Is it safe to cut a hole for 1/4" waste pipe in floor j

[freestyle]

The floor joists are around 4 inches in height from the lower ceiling to the floor upstairs and around an inch thick.

I am replacing some old 28mm copper with this new 1/4 inch stuff to have a good bath/shower empty arrangement. However I am not able to use the existing grooves that have been noticed out at the top of the beam because it causes backflow. By this I mean not enough gradient in the right direction on a 1.5meter span.

So back to my original topic question. I am thinking about cutting a hole in the center of the beam to accomodate the pipe. This will be quite close to the existing notch.

Is this safe ?
Any alternative for negative flow direction otherwise ?

PS: This is all in an effort to have the waste pipes hidden and NOT on display

 

[sooey]

If your joists are only 4" you cannot notch them, they shouldn't have been notched in the first place either. In any case you cannot notch any joists in the centre of the span if that's what you meant.

 

[Bahco]

The floor joists are around 4 inches in height from the lower ceiling to the floor upstairs and around an inch thick.

I would replace the joists before you do any plumbing
I believe floor joists should be at least 7 x 2

You are only allowed to notch 1/8 of joist.

 

[freestyle]

Ok, I am not very good and working in imperial.

They are pretty big indeed, if they are the standard size say 7" or more will that be ok to drill a hole rather than enlarging the notch.

That said it's good to know the ratio of the notch allowed, because at least I can work that out if nothing else. The idea of the hole as opposed to enlarging the notch was to get a better gradient.

The house was built in 1960

Thank you for fast reply, because at the moment I can't crap, pee or wash so I need a solution so please keep replying if you can

 

[Bahco]

To get the correct fall over 1.5 m you will have to notch 2.5 inch out of the 1 joist which will weaken your floor.

I have seen it done before with extra noggins put in but its your choice.

1.5 m of pipe will hardly be noticed on show anyway.

 

[Agile]

1/4" waste pipe will not give much flow!

Perhaps the 28 mm was used because of the problem with notching?

The usual solution is to fit a 1.5" waste and run it around the skirting and box it in.

Tony

 

[Bahco]

1/4" waste pipe will not give much flow!

Assumed OP meant 1 & 1/4 inch pipe

Pipe should be 40 mm for bath which will need nearly 3 inch notch.

Run it above.

 

[JohnD]

a hole is better than a notch. it does not weaken the joist so much.

 

[megawatt]

True, but the advice not to run 40mm through a joist is still sound ... Run it above.