shop floor vs shopfloor

shop floor

noun
  • The work area of a workshop, separate from the offices and other rooms. 

  • The public area of a retail shop, as distinct from the offices and other rooms. 

shopfloor

noun
  • The area of a factory or workshop where the operatives work; used especially to distinguish the productive part of a factory from the administrative part. 

How often have the words shop floor and shopfloor occurred in a corpus of books? (source: Google Ngram Viewer )