- Messages
- 6,339
If I insulate it and completely replaster this is going to become a massive job.
TBH looking at the state of the walls your easiest option is going to be board over the existing its fruitless to re-board and not insulate, with 9" solids you are just throwing £££ notes away year in year out.
You don't need to buy the backed board its easy to use but expensive, you could use seconds for your insulation board, batten over for the air gap then board on top. none of that will cost you fortunes in material, labour is what kills building work.
I have got a shed load of 20mm battens left over you could have, 25mm give you more to "hit" but 20mm would do.