Soil pipe inside or outside of the property

[ifti12]

Hi,

Need some advice on the soil pipe inside or outside, I have searched on google and read couple of forums but don't find the right or wrong answer of soil pipe being inside or outside the property.

We are adding two rooms on the side of the house and one loft into dormer conversion. Please see in the attached image the two bathrooms on the side of the property will go directly into main sewerage.

My question is regarding the highlighted circled image with two options.
1) OPTION 1: Soil pipe for main first floor bath and dormer ensuite to pass through inside the property, the advantage I can see is less travel hence less chances of problems but I am thinking in the long term if there would be a problem, my floor would be concrete, underfloor heating so it would be a complete mess if we have to diagnoses something inside the property plus odour/smell is also what might causes a problem. (The house was built around 1970s and this is how the current soil pipe was, it was boxed from first floor bathroom to kitchen below but now we have added another bathroom in dormer just above the first floor bathroom)

2) OPTION 2, Soil pipe all the way outside the property to the main sewerage as shown in the image. Advantage less pain in case of problems, no odour because less soil pipe inside the property. Long travel of pipe which may or may not be a problem. My house is on slightly sloppy ground all the way from front to back but I think the slope will be same even if we go inside the house.

Can you please comment on both options or do you have any better option than these ? Builder is towards OPTION 1 because less digging and less labour.



Thanks
ifti

[nod]

We put all of our soil pipes outside 

Mainly to save having nibs in bathrooms and kitchen 

Though I must say Nearly all the new builds that I work on are internal

Might be worth checking with BC

Ours didn’t care either way