About timber construction

Are you unsure if wood can meet all your requirements for the buildings? Please read here about what benefits wood has. Let yourself be convinced by this natural building material and our Renggli-way of building.

1. Do wooden houses rot? Do they have long durability?

Generally speaking, wooden buildings have the longest lifespan among all types of buildings. In Europe and Japan, many timber buildings that were built hundreds of years ago are still in use today. They demonstrate well the longevity of the natural building material wood. The oldest wooden house in Switzerland has existed since the 12th century. 

Professional execution is the most important measure for the almost unlimited durability of timber constructions. Modern timber construction maintains a dry environment on site from the beginning. 

Clients who decide to use wood not only in the building, but also in the facade, will receive support and advice, with proper planning as well as a clean and detail-oriented execution. It is important that wood is able to repeatedly release and absorb moisture in the air. That’s why we use ventilated facades and pay attention to sophisticated details to adopt optimized rainwater drainages.

2. Do timber buildings meet the requirements of fire protection?

The level of fire protection can be measured by time. According to the Swiss Association of Cantonal Fire Insurances (VKF), a load bearing structure must be able to withstand fire for 30, 60 or 90 minutes (depending on the detailed requirements and the location of the structures in the building). Timber buildings can meet these requirements. 

In fact, wood as a building material has some good characteristics in fire resistance. It has a slow, uniform and predictable burning rate; thus the load bearing capacity or stability is guaranteed for a relatively long time in fire. 

It doesn’t matter which type of the building it is, either timber or concrete, both building owners and investors agree that, in most cases, toxic smoke in a fire is the most severe issue, and it is caused by the combustion of interiors (cables, plastics and all kinds of textiles). 

Renggli buildings comply with the Swiss fire safety standards, State Fire Insurance Association (Vereinigung kantonaler Feuerversicherungen, VKF). According to the latest version, timber buildings and other buildings, such as reinforced concrete buildings, are not treated differently. Therefore, timber buildings can reach a height of 100 meters, and even fire escape stairs are reliable. Our in-house experts will provide fire protection concepts and request approval from international regulatory agencies, according to fire safety rules and regulations.

3. What changes can I consider with wooden facades?

Untreated natural wooden facades change color and become gray during outdoor exposure. This can be prevented by treating wooden facades, e.g. by coating the wood with glaze, paint, etc. 

Alternatively, you can also choose other facade materials such as a fibre cement facade, glass or solid-core panels on a timber building, or plastered walls – like a concrete building with exterior insulation. 

The advantage of a natural wooden facade is that it is almost maintenance-free. All other types of facades, no matter whether it is treated wood, plastered exterior insulation, fibre cement facade or glass facade, must be treated at most every five to ten years.

4. Where does the wood that Renggli uses come from?

We use local wood from the Alpine region that is certified either by the Forest Stewardship Council (FSC) or by the Programme for the Endorsement of Forest Certification (PEFC). For manufacturing timber building elements we mainly use spruce. For facades and parquet floors, we also use other types of wood, such as fir from Emmental, Switzerland, depending on the requirements of the clients. In a few cases when the clients want exotic wood species, we make sure that the wood comes from sustainable forestry.

5. Renggli uses wood from the Alpine region. Will the material adapt to a hot and humid climate?

Firstly, the experts from Renggli can design, manufacture, and assemble the buildings in different ways in order to adapt to different a environment and climate. Secondly, the technology of using wood as a building material in hot and humid places has been well established worldwide. For example, the Nanyang Technological University built their new stadium with wood in Singapore, which has a typical tropical climate with abundant rainfall.

6. Do timber buildings have sufficient sound insulation?

Soundproofing can have a large impact on the living quality of residents. With our ceiling structures and reliable details in fire protection, partition wall and facade, we can meet the requirements for sound insulation of the Swiss soundproofing standard SIA 181. Even in areas with low impact sound that are difficult to attenuate, our sound insulation levels are comparable to those of a 25 cm thick reinforced concrete floor. For multi-storey buildings, we identify and implement suitable solutions for each project with our flexible building system.

