Don't put plaster up there. It presumably currently is a ventilated cold loft space. Converting that to an insulated pitched roof is not straightforward and would bring in building control requirements. If done improperly the plaster will just disintegrate.
The description of putting insulation between rafters and plastering over would not be correct. There is a potential it'd lead to cold spots, condensation, rot to the timber and the plaster turning to porridge.
The description of putting insulation between rafters and plastering over would not be correct. There is a potential it'd lead to cold spots, condensation, rot to the timber and the plaster turning to porridge.
