Hi, I am looking at damp-proofing a bathroom with 3 external walls and a plasterer has suggested Vandex on the internal walls. Two things concern me which the plasterer seems a bit vague on 1) does the surface have to be taken back to clean brick or just cleaned of loose old paint/materials? From the looks of it a lot of layers have gone on these walls in the past. 2) If plastering over the vandex should there be a time gap between the vandex going up and the plaster being put on? The data sheet seems to say 4 weeks of curing is required before anything is added, whereas the plasterer said the job would be done in under 3 days. Any answers much appreciated.