when did cavity wall insulation become part of building regulations
Cavity wall The typical cavity wall method of construction was introduced in Northwest Europe during the 19th century and gained widespread use from the 1920s. In some early examples stones were used to tie the two leaves of the cavity wall together,[3] while in the 20th century metal ties came into use. Initially cavity widths were extremely narrow and were primarily implemented to prevent the passage of moisture into the interior of the building. The widespread introduction of insulation into the cavity began in the 1970s with it becoming compulsory in building regulations during the 1990s.[clarification needed]