Is it okay to cut through ceiling joists?

anotheruser

They aren't the main house ones but they seem to hold up the ceiling plasterboard.



I want to run a plastic water pipe through three of them.

Niv

Without knowing exactly what they are holding up I would not willing to give a definitive response. But I understand it is considered acceptable to drill through a joist rather than cut a lump off the top and/or bottom as the former does not reduce the strength of the joist to the same extent.

JimmyChanga

Do you want to cut it completely? What are you trying to achieve?

king132

you can notch the joists to get your pipes flush in - yes.

Grenage

Generally no; not unless you're adding additional support. Pipes should go through the middle rather than into notches.


More info would be useful.

Jonesya

There's a lot of rules about how you should notch and drill joists, including size of holes and the positions where you can and cannot cut them, to ensure your cutting doesn't weaken them and cause them to fail - suggest you search for it online.

Why do you need to cut them? If it's a new pipe, why not just run it above or around the edge and lag it? Or if boarding out, fix some timber to the joists to lift the floor off the pipes and the loft insulation.

southcoastrgi

They are ceiling joists & aren't designed to take any weight & if you drill them you may wake up with the ceiling in the middle of the bed, have you felt the weight of plasterboard & plaster

markin

They look like 2"x5" so it could be risky given you are already likely to be overloading what was only meant for plasterboard.


What size are they? What load are you planning to put up there? If they were 2x3 or 2x4 just the chipboard could be close to overloading, and what is the span on that part? 5ft? 10ft?

anotheruser

I assumed they were there for more than just holding the ceiling up.

I need to thread the copper pipe (changing to plastic) through them to get to where it needs to go. Although as I bought 6m worth of plastic pipe then I could route it elsewhere as there will be a small gap next to the main beam.

They look like a bit of 2x4 but longer on one side, spa ming the width of the loft with about a foot between them.
I've already boarded over most to store stuff. This area is an access area so will just be used to get to other areas of the loft.

Risteard

southcoastrgi wrote: »

They are ceiling joists & aren't designed to take any weight & if you drill them you may wake up with the ceiling in the middle of the bed, have you felt the weight of plasterboard & plaster

Good to finally come across a plumber who knows they must not be cut.

JimmyChanga

The weight of the chipboard you're placing on those joists is plenty in itself, make sure whatever you store is well distributed and not too heavy. Or keep heaviest on top of dividing stud walls. Otherwise you'll see sagging over time.

You can always reinforce the joists by screwing in additional sections along their length.