View of the Citadel – A 19th-century residential building in the heart of Budapest has been expanded with two new floors and smart apartments.

Complex logistics in the city centre

The scheduling and planning of the work was greatly influenced by the fact that the building's three floors were occupied and the house was located in a bustling city centre environment dotted with restaurants and catering establishments. For this reason, the use of a debris chute for demolition was rejected. Instead, containers were lifted from the work area by a tower crane and used to selectively collect the demolition debris. Dust was prevented by spraying water and using geotextile covers.

One of the spectacular milestones of the project was the installation of the tower crane, which required considerable organisation and preliminary soil mechanics tests.

During the works, a complete road closure had to be ordered, bus traffic was diverted, and a 200-tonne mobile crane was manoeuvred into the street, which had been narrowed by parking barrier posts. Prior to the installation of the crane, some of the branches of the trees in front of the building were also removed with the involvement of Főkert.

Construction work in occupied buildings

A particular challenge during construction was that the residents remained in the building throughout the entire duration of the work on the lower three floors. During the project, the sewage and rainwater drainage system in the courtyard was completely rebuilt and new utility connections were installed. To install the new main pipe, the driveway was demolished by hand, removing approximately 60 cubic metres of soil. Residents were able to move around on a temporary wooden false floor, which was raised half a metre above the existing floor level, while excavation work continued underneath. Parallel to the demolition of the roof structure, unused chimneys were also removed, which required access to several flats. The work was completed with industrial chimney sweep inspections.

Out of consideration for the residents of the building and tourists, a significant portion of the work was carried out manually.

Construction work began in May 2024 with the demolition of the roof structure. However, before that, the contractors had to clear out the attic space, remove the fillings and attic tiles, which resulted in a load reduction of approximately 120–150 kilograms per square metre. The construction of the guest floor was crucial for the safe design of the superstructure. This played a key role in ensuring that the existing floor structures were not overloaded during the demolition work. After the roof was demolished, the firewalls, which were in poor condition, were also demolished. Due to the popularity of the area among residents and tourists, a significant part of the demolition work was carried out manually.

The structural legacy of several eras

Exploring the structure of the building proved to be a journey through time. We learned from Regő Gosztolai that

The 19th-century load-bearing walls on the ground floor were constructed from large solid bricks, typically 75–90 centimetres thick. As the load decreases on the upper floors, the walls become thinner, measuring 60 centimetres on the first floor and 45 centimetres on the upper floors.

On the ground floor, during the renovation of the Alföldi restaurant in the 20th century, large portals were created in accordance with modernist requirements, using steel and reinforced concrete structures, and several original wall pillars and arches were removed. The floor slabs between floors were constructed with steel beam truss structures on all levels, with beam spacing of 1.1–1.2 metres. Above the vaults, there is sand or slag filling, on which a traditional parquet floor structure was built. The design of the wet rooms is the result of later intervention, where the filling was partially removed and concrete screed and tiled floor layers were created. The structure of the attic ceiling above the third floor has been modified several times: the street wing has retained its exposed and covered beam ceiling, while the other parts of the building were fitted with prefabricated reinforced concrete „G” beam ceilings in the 1970s.

The supporting structures for the new floors and the base slab for the basement level were built simultaneously.

The supporting structure for the extension was built in the second phase, where high stability and low weight load were essential considerations. The Szabadics Group used state-of-the-art CLT (cross-laminated timber) technology, which was used to construct the new walls, floors and closing structures. At the same time, a 20-centimetre-thick reinforced concrete slab was installed across the entire floor area of the basement, significantly increasing the load-bearing capacity of the foundation.

Ten new, modern flats have been added to the new floors.

Ten new flats were built during the extension, with floor areas ranging from 60 to 150 square metres. Several flats are two-storey, with galleries and internal staircases, which are also made of fire-resistant CLT panels and steel structures. The new roof structure was built using traditional carpentry and beavertail tiles. The flats are insulated with 15 cm of rock wool in the facade and 20 cm in the roof structure for added comfort.

State-of-the-art engineering in new homes

The new flats are cooled and heated by an air-to-water heat pump system installed in each flat, with underfloor heating and fan coil cooling. As part of the investment, the building's main electrical wiring was renewed and a new intercom system was installed.

New transport system

As part of the extension, a new panoramic lift was built in the courtyard, which can carry eight people and has a load capacity of 630 kilograms. The main staircase on the street side was extended to the fourth floor, and the rear staircase to the fifth floor.

Renovated façade with a focus on heritage preservation

As part of the investment, the entire façade of the building will be renovated. The yellow brick cladding will be cleaned, the plaster decorations will be restored and the damaged elements of the main cornice will be replaced. Due to the extension, part of the main cornice and the attic wall have been demolished and will be reconstructed based on samples of the ornamentation. The façade's tinwork will be renewed, the doors and windows will be renovated, and the rainwater drainage system will be modernised.

Reference project

The Kecskeméti Street extension is a milestone in the history of the Nagykanizsa-based contractor, Szabadics Group. This was the first project in the capital for its Budapest-based chief engineering department. In the near future, the group will implement several similar, larger-scale property development projects. The investment is a good example of the modern expansion of historic buildings with complex engineering preparations, innovative structural solutions and careful consideration of heritage.