The highest wooden building in Germany now measures 25 meters

Eight-story wooden building in the zero-emission district
The original buildings of the military base will either be removed or modernized according to the latest standards. At the same time, they will be complemented by new constructions that will be realized using an innovative wooden construction system. Two new structures are already present in the area - in a green environment next to single and two-family homes (which are built to passive house standards), two multi-story buildings have emerged, constructed innovatively from wood-based materials. These multi-story wooden buildings set new benchmarks in terms of living comfort, energy efficiency, and building physics in Germany. As early as 2010, a four-story wooden building was constructed on the site as part of a pilot project, and in April 2011, another, even more ambitious project was launched: with the support of scientists from the Technical University of Munich, the University of Rosenheim, and ift Rosenheim, the design and construction of an eight-story building began - currently the tallest wooden building in Germany at nearly 25 meters.

The previous record holder was a 22-meter high seven-story apartment building in the Berlin district of Prenzlauer Berg, whose fire protection concept using highly effective fireproof cladding with FERMACELL fiber cement boards was similarly developed by Fermacell, the largest European manufacturer of fiber cement materials.

The construction of the new eight-story building took place from April to September 2011, with the wooden structure realized according to the design of the Munich firm SCHANKULA Architekten by Huber & Sohn GmbH & Co.KG Bachmehring, and the effective fireproof cladding designed and supplied by Fermacell GmbH, Duisburg. The entire load-bearing structure of the building is wooden; only the staircase core is made of concrete for fire protection reasons. The facade cladding is largely made of wood, complemented in places by plastered surfaces. Wood is also "exposed" in the interior - in the inner space, wooden ceilings and walls are partially visible to ensure that the basic building material of the building can be perceived. The wooden construction system developed by Huber & Sohn GmbH & Co. KG is also ideal from the standpoint of placing the new building in dense urban areas. Due to its slim design, additional living space was created, and thanks to the high degree of prefabrication, the building was constructed to a high quality in a very short time - wall elements arrived at the construction site already with built-in windows and a finished facade, allowing the eight stories to be completed in just three and a half weeks. As a result of the high degree of prefabrication, the disturbance to neighbors from large construction machines was also minimized.

Both lower floors will contain offices, while the remaining six floors will feature apartments of various sizes and floor plans - from one-room apartments to two- and three-room units, to a spacious penthouse with a roof terrace. With only a small number of internal load-bearing walls, the floor plan is maximally flexible and there are also apartments that are accessible for wheelchair users. All floors are accessible via a concrete staircase and an elevator. An open walkway connecting the staircase with the apartments eliminates smoke filling the staircase and optimizes the escape route in case of fire. Each apartment has available spaces in the form of steel balconies anchored to the floor ceilings - the colored railings of the balconies further create a significant characteristic of the building's appearance. The building is powered by a newly constructed chip power plant on the site. With a heat consumption level for heating of only 17.2 kWh/m²a, the building almost meets passive house standards.

Insulation with non-combustible boards
Since all load-bearing components of the eight-story building had to be executed according to the fire protection concept F 90+K260, a fireproof effective cladding made of non-combustible construction and insulation materials was designed. The load-bearing facade elements were initially prefabricated at Huber & Sohn in Bachmehring - the basis is a solid wooden wall developed in-house, reinforced on both sides with FERMACELL fiber cement board cladding. Non-combustible ROCKWOOL mineral wool boards with a melting point of > 1,000 °C were used for the insulation of these elements. These provide excellent thermal protection, are treated to be water-repellent, and are particularly shape-stable. FERMACELL fiber cement boards, in combination with the insulation, safely protect the load-bearing structure from fire.

Effective fire protection
On the room side, an effective fire protection cladding was implemented in two layers of FERMACELL fiber cement board cladding. The used boards guarantee fire protection F 120 according to the construction and are classified according to EN 13501 as non-combustible building material of class A2. Additionally, Fermacell met the general acceptance tests of the building authority for the encapsulation criterion K 60 for multi-story wooden buildings and for extensions. In the development and optimization of new building components for multi-story wooden construction, tests of building components were carried out by three partners - Huber & Sohn, Fermacell, and Rockwool - that document and illustrate the effectiveness of the systems and enabled their use.

