Prefabrication experiments - 529 - Underlaying modernism

Architectural modernity’s idioms sustained by industrialization envisioned a new formal language seemingly detached from any classical references. One concept perhaps above all others supplanted historic composition considerations and other preindustrial planning traditions: the industrially coordinated grid. Used as an underlayment for form and space creation, grids were deployed to shape uniqueness, detail modern construction and reject conventions. Mass production inspired material criteria as guides for rationalized design.

 

Grid compositions were not specific to modernism, both classic and vernacular buildings used dimensional planning aids to rationalize architectural designs or standardize material use: geometric proportions based on instructions such as the Golden Ratio, or the Ken in Japan predate modernism's fascination with patterns that drive designs. The grid in the modern era referenced industrial parameters or material production more than any other dimensional principle. Efficient factory supply drove many theories of dimensional coordination based on facilitating the conceivable interoperability of building components in a Design for Assemblyparadigm. The 42-inch or the 48-inch grid became the most recognizable canon of modern planning. Other frameworks were also determined by modern material choices: 20-foot spans for flat slab reinforced concrete, 8-foot singlewide mobile home volumes based on their transport requirements or even 16-or 24-inch stud placement in timber framing all related to fabrication logistics. 

 

Education also linked building design to preset mathematics to expedite its organization and to define the modern architect's planning doctrine. Grids used as coordination devices outlined simplified arrangements for everything from structural to spatial and mechanical dispositions. Mies, Eames, Prouvé, and Wright, the same architects who perceived in industrialization a means of reforming of architectural production became the masters of grid use and elevating industry's architectonic potential. Their careful use of square or rectangular grids was masterfully deployed to reveal spatial dynamics - sliding, aligning, juxtaposing or separating spaces. The grid was analogous to a musical score onto which elements were positioned as notes to create rhythm, symmetry or dissymmetry, axes - all classic elements of architectural planning - showcasing modernism’s claim to novel geometry was deep-rooted.

Grid use at Mies van der Rohe's S. R. Crown Hall at IIT (Illinois Institute of Technology) (1956)

Prefabrication experiments - 528 - Modularized mechanical systems

 

Modular volumetric construction requires more planning than conventional construction to reap its potential benefits of time and cost savings. On-site stitching details to guarantee structural and climatic performance are just the tip of the iceberg when it comes to the required systemic coordination. The rigorous design of connections and networks to produce code-compliant electrical, plumbing, and HVAC systems involves upstream, rational modularization. In a typical flat composed of two neighbouring modules, or two stacked boxes, connections to building systems are sectioned and capped, or in the case of electrical systems, cable lengths are provided to connect individual private dwelling systems to collective grids. 

 

Precise planning according to how modules will be positioned on site means that mechanical design and coordination is complexified with teams having to not just plan systems but also understand and manage manufacturing logistics for streamlined production and comprehensive functionality. In the best cases, the entanglement that is synonymous with on-site coordination is avoided or at least minimized as systems are planned as discrete components with efficient clear distributions and links. 

 

Access hatches, loose cable lengths, vertical service stacking, repeating mechanical distribution using corridors as runways and vertical stacked wet cores adjacent to pipe chases facilitate mechanical distribution. All system locations should be carefully noted and catalogued in the factory for onsite and future reference during building construction and operation. Along with professional cooperation and collaboration, strict factory management and control tools as well as DfMA digital software platforms for virtual design of systems networks aid in determining the most efficient paths for pipes, wires, ducts, equipment placement and optimal arrangements for onsite completion, without deconstructing what was efficiently assembled in the factory.  

 

While the upstream planning requires greater synchronization between professionals and builders, a repeating pattern of flats from floor to floor makes it easier to scale these strategies for connecting systems along with confirming all the code-required fireproofing and acoustic performance at specific modular touch points. This comprehensive and coherent modularization has multiple advantages for initial construction, but can also facilitate repairs, retrofitting, and replacement of elements during a building's lifespan. 

