Floor joists are the principal elements in a wooden floor ... In residential construction, these rafters, beams, and joists are mounted and then fitted with firings, lengths of timber that are cut ...

Mold on floor joists can weaken the wood, lead to health problems, and result in costly repairs if not handled quickly.

Where and how to drill floor joists for electrical cables or plumbing runs depends on what type of floor framing you have.