Unique demolition project in StockholmPublished 8/7 at 17:33
Back in 2017, a fire broke out in the cultural-historical building Vildmannen 7 in Stockholm, Sweden. The building is now being reconstructed and the company Destroy are responsible for the demolishing. PDi Magazine has met their production manager Niclas Gustavsson.
The Vildmannen 7 (“The Wild Man 7”) building was constructed between the years of 1895 and 1897, based on drawings by Erik Josepson, a well-known architect who designed the Handelsbanken headquarters in Stockholm. The building is located in the intersection of Biblioteksgatan and Jakobsbergsgatan, and is known for its unique façade embellished with flowers and animals, as well as for its construction material Roslagen sandstone, which was also used when building the Royal Palace in Stockholm. The Stockholm City Museum have given Vildmannen 7 a so-called blue marking, the highest category for cultural-historical buildings in Stockholm.
In 2017, the property was damaged in a great fire, which destroyed the interior of the building. Fortunately, it was possible to save the 120-year-old stone façade, and the property owner Hufvudstaden will now rebuild the interior of the building. Before construction can begin, the remains of the burnt interior needs to be transported and demolished. For this job, they have hired the demolition contractor Destroy, based in Skogås south of Stockholm City.
Destroy was founded in 1995 and have a staff of 53 people and a revenue of approximately 80M SEK (approximately €7,9M) . They have experience in working with larger projects such as the demolishing of the Nattugglan block on Södermalm and demolishing/concrete cutting of the Nöten block in Solna, which went on for two years. They are mainly working in the Stockholm area, but occasionally carry out work in the cities of Uppsala and Västerås. Destroy have had over 6000 commissions and over 700 customers, one of them being Hufvudstaden with this unique project.
A project out of the ordinary
“It is a very unusual job, it is the first time I’ve ever done anything like this”, says Destroy’s production manager Niclas Gustavsson when we meet him on the worksite. At this point, Destroy have already demolished the entire interior, with the façade being the only thing remaining, standing like a high wall around us. Interestingly enough, preserving the façade of a demolished building is not the only unique aspect of this project.
On the worksite we meet a scuba diver on his way down to the ground water. The basement floor of the new building that will be constructed will have a higher ceiling height than the previous building. To do this, a new concrete foundation has to be cast an additional 1,5 meter down the ground, below the ground water. The casting process is carried out using the same technique as with the casting of bridge abutments and will be carried out until the summer of 2021. “It is very important that the ground water remains unchanged, otherwise the whole wall can fall.”
The underwater casting is carried out by a specialized underwater contractor. Not too far away from the scuba diver, Destroy’s workers are demolishing the old, remaining concrete foundation. The concrete foundation is removed with the help of diamond tools from Swedish manufacturer Drome.
Demolition in several steps
Destroy’s working process can be divided into five parts: clearing, demolishing, heavy-duty demolishing, basement demolishing and work with the concrete foundation. In the initial phase, it was important to empty the area of material that has been damaged by the fire. Jack posts and rubbish chutes made it possible to securely transport all of the debris. The next step was advanced demolishing work which had to be carried out in several steps. For example, the floor structures were connected to the façade, which means that they had to be removed carefully without damaging the parts that were to be preserved.
“When we’d cleared the interior it was time to start reinforcing the façade”, says Gustavsson. The façade was reinforced with a new foundation where piles were drilled through the existing dry stone and down to solid rock. Other stages included sawing of a slot as well as replacement of trusses which had been put up to carry the façade right after the fire.
In total, 15 people have participated in the demolishing work which has included a combination of mechanical demolishing and demolishing with reciprocating saws. They have used the demolition robots Brokk 100 and Brokk 160, excavator 14t Doosan, as well as reciprocating saws and other equipment from Hilti. As with all larger demolishing jobs, there are large portions of demolition debris which has to be removed. “We have carried out 1031 discharges of construction materials, each container holding 10t. It has mainly been bricks and beams damaged by fire. Apart from that, we have sent mixed demolition remains such as metal, asbestos, “blåbetong” [a type of autoclaved aerated concrete] and granite rock and boulders to the landfill.”
The demolishing of the internal parts commenced on September 2 in 2019 and was completed in September 2020. When the foundation work is done, the workers begin the process of constructing a concrete frame cast on location, so that the new internal parts can begin to take shape. The new Vildmannen 7, complete with four floors and basement, is expected to be completed in early 2023, with room for shops, restaurants, offices and residences.