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Prefabrication and Off-Site Production 489
(a)
(b)
Photograph 8.1 Timber- and steel-framed house construction.
Concrete panels were developed during the 1900s and have proved to be popular in some
countries (such as Denmark) but have had more limited application in the UK. Advances
in the development of lightweight concrete panels and material technologies, such as
carbon reinforcement, have helped to keep concrete an effective choice for some developers.
The majority of systems currently in use in the UK are based on a framed construction
of timber or lightweight steel (Photograph 8.1). Concrete systems are primarily based on
loadbearing concrete panels. The main concepts relating to cut timber, lightweight metal
and concrete, and the extent of off-site production associated with each technology, are
discussed further.
Prefabricated units are usually produced at a location independent of the building site,
and the term ‘off-site’ prefabrication is sometimes used. There are some situations where
the prefabrication is undertaken at the construction site and the term ‘on-site’ prefabrication
is used to describe this activity. The extent to which construction activities are moved
to a factory (or workshop) setting will vary considerably on the type of prefabrication
employed. Some buildings are built on site from factory-produced elements, while others
are delivered to site as complete units, merely craned into position, bolted to the foundation
and then ‘plugged in’ to the services supplies. The primary use of prefabricated units is for