Waste pipe through joist help

[Tadge]

Hi all, usual question but I have no alternatives.

I'm having a loft conversion and have a shower enclosure to install. I can run the waste paralell with joists but need to go 90 deg across about 3-4 joists.

The tray has to sit on the floor as I have not enough head height, so no raised boxed in option.

I cant go below ceiling for obvious reasons and I cant go outside.

Is there any metal reinforcment bars (or other suggestions) which will enable me to go throught the joists without reducing their strength?

Thanks

 

[swidders]

Joists should only be notched up to 1/8th their depth, at a distance of between 25% to 40% from a supporting wall.

 

[Tadge]

Thanks, appreciate the notching theory but how can you achieve a fall in the pipe if you can only notch?

Rgds

 

[swidders]

Thanks, appreciate the notching theory but how can you achieve a fall in the pipe if you can only notch?

Rgds

By lifting the shower tray, which you can't do, or by taking it through the ceiling and boxing in, which you can.

I doubt that anyone here will advise on metal straps, bolting timbers or metal by using coach bolts etc. Since this is a structural question, you could try posting on the building forum - give details of lengths of span, joist and proposed notch depths as a starting point.

 

[powermaxer]

you will need to pump it out.
www.dry-deck.co.uk
whale pump.
there are others available.

my fee is a drink.heck i get thirsty then after dink i like a curry.

 

[^woody^]

A metal plate, another section of joist, or better still ... about 400mm of 9.5mm ply - glued and screwed to the sides of the joist will let you notch it more than that detailed in the approved documents and commonly refered to as being the "maximum allowed"

 

[swidders]

A metal plate, another section of joist, or better still ... about 400mm of 9.5mm ply - glued and screwed to the sides of the joist will let you notch it more

Where does it say that and who says it?

 

[^woody^]

It's something to do with basic design principles, and you wont find it in the plumbing books or the Approved Documents

Strengthening the joist at the weak point solves the problem

Anyway check this notch out - and the floor is still up!

Untitled

• ^woody^
• 16 Jun 2008
• 7

 

[seco services]

thats just a mess.

 

[swidders]

Scary notch! Can't even see anything going through it to justify it. Also, that wet room floor looks remarkably unsupported.

 

[Bahco]

I'm having a loft conversion

The building Inspector will not pass it either.

You should be able to raise the tray a bit to accomadate a shallow trap and then take it outside.

 

[Tadge]

thanks all,

I know cutting beams and notching is best avoided, I just thought someone may have a cunning plan. I've looked at it more and I can run the pipe parallel with the joist and then down the outsde of the house (which I was trying to avoid) but will have to install an extension to my underground drainage system where the pipe can connect into.

Thanks again

 

[RigidRaider]

I wouldn't notch as the corners would provide stress risers, especially along the grain. I'd drill holes carefully measured to give me the fall. Then I'd reinforce around and each side of the holes with either steel sheet cut and drilled or ply screwed and glued to the joists like a laminate. In fact I'd do that before cutting my holes, so as to achieve maximum strength. I'd use a hell of a lot of PVA glue and many screws so as to really achieve a close bond.

 

[SUPERPLUMBER]

could you notch the ist joist at the exit from the trap and go parallel with the joists for part of the run, and then do a 90 deg bend into the centre of the joist across to your stack? you can drill larger holes in the centre of the joists.
This means youd only have a fall from the top of the joist to the centre of the joist and then a level section. Would the momentum of the first fall take the waste through the level section?