In Norway the use of weathered unpainted, wooden façades has increased in popularity the last 20 years, both in single family houses as well as in multi-story and non-residential buildings. The benefit of using unpainted wood as façade material can be several: low maintenance costs, low environmental impact and low carbon footprint as well as contemporary and trendy aesthetic appearance. The variation in colour and pattern seen in an unpainted weathered wooden façade tells the story of the chosen design and construction and the loads of the environmental factors the building is exposed to. Usually unpainted façades do not get an even and homogeneously grey façade, but the weathering rather gives a variety of grey and brown tones in the wood. For building owners, architects, building contractors and others, the gradual colour change and patchiness of the wood can be rather surprising and sometimes unwanted. In some building projects, the character of the colour development did not reflect the consumer expectations, and entire façades were exchanged or given a surface treatment after some years even though an unpainted wooden façade can fulfil its function for more than 60 years if correctly executed. It is therefore important to disseminate the information on how an unpainted wooden façade changes its colour over time and how construction details and design options influence this process. The ‘visual guide’, Colour changes of unpainted wooden façades - examples and experiences, has been published as a report in Norwegian as collaboration between the Norwegian Institute of Bioeconomy Research (NIBIO) and The Oslo School of Architecture and Design (AHO) in the course of the Wood Be Better project. The guide is based on building projects from different climatic regions in Norway and the target group of this publication are architects, house owners, building engineers and contractors and others who are interested in exploring the possibility of using unpainted wood in façades. Our main goal is to show through examples of building projects that colour changes on unpainted wooden façades are not random but follow predictable patterns and logic. We want to illustrate some of the requirements and mechanisms of weathering of wood to give a structured overview over features and constructive details in a façade that is followed by colour changes and describe how these details influences the colour of the wooden façades in existing buildings.

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