This is the 2nd time I've had this guy out (and it was only to correct his mistakes the first time, although he charged me another $180.00) Obviously he's not coming back.

Here you can see he cut halfway into the support beam holding a very heavy plaster ceiling- right near the wall. Apparently he didn't want to go back to the store and get a pipe extension.
You can see earlier where he drilled into the floor and hit the rafter on his last visit, bored about 3" down, then discovered his mistake and started drilling elsewhere.
Obviously the boards were put there for a purpose, and I half think he has a 2nd agenda of bringing the house down.
How do you structurally repair dumfuk cuts like this? I just don't want breaking sagging or failure in the years to come.

 

Can you sister in a joist on the other side?

 

It's hard to tell from the pictures if any structural damage was done or not. Joists or rafters can be load bearing or not, we would need a lot more info to determine that.
Whatever that board is, it doesn't look like a truss.
Assuming you have joists 16" on center, weakening one will not bring the house down. This isn't advice to start cutting joists at will, ha, but it may not matter in this case.

 

The strange thing is in that picture it looks like a 2x4. I'm sure it must be larger and just an optical illusion. Even a 2x6 wouldn't be much of a floor support.

 

I agree, more pictures and a better description of the area is needed. I don't see plaster, but sheetrock, unless it is in a different area, but often you do not see a mix of the two. Is it possible where this pipe emerges is actually a 2x4 stud in a wall, rather than a ceiling joist?

 

On closer look, this does look like a wall stud. The strap is holding the pipe "up"
Looks like the first 2 pictures were rotated left 90°

 

Yes sorry, I have been kind of limited with my camera access. I'll see if I can get some more. The last picture is what was done first and that was boring down into a floor joist from the top, which was obviously an accident he started in the wrong place.
I never said anything to him about this, but I was most mad because he didn't even tell me he did it, just covered it hoping I wouldn't notice. So its a full size floor joist with about 2 1/2" of the top of it removed.

What's going on with the top pictures is extra large 2x4s (wider than normal, as this is an old house, circa 1930). They built some sort of elaborate separate wooden support structure and then to this screwed a super heavy plaster ceiling. Its about an inch thick plaster and heavy as concrete.

I finally complained about this after the other and he replied all he did was 'nawtch' it. I dunno. The problem is on one side (you can't see) he actually cut further down in the notch, so the board really only has about an inch left. It spans out over the ceiling holding up the plaster.
It could be nothing, but why do this? Its really sad to see such a well built old house butchered anyway.
I'm wondering if just for peace of mind you can nail maybe one of those joist mending plates on the top or side, though I'm no structural engineer. As for the floor joist, not sure if it matters but again, why?

 

IMO it would be a good idea to sister a joist the same [or close] size to the other side of the notched joist at least extending several feet each side of the notch.