Architecture is – or ought to be – a long-term investment. Construction is a resource-demanding activity, and most buildings are here to stay, whether that was the original intention or not. Ageing and patina are thus basic conditions. Nevertheless, we tend to regard the building as completed as soon as the paint has dried, and the key is handed over to the client. What we ought to do is see this as the beginning of the building’s life. There was a time when architects routinely considered the long-term perspectives whenever they selected a material or a detail for a building. However, much have changed since then, and new building technologies, resource strategies and social structures have prompted a different view of patina. These days, a lot of effort and resources go into battling architectural ageing and patina, which are often regarded as undesirable. The thesis calls attention to the fact that the interest in architectural patina has been replaced by an architecture that – by virtue of its materials, detailing and building technology – often becomes an image of something, without fully realizing that the object it copies is something in itself, something that arose as an architectural response to constructional challenges, and where patina served as an architectural theme and source of information. The result is buildings that decay at a fast pace and patinate in undesirable ways. The thesis examines, explains and applies the field of architectural patina while raising the following questions: if patination is unavoidable, is it then possible for architects to work with it, so that patina, instead of subtracting and blurring, can be something that adds and improves? And, if so, what do these added values consist of, and how can the appreciation of patina help us create architecture with the future in mind? To qualify the answers, the thesis establishes an applicable terminology and draws up a theoretical and historical framework that can be used as a guide when architects consider how to take time seriously as a condition that should not be ignored and cannot be avoided but may be used as a resource. It then looks at different approaches to working with patina by studying two buildings by C. F. Hansen and two buildings by Gigon / Guyer where patination has been a determining factor, and where patina, in various ways, played a part already at the drawing table as reflected in the architectural representation. Finally, it explores how a better understanding of patina can inform the architectural practice already from the initial concept and design stages by reviewing three computer/hand-drawn study projects. Together, the three main chapters demonstrate that patina is not a romantic fad but a highly relevant issue with informative and thematic potential; that patina is unavoidable but may, to a certain extent, be channelled in a given direction; that the (re)presentation has a potential for serving as a productive tool in the architect’s approach to patina; and that patina should be included as an important factor in sustainable long-term strategies. The thesis demonstrates, with its definition, elaboration and interpretation of patina, that it is possible for architects to work deliberately, constructively and attentively with architecture’s ability to grow old. Ageing and patina not only subtract, they also add new layers.