ZÜBLIN Timber starts construction work for high-rise building in Pforzheim

ZÜBLIN, Timber hybrid high-rise CARL, Pforzheim; rendering Peter W. Schmidt Architekten GmbH
ZÜBLIN, Timber hybrid high-rise CARL, Pforzheim; rendering Peter W. Schmidt Architekten GmbH
The timber panels for CARL are prefabricated at ZÜBLIN Timber`s Aichach plant. Photo: ZÜBLIN Timber, Sandra Sitzmann
The timber panels for CARL are prefabricated at ZÜBLIN Timber`s Aichach plant. Photo: ZÜBLIN Timber, Sandra Sitzmann

Work began on the distinctive wooden structure for the CARL high-rise in Pforzheim’s Arlinger district at the end of August. Using the slipform method of construction, considerable height was added to the 14-storey reinforced concrete core of the timber hybrid building in just 11 days, so that ZÜBLIN Timber could begin with the timber construction works on 31 August 2022.

Ed. Züblin AG’s Karlsruhe subdivision, in the capacity of general contractor, is building the new 45-metre building for client Baugenossenschaft Arlinger eG on a turnkey basis. The design for the three-part building complex, which includes not only the high-rise tower but also two additional buildings with apartments, underground parking, a day care centre and a restaurant, comes from Pforzheim-based architectural firm Peter W. Schmidt.

ZÜBLIN’s Karlsruhe subdivision has already completed the reinforced concrete staircase and lift shaft. Now ZÜBLIN Timber will construct the individual storeys of the high-rise building with its visually striking, vertically structured timber façade.

Wood trumps all!
The individual storeys of the building consist of load-bearing timber frame walls with supports made of laminated veneer lumber, beech and glulam to hold up the wood-concrete composite ceilings. The supports are integrated into the exterior walls, so that the load-bearing structure is not visible to the naked eye. The ceilings are made of 100 mm thick LENO® cross-laminated timber panels topped by 12 cm of in-situ concrete.

Of the 14 storeys, 13 are being built using wood. Construction will include around 2,900 m² of LENO® ceiling modules made of cross-laminated timber as well as about 1,500 m² of timber-frame exterior walls with a length of up to 11.2 m and integrated supports made of laminated beech veneer lumber. The façade formwork is made of Douglas fir, and the nearly 1,000 m² of partition walls are made of LENO® cross-laminated timber and gypsum fibre boards. The end-to-end use of CAD systems, in conjunction with CNC-controlled production facilities, enables the precise and economical prefabrication of the individual timber construction elements. This guarantees the quality of the construction and ensures that the ambitious targets are met.

Locally sourced wood from Pforzheim
CARL is all about efficiency, sustainability and regionality. As a timber hybrid building, it is certified energy-efficient to KfW Standard 55. To produce the cross-laminated timber panels at its plant in Aichach, ZÜBLIN Timber uses wood from the local Pforzheim forest. Around 375 m³ of the locally sourced timber is used in the ceilings of the high-rise building alone. The municipal forest is managed according to sustainable and natural principles to provide high-quality wood, which is a climate-neutral building material. The use of timber from a local source benefits the climate twofold, allowing 2,000 t of CO2 to be saved in the construction of CARL compared to conventional construction methods.

A script for CARL
“In a construction project of this scale, work has to be carried out with the utmost precision. This starts as early as the design and planning phase with the detailed coordination of the individual trades and consideration of the fire safety requirements, which are not yet governed by official standards for timber high-rises,” as project supervisor Andre Essig from the Turnkey Construction business unit at ZÜBLIN Karlsruhe explains. “All additional steps, from material procurement and cutting to assembly of the panels at our plant and installation on the construction site, also require the greatest care.”

The wooden ceiling and wall panels are transported by truck from the plant in Aichach to the construction site. The façade sections are prefabricated to such an extent that they only need to be installed as finished elements following the sheet metal work and installation of the windows. The individual storeys are built in a two-week rhythm: “Together with ZÜBLIN Karlsruhe and the various trades, we drew up a script to coordinate the assembly work,” explains project manager Fabian Krug from ZÜBLIN Timber. “This ensures the smooth workflow between the trades – which is also important given the very confined space on the construction site. To achieve the best possible results, deliveries are planned down to the last detail and delivered on a just-in-time basis.” Assembly of the timber panels is planned from September 2022 to May 2023.

Further details on the CARL timber hybrid high-rise can be found in a video animation of the project and at carl.arlinger.de