Surface protection of wood components in indoor spaces
Transparent, thin-layered coatings that provide UV-stable surface protection and which control moisture-level changes in the wood were developed in this project.
Factsheet
- Lead school School of Architecture, Wood and Civil Engineering
- Institute(s) Institute for Building Materials and Biobased Products IBBM
- Research unit(s) Wood Modification and Gluing Technology group FGHV
- Funding organisation Innosuisse
- Duration 01.02.2019 - 07.11.2023
- Project management Prof. Dr. Thomas Volkmer
- Head of project Prof. Dr. Thomas Volkmer
- Project staff Barbora Starovicova
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Partner
Bosshard-Farben AG
Blumer Lehmann AG
neue Holzbau AG
Nägeli AG - Keywords Wood surface, interior space, UV protection, cracks
Situation
Load-bearing elements are increasingly being installed in visible areas in modern timber-framed construction, which means they also perform design and aesthetic functions. However, systems and product lines guaranteeing the transparent surface protection required for these elements long-term – like in conventional furniture and interior design – are currently only available to a limited extent. The main goal is to protect the surfaces against rapid ageing and discolouration and to avoid dirtying. In view of the relatively large amounts of wood used for such construction elements, swelling and shrinkage – which causes deformation and the appearance of cracks – are a major consideration. The surface protection required also plays a key role in controlling the moisture content of these elements. In addition to general surface treatment, surface cleaning is another significant factor as these surfaces are exposed to high levels of stress in interior spaces (e.g. schools, sports halls and children’s nurseries).
Course of action
Two key priorities were analysed as part of a broad-based testing programme. Firstly, the aesthetic appearance was assessed based on changes to colour and gloss in various ageing tests and, secondly, the sorptive behaviour of coated components was evaluated by measuring water vapour diffusion resistance. These results were supplemented by testing on the simulation of crack formation due to varying climatic conditions. Testing was also carried out to determine the potential suitability of the coating systems to bridge cracks directly thanks to their elasticity. Sheeting and solid wood based on spruce and ash were tested for use as a substrate. The new in-house developments were compared with solutions available on the market for use as coating systems.
Result
Results showed the new coating systems developed in the project are highly suitable for the coating of wood components in indoor spaces. The colour change to the surface after exposure to various ageing procedures was minimal: ΔE < 3-4. The very low viscosity of the systems enables good penetration and, as a result, effective UV protection of the wood surface. The systems are made up of a thin layer, which means they are in line with the trend and meet the requirements for this kind of treatment of wood components. The surfaces still look very natural, retaining the wood’s character. Results indicated that all new systems developed helped to reduce the formation of cracks. Even though the systems have no diffusion barrier, crack formation was cut by 30 to 70%. The surfaces can be cleaned after mechanical pre-treatment. The new systems are very sustainable and well suited to indoor applications. They are currently undergoing a testing phase and are already being used in major projects.
Looking ahead
After completion of the project, the product was again evaluated internally at Bosshard-Farben AG in accordance with the quality guidelines and is now available under the name ArboShield UV. The coating gives the wood a matt finish while retaining its natural appearance. It protects the surface, reduces changes to the colour tone thanks to the special combination of light protection agents and prevents cracking or delamination. Thanks to its high environmental compatibility, the product is very suitable for indoor use - even in rooms with high humidity, such as swimming pools. Outdoors, ArboShield UV is used for roof soffits and as temporary protection against moisture and yellowing of wooden components during transport and the construction phase.
