Be prepared: prefabrication is becoming more cost-effective for more and more types of buildings

Examining another aspect of prefabrication, we discussed the advantages of using flat-base and traditional pillars with the product design team leader for INETON Kft.. Donát Szerencsés-Aranyos highlighted the main difference between the two types of columns, namely that base columns are assembled with the base plate at the factory. „This means that no on-site concreting is required, only the installer's concreting, which can be finalised by pouring concrete underneath,” explained the expert. With traditional pillars, however, the on-site work also depends on the technology. „In Hungary, the cup-neck solution is widespread, but bolted connections, so-called column caps, are also used.” He emphasised that the INETON can be used with all of the above solutions, depending on what is most optimal for a given project and building.

Looking back at the history of the technology, he said that although it has no great tradition in our country, the pillar is not a new method, and in Germany it was first used in areas where there is no fear of earthquakes. "Basically, it's worth using it when there is no need for piling, because if you have driven piles, it can be cumbersome to drive the piles into the footings. However, if that is the need - of the contractor, of the client - then it can be done, as we have successfully done in the own D2 building in Csepel Free Port, built from our own elements and our own design."

He said that, with the land outside the green belt largely full, greenfield investment without piling is now rare. "With that said, if there is no driven pile, it is easy to tie in a footing pier."

Whether you need one or four teams to work on the ground

One of the advantages of the foot pillar is that its weight starts at over 10 tonnes, while traditional pillars usually weigh between 5 and 15 tonnes. „Another advantage is that the amount of work required on site is much lower, as a single team can install them: they pour the concrete, bring out the footing pillar and position it using wedges. In contrast, with traditional methods, the point foundation is installed by the ironwork team, then the assembly team installs the cup neck, and finally the formwork team pours the concrete. This already requires three teams, and only then is the pillar placed in the cup neck.”

However, the transport of the pillar is more challenging due to its weight. "While we can carry up to four or five of the classic pillars in one transport, we can only carry two of the pedestal pillars." With the pedestal pillar, on the other hand, there are significant savings in both time and labour costs, as it is practically only necessary to wait for the concrete to harden. "With a pedestal pier, the pier can be delivered and erected within a week in many cases, compared to three to four weeks with a conventional pier. Another important advantage is that the measurements are concentrated in one hand, and the connections are cleaner, resulting in a building with a cleaner force play."

The team leader said that the benefits of the sleeper pillar were also seen in the construction of the D2 building, where eight to nine sleeper pillars were installed per day after overcoming initial difficulties due to the pioneering nature of the project.

At the same time, the exceptional advantage of the INETON plant, which is in an extremely favourable geographical location, was that it was able to supply the construction site with products from very close by.

Even complex ironing can be prepared quickly in a factory environment

In response to a question, he said that in most cases, it is necessary to consider which is the more appropriate solution. "Where there is no pile, we immediately consider whether to use a pedestal, because it is better for everyone, especially if we do the installation ourselves. But if we're talking about a high pier, an earthquake-prone area and a piled building, we go for the conventional technology, using cup shafts or bolted connections."

Another option is the use of columnar stairs, which have recently appeared in our country, which also speeds up the process. They have the advantage of being lightweight: compared with 2.5-tonne spindle cups, they weigh less than 200 kg, if the structure requires it, calculated at the maximum load. "In addition, we also get a cleaner connection than between two layers of concrete with bolted connections, because there is a receiver assembly in the pillar, to which we use stud bolts inserted in a header made on site." Another important consideration for a footing pier is that the preparation can be done in the factory:

"The ironing is relatively complicated, but we can do it in a factory environment in about half a day and have it ready for delivery in two days. Also, here the concrete doesn't have to be poured twice, the base is poured at the same time, which is more economical."

Why a professional repair team is important

The above is further exacerbated by the fact that the labour needed for a project is increasingly difficult to obtain compared to the material needed. "In Hungary too, more and more people are realising that it is not the material that is expensive, but the labour. And to build these pillars properly, you need skilled workers, but there are fewer and fewer of them." He added that other professions sometimes take on the on-site work on the pillars on a polyhistor basis, but this is not the right way to go.

"It's best if the whole process is managed by the same team of professionals, from design to production to implementation."

If the work on the pillars is not carried out by a professional installation team, it is not usually - directly - structural failures that occur, but usability is compromised. "For example, the cracking of industrial floors is a classic case of inadequate foundations." He pointed out that the column is usually the only element in an industrial hall that carries loads vertically; among other things, the global stiffness values of a hall are determined by the properties of the columns. "Once the safety values of the halls are three to four times higher than expected, it is not safety that becomes the problem. Having said that, if the nodes are badly designed, for example, the building will have more deflection than necessary or the insulated sandwich panel will crack. These all cause inconveniences during the operation of the building, which can have serious cost and warranty implications."

The above perspective, which emphasises professionalism and due thought and preparation, applies to the whole industry in general, not just the pillars. "In the 2020s, we see Hungary moving in the direction where all the divisions needed for a construction project are beginning to be concentrated in one hand. In the old days, when there were fewer technologies and simpler divisions, a division could work well in a single company, but now there are several sub-divisions of a division."

A single-family house can also save money with a pillar

As regards the optional dimensions of the pillars, he stressed their flexibility. "We have recently made a 1 metre long pillar with a base, which is a very large size." He added that they can design short brackets on three or even all four sides of the pier for any pier. They can increase the thickness of the base up to 60 centimetres and the cross-section up to 3×3 metres. For a pedestal pier, they can generally produce a pier body of 108/90 centimetres.

Looking at the functional use, Donát Szerencsés-Aranyos considers the use of prefabricated pillars even for a prefabricated house.

"If you're building with prefabricated elements anyway, and that's why there's a crane on site, say for a pitched roof, it's worth looking at that option, because it might turn out that with a pitched roof, that part of the construction costs half as much, because you don't have to pay as many people."

However, he added, for a large-scale condominium project, hybrid solutions may be the most cost-effective. "That will be the case for a while, but we have to be prepared for the fact that after a while, prefabrication will be entirely cost-effective." This is important because there is not much of a tradition of this in Hungary at the moment, but buildings will be constructed from prefabricated elements for apartments and office buildings."