cross-member vs joist

cross-member

noun
  • A beam lying crosswise; a rail. 

joist

noun
  • A piece of timber or steel laid horizontally, or nearly so, to which the planks of the floor, or the laths or furring strips of a ceiling, are nailed. 

verb
  • To fit or furnish with joists. 

How often have the words cross-member and joist occurred in a corpus of books? (source: Google Ngram Viewer )