I'm laying a new concrete kitchen floor shortly, and need to bury a 1.5"
waste pipe throught/beneath it. (This is because the sink will be on
the wrong side of an internal doorway, and there's no other route to the
gully outside).

The pipe will run through the screed, with suitable fall on it, and
emerge at the outside wall about 1.5" above the outside ground level,
and will be about 2-3" below the floor level and DPC on the inside; so
it will enter the house above the Kingspan insulation and polythene
dampproof membrane I'll be installing.

Question - I'll obviously need to penetrate the membrane with the waste
pipe, but how do I do that without compromising its dampproofness?
Presumably there must be a recognised method, as what I'm doing isn't
particularly unusual.

Thanks
David