Diversity in stone

Like a 3D puzzle: New rear-ventilated stone façade in Kastav

The rear-ventilated façade of the new “Cedar” administration building in Kastav, Croatia has the appearance of a gigantic 3D puzzle. The travertine slabs used to cover each of the five facade and roof surfaces are almost all of differing sizes that had to be correctly cut, positioned and attached. Substructure systems by BWM Fassadensysteme GmbH were used for the secure installation of the natural stone slabs. The firm is part of the fischer Group of Companies.

A total of five facade and roof surfaces were covered with large-sized natural stone slabs. Their dimensions range from 0.5 m x 1.0 m to 1.5 x 2.0 m with a thickness of 3 cm. Almost every format is different. Each slab was assigned its own position number on the installation plan. Staggered joints were also part of the tender. The facade construction firm Keratek from Zagreb, Croatia was commissioned to install and supply the natural stone slabs for the approx. 400 m² rear-ventilated facade and the approx. 350 m² roof. A natural stone called Travertine Roman was used for this installation. Mramor Commerce from Jurdani, Croatia cut the required stone slabs down to the desired dimensions and delivered them to the construction site in accordance with the requirements and assembly plan. The architecture firm ZDL Arhitekti from Rijeka led by construction engineer Siniša Zdjelar was responsible for the project.

Installation of roof surface and vertical walls

A lateral fixing system with brackets which supports its own weight provides a firm hold to the rather porous stone with relatively low strength directly mounted on horizontal BWM carrier profiles. The concrete slab on the slanting roof surface with a 30° inclination was covered in tar. The facade constructers then mounted L-brackets and material for thermal separation. This was followed by installing mineral wool with a thickness of 20 cm. The BWM carrier profiles ATK 100 were subsequently installed on the L-brackets, which the facade constructers attached sealing material to that is fixed in place using the ATK 103 V3 cap profile by BWM in addition to a self-adhesive tape. Particular care was required for the window connections, which prevent water from penetrating the building.

Special profiles were also used and were specifically developed and supplied by BWM for the purpose of this project. BWM can supply custom solutions individually tailored to the customer’s requirements, if required. A horizontal carrier profile from BWM’s ATK 102 product range was installed on the vertical cap profiles. This will later allow the slab to be situated elastically. This was followed by the installation of a second carrier profile by BWM Fassadensysteme. Depending on the size of the format it was either placed above or halfway up the slab. These profiles contain a slot into which a bracket is inserted from the side. They were inserted in lengths corresponding to the respective width of the slab. The slabs were installed with an open joint width of 10 to 12 mm. Each slab can be replaced, if required, similarly to other applications where BWM’s engineering has been used.

All sides of the building’s entrance and balcony have been covered with HPL panels with a width of 15 cm. The total surface covered in this material is around 150 m². The fitters affixed the HPL panels to the BWM ATK 100 Minor substructure using a suitable adhesive.

Design of the facade surfaces

 The facade surfaces have been designed as a rear-ventilated stone facade with mineral wool with a thickness of 16 cm and a vapour-permeable black mat of fibres without a diffusion barrier. The facade constructers installed the vertical ATK 100 Minor T-profiles (base construction) at intervals of 50 cm on top of which they placed the horizontal ATK 102 carrier profiles. The horizontal ATK 102 carrier profiles with EPDM rubber bands and brackets were inserted horizontally into the slits of the stone slabs. A ventilation net is attached to the bottom of the facade.

This has resulted in a building with a unique and secure architecture, construction details and an RVF facade.


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Multifaceted on all ten sides: The five facade and roof surfaces of the “Cedar” administration building in Kastav were covered in travertine slabs, almost all of which are of different sizes. Carrier profiles and substructure systems by Fassadensysteme GmbH as well as a bracket fixing give the slabs a firm hold.

Image: KERATEK d.o.o.

Unique formats all around: Almost all of the natural stone slabs are of different sizes and the joints have been staggered. The individual pieces were attached to BWM carrier profiles and substructures in their respective assigned positions.

Image: KERATEK d.o.o.

Sophisticated multilayer: The suspended travertine facade is stylish and functional to the benefit of improved energy efficiency and security. A lateral fixing system with BWM carrier profiles and substructures secures the natural stone slabs.

Image: KERATEK d.o.o.

The travertine slabs are almost all of differing sizes and had to be correctly cut, positioned and attached.

Image: KERATEK d.o.o.

The five facade and roof surfaces are all covered in travertine slabs in accordance with the tender.

Image: KERATEK d.o.o.

The result is a unique RVF stone facade that combines sustainability and style.

Image: KERATEK d.o.o.

Katharina Siegel

Press relations officer
fischer fixing systems