Hello, I am trying to sort out our halfway floor. The house is victorian and had the original tiles in place (albeit very damaged by a bodge-job gas pipe that had been put in at some point). The old owners had put a truffle of various toppings above the tiles (lino, laminate, and underlays in between). We took these up hoping to restore the tiles but it is too costly for us to do. Instead, I am taking the tiles up to replace them (keeping some so that we may use them as a feature somewhere in the future). As I have done so, salts have started to appear on top of the screed (which is cracked in places and needs replacing). I was going to replace the tiles with quarry tiles and use a self-levelling screed (Mapei), but am worried about these salts. Do I need to do anything such as put a liquid dpm down before laying the screed and new tiles? Or should I use specific grout or screed to rectify? There are no signs of damp in the walls or anything. Any help greatly appreciated! Thanks!