In contemporary architectural discourse, the concept of space is ubiquitous, yet its historical genesis and theoretical underpinnings in Gottfried Semper's seminal theoretical work remain under explored. This study investigates the reception and integration of Semper’s architectural theory into modern discourse, tracing its trajectory from August Schmarsow, to Nikolaus Pevsner, to Sigfried Giedion. While Semper’s “cladding theory” had initially been understood in terms of both its relation to physical properties and structural and functional values, leading to an expansion of cladding as a new genre of art, i.e. arts and crafts, Semper’s “architectural theory” instead explained cladding theory in terms of space. In disseminating Semper’s theoretical work, Schmarsow was especially important as he himself played an increasingly prominent role in expanding the boundaries of modernist architectural theory and practice from the beginning of the 20th century on.