A school made of regional wood



Over the next ten years, school buildings will need to accommodate about 3,000 additional classes. These will preferably be made of regional wood. One good example is currently under construction in Prêles, above Lake Biel.

The number of births is increasingand these future pupils need space. Over the next ten years, classrooms for about 3,000 additional classrooms will be needed, states the NZZ on Sunday, June 26, 2022. If these 3000 classrooms were placed in new buildings, about 200 new secondary and elementary school and 250 new kindergartens would be needed. In theory, almost every week one new school building would have to be built.

Best choice - timber buildings 

It makes sense to meet this enormous demand for new classrooms with timber constructions. Timber constructions are quickly completed thanks to short assembly periods. The components can be prefabricated in the factory, stored in a weatherproof location and then transported to the construction site where they are quickly assembled. Cost-effectiveness is also guaranteed: Thanks to lower heating, maintenance and demolition costs, timber constructions are cheaper than solid constructions over their full life cycle, despite the sometimes higher construction and planning costs. 

Wooden buildings as CO-sinks

Wooden buildings have the justified reputation for being climate-friendly, because wood is a resource that requires only solar energy and water for its creation. Through photosynthesis, trees extract CO2 from the atmosphere, transform it and store it. Wooden constructions thus become the CO2 sinks, which are called «NET negative emission technology», with which we won’t be able to do without in the future according to the Federal Office for the Environment  (Link).

Harvesting and processing are also energy efficient. A timber building, made with wood from the nearest forest, is particularly environmentally friendly. The new school in Prêles is a good example for that. The trees come from the surrounding forests of the Plateau de Diesse, south of the Chasseral, and were transported only a few kilometers b e fore processing. This greatly minimizes the grey energy contained in the construction elements. After the harvest in the winter of 2020/21, the forestry companies delivered the wood to the company Despond SA in Bulles to produce lamellas which were then delivered to JPF-Ducret for gluing. A part of the wood was also transported to Schilliger Holz AG for the manufacture of tri-ply panels, the only Swiss company currently manufacturing this type of product. 

The way to your own wood 

The use of regional timber is not a problem for privately financed construction projects. Yet, the situation is a little more complex for large public construction projects: according to the Federal Act on Public Procurement (PPA), different types of procedures are prescribed depending on the value of the contract. Construction projects exceeding the threshold value of CHF 9.575 million must be put out for public tendering. The same applies to services in the main construction sector (e.g. carpentry work) or certain supplies (e.g. sawing of logs) if they exceed the threshold value of CHF 500,000 or CHF 250,000. 

Construction projects for new buildings, such as schools, must therefore generally be put out to tender. According to the principle of non-discrimination of the PPA, no requirements can be made regarding the origin of the materials. Unfortunately, it is not possible to specifically demand regional wood. It is also not allowed to require that the wood comes from a certain perimeter around the construction site, which would obviously be very reasonable from an ecological point of view. Nowadays the contractor who gets the contract can decide where the wood they want to use comes from. Often, it's a cheap alternative that's chosen, and most of the time that is not the regional alternative. There are, however, possibilities to use wood from the surrounding area despite the tender: The provision of wood by the client himself, the so-called in-house supply, is one such possibility. Municipalities, such as the mixed municipality of the Plateau de Diesse, which have expendable raw material at their disposal, can provide thei r own timber and thus demand this in the tender. It is also particularly interesting that the degree of processing of the products is free of charge . This means that entire logs, sawn timber a nd even glued products can be made available. 

Two possibilities for in-house procurement

There are basically two types of in-house procurement. Direct harvesting guarantees that the wood felled in the company's own forests is used for a specific construction project. Each tree felled is planned for a specific use and traceability is guaranteed at all times. Indirect harvesting consists of cutting as much wood as is used for the given construction project. This principle allows a forest owner to exploit its own resources. The wood is not used directly for the construction in question, but the same quantities of wood are t hen traded on the Swiss market. 

First-hand timber for the school in Prêles 

For the school in Prêles, the choice was made to use local wood. The spruce trees that once grew on the Diesse plateau were used for the pillars, beams, walls and ceilings of the new school building. Spruce grows quickly and has good timber properties for building construction. Beech wood is also used in some places. For example, as a support for the 13-ton staircase at the center of the school. It was delivered to the site as a prefabricated concrete element and mounted onto the beech beams. 

Betontreppe auf Fagusträger

For the planning process, it is essential that the decision to use l ocal wood is made early on. Timber can only be cut in the winter, so the planner and owner must know which trees will be used for the project in the previous fall. A rough planning of the cross-sections, including reserves and the approximate proportion of hardwoods and softwoods, is essential at this point.

A good indoor climate 

The new school building skillfully combines solid wood and frame construction: All load-bearing walls and floors are made of solid wood and glulam. The interior walls are non-load-bearing frame construction. The warm surfaces of the wooden walls and ceilings, as well as the constant exchange between the wood and the air humidity, provide a good indoor climate. Well insulated walls are important: the smaller the difference between the surface temperature of the walls, floors and ceilings and the air temperature, the better the room climate. Therefore we feel comfortable in wooden buildings with good thermal insulation, even when the ambient temperature is slightly lower. This allows buildings to operate on higher energy efficiency. In addition, wood has a higher surface temperature than concrete, steel or glass, which further increases the feeling of coziness.

Film project 

The construction work is currently underway and next summer the students of the surrounding communities will take possession of their new school. Until then, we are accompanying the entire construction process with a film crew.


Beteiligte Schulhaus Prêles

Architektur: Chapuis Architectes SA http://www.chappuisarchitectes.ch/ 

Holzbauingenieur: Timbatec AG in Delémont https://www.timbatec.com/en/index.php

Holzbau: Charpentes VIAL SA https://www.vialcharpentes.ch/fr/ 

Brettsperrholz: Schilliger Holz AG https://www.schilliger.ch/ 

Verleimung von Brettschichtholz: JPF-Ducret in Orges 

Sägerei: Despond SA Scierie, Bulles



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