You should see the joists at a barn conversion I've been working at. The "plumbers" have drilled holes in each ceiling joist to route the underfloor heating pipes through, the holes must be 40mm, and the joists are only 150mm. But its the fact that the holes are everywhere, some on the centre line, some well below, some well above. In some joists there are two holes one vertically, well they offset them slightly, but that's 80mm out of 150mm!!!
And that's after I drilled two 25mm holes in each joist between 0.25 and 0.4 of span.
With under floor heating pipes why don't they just batten the top of the joists? Then all they have to do is notch a small piece out to get past the joist, and the pipe stays near the floor?
It does make me wonder why we all bother so much when no other trade seems to give a monkeys!