hammer beam vs joist

hammer beam

noun
  • A member of a kind of roof truss (a hammer-beam truss), so framed as not to have a tiebeam at the top of the wall. Each principal has two hammer beams, which occupy the situation, and to some extent serve the purpose, of a tiebeam. 

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 hammer beam and joist occurred in a corpus of books? (source: Google Ngram Viewer )