There have been a lot of blogs about various things that are found on home inspections. This one is structural. We inspectors spend a lot of time in crawl spaces, looking at many things. One common one is caused by plumbers and HVAC technicians. This isn't to badmouth them. They have their job to do and may not know about how structures are supported.
The above joist has been deeply cut to make room for the waste pipe. Now this particular picture isn't of a brand new house, but the effect is still there. This joist was originally a 2X10. With more than half of it notched out it is effectively a 2X4. Definitely not strong enough to support floor loads.
This joist has a section completely cut out of it to accomadate heating ducts. This was a retro fit furnace duct, the HVAC tech decided that that section of floor didn't need support (I guess).
In both instances, with a little thought, these cutouts could have been avoided. What were they thinking?