Innovative timber construction for social housing in Germany

Focus on timber 

The building's foundation consists of load-bearing and non-load-bearing exterior walls in timber frame construction. In total, 500 cubic meters of wood were used. Wood also absorbs pollutants from the air, improving indoor air quality. "The client wanted an ecological construction method. Cement, concrete, and steel were therefore excluded. With wood, we chose a renewable resource that stores CO2, thus fulfilling the sustainability concept," explains Manfred Gilg from the architect company Streidl, Gilg & Wolff Architekten. In the later usage phase, a solar system will contribute to efficient building operations. Rainwater will be collected and used, the roof areas will be greened, and spaces for gardening will be provided. 

LVL enables cost- and energy-efficiency for high-standard construction 

The deep stud level of the exterior walls is also made using laminated veneer lumber (LVL). The decision to use Metsä Wood’s Kerto® LVL products was based on the company's ability to deliver custom-made laminated veneer lumber in large widths, compared to other suppliers. In the project, beams measuring 63 by 300 millimeters were used. Kerto LVL significantly contributed to the realization of an efficient and cost-effective frame construction that could easily accommodate energy-optimized wall elements with thick insulation. This ensured that the building met the high Efficiency House Standard 40. 

Prefabricated wall elements minimise installation time  

Gumpp & Maier was responsible for prefabricating the exterior wall elements. The individual wall elements have a maximum length of 10.5 meters and a maximum height of 3.55 meters. They were prefabricated in the factory including windows, shading, and façade cladding and could be easily and quickly assembled on-site. "Prefabrication provides significant relief for work on the construction site. The individual elements only need to be installed there. Most of the work can be done in the factory, shielded from the weather and under optimal conditions for employees. The high degree of prefabrication and the slim designs also significantly reduce the time spent on-site", explains Wolfgang Krettenauer, Project Manager at Gumpp & Maier. 

The building's outer shell consists of 21-millimeter-thick vertical spruce cladding with tongue-and-groove profiles. This is mounted on ventilation battens and an 18-millimeter-thick underlay. The timber frame of the load-bearing exterior wall elements was insulated with mineral wool. For the non-load-bearing elements, Gumpp & Maier filled the cavities with cellulose. Two layers of 18-millimeter-thick gypsum fiberboard with a vapour barrier in between were used for reinforcement. For non-load-bearing elements, an 18-millimeter-thick particle board served as the reinforcing layer. On-site, an 8-centimeter-thick installation level was added, consisting of CW profiles filled with mineral wool and clad with two layers of 12.5-millimeter-thick plasterboard. Overall, the load-bearing exterior walls achieve a U-value of 0.107 W/m²K, while the non-load-bearing exterior walls achieve 0.099 W/m²K. 

The individual elements stand out for their exceptional strength-to-weight ratio and resistance to warping and twisting. They are lightweight for easy transport and quick to install. This also benefited timber constructor Gumpp & Maier GmbH: "The dimensional precision of Kerto LVL is especially advantageous in prefabrication, offering numerous benefits to us as wood processors. Its minimal deviations greatly enhance industrial processes in timber construction, facilitating the production of high-quality elements," explains Wolfgang Krettenauer. 

Material efficiency means more floor space 

Thanks to its advanced design, Kerto LVL enables much slimmer constructions. This allows for timber and hybrid structures with longer spans while reducing the amount of material needed. In residential buildings, this results in more usable square meters with lower material consumption. These are important factors for Christine Kamm, Managing Director of Tür an Tür miteinander wohnen und leben e.V.: "Of course, we must keep an eye on cost-effectiveness alongside ecology and healthy living. The prefabricated timber elements were by far the most cost-efficient solution for us." 

Objective: long-life buildings 

Metsä Wood products were also used for the threshold on the ground floor, made from Kerto GLVL, a glued laminated veneer lumber with larger cross-sections. Thresholds measuring 100 by 360 millimeters and 100 by 300 millimeters were manufactured for the project in Augsburg. These high-load-bearing components are primarily used in multi-story buildings and their high load-bearing capacity effectively prevents settling damage and increases the building's longevity. Dimensional stability and accuracy lead to particularly high quality, especially in ecological timber frame construction and multi-story buildings. Kerto LVL provides the foundation for the sustainability and cost-efficiency of the construction project. This is supported by PEFC-certified wood (PEFC/02-31-03) and innovative product characteristics that distinguish it from conventional solutions in the field.