Meaning of bridging joist in English:

bridging joist

noun

rare Building
  • (In a wide floor requiring two layers of joists) each of the joists resting transversely on the larger binding joists below and supporting the floorboards above (now historical); (also more generally, regardless of the type of floor) each of the joists which directly supports the floorboards.

Origin

Mid 18th century; earliest use found in Francis Price (bap. 1699, d. 1753), architectural surveyor and author.