This chapter provides examples of the manufacturing of medium/high-level building blocks (in the following referred to as modules; building modules, prefabricated bath modules, or assistance modules that can also be referred to as building subsystems). Those medium/high-level building modules are in hierarchical, modular building product structures independent building blocks (see Volume 1, Section 4.2) that are delivered by the companies that produce them (Tier-1 suppliers) to original equipment manufacturers (OEMs; for a detailed explanation of the OEM-model, see Volume 1, Section 4.3.3) as, for example, large-scale prefabrication (LSP) companies (see in particular Section 5.2.6 in this volume), conventional construction sites or automated/robotic on-site factories (see Volume 4). LSP companies such as Sekisui Heim, Sekisui House, Toyota Home, and Misawa Homes (Hybrid), in particular, have altered the building structures, manufacturing processes, and organizational structures dramatically in comparison to conventional construction in order to be able to assemble in their factories and on their final assembly lines as many prefabricated medium/high-level components from Tier-1 building module suppliers as possible. As outlined indetail in Volume 1, Section 6.3.7, this practice can be considered an ROD method that reduces the amount and variety of assembly activities on the assembly line and thus helps to create a SE in the LSP factory or automated/robotic on-site factory. In particular, in Japan, both prefabrication companies (OEMs) and module manufactureres (Tier-1 suppliers) are integrated in a well established OEM-like industry organization. Toto and Inax (both major suppliers of bath and kitchen equipment in Japan), for example, prefabricate plumbing units (especially bath cells) and deliver them as Tier 1 suppliers to LSP copanies, contractors and automated/robotic on-site factories. The use of prefabricated plumbing modules in the form of completely equipped three-dimensional cells is widespread in Japan.

The industrial manufacturing of bathroom and kitchen modules began in approximately 1920s in the Scandinavian countries (Sweden, Finland, and Norway). Long winters and short summers, and therefore short periods in which final on-site construction was possible, necessitated the use of prefabricated elements. In Germany, the industrial production of rapidly installable, three-dimensional subsystems/modules became popular in the early 1960s.