Hello all,
I need to replace a 22mm pipe under the kitchen floor. The original one, it appears, was put in when the house was built as there is no way I can get a length under the joists.
The joists are 4" x 2" resting on brick supports. The routing would take the pipe parallel to and 12" from the support.
Q. Can I cut a U shaped notch 22mm deep in the top of each 4" joist, 12" from the support, without seriously weakening the joist?
Thanks
AndyM
I wouldn't, in that situation I would run the pipe under the joist, held up with copper U clips... assuming there's room
LJ
================ Can you knock out an airbrick to feed the pipe in from outside the building? If not, you can usually feed in short sections of pipe (through a gap in the floorboards) and make soldered joints until the desired length is made up.
Cic.
It depends on the joist length, all the info is here in simple form (or look in bldg regs):
joist, 12" from
Use Hep2O and you can feed in as much as you like in a coil !
AWEM
Can't answer your queston without delving into the beam equations, but the highest stressed parts of a joist are the top andthe bottom: something called the 'neutral line' runs through the centre, which suffers neither tension nor compression, only the shear (45 degree) forces that beams have. Thus, it is true to say I think, that the least weakening of the beam will occur if the hole goes through the middle of the beam.
Andy.
Easier to run the pipe underneath in this case, I suspect.
Thanks very much.
(Looks like I'll go through the wall)
AndyM
So should I be worried that the guy that's installed central heating into a renovated house cut a U section in the top of the beam ,of 1st floor.
If its then had e.g chipboard nailed on top, a lot of the strength and stiffness is restored.
Note that the building regs tend to look at maximum defelection under load, as ultimately failure load is way higher. You could have maybe 6" of sag on a beam spanning 5 feet before it broke, but this is unacceptable in a floor :-)
No chipboard just t&g floorboards....
The strength will be restored to a degree far better by using screws, not nails.
Possibly, but you'd need to do the calculations to determine whether or not it is acceptable without comprising the strength of the beam. Have you considered cutting the old pipe out in sections and then feeder plastic pipe in instead (e.g. Hep20 or Marley Equator)? Unless the joists are seriously close together you should be able to fit plastic quite easily.
Cheers Clive
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