Routing new shower waste

[Jonny71]

Hi, I've got a problem which I can't see a solution to, a future customer of mine wants to add a low level shower where a bath used to be, the shower tray is 1600 x 900, this would require a 40mm waste to go below the floor, but the joists are not big enough to allow a 40mm waste to be drilled (based on a allowing 25% hole size in relation to joist size), I can't see a solution, raising the tray is not an option, it's too big and would have to be too high....any ideas? The picture shows the location of the tray and you can see the old bath waste in the wall. The waste has to run under the floor where the legs are in the photo.

 

[ShaunCorbs]

Internal stack ?
What’s left and right of the picture ?

I would want a structural engineer to have a look at them houses as they look skinny

 

[Jonny71]

Internal stack ?
What’s left and right of the picture ?

I would want a structural engineer to have a look at them houses as they look skinny

This is the view to the right

 

[ShaunCorbs]

Sorry I mean the next room external wall left or right of the first picture?

 

[Knappers]

Waste pump?

 

[Jonny71]

Sorry I mean the next room external wall left or right of the first picture?

Stairs to the left, outside wall is top of the picture external soil stack, you can see the toilet connection, to the right is a bedroom with a sink hence the waste pipe coming through the wall.

 

[Jonny71]

Waste pump?

That is an option, put it under the floor and pump up to existing bath outlet or use smaller diameter to go through joists

 

[Ben-gee]

What’s room below? Can you drop waste through ceiling and box it at high level?

 

[ShaunCorbs]

After the bedroom to the right external wall ?

 

[Ben-gee]

If no good below, run waste between joists to external wall and then around building to stack - do this in 50mm pipe internally, possibly stepping up to 110 before the stack if it’s a long way.

 

[Jonny71]

Thanks for the advice chaps, I've confirmed the joist size which is 175mm so I can take 44mm out according to regs, I'll just stretch by a few mm and the pipe will go.