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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Carpentry Questions >> Drilling Joists https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1104411288 Message started by AndyOlds on Dec 30^th, 2004, 12:54pm

Title: Drilling Joists
Post by AndyOlds on Dec 30^th, 2004, 12:54pm

I'm currently renovating a bathroom and need to run a 41mm waste pipe under the floor - perpendicular to the direction of the joists (i.e. to go through the joists).

I want to make sure that it will be ok to drill a 50mm hole though each joist - about 6" from the ends - for the pipe run. The joists are 9"x2", so the hole would take up about a quarter of their depth. The holes would be mid way down the depth of the joists (i.e. about 4.5" down from the floor level).

The reason I ask is that my Collins DIY book states that holes through joists should not be near the supported ends - which is exatly where my pipe needs to go!

Any guidance would be greatly appreciated. ???

Title: Re: Drilling Joists
Post by JerryD on Dec 30^th, 2004, 7:10pm

Even if you could drill these holes, how on earth would you thread the waste pipe through them? (don't say cut the waste into 12" pieces and use lots of straight connectors ;D ::)) However if that's what you intend then drill between 0.25 the span away from the wall to 0.4 the span away from the wall, drill the centre of the joist depth and max hole size is 1/4 joist depth. (in your case 56mm)

You could notch the top of the joists. There's a link somewhere here to tell you where you can and cannot cut notches but generally between 0.7 to 0.25 of the joist span is the area you can notch from one end. The notch depth must not exceed one eighth of the joist depth. So a 9" joist allows a max notch of 28mm!

Title: Re: Drilling Joists
Post by JerryD on Dec 30^th, 2004, 7:44pm

try this link

http://www.zurich.co.uk/NR/rdonlyres/98C95CE7-4EEC-4C76-A0FF-0C6B2CD53EED/0/NotchingDrilling107780A02.pdf

Title: Re: Drilling Joists
Post by Chaddy on Dec 30^th, 2004, 10:58pm

Could you not run the pipe above floor level and box it in?
Surely a lot easier and safer!!

Title: Re: Drilling Joists
Post by AndyOlds on Dec 31^st, 2004, 12:54am

Yes - I think I'll probably just try to run the pipe above the floor level and box in - seems like the safest option. Thanks for the advice everyone.

Title: Re: Drilling Joists
Post by jasonB on Dec 31^st, 2004, 8:00am

What floor covering are you going to have?

If tiling you could notch the joist 25mm, leave a gap in the floorboards above, say 20mm. This would just give enough clearance for a 40mm pipe, then run your ply and tiles straight over the top.

OK for short runs but may not give the fall required over a longer distance.

Jason

Title: Re: Drilling Joists
Post by JerryD on Dec 31^st, 2004, 4:23pm

If you buy a macerator you can hide the waste pipe behind the coving ;D ;) ::)