An innovative method of sheet glass production (by means of drawing) that appeared in the 1900s led to larger/wider windows.

The closing up of large window cavities required the use of iron beams, which became commonplace within a few decades and especially in the 1930s, where buildings on the whole were characterised by their extensive use of iron structures in exterior walls, typically in bay windows and balconies.

Recommended literature in Danish:
Gjerløv-Knudsen og H.Bonnesen: Husbygningsteknik (1948)
Byggebogen: Ydervægge, alment

Grundejernes Investeringsfond, Realdania og Byggeskadefonden