The term prefabricated construction leads many to think about complete structures built in a factory which are then transported to the site and set on a foundation. While this building method is becoming increasingly popular, there are other ways builders are using factory precision and efficiencies to create quality structures.
- Panelized Wood Framing
Typically used in roofing, these frames are built from long pieces of laminated timber, covered by a plywood or other board roof deck. The frames can be up to 72 feet in length. These roof panels save time on the construction site, and make roof construction much safer. - Sandwich Paneling
Sandwich panels are made from two thin facings of materials such as plywood, stainless steel, or concrete. The facings are then bonded to an insulating core, typically made of foam, rubber, paper, or cloth. - Steel Framing
Steel has long been a popular building material for both residential and commercial construction. Steel framing takes this strong and durable material and creates prefabricated panels from it. These panels can then be used to construct buildings. - Timber Framing
Like steel framing, timber framing panels are built in a factory and then used to quickly erect prefab buildings. Many timber homes today are constructed onsite using this prefab system. - Concrete Systems
Having concrete parts of a prefabricated building cast in the factory allows for more versatility and saves time. Although precast concrete panels and other architectural elements are heavier than building components made from other materials, they are typically more durable, and can improve a building’s aesthetics. - Modular Systems
Modular construction systems make use of all prefab styles to create a complete building, made from factory-constructed modules. The buildings are then brought to the construction site and connected to a prepared foundation and each other.
Prefabrication and modular construction
Construction elements and modules are produced off-site in factory-like settings, transported to site and assembled there. The prefabricated units may be e.g. smaller elements in a façade or entire factory-fitted bathrooms.
The terms prefabrication and modular construction are often used interchangeably. Prefabrication refers to the manufacturing of construction elements away from the construction site and assembly on site. In principle, these prefabricated elements can be customized for the specific project. Modular construction specifically describes instances of prefabrication where the elements are standardized modules. Each modular unit can be e.g. a dorm room, a factory-fitted bathroom, or an element in a façade.
Prefabrication and modular construction is especially relevant if
the building consists of multiple similar units (e.g. office rooms) and/or has a complex design that is difficult to construct on-site (e.g. special façade elements or steel frames)
the construction site is very remote, or in a highly dense urban area.
there is access to an efficient off-site production site
the construction site planning is complex due to e.g. many stakeholders, limited space or time
the construction site has a short build season, e.g. due to the climate, or is on very expensive land.
Benefits and challenges
Faster construction
Greater degree of predictability in cost
Less dependency of weather and site conditions (leading to higher productivity of workers)
Reduced material waste and transport carbon emissions
Increased safety to workers
Design options can to some extend be restricted by the use of standardised modules
Over-engineering e.g. wall thickness as several modules are assembled
Limited ability to change the structure through future renovations
Application examples
Scandibyg is a Danish market leader within industrially manufactured construction. They produce residential housing, office facilities and institutions by assembling prefabricated room-size modules on-site (www.scandibyg.dk).
Baufritz is a European company based in Germany, which is well-known for producing sustainable turn-key homes based on modular elements, such as prefabricated timber frames (www.baufritz.com/uk/).
Development stage
In Europe, the prefabricated housing market has been steadily growing up by 6.1% compound annual growth rate (CAGR) between 2014-17. Germany remains the largest market in Europe with about 25,000 units in 2017. The market is expected to continue growing in the coming years.
In contrast, prefabrication and modular construction for permanent buildings is an emerging market in North America.
Construction impact
The design phase is affected as the modules will somewhat restrict the number of possible designs. The construction phase will become more efficient, as more of this process will take place in factory-like environments.