Types of prefabricated housing

The categorisation adapted here follows (Huang, Krawczyk, & Schipporeit, 2006), where they defined six different types of prefabricated housing systems from a component-scale point of view: fully modular, sectional, panelised, pre-cut, components/kit of parts, and chassis and infill.

They based their categorisation on the scale of individual components. Other categorisations are often simpler with only four categories: Manufactured homes (which is another term for mobile homes), Modular homes, Panelised homes and Pre-cut homes. The following section provides definitions and examples of prefabricated housing based on the broader categorisation which is more comprehensive at this point.

2.3.1 Fully Modular

All the components of a single housing unit are entirely made, assembled and finished at the manufacturing plant; as three-dimensional modules requiring only simple connections to the foundations and main service conduits once at the site. The size of the modular unit is restricted by highway law or shipping constraints. Prefabricated modular and capsule architecture on a large scale was explored in the 1960s and 1970s (Figure 2-3), most famously by Moshe Safdie in the Habitat ’67 project in Montreal; contemporarily by the Spanish architect Ricardo Bofill for the Kafka castle project in Barcelona and later by Kisho Kurokawa for the Nakagin Capsule Tower in Tokyo.

27 2.3.2 Sectional

Small and easy to transport sectional modules but incomplete, as they need complementary components or processing once they reach the site. An approach largely used in ship and plane building. A sectional module housing based on the same techniques used for concrete sewage pipes was a project introduced recently in the Venice Biennale of Architecture 2016 by the Portuguese architect Samuel Gonçalves. The concrete modules match the shapes and dimensions of standard concrete sewer pipes, which means they can be produced by modifying existing production lines.

2.3.3 Panelised

Flat component assemblies such as completed wall panels, roof trusses, partitions, and floor assemblies are built in the factory and then shipped out to the site where they are assembled thereby saving on-site framing labour. Components like wall panels will often be nearly finished with windows, doors, wiring, and exterior siding. Panelised homes are built to be site permanent and are therefore built to local, state, or regional building codes. Panelised homes are generally

Figure 2-3: (a) Habitat 67 by Moshe Safdie, Montreal, (b): Kafka Castle by Ricardo Bofill in Barcelona, (c) Nakagin Capsule Tower in Tokyo. Source: a - Wikipedia, b and c – Archdaily

Figure 2-4: Concept Diagram of Sectional Housing System "Gomos". Source: Dezeen, 2016

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easier and cheaper to ship as they can be compactly bundled and moved on fewer and smaller vehicles. In most cases, the panelised components are load-bearing walls to replace post and beam framing system.

Figure 2-5: (Left): Panel preparation in Factory with openings already cut and prepared, (Right): Erection in site using cranes and trained workers. Source: Left - https://www.oremonte.org/enchanting-panelized-homes-texas/, Rigth:

prefabaus.org.au

2.3.4 Pre-cut

Many names are used to describe this type of prefabricated houses such as: Kit houses, Mill-cut houses, Pre-cut houses, Ready-cut houses, Mail order homes or Catalogue homes. Unlike modular homes, which are built in sections at a factory, in a kit house every separate piece of lumber is shipped already numbered and cut to fit its particular place in the house, thus eliminating the need for measuring and cutting, and likewise the waste of time. These pre-cut materials are the basic elements of the house and are not yet assembled into more detailed components and assemblies like in the panelised house.

Prcut wood framing systems have been developed in Japan. It is possible in Japan today to e-mail, fax or otherwise send a plan to a housing system provider, receive an estimate the same day, place an order for your custom house, and have it delivered the same week. The materials you would receive include the entire framing and enclosure package including roof framing and decking and exterior insulted panels. Using numbered pieces of lumber and unique metal connectors, frames can be assembled quickly and accurately with low-skilled labour. Pre-cut, numbered wall panels are also placed and secured easily (Brew, 2005).

29 2.3.5 Components/Kit of Parts

A kit-of-parts is a collection of discrete building components that are pre-engineered and designed to be assembled in a variety of ways. Components are sized for convenient handing or according to shipping constraints. LV Series developed by Rocio Romero is an example of a modernist house by kit-of parts system. All LV models have a standard width of 26’-0”, but vary in length. The architect offers customisation and unique solutions based on client requirements.

2.3.6 Chassis and Infill

This is a hybrid system that includes prefabricated posts and beams to form a framing system as the primary structure, and using the automobile industry’s term – chassis. This is made possible by dividing the house into two notional elements: the chassis, the standardised, mass produced part of the system, provides the structure and services for the building, and the infill, which consists of interchangeable wall and floor components, provides for customisation and adaptability. This system was proposed through a master thesis in the department of mechanical engineering in MIT in 2003, but its roots can be traced back to “supports” by Hebraken as will be discussed in 2.5.6.

Figure 2-6: An example of kits and parts available for the end-user to choose from. Each element has its pricing and the client can ask for different combinations. Source: LV Series Homes Brochure downloadable from:

www. http://www.rocioromero.com/LVSeries.html

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Although the concept is different and the houses are not prefabricated, Chassis and infill recalls to the mind the recent housing efforts made by Pritzker winner architect Alejandro Aravena in his

“incremental” approach. The government in this approach provides each family in the housing development with a half-finished house and the rest is left for them to complete and expand based on their available resources. While initiated by different motivations, both approaches share the general idea of the residents having strong input to the design and construction of their own residences by deciding on many variations of the infills within a framework of an existing chassis.