Now when you install pipes under a floor, especially copper ones, you have no choice but to cut a notch in the floorboard, run the pipe then close the floor back up. If someone puts a screw through it at a later date they will cause a leak, but wont risk anyone’s life.
When installing cables, they MUST not be run like this, but be run in holes drilled in the joists and threaded through for the reasons mentioned above!
In the photos below, the joists are suspended and a cable can be run underneath them – even safer and very easy indeed. So why has some IDIOT notched out the joists and run the cable in them?
We will never know – it’s history to us and impossible to trace!