Blimey that's lime + horsehair render over cleft laths. You could use stainless steel expanded metal lath to get a good key but you need to do a bit of research about lime plasters - there are specialist sites, and you don't need to buy cwt.s of it Must be an OLD house. Out of interest whereabouts in Norfolk, my ancestral roots are there.
Thanks for your reply. I've done it know, I hope I've done it right, looks good, I'm pleased. Painted SBR on first, then 4 sharp, 1 lime, 1 cement (got speaking to a guy in Jewsons). I managed to fix some screws into some timber that was contained in the wall and built it up in layers. We're in Honingham, Norfolk.
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