Drainage - Extension

[Tornado]

Hi,

I've just started planning the single story extension which we hope to start 2012.

The extension is going to be 4 metres x 5.8 meteres, with a internal wall where we will be having a small bathroom with toilet, sink, and shower cubicle.

The drainage for all of house is on left hand side but we want the bathroom on the right hand side to give us a extra wall from house joined on to save soundproofing etc.

Question is where would the drainage go ???

would it be best going under the new concrete floor or would it have to come through the extension ??

Thanks in advance

[welsh brickie]

you can connect to your existing system and lay it under the floor before laying the concrete.The building control officer will need to inspect it,once laid.