The construction company CGP, Novo Mesto has taken over the execution of all works of the DARS office building in Grič, Ljubljana. Construction was monitored from September 2022 to October 2024. The work carried out is presented on a separate website.
September 2024
Construction work on the exterior is complete, followed by landscaping, laying of the grass sward and tree planting. The planting work will wait until autumn, as the young trees would not withstand the drought and the rain. The paving around the building has also been completed and the ground floor pillars have been painted. This also completes the work on the façade, giving the building its final look. The simple geometry, with an almost identical façade design on all four facades, reveals itself in many guises depending on the angle of the sun, the colour of the sky and the weather conditions. The relationships that the building’s design establishes with the surrounding, mostly industrial buildings are multilayered, rich and harmonious in meaning. Even though it is an office building set in a dispersed landscape of industrial halls, silos, large covered car parks and numerous fireplaces, there are no conflicts or visual incommensurabilities between the existing and new spatial elements.
Inside, there are large round lamps in the central atrium. A jigsaw of circles winds through the entire volume. Reflections and views into the depths are interwoven in the many glass surfaces of the interior walls of the atrium. The circular motif, almost chaotic, glides through the space and opens up many views.
July 2024
As part of the external redevelopment, the car parks are being further developed. The locksmith contractor has installed steel mesh around the fire escape and the bike shed. The steel mesh is designed on the same principle as the façade of the building. They are opaque and seemingly solid in perspective view and almost completely transparent in frontal view. As the angle of view changes, so does the appearance of these ancillary buildings. A safety net is also installed around the external diesel generator. A roof made of prefabricated benches is laid over the rainwater tank. Next to the bench, a pit is dug to create a lake on the south side of the lawn next to the building.
The installation of wooden handrails in the staircases is also continuing. The combination of the natural handrail detail with the rough and cool concrete surface transforms an otherwise utilitarian staircase into a pleasant space, with natural lighting at the top. On the fourth and third floors, the textile flooring and acoustic cladding in the offices are fully laid. The work on these two floors is now complete.
July 2024
The scaffolding in the inner atrium of the building has been completely removed. It is revealed in its full dimension and elegance. Although the roof hatches are closed to shade the zenithal light, there is enough natural light throughout the building for work to take place in natural light. This demonstrates the primary purpose of the central atrium – to provide good quality natural daylighting in all working areas of the building.
The wall and ceiling coverings of the central lobby provide a pleasant acoustic atmosphere and dampen unpleasant spatial reverberations.
June 2024
In the last month and a half, all the flooring inside the building has been completed, the technical floor has been raised and the floor base in the wet rooms and the central lobby has been poured. Work continued on the installation of floor and wall ceramics, acoustic wall coverings in offices and wall and ceiling coverings in group work spaces – meeting rooms, classrooms and informal work spaces. A major challenge was the installation of the ceiling cladding in the central lobby, as the scaffolding accesses had to be rebuilt. They have been placed in this space three times.
The wooden ceiling and wall coverings complement the texture of the visible concrete and create visual and semantic contrast. They also create a pleasant acoustic atmosphere. The rhythmic change in the direction of the pattern emphasises the basic geometry and the reinforced concrete structural frame. At the same time, the glass walls in the central part of the building have been installed over the last week. The remaining timber partition walls are fully keyed. In the offices, the final installation of the equipment is underway, followed by the laying of the textile flooring.
A control measurement of the illuminance of a typical office was also carried out at the beginning of the month. During construction, several types of free-standing luminaires with direct and indirect lighting were tested. The biggest challenge was how visible concrete would affect the distribution of reflected light.
The roof has been completed and the vegetation and façade cladding of the technical rooms has been completed. The design and layout of the technical installations have created an interesting mix of machinery, green spaces and small-scale buildings on the roof, giving it a unique character.
Work on external area is also being accelerated. Concrete paving is being laid on the eastern side of the building, and the paving on the immediate perimeter of the building is being concreted and will be trowelled later. The façade is fully finished on three sides of the building, including the corners and the attic. The work is slowly coming to an end and the technical inspection is approaching.
