Basin and shower waste best method

[tommyleestaples]

Hi all,

 

Currently I have full access to the ceiling underneath the ensuite and I need to run waste from basin and shower into a vented at roof level soil stack. 

 

Would you advise running two separate wastes for basin and shower into the soil stack or just have one run coming from basin to the shower and then into the soil stack?

 

Would really appreciate peoples thoughts. 

[Nickfromwales]

Do you have to cut solid timber joists or are there posi-joists?

[Kelvin]

I ran two but mostly because I could run the basin waste in the wall and into the roof void then the stack and the shower waste  through the ceiling into the stack as if comes down into the downstairs toilet. We have posi joists though. 

[tommyleestaples]

I don’t have to cut joists the pipework will run parallel to the joists and then run internally towards the a wall where it can run under the joists and into the soil stack. This area will be then boxed in