I am about to raise the ceiling of two bedrooms in the our recently purchased cottage. The new plaster board ceiling will follow the slopping roof line roughly half way up before leveling off across the roof. I had planned to insulate behind the plaster board with kingspan or another type of sheet insulation.
Can anybody tell me what gap I need to leave between the roof lining and the insulation? The lining looks to be a form of polythene sheeting.
Can anybody also give advice on roof ventilation? The cottage has very thick stone walls and the wall reneder meets near enough flush with the bottom tiles so at present there is no soffit area. If I added a form of ventilation at eave level both sides would this be adequate?
Any other advice on this subject much appreciated.
Thanks very much