The purpose of this dissertation is to describe, understand and explain the role of modernism in Swedish urban planning, and analyze if modernist urban planning ideas influenced building legislation in ways that can explain the structural changes of our cities during post-war period. Earlier epochs were characterized by intense construction of working-class housing in garden cities and large courtyard housing blocks with double-sided lighting in residences.

   The dissertation has been carried out within the tradition of historical institutionalism with a counterfactual approach. It covers the time from 1928 to the present with a focus on the period 1928-1975. The object of study is the formal regulations in building legislation. The central analytical instruments are formative moments and path dependence. A formative moment should be characterized by uncertainty, significance and unpredictability. Path dependence is studied with the help of theories of experience-based learning and the power of bureaucracy. 

   The dissertation shows that modernist ideas were written into the building code of 1931 in accordance with functional partitioning and a diagram by Walter Gropius from the 1920s calling for relative distances between houses, the longer the higher houses, and direct sunlight on facades, permitting one-sided lighting in residences. Instead of prevailing praxis, cities were built in conformity with principles of buildings-in-the-park with slab blocks. These regulations were gradually tightened over time and also guided redevelopment policy. In the sixties higher slab blocks and tower blocks began to be frequently built and functional partitioning assumed a unique guiding role in traffic policy and urban planning. Starting in the middle of the 1970s, modernist ideas gradually were dismissed in government policy.

   Leading modernist architects where driving forces in the formative moment, supported by the Association of Property Owners. Their colleagues could, in the path dependent process, augment the modernist ideas by virtue of their profession. They led state agencies, participated in commissions on building legislation and wrote referral comments on proposals, as well as sitting on building committees together with building contractors, entrepreneurs and construction workers.