies in becoming commonplace and widely used in construction projects. Framing on site is time consuming and generates large amounts of waste. Fabricating wall, floor or roof surface sub-assemblies in factories is an efficient way of erecting a building's structure without the more complex wrapping, transport, lifting and setting required in modular construction. Further, lightweight panel systems come with design freedom as their dimensions and parameters are less constrained by delivery prerequisites.  The advantages of panelization also include their low impact on conventional construction culture; Specifically for open panels used for framing, their implications for systemic coordination are minimal.

 

Timber panels are straightforward construction elements organized as stressed skins, composites, or even as hollow box-beam formats. While they range in configuration, the building method remains a standard lightweight timber platform construction. Beyond their onsite flexibility, their manufacturability and relatively simple tooling has made panels effective: A framing table with an insulation or sheathing table in a shed, organized in a linear sequence where elements can be cut, framed and then finished at arms' length is a prevailing factory arrangement. As compared to modular volumetric which offers its own advantages in terms of offsite systemic integration, panel-making reduces the number of trades, systems, components and logistics required in a factory. 

 

The single line setup with framing and sheathing tables is an affordable path for panel production:  The drawing accompanying this post shows a cut-off saw that prepares timber stock according to design documents. The cut timber elements are then carried to framing tables with conveyors reducing human effort required to carry materials. Using non-automated tools reduces important upfront costs but limits factory output. Weinmann is a well-known manufacturer of panel-fabricating equipment that has developed completely automated lines for increasing output. With this type of relatively affordable democratization of computer-controlled tools, tables equipped with panel bridges to place, cut, nail, lift and perform any number of programmed tasks are becoming common.  

Weinmann framing table and bridge + Simple linear panelization process