Waste pipe through raft foundation

Hello all,
I need to route a 100mm waste pipe from one side of a new extension which will be build on a raft foundation which will have re-bar incorporated, only the kitchen sink will use this so no toilet waste. My question is how or even can I pass through the raft foundation

 

Raft foundations usually need to be designed by an engineer and he would need to include the drain in those calculations, if it can be done.

IME rafts are relatively unusual, I find foundations tend to be either trench foundation or driven piles.

 

Just a sink waste - is there any way it can go out through a wall and into a 110mm gulley outside of the wall/raft ?

 

You should not be putting drains under rafts

 

That’s the plan but from the gulley to existing sewerage I need to access the other side of the building

 

That’s what I thought in my mind but need to confirm before I start attempting the alternative of cutting into the existing floor

 

Being built on made up ground and didn’t want to go down 7ft for strip

 

I would still use trench fill footing for a 2.1m depth -its usually cheaper than raft foundations.

it needs a bigger digger -3 tonne I think, but for a builder its easy provided its stable ground and the trench walls dont collapse.

 

2.1m deep. LOL

 

made up ground can be stable enough to cut trenches without the sides collapsing......

 

No access to the rear of the property other than a mini digger 1 ton

 

Did you make that up?

 

That’s right.

 

Just been told by the guy who did the calculations I can pass through raft with out a problem.

 

Then he does not understand the issues, and should stick to calculations.

A raft is designed to float, hence the name, and it will move seasonally. So cutting a hole through it is possible, but then ensuring that your drain or joints do not leak as the raft moves is the issue. And you wont even know about it untill the raft starts dipping.