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Prefabrication and Off-Site Production 507
and the availability of expertise to carry out the required work. A similar concern may be
expressed for future extension and adaptation of modular buildings.
Durability
Although manufacturers provide warranties for their modules (15 years is common), the
long-term durability is less certain. Manufacturers tend to quote design lives of around
50–60 years, depending on the system. As more modules are produced and their durability
monitored, we should be better informed about anticipated durability compared with more
traditional forms of construction.
Access
Some construction sites pose physical challenges with ensuring clear and safe access,
making the transportation and craning of large components very difficult or impossible.
This is a constant challenge for those working on the extension of existing buildings, especially
houses (e.g. Victorian terraces).
8.4 The production process
Given the repetitive nature of the manufacturing process, it is crucial from a business
perspective that customer (market) needs are clearly identified and exploited. Thus research
and development activities are concerned with market trends and technical (production)
factors. Results of the research and development activities are applied to the design and
specification of the production process to ensure a profitable manufacturing process. Some
manufacturers may use lean manufacturing methods. The extent of robotic manufacturing
processes will vary between manufacturers; however, most manufacturers will follow a
production process similar to that described here, with rigorous quality control conducted
by trained personnel at the end of each step in the production process.
A typical production process
The main steps in a typical production process are described here for a timber- or lightweight
steel-framed unit:
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Discussion and confirmation of the customer’s technical specification (in relation to
production capacity and production constraints).
Planning and scheduling of the manufacturing process, from ordering of materials
through to site delivery and hand-over to the customer, is agreed prior to commencement
of production.
Automated pick-up systems are used to coordinate production information and ensure
that components are ordered from suppliers and delivered to the production line on
time.
Components are allocated to a specific project and supplied to the production line
(approximately 3000 components may be required for an average-sized house).
Main floor, ceiling panels and external wall panels are assembled (e.g. automated
nailing or screwing of panels to joists).
Frames are assembled in a box-shaped structure for rigidity (e.g. by automated spotwelding
machines). Floor and ceiling panels are fixed to the frame, followed by the