I agree with everything you say Softus, there is dpm under concrete floors, 1800 gauge now, thicker than 10 years ago, was using 1200 or even 1000, I don't know what the gauge is only know its thicker! That is then overlapped on the internal leaf of the dwelling and dpc laid on top. The EXTERNAL leaf dcp is at the same course, only its origin is from a 450mm wide dpc which is fixed one course of blocks higher on the INTERNAL leaf, producing a damp tray, thus any moisture or water from cavity ties fall and is made to go outside via weepholes in the perps. Theoretically it is all damp proofed internally with an EXTRA dpc one course of blocks (225mm) on the internal leaf. When this is done properly, it is IMPOSSIBLE for moisture to rise on the internal leafs wall covering, like you say is the most common, and I also agree is. Damp trays are also put above all openings as we all know AND common practice is to "seal" each floor with a complete tray all around a dwelling (especially on these "hip city apartments" springing up everywhere) I've always known them as flats!