Organizing mechanical systems in a factory setting

Prefabrication experiments - 527 - Modular volumetric structural organizations

 

Buildings generated from modular volumetric construction in timber, steel, reinforced concrete, or from hybrid compositions of these materials follow two principal structural strategies: As the modules are self-supporting, the first simply stacks volumes; loads are distributed through their faces from one box frame to another. The second, architecturally iconic, employs a mega support structure onto which the self-supporting boxes are inserted as if carefully placed in a scaffold or on a shelf. The first strategy remains the path of least redundancy as having a mega structure has proven to increase costs, although it becomes necessary in tall modular buildings.

 

Without a secondary supporting rack, gravitational loads are distributed through bearing walls or vertical columns creating paths or grids analogous to those found in post and beam or wall and slab construction. In lightweight timber construction, module corners are sometimes reinforced with columns composed of 2-by stock or by using steel elements. As vertical loads are distributed through modules, lower modules bear the weight of the entire structure. In a six-story building, the lower volumes must be structurally more robust, which also implies a production management strategy to sequence and nuance production according to each module’s placement within the overall structure. 

 

Efficient structures are also contingent to alignment. All elements that are cantilevered or out of alignment, angled, or rotated complexify structural design and particularize the manufacturing of those design elements, which in turn increases costs. To account for horizontal loads and bracing, module walls and floors can be designed as rigid diaphragms active over multiple modules. In skeletal modular structures, in steel for example, bracing strategies vary from rigid connections to conventional X-bracing of each unit and external surface materials that brace adjacent units.  For tall buildings, reinforced concrete cores and complex structural connections between units and cores are designed to respond to seismic criteria.

 

A combination of the two structural archetypes can also be designed. A stack, 3 or 4 modules high (the feasible economic limit without structural reinforcement), is carried by a mega-structure. A tall building can be organized in this manner by providing a specially designed structural floor at every 4 stories as shown in the project shown below. 

TREET project's structural strategy

Prefabrication experiments - 526 - Planning process

 

Along with fragmenting design and building teams, conventional construction takes place in a linear process. Planning (design, financing, and budgets) is followed by construction document production by licensed professionals, open tendering, contracting, building, and commissioning. Tasks are sequenced and managed onsite until the finished building is handed over to its owner, who mandated a general contractor to complete the project as designed by the retained professionals. Within the process, subtrades are also contracted and made responsible for their coordination and adjustments in line with construction documents provided to them, often with little description or explanation. In opposition to this,  offsite construction proposes a process that begins the manufacturing of sub-assemblies in parallel with site work and that includes manufacturing criteria in the planning process. 

 

The overlapping of manufacturing tasks with onsite construction has been clearly established as one of prefabrication’s most notable advantages, as the shortening of a project’s timeline reduces everything from construction management costs and borrowing costs to construction waste, and the number of production days. Handover of the finished product and making it useful for the owners happens quicker than for onsite-built edifices. Project acceleration can also lead to a decreased environmental footprint, as worker-hours travelled to and from the building site are minimized. While these potential advantages are not subject to debate, the cost of ensuring they are realized is greater upfront planning. This planning should include a collaborative framework that puts manufacturers in the design phase of a project for professionals to consider manufacturing logistics and criteria. Good communication is the key with all design stakeholders to predefine and coordinate structural, architectural, and mechanical systems. 

 

Respecting manufacturing possibilities from the start also implies construction documents, drawings and specs, that outline their specificities. Transport criteria can define structural grids, along with modularity, and material supply chains can limit design choices. Material constraints, coordination responsibilities, infrastructure connections, and site versus offsite assignments must all be established upstream. This intensive upfront planning upends conventional construction methodologies, and increases design costs but can lead to efficient and cost cutting timeline compressions in the long run. Repeating this harmonized process and team-based design, while considering manufacturing, adds value to individual projects and for serial production can lead to even greater economies by spreading costs over multiple projects.

Traditional planning versus planning with Offsite construction