May 2024
Work continues on the interior and exterior of the building. A composite aluminium panel cladding is gradually applied to all horizontal surfaces of the steel façade – gradually giving it its final appearance. The vertical articulations of the façade glazing are reflected in the reflective surface of the deep façade. A steady rhythm follows the entire perimeter, with the occurrence varying greatly depending on weather conditions.
Inside, the installation of wooden partition walls continues. The internal circular staircase is fully welded and freed of all additional supports. In the atrium, the building’s magnificent steel structure winds from the ground floor to the first floor, where the building’s most important offices are located. More and more, the central atrium is becoming the heart of the building. Although the amount of peripheral daylight is shrinking as offices gradually close, there is enough daylight to make it virtually unnecessary to use artificial light even in bad weather. External landscaping work is also in full swing, with a car park next to the building, a water treatment plant and a large storage tank for the sustainable treatment of the water of the outer lake.
April 2024
The construction site is boiling. Installation work is well underway. The technical floors on each floor are gradually being “sealed”. Wooden partition walls began to be placed on the individual floors. We have checked some options for the handrail on the staircase, and the damage to the visible concrete is being repaired.
The steelwork contractor has started painting the steelwork – the building is almost glowing in its final form. The play of shadows and light reflections complements the dynamics of the construction site.
The new construction frontage opens up in the area of landscaping and traffic management. The basic principles of preparing the ground for tree planting in car parks have been agreed, and the implementation of a large drip water retention basin and a regional wastewater treatment plant is almost complete. Most of the issues related to the implementation of the utilities infrastructure are also gradually being “closed”.
The central atrium is gradually acquiring its final form and purpose. The steelwork contractor built the internal spiral staircase connecting the ground and first floors in three pieces. These will be transported to the central atrium, welded together and carefully prepared for the final paint finish.
March 2024
The colour for the final coating of the steel façade columns has been approved. The scaffolding has been removed from the central atrium and work is progressing at full steam inside. The building is taking on the expected shine.
February 2024
Work continues on the installation ductwork in the technical floor area. Crossing different types of ducts, electricity and mixed fire zones involves several complications that require careful handling on a case-by-case basis. The second and third floors are located in separate fire sectors, so the wiring of the installations on the third floor is particularly challenging. All the ducts used for ventilation of the lower floor are separated from the rest of the installation by a fire wall made of aerated concrete.
On the ground floor, work on the technical floor is being completed, the top surface of the floor has been laid, and the offices are gradually taking on their final geometry and proportions. Full-wall façade glazing dominates in all rooms.
A suitable density of dry-laid ceiling has been chosen in the central lobby, while the bare concrete ceiling remains visible in the offices, in accordance with the design. The façade envelope is practically complete. The west façade is particularly impressive, although it has the deepest blinds.
January 2024
Work on the steel structure of the façade is gradually being completed. The building is fully enclosed thermally, which increases the scope and type of different subcontracting works inside. There is a large skylight on the roof, which completely covers the central atrium.
A prototype of the wooden internal partition wall has arrived on site. Installations in the technical floor area are gradually filling the available space, and in addition to ventilation, heating and cooling, electrical contractors have started laying conductors and metal cable racks. A wooden drop ceiling has also been installed on a trial basis and will be placed in the spaces around the central atrium.
Great care shall be taken in the design to ensure that the joints between the individual partition elements and materials are properly made, as well as the acoustic sealing at the penetrations between them.
Over the next few months, the technical sub-structure will be gradually implemented, giving the individual spaces their final proportions.
December 2023
The year is coming to a successful close on site, with the final concrete work on the building’s basic structure having been carried out last month. The roof slab was covered with the planned waterproofing, and the roof glazing for the central atrium was delivered at the end of the month. Gradually, the vertical design of the central connecting space is revealed in the interior of the building. Each week a new segment of the supporting formwork is removed, opening up more and more dimensions of the space. We are impressed by the gradually unfolding relationships between the vertical and horizontal parts of the central atrium.
The façade construction is also taking its final shape. Steel supports were installed on the fourth floor. The final steel wreath will follow shortly after the New Year, completing the building’s exterior appearance. Most of the carpentry work for the aluminium cladding of the horizontal connections and the façade blinds has also been finalised with the selected subcontractor.
