On 24/05/2017 10:13, Jon Fairbairn wrote:

I want to run two pipes along under our landing floor (which
means going through all the joists).

Joists are 180×50mm Unfortunately there are
already notches and holes, with the result that the calculator
he

http://www.diydoctor.org.uk/projects...ist-calculator

which mostly agrees with the wiki says there is only room for
one more hole. But it also says that the maximum hole size is
45mm, which means that I could put the two 22mm pipes through
one big hole. I dont want to do that because one is hot and the
other cold. So my question is, can I put two 22mm+minimal
clearance holes say 66mm apart (3 diameters as per the wiki) and
still meet regulations?


I ain't a structural engineer but, in my experience, these rules are a
bit conservative, and deviating slightly from them is unlikely to bring
the house down. I would have thought that two (say) 25mm holes a
reasonable distance apart would be preferable to one 45mm hole.

I assume that you're using plastic pipes, 'cos feeding copper pipes
through holes in joists would be a bit of a challenge?!

Are you doing something which needs to be inspected by a BCO? If not,
and if the holes will be hidden by floorboards and ceilings, I wouldn't
worry too much.

Others may disagree!
--
Cheers,
Roger
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