The history of modern premanufactured building
The history of modern premanufactured building began in the middle of the 19th century, when in the USA in times of the gold rush quickly completed houses were needed. Since then, premanufactured building has been the usual building method there.
In Germany, representatives of the BAUHAUS School of Architecture in Dessau discovered prefabrication for the construction of private homes at the end of the 1920s. The idea: Standardised series production of architecturally consistent and functional premanufactured houses that are aesthetically pleasing and affordable. Even at this early stage, the advantages that still characterize premanufactured building today can be seen: the prefabrication of building elements in the factory and the short construction time on site.
The premanufactured building industry, which had developed from carpentry after the Second World War, took up this idea again. Wood became the building material of choice. Because more and more people could afford their own house, a real building boom followed in post-war Germany, culminating in the 1970s. At that time, premanufactured houses were considered cheap - and sometimes inferior and uniform. Affordability was a positive consequence of the serial prefabrication of houses. This is still one of the advantages of premanufactured building today.
In the 1980s, the industry detached itself from the image of "cheap building" and launched a quality offensive. This culminated in the establishment of a Quality Association for German Premanufactured Buildings (QDF) initiated by the leading manufacturers. Since then, the manufacturers have been inspected several times a year in the factory and on the building site by independent inspectors. The requirements for building quality are laid down in a statute which is binding for all members of the quality community.
Without denying its roots, the premanufactured building industry dared to reorient itself. Today, the manufacturers in the sector see themselves as service-oriented house building companies. As in the BAUHAUS Decade, they attach importance to sophisticated architecture, which can be both classic and contemporary. Above all, however, it is diverse.
Type of construction
A wooden board that has it all
Premanufactured houses are based on wooden construction. As the name suggests, wood is the main component and therefore responsible for the statics of the building. There are different types of premanufactured buildings with wooden elements. The two most important are the panel building and the skeleton building method.
The Timber Panel Construction
Image © BDF/FischerHaus
In timber panel construction, the construction consists of large-format and premanufactured building elements that are used to support loads and to close off the room. The interior spaces of the building components are filled with insulating materials. The walls and ceilings are, for example, "planked" on both sides with wood-based material or gypsum construction boards, i.e. mechanically closed with staples or nails or with special adhesive. First, a framing is assembled from dried and precisely cut wooden beams. For this purpose, beams called upper and lower chords are connected to form a wooden construction element. Inside, individual chambers in the wall are separated by stems. The transom is then closed on one side and filled with insulating material on the inside.
Depending on whether the walls are external or internal or ceiling elements, ducts for electricity, water, heating or ventilation are integrated. The panels are initially only temporarily closed at these points on one side. At the construction site, pipes, tubes and the like are later inserted into the walls for building services. The recesses in the wooden panels for windows and doors are made by cutting the panels to size on the outside and inside. The materials used for planking the panels vary, depending on the type of fixtures or the purpose of the wall in the house structure. Ceiling elements are made of wood or a combination of wood and concrete.
On the outside of the wall, a thermal insulation composite system with additional insulation or, for example, a ventilated wooden facade is mounted. In industrial premanufactured construction, windows and doors are already installed in the factory, the basic plaster or facade elements such as wooden panels, metal panels or curtain glass are applied to the exterior walls. After a final inspection, the finished building elements are taken to the construction site by truck and assembled there in one to two days to form a rainproof, ready-to-extend house.
The Timber Frame Construction
Image © BDF/Meisterstück-HAUS
Besides the timber panel construction, the timber skeleton construction method, which was to be found classically in half-timbered buildings, is the most frequently used construction method in the industrial premanufactured building. In modern premanufactured construction, a further development of this construction method is used.
In the wooden skeleton construction method, the wooden skeleton represents a load-bearing system in which a bar-shaped load-bearing structure planned in the grid system, consisting of supports and girders, ensures that the loads are discharged. To put it simply: cross and longitudinal beams are the supporting elements of this construction. Vertical columns and horizontal beams form the skeleton of the building.
Non-load-bearing elements take over the function of the space-closing elements. This means that the space-forming components are independent of the load-bearing structure and are therefore generally not used to transfer vertical loads. The freedom gained in this way makes it possible to use any materials, e.g. glass, masonry, lightweight structures and premanufactured panel elements, to infill the skeleton structure.
Skeleton construction has thus become the initial construction for modern engineering timber construction. Through the use of tempered wood, e.g. glued laminated timber, and sophisticated, modern metallic fasteners, this construction system today enables impressive yet extremely filigree wooden skeletons. Premanufactured houses in skeleton construction therefore often have their architectural language and are usually elaborately built. Nevertheless, the skeleton construction method is nowadays rather rare for new buildings.
Wooden premanufactured houses are energy-saving homes
Image © BDF/WeberHaus
More and more house builders decide for a wooden premanufactured house. There are various reasons, supporting such a decision, since modern premanufactured houses have several advantages compared to conventional house building. Its industrial prefabrication makes it easier to plan and carry out the building project: A fact, that guarantees high quality, shortens the construction time and saves money. Your dream house can be planned individually - thanks to modern computer- and construction-technologies. As a result of their construction method and the construction material “wood”, premanufactured houses above all have an exceptionally high energy-saving potential. Due to long term rising oil- and gas-prices, operating costs of houses gain more and more importance. Under these circumstances an excellent, a whole life long working heat insulation turns out to be the best long-term investment.
High-quality wooden premanufactured houses always prove to be highly energy efficient, as a result of their perfectly working heat insulation. Reasons are a progressive construction, an exact building construction and last but not least the physical qualities of the building material wood. This natural material is extraordinarily capable of insulating heat, which is why wooden houses are highly-demanded within the cold and energy-conscious countries of Scandinavia as same as in many mountainous regions.
House and heating perfectly combined
Within each heating system it is important to thoughtfully co-ordinate all its components. An example: The pipe system should be installed in a way, that guarantees as less pressure loss as possible. Building a premanufactured house means getting the best possible complete solution out of one source, leading to the fact, that there is only produced as much energy as the house is actually in need of. Which energy source is to be called best, can not easily be generalized. In each case the last permissible primary energy need has to be kept. Concerning the overall balance sheet ecological arguments as well as the tenant´s individual behavior of use play as an important role as the question of cost does.
Image © BDF/Vaillant
Ready for regenerative energies
Image © BDF/BAUFRITZ
Oil and gas are still in great demand. There is nothing wrong with that, since modern boilers achieve high efficiency factors. Nonetheless, house builders should take into consideration to use renewable energies: Solar- and geothermic allow it to be independent of fuels, since they are able to gain heat out of insolation or the ground. Biomass does also offer a great energy-potential for the future: Heating with wood means that only that amount of CO2 is going to be released into the atmosphere, that the tree has absorbed during his growing-period before.