How do I repair a floor joist which has a hole drilled less than 2 inches from the bottom?
Replacing them? Getting an engineer? For a 1/2 hole in at least 8in joist? Seriously? I mean I'm sure the joist has lost some percentage of its strength. Like  pretty small percentage. I would speculate that the lost strength is within tolerance limits for wood, which is not uniformly perfect. Unless you plan on having sumo wrestlers fight on top of those joists, I would just let them be....