This article presents a framework model that defines knowledge building as a co-evolution of cognitive and social systems. Our model brings together Nonaka's knowledge-creating theory and Luhmann's systems theory. It is demonstrated how collaborative knowledge building may occur – in an ideal situation – within an organisation, when people interact with each other using shared digital artefacts. For this purpose, three different technologies are introduced as examples: social-tagging systems, pattern-based task-management systems, and wikis. These examples have been chosen to demonstrate that knowledge building can occur with respect to both declarative and procedural knowledge. The differences and similarities between these technologies, as far as their potential for organisational knowledge building is concerned, are discussed in the light of the framework model.