7. Are timber buildings earthquake- and typhoon-proof?

Timber is a more resilient material than concrete, bricks and other building materials. It withstands earthquakes, typhoons and other types of extreme weather. Not only in Europe but also in earthquake- and typhoon-prone countries and regions, such as Japan and Taiwan, the earthquake and wind resistance of wooden buildings is well known. In China, many post-earthquake reconstruction projects, such as in Wenchuan, Sichuan Province, have been realized in timber construction.

8. Do Renggli buildings have special requirements for the foundation?

The requirements for the foundation of each project vary, depending on the geographical and geological conditions of each project. The standardized solution is to use reinforced concrete to provide a flat foundation. In some places where the geological conditions are harsh, additional requirements will be needed, such as piling. 

Generally speaking, Renggli buildings do not have special requirements for the foundation. Instead, because timber buildings are much lighter than concrete/iron and steel buildings, the standards for Renggli building foundations are easier to meet.

9. Wood is alive – so are there cracks in the wall?

No, the joints between ceilings and walls in our buildings are 1 mm wide. This so-called shadow joint does not cause any cracks in the connections of building components. In addition, our walls are usually covered with fiberglass wallpaper, which has long-lasting and durable structures.

10. How long is the lifespan of Renggli buildings?

The expected lifespan of modern timber construction and their built-in technologies highly depends on the environment and the client’s investment in quality and durability. In Switzerland, buildings generally have a lifespan of more than 60 years. Renggli is following this high standard and is aiming to provide sustainable and tailor-made solutions to its customers. In addition, Renggli provides advice on building technology and plans for renovation cycles to further expand the lifespan of a building.

11. How does Renggli protect the buildings from insect pests, i.e. termites?

Renggli uses pre-processed wood to manufacture building elements. Based on the specific external environment and possible types of pests, Renggli chooses the appropriate pre-treatment methods. In Switzerland, there are many wooden buildings that have been exposed to natural conditions for more than 400 years, without being threatened by pests. Therefore, pest control is not a problem for timber buildings as long as the right treatment has been undertaken.

12. What products and services does Renggli offer, i.e. on-site assembly, electricity cables, and water pipes?

Renggli offers much more than just a product. Renggli provides customers with highly energy-efficient prefab-timber buildings and a series of services related to the buildings. Renggli's business scope covers consulting, preliminary projects, feasibility studies, as well as planning, engineering, manufacturing, transportation and on-site assembly of timber buildings, etc. 

Wiring ducts for electricity cables and water pipes are integrated in building elements when they are manufactured in the factory. Afterwards, cables and pipes can be easily inserted into the ducts during the on-site assembly. Therefore, clients need to decide the exact location of electrical outlets and the laying of water pipes, etc., with architects and engineers at the initial planning stage of the project.

13. How long does Renggli need to realize a project?

Construction approval is typically the critical element of a building project, which heavily depends on the regulatory systems in each country. 

Renggli can substantially save project construction time by prefabricating building elements and assembling them on site efficiently. Furthermore, Renggli can save more time through process optimization. For example, Renggli built the Langhäuser (long houses) Freilager Zurich project from 2013 to 2015, which were the largest residential timber structure buildings in Switzerland. This project consists of three 6-storey residential buildings with 187 rooms in total. The buildings are 18 meters wide and 20 meters tall. The lengths of the buildings are 70 meters, 90 meters, and 100 meters, respectively. The production time for each building was about 12 months. All the processes (assembly inclusive) were coordinated and conducted in parallel. The Langhäuser Freilager Zurich project was certified as a Minergie-P-Eco building. It strongly demonstrates the competitiveness of modern timber construction – both in cost and in construction time.

Langhäuser (or long houses), Freilager Zurich
Renggli Reference – Langhäuser (or long houses), Freilager Zurich
Photo: Zeljko Gataric, Zürich

14. What after-sales services does Renggli provide (i.e. warranty period)?

As a family business founded in 1923, quality and service, as well as after-sales service, are important factors for Renggli to establish a well-known brand and gain a good reputation in the Swiss market. Generally speaking, the warranty period is 2 years, and for hidden defects it is 5 years. The specific conditions are determined in the contract of each project.