Designed by Office ParkScheerbarth, Haus 2+ expands the cultural offerings of Holzmarkt 25, which attracts nearly a million people annually.
© Jan Bitter / Office ParkScheerbarth

Haus 2+ is a 200 sqm mixed-use building constructed almost entirely out of timber. The bright-red-coloured structure, explains Benjamin, marks the main entrance of Holzmarkt 25, an important cultural quarter in Berlin.

The building comprises six spatial units across three floors, serving local businesses including a bakery, a tattoo studio, a photo studio, and a physiotherapy centre.

Each one of the six units can connect with the outside either through balconies or windows. A shared terrace facilitates interaction between tenants.
© Jan Bitter / Office ParkScheerbarth

Three different timber systems were used in its construction: timber box-panel slabs and timber frames for the building’s structure, mass timber for internal walls, and wood cladding.

All building components were pre-fabricated and designed for rapid-onsite assembly to save time and cost. Load-bearing elements are screw-connected, which also allows for easy disassembly.

Conceived by Boltshauser Architekten, High-Rise H1 Zwhatt Site is one of the tallest timber buildings in Switzerland.
© Boltshauser Architekten

Currently under construction, High-Rise H1 Zwhatt Site (H1), explains Matthias, will be a 75 m-tall residential building, designed as a hybrid timber structure that will combine engineered wood with concrete, as well as clay and trass lime. At 17,200 sqm in area, it will be 86 times the size of Haus 2+.

H1 will house 2,000 people, and provide public facilities such as co-working spaces and a cafe on its lower three floors.

Photovoltaic panels will be installed on the facade and the roof of High-Rise H1 Zwhatt Site, and generate 50% of the apartments’ energy needs.
© Boltshauser Architekten

The lower levels and the building’s core will be entirely composed of concrete, whereas the upper part will be built mostly with beech wood sourced from within Switzerland.

The conversation begins by highlighting the significant advantages of timber.

Haus 2+ uses curves in its form to exemplify the possibilities of timber, typically associated with angular construction.
© Jan Bitter / Office ParkScheerbarth

Benjamin, for example, points out that using engineered wood allowed Haus 2+ to achieve a carbon intensity of 217 kg CO₂e/sqm. This is significantly lower than that of concrete, which can range between 300-400 kg CO₂e/sqm.

He also adds that engineered timber can now be designed to match the structural abilities of concrete and steel. Matthias reinforces this point by explaining how composite timber elements, which will be used in the columns and beams of H1, will offer high structural performance.

The high volume-to-weight ratio of timber, however, can be an issue. For instance, Matthias explains that for a unit of load, timber columns tend to be wider than concrete ones, which can result in a loss of floor area.

The residential floors will be built with timber beams and columns in combination with concrete ceilings, which will reduce noise transfer between units.
© Boltshauser Architekten

One of the big fears associated with the use of timber is fire.

However, Benjamin clarifies that modern engineered wood is much safer to use than its traditional counterpart. Moreover, unlike concrete and steel, it has a predictable burning rate, which allows for the integration of appropriate fire safety features.

When it comes to cost, timber construction can be about 10-20% more expensive than traditional methods, says Matthias. But this additional expenditure can be compensated by the material’s other advantages. For instance, wood elements can easily be prefabricated, thus saving construction time.

Each unit at Haus 2+ was designed with provisions such as ample openings, wooden ceilings, and natural finishes, no matter its size.
© Office ParkScheerbarth

Moisture, it turns out, is timber’s biggest enemy.

For H1, the wood components, primarily used in the building’s interiors, had to be protected from exposure during construction. The outer envelope of Haus 2+ will undergo maintenance every four-to-five years to repair damage from weathering.

Another con of wood is its low thermal mass, which is crucial for indoor comfort. This issue, reveals Matthias, can be overcome by using timber in combination with other high-thermal-mass materials like concrete, as will be done for H1.

The timber columns at H1 will be akin to “trees” that can be “hugged”.
© Sandro Livio Straube / Boltshauser Architekten

Both guests agree that the biophilic effect of timber significantly elevates the user experience. Benjamin gives an example: even after a year of use, the tenants of Haus 2+ have left its wooden ceilings untouched.

They also acknowledged that while their projects are located in regions where timber is known to be abundantly available, sourcing the material sustainably was a challenge. The least one can do, admits Benjamin, is to use certified timber and source it locally.

The discussion shows that today, timber offers more possibilities than ever before. At the same time, it still has its limitations, especially in large-scale construction. Using it in a thoughtful combination with other more traditional materials, suggests Matthias, can lead to the best outcome.