Short construction times due to prefabrication
In the woodworking company Huber & Sohn GmbH & Co. KG Bachmehring, completely prefabricated facade elements including built-in windows were created. "Thanks to close collaboration with all project participants, the overall building concept could be continuously optimized regarding construction costs. The floor plan concept from which we started allows not only the construction of apartments but also various types of offices. Because only a small number of load-bearing walls were needed, all floor plans could be modified according to individual wishes," stated Josef Huber. Optimal building physics and biological values, and above all outstanding living comfort, are ensured by the interplay of three materials - wood, fiber cement boards, and mineral wool. Specifically, the exterior walls had to meet strict fire safety criteria, as well as ensure the best protection against cold, heat, and noise. To achieve parameters close to passive house standards, insulation with a thickness of 240 mm was designed and used in the facade elements of the new high-rise building.

The eight-story wooden building sets benchmarks
The building constructed in Bad Aibling vividly presents the potentials and possibilities offered by modern wooden construction. It is further proof that wood as a basic building material can replace conventional construction materials such as concrete, steel, and brick in high-rise buildings. The interplay of innovative prefabricated wall and facade modules, special insulating materials, and fiber cement cladding has now made the "perfect leap" upwards possible for the first time. Although the Model Building Regulation (Musterbauordnung - MBO) was amended in 2002, creating legal foundations for multi-story wooden construction in Germany, it was only through practical construction of new structures that the industry and construction companies were faced with new solutions.

A series of mid-rise wooden buildings were first realized, which had to prove highly fire-resistant constructions according to MBO, building class 4 (this class includes buildings defined by the height of the highest floor with residential spaces of up to 13 m and usable unit areas of up to 400 m²).

For the building in Bad Aibling, a comprehensive fire protection concept was developed, tested, and approved to pave the way for even taller wooden structures. Because the MBO requires fire-resistant constructions with additional structural material characteristics in case of fire for buildings of class 5 with floor heights greater than 13 meters, special insulation materials and constructions with fiber cement board cladding were used.

Construction of external walls (material data/thicknesses):

Load-bearing external walls with wooden cladding:

• Vertical wooden cladding 21 mm
• Horizontal battening 40 mm
• Facade strip Stamisol
• Insulation
• FERMACELL fiber cement board 18 mm
• Air-tight layer and vapor barrier
• Solid wooden wall 85 - 120 mm
• FERMACELL fiber cement boards 2 x 18 mm

Non-load-bearing external walls with plaster:

• Plaster 8 mm
• Insulation
• FERMACELL fiber cement board 18 mm
• Air-tight layer and vapor barrier
• Solid wooden wall 85 mm
• FERMACELL fiber cement board 18 mm

Floor construction:

• Foundation slab concrete 1000 mm
• Sealing against rising moisture
• Insulation
• Impact noise insulation 40 mm
• Cement screed 60 mm

Ceiling construction:

• Cross-laminated solid wood (CLT) 197 mm
• Fast-setting underlayment 90 mm
• Impact noise insulation 40 mm
• Cement screed 60 mm
• Parquet floor 20 mm

Roof construction:

• Cross-laminated solid wood (CLT) 147 mm
• Vapor barrier
• Sloped insulation 240 - 340 mm
• Roof waterproofing insulation 2 mm
• Silica sand topping 50 mm

Wall finishing:

• In the penthouse - visible wooden surfaces, white glazed
• Other floors - FERMACELL fiber cement boards with white coating

Basic data
Investor: B&O Gruppe, Bad Aibling
Building location: Dietrich-Bonhoeffer-Straße 14, 83043 Bad Aibling
Construction period: April 2011 - September 2011

Project: SCHANKULA Architekten/Diplomingenieure, Munich
Load-bearing structure/project fire protection: bauart Konstruktions GmbH S Co. KG, Munich
Sound protection: ift Schallschutzzentrum, Rosenheim
Wood construction: Huber & Sohn GmbH & Co. KG, Bachmehring
Quality assurance: Materialprüfanstalt der TU München,
Univ.-Prof. Dr.-Ing. Stefan Winter

Technical consulting
Facade insulation: Deutsche Rockwool Mineralwoll GmbH S Co., OHG, Gladbeck
Fire-proof effective cladding: Fermacell GmbH, Duisburg

Built space: 5,320 m³
Office area: 340 m²
Residential living area: 970 m²
Total costs: 2,500,000 €