De Karel Doorman 16 floors extension with prefab floors made from Kerto beams and Metsä spruce plywood


Image by Ibelings van Tilburg architecten

De Karel Doorman – 16 floors extension

Location Binnenwegplein/Lijnbaan, Rotterdam Netherlands
Building Year 2012
Architect Ibelings van Tilburg Architecten (
Products Used Kerto LVL, Spruce Ply
Type Residential Buildings And Gardens

Prefab floors made from Kerto beams and Metsä spruce plywood

De Karel Doorman consists of the renovation of a shopping building: Ter Meulen and an added residential building. This was an unusual project as the new building literally rests on the columns and foundations of the existing structure.


The Ter Meulen building has a special place in the hearts of the inhabitants of Rotterdam. It was constructed in 1948 as a shopping centre and designed by Van den Broek and Bakema. With its extensive glazed facades the building was remarkable in its time for its transparent appearance. The building was partly demolished and redeveloped in the 1970s and 80s, including the addition of two shopping floors. Ibelings van Tilburg architecten proposed not to demolish the building, but to restore the Ter Meulen building to its original condition and build apartments on the top of existing building.


On the columns and foundations of the existing structure was placed an extremely lightweight construction in steel and wood. With this unconventional construction method for the Netherlands a 70 meter high 'glass' residential building was realized.  New residential building includes 114 apartments and 156 parking spaces. A roof garden was also created between the two parts of the residential tower, 40 metres above street level.

As a light structure was needed to add the 16 storeys, it was decided that wooden floors in combination with a steel frame, should be used. In partnership the involved timber frame builder and engineer specifically selected engineered wood products from Metsä Wood. The floors lie on a steel structure and have a span of approx. 4 m. Due to their strong and rigid construction, Kerto LVL S-beams (45/51 x 225 mm) and a 6-layer top plate of 18 mm Metsä spruce plywood  were selected.

The grain of the Kerto® veneers runs predominantly in the same direction and its 10% compaction gives the panel considerable strength and rigidity. Gluing and screwing these products together in a controlled environment gives the floors good performance (in terms of vibration and contact noise). For the occupant this results in excellent comfort.


A particular Rotterdam building was preserved for the future. At the same time in an almost impossible place in the center of the city new homes were built which contribute to the quality of life and social security in this area.

References related to extension construction

  • De Karel Doorman – 16 floors extension

  • Rakuunantie extention storey

  • Cockfield Windmill – conversion to accommodation using Kerto® LVL

  • Extension to a building in Paris

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