A friend of mine is having building troubles (all in another post) but she has had the correct procedure outlined by an expert and this states to use building sand as a blinding layer between hardcore and damp proof membrane when doing a floor. I recently build a conservatory and I used sharp sand for this as I was told it would be ok and I was obviously buying a large amount anyway. But after seeing it stated that this has to be building sand I am a little concerned. Will this compromise the damp proof membrane in any way? It's a bit late now as the floor is finished, but should I expect damp problems in the future?