Art historian Juan Pablo Bonta has presented a nine-step model for analysing how the interpretation of architectural oeuvres becomes canonised. We suggest that in terms of the built heritage, canonisation and heritagisation are essentially the same process, so Bonta’s model can be used for analysing heritagisation processes. This article testifies to this assumption by examining how the interpretation of historic Nordic wooden towns became stabilised in Finland. The concept was introduced in the 1960s to describe the Nordic urban heritage that was threatened by massive town development projects. The identification of the heritage category enabled the preservation of some remaining wooden districts. Examining this process allows us to discuss the role of expertise in the building preservation. In the case of wooden towns, experts’ early recognition was a crucial precondition for the preservation of the heritage, which enabled novel generations to form a living relationship with it. Seen through the experts’ writings, the heritagisation process of the wooden towns also reflect the expanding scope of the built heritage discipline. Based on our findings, the canonisation model is applicable not only to the individual oevres, as Bonta addresses, but also to broader built environments and, more conceptually, to heritage categories.