Damp marks on walls - why?

[@tonyaustin4472]

Good example from me:-) I restored a 17th Century former small farmhouse with no foundations resting on a solid gravel bed in the Fens. Beautiful 5 paned Georgian sash windows. No damp problems at all, dry as a bone. Property sold to an idiot, it turned out, who ripped all the sash windows out, sealed the fireplaces, got rid of the night storage radiators; put in gas fired central heating, plastic double glazed windows and started getting damp patches on the walls and condensation on the windows. He got a ‘damp proofing surveyor’ and his company took off all the lime cement off the front wall and replaced it with concrete, dug down below the bottom of the front wall, exposing the underlying gravel and now the house is beginning to crack. Water will continue to penetrate into the gravel bed and freeze and expand in the winter…the house is directly on the pavement and gets splashed by lorries and cars when it rains. It just gets to me that all the work I put into carefully restoring this beautiful little former farmhouse has been wasted by idiots.