costs to raise ground floor ceiling height if can't take from 1st floor

All depends how much room is under floor boards if any .and how far damp coarse is .

Yes you can reduce dig depending on a number of factors damp foundation can all be got over but you would have to expose floor and do a trial hole

If it’s a new build, it is likely a block and beam floor. Concrete blocks and beams with little room to do anything without digging out the whole floor system (or a large area of it, I.e the living space) and starting again, including adding your underfloor heating and insulation. This would be quite a task, cutting through and digging out the beams in particular. And then there is the issue of having a different height damp proof course, potentially. I’m sure you *can do this but it will probably be very expensive and time consuming. It might be worth seeing if you could take both ceiling heights up perhaps, with the upper rooms becoming more ‘loft’ style. Hard to say if that’s possible or easier without viewing/plans. The only other alternative I can think of would depend on the floor make up. If there is insulation under the floor finish (above the block and beam and under screed and/or floor boards/whatever your floor is finished in) you might be able to reduce the thickness of the insulation with a more expensive and better performing but thinner insulation board. Moving from a 150mm to 75mm insulation board wood gain you 75mm in height, for example. But I’d be surprised to find lots of floor insulation in a new build without underfloor heating. Hope that helps

If the floor is constructed with floorboards then it would be quite an easy fix, but if it is built directly on solid ground you will have to replace and probably improve the damp proofing system. However this is not as complicated as it sounds.