The Lumo One skyscraper in Kalasatama, Helsinki, will be the tallest rental property in Finland. For supervisor Antti Ruponen, the site offers a unique opportunity to work with new construction techniques.
November has been exceptionally warm this year, but Antti Ruponen needs to dress for near-arctic conditions. Several days of his work week are spent high above the roofs of Kalasatama on the Lumo One skyscraper construction site. The Lumo One skyscraper construction site. At the time of writing this article in mid-November, 17 floors of the concrete frame have been completed and the contractor is casting the 22nd floor of the core shaft.
Despite the mild weather, gusts of cold wind at the top of the skyscraper mean that warm layers of clothing are necessary. In exchange, you get amazing views of the sea, over Viikinlahti towards Kallio and downtown Helsinki.
“When the city lights come on in the evening, the view is pretty spectacular,” says Ruponen.
Upon completion, Lumo One will stand at over 120 metres and be the tallest rental property in Finland, and one of the tallest buildings in the Nordic countries.
With Lumo One’s completion in the autumn 2022, Lumo residents will be able to enjoy the same view. The 31 floors of the building will feature as many as 291 rental apartments. Most of them will be studios and two-room apartments, but the building will also feature larger apartments.
Ruponen supervises structural engineering at the Lumo One site. The building is being constructed by SRV, the contractor of shopping centre Redi located below Lumo One, and Ruponen is in charge of monitoring the conformity of the work in terms of contracts and quality requirements.
Inspiring new techniques used at the Lumo site
The task is as unique as the site.
Tower buildings like this have not been constructed in Finland before, with the exception of the neighbouring Majakka and Loisto. The 35-storey Majakka was the first to be completed a year ago. The 32-storey Loisto has not yet been finished.
“In principle, we’re using the same materials as any other site, but the techniques are, in part, new. For the lift shafts, for example, we’re using completely new formwork systems that I’ve never seen before,” says Ruponen.
By 2027, five more tower buildings will be built in the complex of shopping centre Redi.
“The company sought inspiration for the construction from places such as Toronto and Germany, but the construction process of the two neighbouring buildings also offered a great deal of useful information,” says Ruponen. The contractor company SRV has refined the process every step of the way. Smooth work and logistics processes play a vital role in large projects such as this. The work stages must be timed so that the right materials reach the right floor at the right time.
“Of course, there’s always waste that needs to be removed from the site,” says Ruponen.
The structure of the building differs from the other tower buildings in Kalasatama, with its floor mainly supported by concrete pillars and with only two load-bearing concrete walls. The lift shaft in the middle of the building is also a load-bearing structure.
Construction materials reach the top floors through various methods. Workers and small machinery use the building’s lifts, which are constructed in step with the concrete frame. The outer wall has a goods lift for heavier loads.
A crane moves materials for the frame all day long, and concrete is pumped through a pipe from the cement mixer truck on the ground level to the topmost floors.
“In one week, as many as 40 cement mixer trucks enter the site,” says Ruponen.
As the frame continues to climb higher and higher, the company is starting to install facade elements. According to Ruponen, the facade of Lumo One will look slightly different than the neighbouring towers. All of the buildings will feature glazed green rooms instead of balconies, but the new facade element will be made of beadless glass.
The inner and dividing walls will be built on-site, making the construction project considerably faster.
“The floors will also feature state-of-the-art building services engineering. The water-circulated floor heating system will offer cooling on hot summer days; a useful feature in a glass building. Intercoms will not be installed in the apartments as residents will be able to access them using their mobile phones. The 5th floor will have a waste collection station with a vacuum system,” says Ruponen.
One of the three lifts will serve residents up to the penthouses on the 31st floor, whereas the two others will run up to the 29th floor. The 29th floor will feature a scenic terrace and sauna facilities for residents. The lower yard will open out to the upper park deck and playground of shopping centre Redi.
“Apartments like these built on top of a shopping centre are pretty rare in Finland,” says Ruponen.
“Moreover, the building is located on top of Kalasatama metro station and at the start of the Itäväylä highway, making use of both public transport and private cars much easier. Residents may rent parking spaces in the underground parking hall of Redi,” explains Ruponen.
Safety is key
The building is estimated to reach rooftop height in March 2021, and roofing work should be completed at that time.
However, there is much work to be done as Lumo One will not be completed until August 2022. The interior construction work cannot start until the facade covers a sufficient number of floors. The weather must not be allowed to damage the structures.
“Kalasatama is famous for its horizontal downpours,” says Ruponen with a laugh.
Safety plays a vital role on the site. When dropped from a height of 100 metres, even the smallest objects can be dangerous. Anything smaller than a sledgehammer must be strapped to work clothing.
“A sledgehammer is so heavy that if you drop it, it’ll pull you down with it,” says Ruponen.
The facade elements will have four layers of glass, guaranteeing excellent thermal insulation and safety.
“Thanks to the new, glazed facade system, any dizzying installation work outside the building has been reduced to a minimum. Only the seaming of the gaps between the facade elements requires outside work,” says Ruponen.
“Once the building is finished, cleaning the windows will be a whole other ball game,” he says with a laugh.
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