BUYER'S GUIDE

There is still not enough experience in building steel homes. People try to learn mostly from the negative experiences of others, but this is not the best way to reach optimal results.
Unic Rotarex® is a pioneer in this field, has a lot of experience, and we decided to put together a buyer’s guide on the recommendation of artificial intelligence (Bing Chat).

We don’t set out to convince you to buy steel homes but, more importantly, to what you should do when you decide to build a steel frame house.

1. Choosing the type of steel structure

Type A. Steel structure made by numerically controlled robots from cold-formed thin-walled profiles with joining operations combined with self-tapping screws.

Operatiuni
Structura metalica usoara pentru case

This is the most efficient type of house structure on the market today, thanks to its automation.

  1. Design and the 3D view are done by importing lines from the 2D CAD drawing so no differences are allowed;
  2. The software exports structure production files for CNC robots;
  3. Export 2D and 3D assembling drawings, profiles and screw quantity lists;
  4. The unique codes printed on each profile identify the profile, the work, the level, the element, and the position of the profile in the element;
  5. Millimetric operations such as countersinking, cutting, punching, drilling, and guillotining help join the profiles into structural elements. After inserting the last screw into the pre-existing hole, the element takes the designed shape;
  6. The structural elements (walls, floor beams, roof trusses, spacers, etc.) are lightweight, easy to handle, and assembled, based on 2D and 3D plans, into the house structure; They contain gaps for joinery or installations, millimetrically designed from the design phase;
  7. The assembling plans are simple and self-explanatory and the assembling is so easy that in some cases smaller houses have been assembled by one person;
  8. This is the structure with the shortest assembling time and the lowest skilled labour requirement;
  9. The possibility to counter any element allows a high resistance of elements made of thin steel and small sections;
  10. The multitude of nodes distributing efforts in many small values does not create vulnerable static zones;
  11. The bolts are manufactured with a concavely shaped overlap area, which increases the strength of the knot and hides the bolt head below the level of the structure;
  12. The amount of technological scrap is negligible;
  13. The structure is produced in the factory in a technological process certified and verified according to EN 1090-1;
  14. The profiles are arranged in such a way that the formed structure is also the secondary structure for the precast cladding;
  15. The finishes are easily made with a wide variety of prefabricated products;
  16. The system is completed with easily obtainable prefabricated materials;
  17. The system is also very flexible in achieving very good thermal, acoustic, aesthetic and fire resistance indicators;
  18. The much lower weight of the system, the flexibility of the structure, the multiple bracing, have very good indicators of resistance to wind or earthquake;
  19. With the same structure, you can build a cheap house but also a luxury house. It’s all about the other materials and workmanship added;
  20. With all the advantages that the Type A structure has, the costs are comparable and sometimes lower than the other two types of structures presented.

Type B. Steel structure made of U and C profiles per meter cut with abrasive discs and fixed with self-drilling screws. A handmade confection that is very similar to the frame system on wood.

Ghidul cumparatorului pentru case pe structura metalica
Structura metalica profile U si C

This type of structure is a derivative of the timber frame system. The profiles are also made with robots, in standard bars that are sold by the linear meter, but the structure is hand-made whether made in the factory or on-site.
People don’t have experience and sellers don’t say that there is a more evolved structure, for a correct understanding, we present a point-by-point comparison:

