I thought this showed the build up of the wall quite well. The outer leaf on the right is 140mm blocks laid flat, with cavity ties in the second bed joint (along with hidden bricktor bed joint reinforcement).  The inner leaf starts with an engineering brick, with dpc laid over the top (to prevent any rising damp), 100mm block, Bricktor SB40 W60 and wall ties, second 100mm block.


There is no dpc in the outer leaf of the wall as there will be ground backfilled against this.  Any moisture that gets though the external leaf into the cavity will drain out through the LECA, which will protect the inner leaf from getting damp.  On the inside of the inner leaf, will be more LECA which will form part of the build up of the Ty Mawr limecrete floor system.  LECA prevents damp from rising, so will protect the other side of the inner leaf  (and the limecrete slab) from getting damp.  The inner leaf was therefore only vulnerable to rising damp from the ground below, hence the dpc on top of the engineering bricks.  We also did not want to create a path for moisture to migrate up into the limecrete slab, by bypassing the LECA and making its way up through the inner leaf of blockwork.