Notching joists for 1” 1/2 waste bath/shower

[Oscart]

Guys I have read the labc advice on notching and I’m all ok, I have calculated a max 38mm notch allowed but that isn’t going to allow for my 1” 1/2 pvc.. what an earth do I do? Notch really needs to be 42mm deep
Thanks!

 

[Ben-gee]

What are you trying to do?

Bearing in mind the notch size needs to increase as you go, to get a fall on the pipe, if your joists aren’t big enough to allow this you will have to route the pipe another way.

Not what you want to hear but that’s how it is.

Or is it just one joist? In which case I would do it and ‘plate around the notch with 18mm ply.

 

[Oscart]

What are you trying to do?

Bearing in mind the notch size needs to increase as you go, to get a fall on the pipe, if your joists aren’t big enough to allow this you will have to route the pipe another way.

Not what you want to hear but that’s how it is.

Or is it just one joist? In which case I would do it and ‘plate around the notch with 18mm ply.

Hi Ben, see diagram, the wiggly lines are planned 1 1/2 pvc to bath and shower and green highlights are notches needed, as only going through joists close to bath and shower these will be shallow 44mm and no need to go through more

 

[Roy_66]

Just a daft thought/question (for the one joist case) as well as Ben's beef up with ply on the sides would it help to put a steel plate over the top of the pipe. Joist would have to be shaved to thickness of the plate. I'm thinking USA do that for pipes in stud walls (more to stop you nailing through the pipe tho I think) but would it help on the joist, or a dumb idea?

Other thought would be double up the ply on each side if it's marginal.

Whatever - does it have to be cleared with BCO? (Yes I'm sure loads done without that)

Cheers,

Roy (Amateur)

 

[Ben-gee]

Can’t the bath waste be above the floor under the bath - come to the right and then go under? (Or is it a a freestanding “egg” bath)

 

[Roy_66]

Hi Ben, see diagram, the wiggly lines are planned 1 1/2 pvc to bath and shower and green highlights are notches needed, as only going through joists close to bath and shower these will be shallow 44mm and no need to go through more

Looking at the plan now, is it not possible to get a bath with waste at the end, similarly the shower tray, and leave the joists alone? (I guess it's too late)

Cheers,
Roy(Amateur)

 

[Oscart]

Can’t the bath waste be above the floor under the bath - come to the right and then go under? (Or is it a a freestanding “egg” bath)

Its freestanding egg unfortunatley so all waste is under floor. Current fall based on that plan for bath is 1 in 50

 

[Oscart]

Looking at the plan now, is it not possible to get a bath with waste at the end, similarly the shower tray, and leave the joists alone? (I guess it's too late)

Cheers,
Roy(Amateur)

Bath is on its way today! as its a egg bath most come with centre waste as is the case with ours

 

[Ben-gee]

You are cutting the same joist twice so not good really.
Can tray go on legs/plinth ?

If the wall “North” of the bath is external you could take the waste out to here come across and re-enter the building between the joists on the right. Use tees with rodding eyes.
I have done this 5 or 6 times with no issues 🤞(usually with a shower) . Then no joists need to be cut.

 

[Oscart]

You are cutting the same joist twice so not good really.
Can tray go on legs/plinth ?

If the wall “North” of the bath is external you could take the waste out to here come across and re-enter the building between the joists on the right. Use tees with rodding eyes.
I have done this 5 or 6 times with no issues 🤞(usually with a shower) . Then no joists need to be cut.

The length between those notches would be circa 2 m.

The only external wall is the 'east' wall. Also in conservation so no external pipework.... I have all the issues with this one!

 

[Ben-gee]

That’s a lot of weight.

If you wish to proceed, put in two extra rows of noggins to help transfer the weight and plate up the notch both sides with 18mm ply glued and screwed - extend this to the wall and back past the bath so about 1 metre long.

 

[Oscart]

That’s a lot of weight.

If you wish to proceed, put in two extra rows of noggins to help transfer the weight and plate up the notch both sides with 18mm ply glued and screwed - extend this to the wall and back past the bath so about 1 metre long.

Thanks Ben, I might have to go with that!

 

[ShaunCorbs]

Could you drill the joist for said waste pipe ?

 

[IND_Nick]

If it is a free standing bath with sides, not raised on feet, normally the waste is central but once you've fitted a trap it may extend passed the joist you wanted to notch, normally there is a void under the bath to house the waste and trap. As Shaun has mentioned I would always prefer drilling a joist and then follow above with a couple of plates and noggins to strengthen. Just be careful as some of these baths are heavy when full, make sure the floor is solid.

 

[gmartine]

As Shaun said and if the amount of fall allows I would absolutely drill rather than notch the joist, that way you keep more of the inherent strength in the beam.

As per your drawing exit the drain hole at three oclock so you can bore a perpendicular hole.

 

[snowhead]

You'll probably still have to reinforce the joists, but given the short runs of pipe across the joists you should be able to drill them lower in the joist instead of notching.

 

[king of pipes]

The guys have it covered you may be lucky enough with one drilling needed rather than a notchings , there will be a slight void under the bath this will allow to drop the right hand side of the said joist . Kop