New home, lots of surprises. Pulled down an old drop ceiling in a "finished" basement to find a sickening sight. Many floor joists appear to have been cut during initial construction to plumb tub drain, and then several more to push heating ducts into ceiling when finishing. I'm trying to figure out how to make the house safe and sound before I repair plaster cracks, replace roof and flooring etc.
Here is the damage: 5 of 6 joists compromised. These are 2by8s 12' spans, 16" on center. There is an intact double joist, the next one over has a 3by10 cut out of the top, about five feet from the wall. The drain pipe then goes through the next two joists, and the second one also has a heating duct through it. This kind of thing continues for the next several joists with one intact joist in the middle. Any experiences repairing joists? Do I need to drop the plumbing below the joists and replace them or is there a way to reinforce them enough to make them secure?