by welsh brickie »
Tue Jan 07, 2014 9:58 am
you will need to lay a hardcore sub base first, a minimum of 100mm is needed, then your insulation if you want, then damp proof membrane
then concrete minimum 100mm thick, then a 50mm thick screed of sand and cement to ensure the floor is perfectly level for tiles,
So overall your looking at a total depth of 300mm to excavate out of the rooms, which should not affect the foundations, if your not going to insulate the floor then you need to use sand to blind the hardcore so that it does not puncture the membrane, but make sure the hardcore is well compacted by using a plate compactor