I need to bore a hole in a joist to take a shower waste. Reading the regs tells me that in a 20cm Joist the max hole can be 32mm
I need to pass a pipe of 42mm diameter!
The joist is right next to a wall at the outer edge of the house - load on it will never be high.
Pragmatically - would you go ahead and bore the hole?
Reinforce the joist by bolting metal plates to both sides?
Or bolt it to the wall.
Access would be very destructive.
So not as simple as just lifting the boards either side of the hole then:-(
The any beam of that sort is in tension along its lower edge, compression along its upper edge, as it takes load. A metal plate along the lower edge should be sufficient, e.g. a long mending plate or flat strap, something like this
Yes.
(noting a hole in the centre is better mid span, and a notch better near the ends)
John Rumm snipped-for-privacy@nowhere.null wrote in news: snipped-for-privacy@brightview.co.uk:
I now reckon I am okay up to 50mm on a 200mm deep joist:
yes. I might add another joist alongside
That is probably a *suggestion* that means in the case of thick plunbers they will never cause the joist to collapse.
Exactly. And yet the regs don't take that into account.
Rules are for the guidance of wise men and the obedience of fools
TBH slap[ping somne falss fibre n each side woul probably do a huge amouint.
I actually did this for a model plane wingh - calculated the increase in strength of a wing with a carbon fibre strip glued along the top and bottom of the main spar.
MASSIVE increase in strength with just a tiny amount of carbon fibre.
Wood is cheap. Its also a crap structural material.
I was going to say what John said. But that link looks pretty good to me!
I was just going to say something similar, even a second piece of timber suitable attached across the weakened point might be enough. It very much depends on the place and design of the building I guess. Brian
The regs on joist sizes have nothing to do with safety. They're more about meeting noise transmission targets. If OTOH it's an old house with bouncy floors I'd add noggings each side of a large hole. But 2" out of 8" isn't large.
NT
Glue and screw an extra bit of wood on to the joist spanning the hole. PVA would do the jpb
Drill the hole through both joist and wood.
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