Extension's DPC abutting existing building

[Woody3]

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. 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.

Any ideas or alternative thoughts on this?

Edited by Woody3 on Saturday 2nd November 00:56

Edited by Woody3 on Saturday 2nd November 01:03

[ATTAK Z]

Woody3 said:

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 (built circa. 1700), but obviously the extension will. The detail on the drawing states that the dpc 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 under a concrete/flagstone floor.

Any ideas or alternative thoughts on this?

DPC - Damp proof course - built into brick/blockwork

DPM - Damp proof membrane - built under ground bearing concrete slab - should be linked into DPC

Both these apply to the new build only unless you are doing remedial work to the existing

[Woody3]

Now edited to clarify dpm/dpc.

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?

[F1SERB]

A pic of the plans would help a lot

[magooagain]

Talk to your building control officer. A house that age may not have an existing dpm,unless one was installed during renovations.

It should work out simple enough.

[Woody3]

Thanks for the replies chaps.

We've sorted it "ish".

Basically the dpm will go under the existing floor slab where there are "knock throughs". 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...

[Spudler]

Woody3 said:

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

Point the wall (if needed) and tank about a meter to 1200 up.