roof vs superstructure

roof

noun
  • The external covering at the top of a building. 

  • The top external level of a building. 

  • The upper part of a cavity. 

  • An overhanging rock wall. 

  • The surface or bed of rock immediately overlying a bed of coal or a flat vein. 

verb
  • To cover or furnish with a roof. 

  • To traverse buildings by walking or climbing across their roofs. 

  • To put into prison, to bird. 

  • To shelter as if under a roof. 

superstructure

noun
  • All that part of a building above the basement. 

  • The sleepers and fastenings, in distinction from the roadbed. 

  • The social sphere of ideology which includes religion, art, politics, law and all traditional values. 

  • Any material structure or edifice built on something else; that which is raised on a foundation or basis. 

  • Any structure built above the top full deck (FM 55-501). 

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