Joists

‘Plate’ either side of the damaged Joist with 18mm Ply Wood plates. Glued & Screwed to the Joist.

Cheers

I won’t be doing it but I’ll tell them it needs doing

The reg's are constantly changing about notching joists and to my mind we tradesmen didn't take much notice.
Electricians are supposed to not notch joists but drill in the middle for a long time now yet they do notch them sometimes.
When installing central heating if the joist needed notching we did it, we were on priced work so always pipes came first.
I wouldn't call it a botched job if it was notched somewhere were it wasn't supposed to be!
You have always have had to use common sense though.

I remember a looong time ago, I was doing a first fix and notching the joints in a new build development, The safety officer came in and shouted up to me, " stop what you are doing and come down now" He told me that " you are not allowed to work off the joists, its dangerous" FFS Thats how we do it, I've been doing it this way since I started work , I told him and the whole site was shut down, After a meeting a decision was made for the joiner to board the floor first but leave gaps for the pipes, That was accepted for a short while but. the safety officer was unhappy because of the gaps that people could fall in so then, In came the plastic pipes and then. the whole site needed wooden posts for the cowboys to tie their horses to, The plumbing trade went in freefall,,,,