  1. It generally has only a 2D design, being a transitional structure. Software development has also developed automatic production lines for Type A structures;
  2. Valid in some cases only for the production of profiles, not structures;
  3. The erection drawings are sketchy and quantities of material and screws are not obtained automatically or at all if the designer does not do this additionally;
  4. Even if you print some codes with the name or length of the profile, it will be difficult to identify which works, level, item, and position it belongs to;
  5. The lack of cutting, drilling, etc. makes it much more difficult to obtain structural elements with exact geometric shapes. This depends very much on the level of skill and seriousness of the person making the structure;
  6. Since it is not possible to easily counterbalance the structural elements, they are made of larger sections and profile thicknesses and are therefore heavier and harder to handle. The exact size and shape of the carpentry gaps again depend on the experience and accuracy of the person making them;
  7. The plans are simple and fairly self-explanatory but require careful attention and skill and under no circumstances can they be put together by one person;
  8. Assembling requires more time, experience, and money than a Type A structure.
  9. We started with this type of structure, but the uncertainty that arises from cross-bracing or pre-tensioned cables led us to move quickly to type A structure;
  10. Due to the required width, the cross bands cannot be pre-tensioned sufficiently and require the nearest joint which, if it fails, compromises the following works and the whole structure. Pre-stressed cables also rely on taking large stresses at one point, which can also be fatal;
  11. The heads of the bolts are a few millimeters above the profile surface. Over-applied tiles warp require more and more expensive finishing work. If the counter-veneer strips also appear over the face of the profiles, please understand what is happening with the cladding and why we consider this to have been a transitional system.
  12. The manufacturing made from profiles by the meter (standard bars) also has quite a lot of scrap.
  13. Unfortunately, in most cases only the profiles are produced in the factory under the rigors of certification, the structure is not and this is not noticed by people. They accept non-certified structures and only have a warranty on the profiles not the structure;
  14. Same as the Type A structure;
  15. Same as the Type A structure;
  16. Same as the Type A structure;
  17. Same as the Type A structure;
  18. Same as the Type A structure;
  19. Same as the Type A structure;
  20. Even if you could get a Type B structure for the same price or cheaper than a Type A structure, do you think it’s worth it? You decide!

Type C. Metal structure made of hot-rolled profiles, welded and assembled with metric screws. A system from engineers' experience with industrial building structures

Structuri laminate

This type of structure is rather a solution for industrial buildings. You often find it in bargain deals on classifieds sites.
It goes without saying why we cannot compare this type of structure with the other two.

  1. For easy recognition I have taken a photo from You Tube showing a main structure made of laminated profiles assembled by welding and metric screws;
  2. In addition to the main structure, it requires a structure that in practice can be made of light profiles, cornices, pipes, masonry, wood, sandwich panels or whatever else people invent;
  3. If you buy the main structure at a slightly lower price than the other two types it doesn’t mean you have the same thing. It can be called resistance structure and secondary structure to be confused with enclosures. Thus you lose control over the overall price;
  4. The fact that there are such offers on the market is due to those who think they can get a house with very little money. In reality, you are getting a space that does not comply with residential building legislation. At best you have built a space with industrial features that resembles a house.
  5. If you put brick-finished sandwich panels on the walls and other sandwich panels in the form of tiles, you have made a house or a hall. If you clad the interior with plasterboard and tile will it be a home or at most an office?
  6. Millions of smart people around the world with software and more recently with artificial intelligence, are trying to invent the cheapest and most efficient building systems. From here the compromises that many people make to build a house with very little money a difference that is not advisable to assume;
  7. It would be advisable to beware of private tradesmen on cheap ads who spot-weld a structure of a few rectangular pipes that resembles a house.
  8. If you want to build a house with this structure anyway, contact companies that do this in the industry and can offer you a certified and guaranteed structure.
  9. This type of structure is successfully used in houses with very large free-spans and overhangs, especially in areas where thermal insulation is not very important;
  10. To obtain the indicators of thermal insulation, sound insulation, aesthetics, etc. It is good to expect a high and very high price.

General considerations

Grinda metalica
Structura metalica pentru casa

Because this guide is for buyers of homes up to three stories high who may be in very different climatic conditions and with very different budgets, it’s worth considering the following:

  1. The best structure that can satisfy any requirement would be a mixed structure between the three types of structures listed;
  2. The Type A structure is the best performing but the thin profiles have no coefficient of mass. You may need a house with a single pillar that is required to be flexible and very strong, in this case, the solution is to use a laminated profile as in Type C structure;
  3. In some cases solving a static problem in a Type A house becomes simple and economical by using a large cross-section, thick U-profile from a Type B structure;
  4. A Type C main structure for a building with large spans and overhangs complements a Type A secondary structure very well;
  5. An ordinary house does not need a Type C resistance structure.

