Prefabrication experiments - 324 - Manufacturing methodologies - 04 - Made-to-order

 

Sometimes called custom made and frequently associated with made-to-measure this type of production method implies a personalized experience and perhaps relates in the most basic way to building construction. Buildings are generally designed and made to specifications to reach an envisioned uniqueness. Like a tailor-made suit in the fashion industry this does not impede the use of certain patterns that communicate ascertained ways of putting things together. For example, A tailor will consistently place buttons according to models, use the same stitchwork patterns or pockets sizes and so on, even if the garment is uniquely suited to the body for which it is intended; repeatable parameters mark out its production. 

 

Building is similar, even though many argue that edifices are singular creations, underlying and existing patterns regulate a building's design, assembly, and construction. Span tables, product catalogues, code requirements, ergonomic standards and bylaws all influence the limits of uniqueness. Buildings may be designed as one-offs, but they rely on made-to-stock production for most of their components. 

 

Industrialized building systems and Offsite construction direct a contrasting methodology where a building is assembled from preset parameters chosen and arrayed to produce or compose an engineered-to-order building. The manufactured steel building, for example, Butler Manufacturing’s portal frame hangar is an obvious example of the difference between made-to-order and engineered-to-order. The same building frame and components could be purchased by a consumer in northern Canada or in the southern United States, and while components are basically the same, each building will have to be designed and calculated for specific contextual constraints, snow loads, wind loads, hurricane and seismic conditions as all these factors will differ; steel profiles may be engineered to be thicker and heavier to respond to greater loads, however the appearance of the building will remain the same. 

 

Customization, in made-to-order is often determined and limited to some basic principles: making certain changes that require little reworking in the factory to get done. Complete customization and taylor made prefab systems are rare and based on artisanal approaches. Light frame panel producers are a notable example where each bespoke design is pushed out of the factory according to a completely customized design.

Butler steel portal frame building

Prefabrication experiments - 323 - Manufacturing methodologies - 03 - Made-to-stock

Made-to-stock is the consequence of mass production. Inventories are managed and derived from anticipated demand. Prognostics synchronized with supply chains determine product quantities, which are tagged, stored, and made available for purchase. Made-to-stock components redefined the way buildings are made in an industrialized economy. Fabrication of pieces, parts, equipment, or assemblies is decentralized, and supply is governed through project-specific documentation. Pieces are described, classified, and specified by architects, engineers and builders. Stocked pieces are brought together by general contractors to complete singular buildings repeating this same integration process from building to building. At best components are dimensionally coordinated but generally building elements and hardware are made without explicit regard to how they will come together. In rare cases manufacturers coordinate or facilitate assembly criteria, however onsite coordination has remained an artisanal and entangled undertaking.   Detailing has been the architectural solution to this very real challenge; architects specify, precisely draft, and arrange how all components are to be juxtaposed and fixed on the building site. In architecture and construction, this made-to-stock or off-the-shelf approach helped define a building culture marked by normalized conventions for itemizing contractual procurement and assembly of buildings. 

 

Organizing systemic hierarchies along with regulating production metrics and dimensions were all established to bring disparate elements together in a coherent and legally framed manner and have contributed to the «catalogued» industrialization of construction. Masonry, timber and steel are all identified by some type of normalized format, modular brick, the 2 by 4 and steel shapes can be ordered, purchased, and specified through industry channels understood and federated by producers, trades and professionals. A notable example of made-to-stock manufacturing in construction is the consistency of timber framing members. Pieces are cut to standardized sizes available for variable building projects. The platform frame, an evolution of balloon framing and box framing before industrialization is perhaps the greatest success story of applying made-to-stock methodology to construction. Each stud, joist or sill is milled to dimensional regularity, both in section and lengths. Timber norms were influenced by years of increasing demand for these versatile elements. Architects, builders, or lumber resellers, all stakeholders required the commodity to be of homogenous quality and compatible from the stock of one lumberyard to another. 

Made-to-stock milled timber

Prefabrication experiments - 322 - Manufacturing methodologies - 02 - Piecework production in construction

Piecework production is a manner of delivering products or their constituents where labor compensation is commensurate with output: number of produced pieces or objects. The apparel industry used piecework notoriously as workers were remunerated for sewing buttons, cutting fabric patterns or for the number of pieces of clothing they were able to produce. Basing payment on yield seems beneficial to both workers and employers as the efficient link between output and productivity frames supply chains. Conversely, it can also lead to workers obsessively toiling to increase earnings while discounting quality and neglecting their own working conditions; quantity becomes the dominant and only metric for performance. 

 

Piecework theory also exists in construction as trades and general contractors sometimes outline contracts and purchase orders based on square footage, on the installation of piping, wiring, bricks or the supply of any other building assembly. The clear standard for compensation, theoretically stimulates a more productive workforce. Sometimes associated with industrialization, piecework does not necessarily involve mechanization or mass production as artisans usually worked on piecework payment in preindustrial society; yield for payment, a legacy of rudimentary barter systems. 

