mansard vs mansard roof

mansard

noun
  • The upper storey of a building, surrounded by such a roof 

  • A mansard roof 

adj
  • having two slopes on each side, the lower being steeper than the upper 

mansard roof

noun
  • A steeper roof that terminates into a flat roof at its high point. 

  • A roof having two slopes on each side, the lower one having a steeper pitch than the upper; this increases the volume of the enclosed space. 

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