alright people im new to this site and relatively new to plastering,got a job to do round a chimney breast,which has damp problems .they had it plastered 1 year ago with sand and cement and multi finish top coat but has blown again they say they had damp proofing done .most of my plastering has been dry lining and re skims so my knowledge of this area is minimum.is there a process of a certain chemical i can put on first and which would be the best plaster to put on any ideas would be most gratefull,cheers