Myths that manipulate your choice of structure type

Structuri metalice usoare pentru constructii case
Test seismic la structuri metalice usoare
  1. A house with larger or thicker profiles is stronger and will last longer” – FALSE – All structures are designed to withstand the loads required by regulations for the area and use for which they are designed;
  2. A concrete beam is much stronger than one made of galvanized steel” – FALSE – A concrete beam is designed to withstand the required loads as well as one made of thin sheet metal profiles. The difference is that the concrete one has a very high dead weight to resist and the only difference is the efficiency in construction resistance. It’s like saying that an obese man is more resistant to physical demands than a thin man;
  3. A concrete house is more earthquake resistant than a tin house” – FALSE – Both houses were designed to withstand the same loads. “A concrete house is more earthquake resistant than a tin house” – FALSE – Both houses were designed to withstand the same loads. The destructive force of the earthquake will be lower in a steel frame home because the total weight of the house is much less. Please also bear in mind that the steel structure, especially Type A, is elastic, whereas masonry is rigid.
Don’t let others think for you, think for yourself and you will be able to understand any myth.

Personal considerations

I am Marius Rotar, owner and manager of Unic Rotarex® lightweight steel structures factory and I am trying to make some personal considerations to show if this guide is clear, useful, helps you to understand unclear or masked truths, and deserves to be continued.

Unic Rotarex® started building steel homes in 2005, Type B steel homes. After building a few more, we realized that an improvement was needed and switched to a Type A structure. Today Unic Rotarex® proudly exports to several continents structures that respect the general considerations listed above.

Before 2005, I personally worked for about two years in Germany making lightweight partition walls from U- and C-profiles. That’s how I realized that houses could be built cheaper and more correctly, so I came back home and graduated in the Hardell® building system. The first system was approved by professors from the Faculty of Construction in Budapest together with the current Professor, Doctor Academician Dubina, who appreciated our scientific works presented at the conferences of structures to which Unic Rotarex® is invited and participates. I recommend you study the scientific paper on the seismic resistance of structures provided by Unic Rotarex®.

As we are pioneers in this domain, we have put the bases to the Google keyword “steel homes”. Today I am here to tell you that I believe that artificial intelligence will clean the internet of falsehoods, myths, and deceptions. That it will know better than we do what the best directions are and that we would be smarter and more successful.

As a professional, I try to be the best at what I do. As a manager, I try to improve the experience with you. As a human please write to me (at our contact address) and ask me or suggest me anything that can improve this guide for the benefit of users. Thank you!

How to choose the manufacturer of the steel structure

Certificare Europeana

It goes without saying that the best purchasing price is obtained from the manufacturers. Here are some criteria for distinguishing real manufacturers from fake ones:

  1. A manufacturer will always be proud and will write on his website that he is a manufacturer. The problem is that others contact companies who are just resellers or who knows what?!
  2. A manufacturer will always put real photos or videos of the production process on their website. The problem is that even the fake ones post pictures of production machinery;
  3. A manufacturer will always have “production” as a service offered and the process is explained on the website. The problem is that even the fake ones can do this on their websites;
  4. A manufacturer has a certification under which it has the right to produce and market lightweight steel structures. The problem with fake manufacturers is that they don’t have a certification in their name;
  5. The certification can be issued by several certifiers, it is not mandatory to have the same format as our certification presented above;
  6. It must instead bear the logo of the certifying company and its name, then it can be verified on the internet;
  7. It must bear the name of the certified manufacturer;
  8. The standard governing the production of lightweight steel structures is EN-1020-1+A1 and EN-1020-2;
  9. The certificate states what it can produce. It can be welded or aluminum structures or it can be just profiles, without the right to produce structures;
  10. Scan the QR code on the certificate with your mobile phone and it will show you the original certificate. This will prevent forged certificates;
  11. A serious manufacturer will always give enough technical details about technologies and advice on any topic;
  12. A serious manufacturer will always have partners and collaborators who can help you with the rest of the works;
  13. Ask to see their certificate even if they don’t keep it in a public place. The correct name is written on the certificate and you can check on internet to see their financial and legal behavior.

Identify your house model, size and finishes

Modele de case
Sectiuni la case pe structura metalica

To be continued!

Finding and choosing the designer, site manager and builder;
Tender, quotation, contract and quality documents

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