Inner and Outer DPC at different levels

[Ajjax]

Im building extension and the DPC in the old house is lower than the ffl, if I continue this into new extension can i place the DPC for the inner leaf higher up to allow me to lap the DPM up the sides of the slab and into the DPC?

 

[KenGMac]

Ajjax, good evening.

Short answer is Yes you can.

The trick is to ensure that the DPC is sealed no gaps, otherwise rising damp?

Have a look at the Plastic / bitumen called "Bituthene"

I have used this material extensively and is really good in concrete foundation situations where at times the differences in DPC level can be quite large.

Ken.

 

[Ajjax]

Thanks Ken, you suggesting sticking the DPC up the side of the wall and then 'stepped' into the extension?

 

[Ajjax]

Does this make and sense?

 

[noseall]

Does this make and sense?

Yes. Your priority is that your new DPC is fitted correctly i.e. at floor level and that it is 150mm above ground level externally. Your new DPM will deal with the (strangely) low DPC on the existing.