A dancing tower of wood

A 41.5-metre-tall wooden observation tower was completed in 2022 in Hardwald, a popular outdoor area near Zurich. This new landmark aims to give visitors a new way of enjoying the 920 hectares of land.

A design competition for the tower was organized in 2020. It received 42 proposals, with Luna Productions, a team of ten young architects from Switzerland, providing the winning submission in cooperation with Holzing Mæder GmbH.

As luck would have it, construction nearly came to halt because of the tower’s location in Zurich airport’s security zone. After review however, the authorities allowed design work to continue with specific conditions.

The tower is built entirely of wood, excluding the building’s concrete foundations and the steel components used in the glulam beam joints. The foundation’s 16 concrete piles extend to a depth of 20 metres.

Seven types of wood, selected for their load-bearing capacity and weather resistance, were used in the tower, which required a total of 380 cubic metres of wood, of which 302 cubic metres are glulam. The wood was sourced from the surrounding forest and processed by local entrepreneurs.

The sculpture-like tower consists of four 10-metre-high blocks, each in the form of an equilateral triangle. This provides a rigid structure. The superimposed blocks are all rotated 60° from the one underneath, giving the tower a unique shape that changes depending on the spectator’s viewing angle. As the viewer moves, the tower also appears to move – dance, even. The slight sway caused by the wind is included in the design.

The support structure consists of glulam beams made from spruce, with the stairs and platforms being ash. The façade grille is pine, the upper platform’s substructure is acacia, and the surface exposed to the weather is larch. The edge structures are Douglas fir with seats made from oak.

All the wood is untreated. The original plans called for a closed façade, but this would have upgraded the tower to a building in terms of fire regulation classes. This was avoided by leaving half of the surface open. The pine slats on the façade enhance the tower’s sculptural appearance while simultaneously allowing air and light to flow through. The creators are hoping that birds will nest in the tower’s structures.

To protect the sensitive landscape, the use of heavy machinery was avoided in construction, and a crane lifted the tower’s four prefabricated blocks into place, avoiding the need for high scaffolding. The lower blocks weigh 35 tonnes each with the top block being 42 tonnes, resulting in a total of 190 tonnes.

Visitors can admire the surrounding landscape through triangular openings in the façade. The first platform at 10 metres provides a view of the forest undergrowth, while the next at 20 metres showcases individual trees and the surrounding forest. The third at 30 metres sits amongst the treetops. Visitors valiant enough to climb the 209 steps to the top are rewarded with views reaching all the way to the Alps.

Visitors valiant enough to climb the 209 steps to the top are rewarded with views reaching all the way to the Alps.

A compost toilet is provided next to the tower, but there are no waste bins. Instead, each visitor is expected to take their trash with them, and so far they seem to be respecting this intention.

The tower’s foundations were laid in autumn 2021, with wooden construction beginning in spring 2022. By July 2022, the tower was ready to welcome visitors. Construction costs were roughly €1 million. Hardwaldturm was later voted Building of the Year 2022 by the readers of Swiss-Architects magazine.

The author Pertti Vaasio, retired CEO of RIA, is an architect who continues to observe the surrounding world with a keen eye, writing books and articles for construction magazines.

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