 

Pieces can also be fragments of an overall process, and in this way, piecework usually refers to a Taylor inspired division of tasks where each hand’s contribution is essential to building a whole.  Piecework in architecture can be elegantly elucidated by a building process and material invented by perhaps the greatest engineer / builder of the twentieth century, Pier-Luigi Nervi. In the Sistema Nervi, pieces (tiles) were conceived as permanent formwork to array geometric molds for large spanning structures assembled from small manageable parts. These man-made tiles could be manufactured à pied d’oeuvre (an example of near-site prefabrication) and commanded a large manual workforce making individual tiles «tavelloni» that once juxtaposed, stitched, and filled with concrete fashioned a monolithic ribbed structural thickness. The laborer’s hand imprinted each tile as the ferrocement shapes were made by troweling and pressing cement-based mortar into multiple layers of mesh over a wooden mold. This type of piecework assembly process helped shape some of the most beautiful architectural structures of twentieth century modernism in Italy and around the world.

Small Sports Palace in Rome (1957), Pier Luigi Nervi, during construction (source : wiki commons)

Prefabrication experiments - 321 - Manufacturing methodologies - 01 - Batch production in architecture

 

Industrialized construction protagonists have always tracked advances in manufacturing concepts to argue for similar efficiencies to be applied in architecture and construction. The next ten blog posts will investigate the generative and contemplated connections between manufacturing approaches and buildings.

 

Batch or lot production denotes a controlled number of items or grouped assemblies characterized by an identical time frame, dimensional constraints, ingredient lists or tooling benchmarks. The «lot» circumscribes quality control measures and performance metrics for monitoring the series’ fabrication parameters and service life.  

 

How does batch production relate to architecture or construction?  A batch of timber trusses, premixed mortar bags, reinforced concrete for a building frame or even a delivery of steel beams and posts for a skeletal frame all carry project specific measures defining their limited serial production on or offsite. The series / batch can be tweaked or charted according to required adjustments for quality, customization, or other contextual requirements. An even clearer example of this type of serial or lot production in construction is architectural precast concrete panel envelope elements. The non-loadbearing panels are conceived with decorative profiles, textures, colors, thicknesses, and dimensions for a single building. This type of set uniqueness characterizes a batch; particularized panels cast in a factory are arranged and organized corresponding to a controlled data set containing unique architectural specifications framed by producers’ capabilities. Once the panels are produced for their site or building, a subsequent lot of panels with their own uniqueness can be launched. 

 

Batch production guides the evolution of mass production toward mass customization as nuanced details and information can be applied to a set number of components. This type of prefabricated building panel is usually employed as a thick curtain wall, set and hung from structural reinforced concrete or steel frames. Lifting point anchors and slab to panel connectors are also project specific depending on scope and spans. Not as industrialized as heavy-duty post war precast panel systems which employed mass produced identical panels across innumerable projects, here the idea of a batch allows architects to use predetermined criteria like transport constraints, modularity, dimensional coordination, connectors, finishes, or aggregate type to design completely personalized panels for distinctive projects.  

Precast concrete panels used as a curtain wall

Prefabrication experiments - 320 - Icons - 10 - Industrialized onsite building systems

Industrialized building systems, prefabrication, offsite construction and factory-made architecture are all related to the idea of generating edifices more efficiently by using methodologies used in the manufacturing of complex objects. The pitch is simple and chronic: if factory production was deployed to offer greater quality products, cars, phones, furniture, etc. at an affordable price, the same principles should be harnessed for buildings. Even with this conceptual clarity, comprehensive factory production is still only employed for a fraction of constructions. A recent uptake and renewed interest is largely driven by acute circumstances; labour shortages, rising costs, environmental imperatives and new digital tools and technologies. 

 

One argument for offsite construction’s pervasive marginal application is that onsite construction is already highly industrialized. Pieces or parts that are actually fabricated on the building site are limited; architects specify manufactured components that are coordinated and installed by specialized trades according to contractual documents (plans and specifications). While it has been proven that this process is inefficient and repeats the same arduous and discord hindered processes, it does allow for flexibility, making changes and adjustments during construction. Further, iconic onsite industrialized building strategies have been largely standardized systemizing construction and their stakeholders’ fidelity. 

 

The light timber platform frame, the steel skeleton and the reinforced concrete flat slab are directed to residential, commercial and high-density construction dictated by years of use and coordinated democratization. The three structural systems, emblems of onsite construction, employ straightforward, shared, understood and easy to detail connections which are taught in schools elevating their status as acquiesced types. Manufactured systems, like modular volumetric systems are evaluated against these basic frameworks. Their intrinsic flexibility is their greatest asset while their relative stability, predictability and stringent compliance to building codes makes them low-risk for builders. In a sense, they are a type of industrial vernacular, a shared knowledge applied according to scale (low-density residential = timber platform frame), their conformity to laws (fireproofed collective housing = flatslab reinforced concrete) and their pertinence for particular types (hi-rise = steel skeleton). Although these definitions are fluid and depend on contextual specificities, the three systems exemplify the success of  entrenched on-site systems’ flexibility with high levels of embedded normalization. 

Timber frame (Levittown); Steel skeleton (Reliance building); Flat Slab (Ford Motor co.)