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Contact: Onetimejob@yahoo.com. This page is about companies having own technology for prefabrication of buildings in various technologies. This companies aim to deliver projects such as hotels, dormitories, family houses, hospitals, medical clinics, schools, educational buildings, data centers, cyber units, kindergartens, schools, educational buildings and many more. We can distinct companies in many ways. Major distinctions follow. They work on limited geographical market. There are companies focusing on 2D (panels) or 3D (modules) prefabrication. They use as a structural material wood, steel, reinforced concrete. For some comapnies prefabrication gives advantages to deliver faster data/it/teletechnical solutions, others focus on prefabrication itself leaving delivery of teletechnical technology for other actors. Some companies focus on private clients, others deliver products to public sector. I will recommend in this internet place, who to use for which type of building in which georaphical region. Because it is my website, I make my point of view.

I used to be in favour of wooden modules. I know the specific of product quite well. Now, if I were to build a new house for myself I would chose wooden one. Moular house, hospital, office, this is different story.

Cons of wooden modules.

Fungus and moisture. Wooden technology need to make product resistant for fungus. Guarantee of the producers for the structure of the modular building is from 25 to 50 years for designed service life of the building. When you read specification of fungicide producers they offer preservation for about 5 years. What abaout the rest of the 25-50 years period? In time fungicide preservation is weaker and weaker and the guarantee is for short period only.

Wood preservation against fire. This is the same thing as with fungus and moisture. There is no producer of wood preservation substance offering protection for a whole live cycle of the building, fife years only!

Span of modular structure without any intermiediate suspensions. Typicaly wooden modules have a span for the opening in modular loadbearing walls (for instance between living room and kitchen/dining) for about 2 m. If you need to make conference room and you expect to have open area of 4 or 6m wide and 26 m long wooden modules producers use steel elements to achieve structural stability and they split conference room in 6 modules 6m longx4m wide. The more floors, the structure is more complicated because of the building weight, structure twisting. lack of loadbearing points and lack of walls making the structural shield.

Steel modular producers cope with the same problems but with more suitable technology for larger structures and they can design and builg conference rooms with 8m long openings between modules.

Modular buildings form intermediate floors using structural ceiling of lower level module and floor of the upper level module. In steel moudlar systems whole structural floor is about 49-52 cm depending on fire requirement REi30, REi60, REi120. In wooden modules structural floor is about 10-20cm thicker. This drives the height of the building up. Investment plots have limits for the height of the new buildings and sometimes you can build less floors using wooden modules then when you chose reinforced concrete or steel modular building. Quite often during the earli stage of development of the project offering/calculation team checks wheter the building can have the same number of floors in modular technology and reinforced concrete technolog. If because of the total height of the building modular building can have less floors, economical analyse of the project goes in favour of steel or reinforced concrete buildings.

The same thing is when you have designing obligations related to the height of the building (fire class of the building). You quicker go into medium or high building and higier safety regulations with wooden modular building then steel one or made of reinforced concrete.

Fire class of the materials. It is important to use fire classified materials and fire tested / fire proofed loadbearing barriers such as walls and ceilings. Wood as a material has low fire class specified as Ds2, d0. Therefore wooden structures need to be protected by other materials from Class A (A is the heighest) to B. This issue drives the design of wooden modules to obtain approval for the building products (walls, ceilings, floors) for individual use in a building. It is costfull, time consuming and not certain to obtain, it puts up a risk for the investor that the project will be delayed or not finished at all.

Accuracy of workmanship. Modules are prefabricted at the prefabrication sites which is in long distnace from the building sites. This determinates errors which occure when the modules are set together. Wooden structers are less accurate. Typically, when the building is 3 or 4 floors and it has a height of 10-13 m facade can wave for about 3 cm at a distance od 1 floor, if modules are made in correct manner. For steel structures and reinforced steel buildings this is about 1,5 cm deviation. The same is when you take length of the building.

