On Monday 10 August 2026, the first school day after the summer holidays, Regierungsrätinnen Bettina Surber and Susanne Hartmann handed the new Kantonsschule Wattwil to Rektor Martin Gauer. Students spent the morning walking through the building instead of sitting in lessons. I know that walk. It is the first time a structure feels hundreds of feet testing whether it was drawn honestly. The clearest account of how this school was made comes from a research setting, the Bern University of Applied Sciences’ Holzbautag 2026. Its report of 17 September says: “Fertiggestellt wurde die Kantonsschule im August 2026.”

Start with what the building is. Gunz & Künzle Architekt*innen of Zurich (Michael Künzle, Thomas Weber, Mathias Gunz) won the open competition with CÉLESTE. There were 52 entries, and on 10 June 2021 the jury chaired by Michael Fischer chose it unanimously. The school has no corridors. Its rooms gather around one central hall under a glass roof, with three terrace levels, two spiral stairs and 800 m² of multi-use terrace. Classrooms line the façades and take borrowed light from the hall through clerestory windows. It is the top-lit centre of the Bauhaus Haus am Horn, scaled up to a Kantonsschule.

A skeleton that hangs its floors on stone

The body is three timber storeys, with an acoustically decoupled attic storey for music over one wing. It stands on a concrete basement on piles, and four concrete stair towers form its spine. The responsible timber engineers, SJB Kempter Fitze, describe it in one sentence: “Rippendecken aus CLT-Platten [werden] horizontal an Massivbaukerne gehängt.” The system, they add, “ermöglicht eine hohe Vorfertigung, verkürzt die Bauzeit und sorgt für eine wirtschaftliche Montage.” Ingeni AG (Francesco Snozzi, Lorenzo Moresi) did the structural engineering at competition stage.

The method story is my favourite part. Blumer Lehmann of Gossau led the building envelope as sub-general contractor (Teil-GU), in a joint venture (ARGE) with S. Müller Holzbau of Wil, Abderhalden Holzbau of Wattwil and Bleiker Holzbau of Lichtensteig. The ARGE proposed timber in place of the planned concrete floor elements. According to Blumer Lehmann, that meant a shorter build, easier assembly and lower loads. The BFH report records who made what: S. Müller built the slabs, Abderhalden and Bleiker the exterior walls, and Blumer Lehmann the interior walls and façade components. These carpenters, and the foresters who felled the wood in the winter of 2024/25, are the people this building owes its body to.

BFH counts about 3,000 Festmeter of Toggenburg roundwood bought early and 3,623 m³ of timber installed. The Ewoks of Endor built their village from the forest they lived in. This valley did the same with a building permit, for its own students. Excavation began on 2 September 2024, and the school opened less than two years later. It cost CHF 73.5m for about 14,000 m², and the Schulblatt reports it has just been certified SNBS Platinum.

The trade-off is simple. The school was planned for 720 students, about 830 are enrolled for 2026/27, and so it is full on its first day. A skeleton tied to four fixed cores is easy to prefabricate but hard to extend.

←TODAY: A cantonal school opens in 2026 on CLT ribbed slabs tied to four concrete cores, built mostly from its own valley’s wood.
→3012: In Zurich 3012, every building carries a record of the forest it came from, and that forest is a short drive away.
Fulcrum: A wooden floor is only regional if the contract leaves room for the builders who know the forest to propose it.

Building-sense: Every water, power and ventilation line in this school runs exposed across the timber walls and ceilings. Nothing in it is hidden from the people who maintain it. A 25-year-old technician can trace a fault by eye, and I value that more than any sensor I own.

Atelier: An office tendering a public timber building has to decide whether the structural system is fixed in the drawings or left open for builders to propose alternatives. Wattwil shows that the people closest to the wood may see the better floor. Monday move: add a clause to your next tender that invites contractor alternatives (Unternehmervarianten) on the slab system, with a fixed deadline for the engineer to evaluate them.

Hack: Estimate the biogenic carbon stored in Wattwil’s 3,623 m³ of timber before anyone quotes you a figure. Use the simplified EN 16449 method: volume × density × carbon fraction × the CO₂/C mass ratio. The 470 kg/m³ for spruce and fir is an assumption, so replace it with the supplier’s value.

V, rho = 3623, 470            # m3 installed (BFH); kg/m3 assumed
co2 = V * rho * 0.5 * 44 / 12  # EN 16449: carbon share x CO2/C
print(round(co2 / 1000), "t CO2 stored")      # ~3122
print(round(co2 / 14000), "kg CO2 per m2 GF") # ~223

That figure is carbon stored, not carbon saved. It stays stored only as long as the timber stays in use.

PAZ covered a sister build from the same season, Kantonsschule Stadelhofen’s Dübendorf modules, also built by Blumer Lehmann. Dübendorf is designed to be taken apart, while Wattwil is designed to stay. Read the two side by side. Then open your current timber project and write down who on the builder’s side is allowed to propose a better floor.