building vs rooftop

building

noun
  • A closed structure with walls and a roof. 

  • The act or process by which something is built; construction. 

rooftop

noun
  • The area atop a roof. 

  • The top layer of a roof; the material covering or composing a roof. 

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