Waste through joists

[koibloke]

Fitting a shower tray directly onto 9'' x 3'' joists. Am I OK taking the 1½'' waste through the joists to couple to existing waste pipe. Sound advice much appreciated.

 

[andekoch]

notches are in the top (or bottom of a joist) while holes are in the centre of a joist (ie the centre of the hole must be on the centre line of the joist.
So a notch can only be from 0.7 to 0.25 of the span length and 0.125 times the depth of the joist.
A hole can be in the area 0.25 to 0.4 of the span and 0.25 times the depth, also cant have holes closer than 3 times diameter from the next so watch for other pipes and cables.

With a hole being on the centre line of a joist it means that a pipe will not have a fall (unless this can be achieved by different size holes or using a 40 mm pipe and drilling 50mm holes and then packing the bottom to get the required slope.

Easier to find a solution that does not cross joists.

 

[Mike Jackson]

The job's probably complete by now the last post before yours was 5 months ago.

 

[pt44]

The job's probably complete by now the last post before yours was 5 months ago.

Nah, I'm still drilling the holes

Just kidding. All finished months ago. Had no choice in the end but to go through the joists. Luckily they were thick deep joists and it was a basin waste so only 32mm. Just made a gentle slope over about 5-6 joists. The holes were already there, about 40mm in size. So just made sure it was wedged, to keep the slope. Not much of a drop, but considering the previous installer had an upward slope (yep, not even a drop) it was an improvement.

Paul

 

[andekoch]

hmmm, perhaps I should check the dates on the posts more closely. Was relying on the recent posts feature.

 

[jono44]

Not sure I'd like to spend the rest of my life sleeping/living in the room below that bathroom!
I've seen some crazy stuff done to joists - some people don't realise they form an important part of the structure of the building.

 

[pt44]

Not sure I'd like to spend the rest of my life sleeping/living in the room below that bathroom!
I've seen some crazy stuff done to joists - some people don't realise they form an important part of the structure of the building.

I think you may be worrying a little too much there. Perhaps you have seen scary holes in joists, but the situation as I listed it - is far from scary and completely within reasonable limits. In fact, I could probably have made the holes bigger. (not to mention that there is no bedroom under the bathroom).

http://tileyourworld.com/construction/JoistBoringGuide.pdf

Good guide here, found from a quick google. 1/3 size of depth of joist is max hole size. And hole must not be closer than 2" from the edge. Sounds perfectly reasonable and sensible to me. I had a similar conversation with an architect and builder when I was having my house done. Absolutely no problem going through the centre of joists with holes. So long you follow that guide.

Paul

 

[ocentric]

I wouldn't follow that guide unless you're in the USA! The post in this thread from Andekoch a few days ago has the definitive guide for England & Wales...

 

[pt44]

I wouldn't follow that guide unless you're in the USA! The post in this thread from Andekoch a few days ago has the definitive guide for England & Wales...

I'm not going to argue guides - as I'm certainly no pro on the matter. However, I would point out the obvious. If I'm in the UK - how on earth does the recommendation differ from the US?

Are you saying our timber is different?

Otherwise, if the timber joist is the same - then the recommendations are the same. Regardless of what part of the planet you reside on. As for rules and regulations? I have no idea. But guides are guides, surely.

 

[helpsy]

Checkout Building Regulation Part A(Structure)

 

[dontknowitall]

I onc had a job putting 12 meters of 110 soil pipe through the house and through the joists. Boy that was fun! Subsequent fitting of two 40mm/50mm shower wastes were a doddle in comparison.

Perfectly possible to do - but I did employ a structural engineer and carpenter had some steel braces made for it as a result.

If you're in doubt, I'd get a suitably qualified structural engineer - once you make a start (according to his recommendations) while it's not easy, it's not that difficult to do.

 

[mogwai]

Hi
Been plumbing now for some 37 years. would just like to say that i never had to cut or drill joists for waste pipe. Waste always goes surface, only below boards if it is running parallell with the joists