koibloke

Fitting a shower tray directly onto 9'' x 3'' joists. Am I OK taking the 1½'' waste through the joists to couple to existing waste pipe. Sound advice much appreciated.

uug197h

If you are cutting a hole in the joist then its best if you screw a block of wood under the hole about 8" long and put nogins in (wood from 1 joist to the other) i also put a metel strap on the top of the joist better safe than sorry

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Matty A

I would advise checkin how many other holes are in the same joist that are near to where you are going to put your waste as not to weaken too much in one place.

If there are too many holes in then you can cut a lengh of 18mm pine ply 9" wide then glue and screw to the joist then drill your hole through the ply as well also brace between joists wi noggins ( as uug197h) said..

nick penfold

building regs state that holes in joists should be no more than one quarter the depth of the joist.

TerryH

Koibloke,
The figures I have are different to Nick's.
To notch into the joist you should be between 7% and 25% of the lenght of the joist away from the wall. The notch should be no more than 1/8th of the depth of the joist.

Obviously a difference of opinion there!
Terry.

ajs heating

yes as you say 7 - 25 of the length. depending on span of joist.
max depth of notch will give you 28.75mm
max size bored hole will give you 57.50mm

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nick penfold

yes yes guys you are right. notches no more than one eighth etc but we were TALKING about HOLES. If your drilling a hole through the joist, it must be no more in diamater than one quarter the depth of the joist.

Sorry if i confused people with the previous post )