As the support of the concrete structure is gradually released, the glazing of the façade continues around the perimeter of the building, from floor to floor. The interior is also gradually taking on a character of its own, with significant changes on the façade, where the rhythm of the columns reflects the bright sky on the smooth glass surface. On the first floor, the area of the raised floor is to be used for the installation and support structure of the partition walls. This prepares the works for the installation of the support legs of the technical floor. The geodetic layout of the planned network of supports will also serve as a check on the accuracy of all previous works. The perimeter of the office building is designed to allow for dividing walls to be freely positioned between offices at a 62.5cm spacing. As the supporting structure is moved outside the heated building body, this ensures full flexibility of the interior content.
November 2023
Concrete works are nearing completion. The contractor will complete the finishing of the stair cores at the top of the building in the next week, thus reaching the final height of the building. The steel façade is also on track and will be completed in a few weeks.
The glazing of the individual floors is being carried out in sequence. The glass can only be installed after the formwork supports have been fully relieved and the steel façade has been loaded. The beams shall sag by 5 mm to 10 mm around the perimeter when the internal supports are released. The process of relieving the intermediate structure is also linked to the dynamics of concrete placement, as this also represents an additional load.
In parallel with the gradual closing of the building’s perimeter, installation work is also taking place inside the building. At the same time, the construction site is preparing to start the construction of a flat roof over the top floor, which will gradually fully enclose the building and protect it from external influences.
Virovitica
The Croatian company Tvin, in cooperation with the Slovenian company Gonzaga, is likely to take over the interior partition walls of the DARS office building. Based on the drawn project documentation, a prototype of the partition and doors of all offices was produced before the contract was signed. Together with representatives of the client, the supervision and the contractor, we visited the Tvin factory to see the product. We were impressed by the careful execution and attention to detail. We were also struck by the extensive industrial complex, which extends over 34 hectares and provides all the necessary production processes from log processing to the finished furniture product. Within the complex, there are well-designed green areas, decorated with sculptures by Croatian sculptor Dušan Đamonja. The spacious factory dining room with its uniquely designed wooden ceiling is also impressive.
The prototype door features a careful acoustic design based on acoustician Saša Galonja’s calculations of sound transmission through several layers of wall of different thicknesses and densities. The partition walls are a unique product, segmented into 62.5 cm wide segments, which will provide the client with long-term flexibility in the structure of the office space. Each element can be moved several times during its lifetime.
In the centre of Virovitica, there is also a Classicist mansion, which today houses the Museum of Wood and Wood Products. Here we had another surprise. In the 1960s, the renowned Croatian furniture designer Bernardo Bernardi also worked with Tvin. Some of his pieces are in the museum.
A meaningful full-day tour of the factory, as well as several sights in the Croatian town of Virovitica, reinforced the common awareness of all those involved in the construction of the office building of the importance of a unique, almost handcrafted product, which to the efforts of all involved, from the designers to the fittings installers, bears the adjective of authenticity and uniqueness.
September 2023
The reinforcement of the slab above the second floor is being completed. The building has reached half of its final height. The steelwork contractor has completed the installation of the steel columns around the entire perimeter, gradually revealing the final structure of the building. The transparency of the frontal view contrasts sharply with the depth and closure revealed in the perspective projection.
The slender, barely 16 cm slabs are interspersed with various plumbing ducts. The heating and cooling pipes for the concrete core, the round EPDM pipes for ventilation and the general electrical wiring run through three layers of reinforcement.
The gradual opening of the supports and formwork on the lower floors exposes certain unexpected patterns in the visible concrete.
September 2023
The installation of the steel façade elements continues. The north façade, where the elements are shallow, is almost complete on the ground floor. Work continues on the eastern façade, where the steel columns are deeper due to the need for effective shading. Installation is proceeding according to schedule. The construction site expects the entire perimeter of the ground floor to be completed in a week and a half. This is followed by the undercutting of the steel columns and the gradual removal of the formwork supports. The decisive moment when the concrete structure rests on the steel perimeter is about to arrive!
