Extension's DPC abutting existing building question

[Woody12]

Just going over the drawings for our extension and I've come across an element/detail I'm not 100% sure of.

The existing building has no dpc or dpm (built circa. 1700), but obviously the extension will have. The detail on the drawing states that the dpm is to be taken under the existing slab. I'm currently struggling to understand the concept of getting through the 2ft solid stone walls, then part way under a concrete/flagstone floor.

Thinking in laymans terms, am I correct in saying that the dpm will have to extend part way under the existing slab to eliminate any moisture rising up the soon to be dividing wall?

Any ideas or alternative thoughts on this?

 

[noseall]

Will the floors ultimately be connected via a knock-through?

 

[Woody12]

The extension runs the length of the house and will be separated by the existing rear wall.

There will be two "knock throughs" where two doors are going to be, one at either end of the extension to access the existing house.

The section is actually through one of the door ways, so will it just be to those areas, which makes sense now?

 

[Woody12]

Sorted it "ish".

Basically as per my last post. The DPM will be cut into the existing wall where there are no knock throughs. Not 100% sure how deep into the wall though.

Just hope this doesn't cause any damp problems in the existing rooms that go along this wall...