The early career of Sverre Fehn, the influential Norwegian architect, is marked by the designs of pavilions which were constructed shortly after each other for two major competitions: The Norwegian Pavilion for the World Exposition in Brussels (1956–1958) and The Nordic Pavilion at the Giardini site of the Venice Biennale (1958–1962). This paper studies the process which led from design to construction for both pavilions, identifies structural changes during that process, and investigates the causes and effects of such changes. A study of Fehn’s hand-drawn sketches and photos of models, made throughout the design and construction stages, reveals that despite functional and formal similarities the two pavilions’ development process and the changes which they underwent are noticeably different. The pursuit of ‘abstract space’ during the competition stage for the Brussels Pavilion was tested by considerations of construction only later on, creating a critical tension in the project. Not only did the organisation of structural components change significantly during the design process but the logic of construction underwent a complete transformation. Nevertheless, this transition between different iterations of the Brussels Pavilion suggested an alternative approach for the Venice Pavilion in which the initial thought of construction became a projection, rather than an abstract imitation of built reality. The spatial intention and construction-related considerations of the Venice Pavilion were addressed by a ‘synergetic’ structural principle, implicit in the competition scheme. This unprecedented feature significantly enlarged the ‘space of possibility’ of the roof structure, which provided for adaptation to indeterminacies without compromising the initial design intentions. Changes in the design of the Brussels and Venice Pavilions, therefore, differ in the ways in which they evolved from design to completion: sequential and abrupt, vs. gradual and continuous. This sheds light on a critical shift in the work of an influential architect and the way he approached design indeterminacies, rather than forcing them into submission.