Bought a 1950s semi about a year ago and have had the whole house skimmed, which was completed 6 months ago (ish). Moved in bank holiday weekend so until then house was empty, no heating on etc. We have now started seeing large blister forming under the plaster in a few of the rooms, up to approx. 100mm in size. All surfaces were PVA’d first. I would of thought if the plaster wasn’t going to take it would of blistered in the first few weeks. Seems strange it is happening now. Anyone come across this before?