I know its been done to death but have a customer complaining of cracks in a room I floated with sand and cement, and would like your view how I can guard against it. the room was bare brick so I pva'd it the day before, scratched a 4 to 1 coat with water proofer in I then left it 4 days, topped it with a 5 to 1 with water proofer in, left it for 4 days to cure. I then brushed the wall off to remove the dust and pva'd it the night before I skimmed it on a tacky coat of pva.. ive been to have a look and everything is sound and solid but with a couple of fine cracks on 2 walls. any advise will be helpful.