Shrinking of wood. Wooden modular building with 4 floors can shrink for about 7 to 15mm per floor. Finished floor level deviates from designed floor level. This is related to wood specific. Wood shrinking causes lowering of floors for about 2-5 cm on the 4th floor. The higher the building the shrinking of wood is more problematic. Furthermore, wood shrinking is not possible to predict, where it will shrink and how much. In some areas it might shrink in other it will not. This causes finished floors waving, steps between steel or reinforced concrete parts of the building which settle a lot less. This also causes of cracking of walls and ceilings. Sevice works are necessary to be done typically up to 3 months after takeover of the building by the customer.

Producers, economy. When we study the history of companies prefabricating wooden buildings we can see the patern. Big comapnies like Boklok, Skanska, Moelven, Lindbaecks, Unihouse, Nordhus, MOD21 can’t get profit of the wooden technology. Boklok is closed, Moelven closed or near closing, Lindbaecks brings losses for years, when is about zero this is success. Unihouse apart of few years brings substantive losses, it went into strategy of low margins in housing, schools, kindergartens and hotels. Nordhus is dead. MOD21 brings losses and doesn’t have concept or strategy how to become profitable.

Cost of guaranteed liability period. It varies but for wooden modules which are typically turn key finished it is 2% per year. They calulate in budgets 1% and cheat investors and this is way to much in relation to 0,5-1% for steel modular companies and reinforced concrete buildings.

Prefabrication fixed cost, overhead cost. This goes into 15-20% of the total cost of the project. Where General Contractor building the reinforced concrete building calculates about 3-5%.

Cost of transport and assembly of the building. In relation to direct cost transport/shipping is about 12-10% of the cost for projects delivered from Poland to let say Norway. Further 10-15% is a cost of assembly of the modules and cost of site office. When the modules are prefabricated and transported within the same country cost of transport can be about 2% of total direct cost. This cost elements (transport and assembly of the building) don’t appear in budget when you calculate project in reinforced concrete technology.

Cost of idle time. It apears when you don’t have project to produce, you have empty slot at prefabrication site and you must pay periodical fixed cost. For a buisness like Unihouse fixed cost it is about 20-30 mln PLN per year. They can produce/have turn over about 200 mln of NET PLN or 3 to 5 modules per day with avarage module 35m2. So, each empty month is about 25mln to be spread between another projects.

Margins. When you have full capacity used and you do product which competes at the same market with another producers (steel, reinforced concrete, onother wooden modular and panel producers) you can’t aim at 10% of margin on avarage. As history says projects are contracted between 0-10% and avarage is between 3-5%. Then you have bad projects, empty slots, unexpected guarantee works, wrongly calculated budgets, investors badly cooperating on the projects. You don’t have cushion in price for any mistakes. This is why all producers make losses. When you add pressure from General Contractors designing and building in traditional technology (reinforced concrete) on site where cost are lower wooden prefabricated margins are close to 0%.

Quality. Some markets value the quality more other less. In Norway, Sweden, Germany, Denmark quality is a key to start bidding and offering. Without it, you don’t have a chance to start. These are highly institutional markets the follow the rules. In eastern Europe you can make many shortcuts, but at the end you are responsible for the permit to use of the building. You can design, produce and build cheaper product then in Eastern Europe. Off site produced and on site assembled buildings should give better quality then on site totally built projects, but it happens that errors appear on site and when product is 80-90% prefabricted prior to transport any mistakes require lots of demolition or redo works. They always cost extra.

Sustainability, nature, enviroment. Wooden modules should be more friendly for enviroment than other types of technology. What modular companies do against being ecofriendly? They transport modules for very long distnace. On site made buildings use local logistic, comapnies to deliver materials, workforce. Wooden buildings are effective in use of wood when they are not higher then 4 storeys. When they cross 4 storeys height they use too much timber per m2 of the total area of the building. Too much forest is wasted. When they want to build high, the use reinforced concrete core of staorcases or reinforced concrete structure to slide modules into concrete shelfs. They double the structure.