The joinery subcontractor Mizarstvo Košak produced a prototype of the façade glazing and a slim window for ventilation. The building will be completely enclosed by a single glass envelope.
August 2023
After several months of preparation, quality control and pre-prepared galvanised steel prefabricates, the construction site of the DARS office building in Ljubljana has started to assemble the perimeter steel structure. Installation requires simultaneous control of the ground floor column position and 1st floor columns, which are fixed in position by a series of tie-bolts. The work is demanding and time-consuming.
Once the steel is in place around the entire perimeter, the bolts are fully tightened and the columns are lined with expansion joint compound, the contractors will release the intermediate supports and allow the concrete structure to rest on the slender steel perimeter.
Concrete is being poured simultaneously on four structural cores in the 3rd floor of the building. The panels are stripped to reveal the smooth structure of the ceilings, which will remain visible as an integral part of the building’s interior even after completion. The key elements of the image of the DARS office building are gradually taking shape, where the form of the relatively rough structural design will be combined with refined elements of partition walls, flooring and fittings. In a poetic sense, we approach the visual expression of a bustling motorway, where the rough shapes of the carriageway, guardrails and traffic signals are intertwined with the precision of automotive design.
July 2023
The site is being prepared to pour the concrete slab above 1st floor. The central opening in the slab, which defines the shape and scale of the central atrium, shifts from storey to storey, requiring some of the formwork to be built over several storeys. An impressive stack of formwork supports was built in the centre of the building for this purpose. The atrium’s varied cross-section is reflected at this point mainly in the density of the formwork columns, but the basic spatial geometry can already be recognized.
The first batch of steel columns and lintels is ready for installation. The columns are hot-dip galvanised and zinc drain holes are provided. The accuracy of the intended joint between the columns and the perimeter concrete structure shall be verified on an ongoing basis by means of geodetic measurements, as the possible tolerances of the joint are extremely small. Installation will be carried out immediately after the slab’s formwork above the 1st floor has been demounted, as the edge formwork obstructs the crane’s work when transporting the columns. Depending on the orientation of the four facades, the depth of the steel column varies, and the height offset in the base of the column follows the contour of the final height of the pavement around the building, so that each column is in fact of a unique dimension.
Mizarstvo Košak has taken over the glazing of the perimeter of the building. On the ground floor, a glazing substructure is installed on spot steel angles and a support lath. The substructure is also a check on the accuracy of the concrete. The concrete slab edge offset over the 38m length of the building is in the order of up to 15mm.
June 2023
The concrete slab above the ground floor has been successfully poured, where the procedure of simultaneous pouring of partly downward and partly upward facing beams and concrete slab has been verified. Expanded metal was inserted at the working joint along the beam, separating the geometrically complex design of the structure into the beams along the central atrium and the rest of the slab.
Notwithstanding this operational improvement, the successive pouring of the individual concrete layers resulted in time sequences that were referred to on site by the working term “tiramisu”. The top side of the atrium edge beams is tapered to a visible 10cm edge and a hidden part that will be covered by the technical floor.
Installation work continues in the basement. The site is being prepared for the waterproofing of the slab above the basement, which will seal the basement against rain and moisture. The erratic summer weather complicates the dynamics of work progress.
June 2023
The concrete of the perimeter wall of the technical building of the underground garage entrance is completed. The word DARS is stamped into the concrete wall. The workmanship of the visible concrete is of an exceptionally high standard. The deepening of the walls in the stair cores was also successful. The deepening ensures that the door to the evacuation staircase will open to the full angle and width required. Another special feature is the corrosion-protected fittings, which are installed in beams that will remain visible.
The slab above the ground floor will be supported by four internal concrete cores and a perimeter façade structure. As a result, the panel formwork is completely continuous and transparent. The rhythm of the formwork supports is interrupted by upward-facing beams between which the technical floor will be placed during the finalisation phase of the building.
In the second half of June, a major milestone was reached on site. With the formwork of the slab above the ground floor, the systematic installation of the thermocouples at the junction of the steel perimeter structure and the reinforced concrete inner structure began. The tolerance for steel is only 2mm, which is significantly less than the tolerance expected for concrete. To ensure that the site still achieved the required accuracy, the placement of the individual thermocouples in 3D space was checked by a surveyor and the elements were stabilised on the formwork using special steel angles.
