To prevent noise travelling between domestic houses, a parge coat has been made and it is applied directly onto the wall before direct bonding. The parge coat is 6mm thick. It must not have any scratches and it must have a trowel finish.
When insulation boards are used for direct bonding, a specific nail (nailable plug) must be used to go through the dab into the wall after the dabs have set. This is done so that if a fire was to start, the boards would not fall off of the wall so would still be protecting against the fire.