Prefabricated houses

Q&A: Prefabricated houses

The widest distribution of the prefabricated method in Bulgaria was in the 70s and 80s, when 90% of the panel residential complexes were built. Although the subsector almost disappears after the changes, there has recently been a revival of this technology. This time, it finds itself in the low-rise single-family residential buildings. The easy execution, the speed and the relatively low price are the reasons for the rapid promotion of these houses and villas. There are many companies on the market that offer a comprehensive service - from designing, through legalization to turnkey construction. There are a few important things that one needs to know before undertaking the project called a prefabricated house... 

Q&A: Why should we prefer the prefab to the monolithic house?

I offer you a brief comparative characteristic between the two methods of construction:

• Price - definitely in favor of prefabricated houses due to the economy of materials used and lower labor, mechanization and transport costs. Interestingly, the fact that their price per m2 is decreasing with the increase of the built-up area, while in monolithic buildings the dependence is direct proportional;
• Deadline - here win the prefab houses again. The pre-fabricated type components are transported and installed on the construction site. Thus, the entire construction process is minimally dependent on atmospheric influences;

• Freedom of architectural solutions - the monolithic method has always been at the forefront of this indicator. Although modern manufacturing technologies impose minimal constraints on composing and combining elements, architects still feel much more with loose hands when relying on good old reinforced concrete.
• Resistance to earthquake - here winner is definitely the prefabricated structures due to their own weight;
• Fire Resistance - Certainly reinforced concrete elements earn this indicator. It is well-known that both wood and steel as the basic materials for the load-bearing structures of prefabricated houses are unstable and require additional protection. However, the market has abundant materials that reliably solve this problem;
• Energy efficiency and ecology - a solid winner here is the prefabricated technology. This type of buildings meet all the thermal engineering requirements for energy efficiency and optimized energy consumption, with the best examples reaching even the passive building performance. Their construction is almost entirely made of environmentally friendly materials and the amount of waste is minimized. It is obvious that more indicators earn the prefabricated structures. However, the assessment remains individual according to the occupants' priorities. That's why I leave the choice to you all!

Q&A: Is the prefabricated house with the same status as the monolithic one?

Both types of buildings are considered as a part of the main building development. Their design is carried out after a visa has been issued by the municipality and the building and use permits are obtained only if they meet all the statutory requirements.

Q&A: What types of prefabricated houses are there?

There are various opportunities for prefabricated houses in the world. An example of one of these is presented on the following pages. The types widely available in Bulgaria are classified according to the material of their supporting structure of wood and steel and have the following characteristics:

• Prefabricated houses with wooden construction - The supporting elements are columns, beams and reinforcing planks. The base is a standard monolithic type - reinforced concrete foundation slab. In the one-storey version, the floor is made of thermal insulation, cement and flooring (parquet, granite, terracotta, etc.). If the house is on two levels, the construction of the inter-floor slab is an up-to-date version of the well-known beamwork. In this case, the so-called "dry floor, consisting of a heat-insulating layer and gypsum fiber boards. Between the rafters a mineral wool is placed, and a bottom of the ceiling is made of plasterboard. The walls also consist of mineral wool placed between the wooden columns and closed on both sides with OSB (plywood-like material) and gypsum fiber. This type of construction allows freedom in the façade treatment (plaster, wood lining, lining, etc.) of the outer walls. Products and systems for dry construction are available in Bulgaria by Knauf Bulgaria;
• Prefabricated houses with steel structure - the skeleton is made up of columns, beams and diagonal anti-wind joints. In fact, the material is the only significant difference between the two methods. Fundamental, floor and wall constructions are implemented in an identical way, with greater attention being paid here to the isolation of the load-bearing elements themselves, as it is no secret to anyone that the steel is much more heat-conducting than the wood. The aim is to avoid the so-called thermal bridges.