Slate DPC problem

[jetstream]

I am building an extention to the rear of my house, and the DPC on the house is made up of 2 layers of slate and mortar, approx 35mm deep

As you can see from the picture, there is the concrete foundation, 4 courses of brick and a 35mm high twin slate DPC


What is the best way to build up to this DPC course when using a Visqueen Polythene DPC level with the top of the original house DPC ?. the concrete footings on the new extention have yet to be poured.

Can i simply raise the footings level 35mm to compensate for the thickness of the house DPC, so that when building up from the DPC level the brick courses will then be to guage with the house ? . .
Obviously below ground each course will then not be in alignment - is this acceptable practice?

Appreciate any help and advice

 

[^woody^]

Your new DPC would ideally be at the new floor level, irrespective of the thickness of the existing DPC joint.

 

[jetstream]

I would want the new floor level to match the old

 

[^woody^]

Well then