May 2023
Reinforced concrete work on the underground part of the building is completed. The construction site is being moved to the office area of the building, where four structural cores have been concreted in the past week in visible concrete quality VB4. The cores take most of the seismic load, so the reinforcement of the walls in contact with the ground floor slab is compacted to such an extent that the installation of concrete of visible quality was very questionable, and the bonding of the formwork through the compacted parts of the reinforcement was also a particular challenge. At the 25mm-thick reinforcement bar splices, the formwork connectors could not be inserted between the reinforcement bars. However, by modifying the formwork system, adding additional bracing and additional tie-rings made of steel formwork beams, the implementation was successful.
In the next few weeks, the site will be faced with formwork and concreting of the beams that extend above and below the concrete slab. The design requirement is that the concreting is not divided into three phases, but that the beam and slab are concreted together. The concrete with increased flow rate, located above the slab itself, will be a new performance test for the site.
April 2023
The design features upward-facing concrete beams. They were chosen because of the required use of a raised technical floor. This ensured a smooth undersurface of the perimeter of the reinforced concrete slab and greater flexibility for subsequent relocation of the system barrier elements over the lifetime of the building.
Reinforcement of this type of structure is a specific feature rarely seen in high-rise buildings. As a result, the dense reinforcement grid of the beams is clearly visible and the structural structure is clearly reflected.
March 2023
The construction site is finishing the underground part of the garage and office part of the building. Several test fields have been constructed to produce concrete of VB4 quality. A key challenge is the large amount of reinforcement, which prevents the concrete from being seamlessly embedded.
Formwork systems for simultaneous concreting of slabs and beams without visible working contact were also tested.
Schoeck has developed a special thermocouple for joining the external steel structure and the internal reinforced concrete structure. Concentration of reinforcement occurs at the critical junction.
A prototype of the steel support column has been built. We checked the quality and accuracy of the geometry and the performance of the visible welds. The columns are slender, only 15cm thick. The cohesive bonding of the concrete and steel structure will be carried out on an ongoing basis, in two-storey increments.
December 2022
After several months of battling with an extremely inhomogeneous subsoil, poor results from the load-bearing capacity testing of the piles, and the subsequent reworking of the foundation mat, the deep foundation work for the garage part of the building is now complete.
In the commercial part, where the substructure has nevertheless proved to be in line with expectations, the concreting of vertical structure 1 has been completed. cellars. The first VB3 and VB4 class concrete tight spots have been made. In particular, the very large amount of structural reinforcement in the supporting stair cores is proving to be a challenge, which has a major impact on the quality of the concrete installation. A noticeable phenomenon is the so-called mapping of the reinforcement on the outer edge of the concrete wall.
The project team has decided to increase the protective layer of concrete, while additional test fields will be created to check the different viscosities of the concrete. Concrete pouring of the most critical parts of the visible concrete structure on the ground floor of the office part of the building is scheduled for early March. Until then, the work will take place in the basement of the garage part of the building.
October 2022
Concrete works have started in 2. the basement of the office part of the building. The Contractor shall test different technologies for the installation of visible concrete. The major problems so far are in sealing the joints at the girder penetrations and door openings.
The special feature of the construction is that the basement of the office part of the building is much smaller than the above-ground part, and is about seven metres in circumference. This part of the building contains the four central circulation cores, which are also the only internal load-bearing part of the building. The staircases are designed in concrete quality VB3 in the underground part and in concrete quality VB4 in the above-ground part.
The coming winter poses a major challenge for ensuring regulatory quality.
September 2022
During the first months of construction, the relocation of the infrastructure connections running through the construction site and the construction of a temporary car park for the existing DARS building were carried out.
This was followed by the protection of the pit construction with a pile wall, and then the deep foundation with piles. Implementation is still ongoing as it is very complex and time-consuming. The ground beneath the building is markedly inhomogeneous, with layers of gravel and clay intermixed.
Reinforced concrete works under the office part of the building will start in September 2022.
