Building regs for running waste through joists

[PistonReg]

What are these? From memory it's a 1 in 40 fall minimum, upto 25% of the joist can be cut for pipes but I forget how near to the top or bottom of the joist I can go - is it an inch?

Got to cut a few joists in the bathroom andcan't avoid these joist cuts :-O

[henrycrun]

If you must do it, put it on the neutral axis

[Ferg]

25% of the joist? You're having a laugh. They'd better be very thick!!
NEVER near the bottom and in the 2nd 10% of the span at either end. Keep away from bolts etc...
HTH

[mackg]

Ferg said:

25% of the joist? You're having a laugh. They'd better be very thick!!
NEVER near the bottom and in the 2nd 10% of the span at either end. Keep away from bolts etc...
HTH

[PistonReg]

Thanks folks. Tey'll be going through the centre of teh joists. 25% is a nono? They've 9" joists and I've got to run 40mm waste through them, which I'm pretty sure is allowable?

[Busamav]

PistonReg said:

Thanks folks. Tey'll be going through the centre of teh joists. 25% is a nono? They've 9" joists and I've got to run 40mm waste through them, which I'm pretty sure is allowable?

It will also depend on the span and how stressed that joist is .

[mackg]

PistonReg said:

Thanks folks. Tey'll be going through the centre of teh joists. 25% is a nono? They've 9" joists and I've got to run 40mm waste through them, which I'm pretty sure is allowable?

What do you mean by through them? If you are going to notch the joists by 40mm effectivley your joists are only going to be as strong as 180mm joist, I'm sure the 225 will have been calculated as the depth required to take the span. like Ferg rightly said you can only notch up to 20% of the span away from any supprt.

[Busamav]

Have a look here for a good guide


http://www.luton.gov.uk/Media%20Library/Pdf/Enviro...

[JR]

mackg said:

PistonReg said:

Thanks folks. They'll be going through the centre of teh joists. 25% is a nono? They've 9" joists and I've got to run 40mm waste through them, which I'm pretty sure is allowable?

What do you mean by through them? If you are going to notch the joists by 40mm effectivley your joists are only going to be as strong as 180mm joist, I'm sure the 225 will have been calculated as the depth required to take the span. like Ferg rightly said you can only notch up to 20% of the span away from any supprt.

But he said that he's going through the centre of the joists and I take that as through the neutral axis. To drill a series of 1 and 5/8" holes in the centre two inches of the beams won't worry them at all being only a 4% reduction in strength.

[Ferg]

JR said:

To drill a series of 1 and 5/8" holes in the centre two inches of the beams won't worry them at all being only a 4% reduction in strength.

But with a 1:40 fall that means that then CAN'T be through the centre of more than one joist. In addition, in the real world, there will need to be a hole of a decent size to allow for lagging around the pipe to avoid expansion noise. Also the holes need a bit of extra size to allow for misalignment.

[JR]

Ferg said:

JR said:

To drill a series of 1 and 5/8" holes in the centre two inches of the beams won't worry them at all being only a 4% reduction in strength.

But with a 1:40 fall that means that then CAN'T be through the centre of more than one joist.

I see that you've not done the maths.

[Ferg]

JR said:

Ferg said:

JR said:

To drill a series of 1 and 5/8" holes in the centre two inches of the beams won't worry them at all being only a 4% reduction in strength.

But with a 1:40 fall that means that then CAN'T be through the centre of more than one joist.

I see that you've not done the maths.

If it passes through the centre of one and has a fall of ANY sort it can't pass through the centre of the next one.
My maths fking good enough for you???

[JR]

Ferg said:

JR said:

Ferg said:

JR said:

To drill a series of 1 and 5/8" holes in the centre two inches of the beams won't worry them at all being only a 4% reduction in strength.

But with a 1:40 fall that means that then CAN'T be through the centre of more than one joist.

I see that you've not done the maths.

If it passes through the centre of one and has a fall of ANY sort it can't pass through the centre of the next one.
My maths fking good enough for you???

Best to read what I said as your statement is not true.

[Ledaig]

Is somebody thinking horizontal and someone else thinking vertical/angled per chance?

[Ganglandboss]

Ferg said:

JR said:

Ferg said:

JR said:

To drill a series of 1 and 5/8" holes in the centre two inches of the beams won't worry them at all being only a 4% reduction in strength.

But with a 1:40 fall that means that then CAN'T be through the centre of more than one joist.

I see that you've not done the maths.

If it passes through the centre of one and has a fall of ANY sort it can't pass through the centre of the next one.
My maths fking good enough for you???

What if he lives here?

[JR]

Ganglandboss said:

What if he lives here?

Lovely: radial joists and a spiral waste pipe all the way down.

[PistonReg]

JR said:

mackg said:

PistonReg said:

Thanks folks. They'll be going through the centre of teh joists. 25% is a nono? They've 9" joists and I've got to run 40mm waste through them, which I'm pretty sure is allowable?

What do you mean by through them? If you are going to notch the joists by 40mm effectivley your joists are only going to be as strong as 180mm joist, I'm sure the 225 will have been calculated as the depth required to take the span. like Ferg rightly said you can only notch up to 20% of the span away from any supprt.

But he said that he's going through the centre of the joists and I take that as through the neutral axis. To drill a series of 1 and 5/8" holes in the centre two inches of the beams won't worry them at all being only a 4% reduction in strength.

Great - I'll be drilling through the centre and luckyily only got 5 joists to cut which are in the middle of the lenght of waste anyway, so perfect.

A bit surprised that a 20% hle in the cntre reduces the strenght by only 4%, but then with the stress and compression being on the top andbottom, it seems logical.

Thanks for your help guys!

[Arthur Jackson]

How long is the waste?
I'm struggling to understand this. If you are going through 5 joists at (maybe) 400mm centres then that's 1.8m, so the waste size is definately going to have to increase to 50mm. There's roughly a 2" fall required too, so from the top of the pipe at one end, to the bottom of the pipe at the other you've got at least 4" allowing for clearance to lag it to allow for expansion noise. Surley you'll either be much to close to EITHER top or bottom to keep the BCO happy?? Or have I missed something?

[Simpo Two]

I'm with Arthur - if you're fitting the pipe at right angles to the joists and need a fall, then it can only go through the centre of ONE joist. The other joists will have to be cut higher or lower.





Can't you just piss in a bucket and throw it out the window like the Tudors?

[JR]

Simpo Two said:

I'm with Arthur - if you're fitting the pipe at right angles to the joists and need a fall, then it can only go through the centre of ONE joist.

If the pipe is at an incline the centre of the pipe can only go through the centre of on joist but there is no requirement for the centre lines to co-incide.