Prefabricated building – also known as offsite manufacturing – is the umbrella name given to construction methods that use structures or components built at a different location than the location of use. The construction of the prefabricated elements usually occurs in a factory that specialises in this type of process. After being designed and manufactured, the elements are then transported to the building site.
The most frequent types of prefabricated building techniques
Under this umbrella term are found the following construction systems: (1) Panel construction; (2) Modular construction – also known as volumetric modular construction; (3) Log construction.
It is important to keep in mind that prefabrication can save a lot of time and money, but can’t completely replace the time spent on site. Using any of these techniques will still require time for installation and assembly on site.
This is a prefabrication technique that is usually used for house building elements such as walls, floors or roofs. This high-performance prefabricated panels consist generally in a core of thermal insulation between two structural facings. Depending on the technology there are different types of prefab panels as steel or timber framed, structural insulated panels (SIP) or cross laminated timber (CLT).
The panels can be manufactured with all the installations required already in place, like electrical sockets and water feed pipes which need only to be connected when the building is assembled.
The panels are manufactured in special factory conditions to achieve high performance. It is a very quick construction method that only needs a few days for assembling on-site, depending on the size of the project and the need for a skilled workforce is significantly diminished.
Also known as volumetric modular construction is a prefabrication technique in which whole or parts of the house are made offsite in a factory and then transported to the site. Before they leave the factory, the panels are already assembled into rooms. This technique requires a minimum finishing job made on site, therefore allowing a quick installation. It has some limitation on the design because of transportation restrictions, which will often require specialised vehicles.
Both panel and modular construction can be combined in one single building. For example, the bathrooms or the kitchen can be made using the modular technique, while the rest of the house elements can be manufactured in the form of Structural Insulated Panels. By combining both systems, even more construction time can be saved on site and the need for a skilled workforce is kept at a minimum.
This type of prefabrication technique refers to construction made with horizontally positioned logs with round or squared sections, interlocked at corners by notching. Traditionally, this type of building system has been used in regions with tall coniferous trees, which are used as raw material. Because of the evolving techniques of offsite manufacturing, log houses can be entirely prefabricated and then transported to the construction site as a ready-to-assemble kit.
A contemporary approach to this type of construction is the manufacturing of logs made of glue-laminated timber, that are produced in factories from raw wood. The final product is stronger and more durable than simple wood and can be used and installed in the same way as traditional logs.