I had large patches of damp appear after having some standard plastering done. I then had a damp survey done by a specialist surveyor and was told the DPC was bridged due to the plastered walls on 3 sides of room meeting directly with the flooring. I was advised to remove the plaster up to approx 2 ft, re-plaster with porous plaster, leave a gap between the new plaster and the flooring and fill with anti damp solution (some kind of spray was used). 3 months later I now have a tide mark under the back window sill (external wall) approx 1 & half feet up from the skirting boards. There are also slight markings around the other walls. Can you explain what has happened?