plastering

[Dodbiz]

is it ok to plaster a wall with some existing plaster still intact as it is still very strong? 

[Nickfromwales]

26 minutes ago, Dodbiz said:

is it ok to plaster a wall with some existing plaster still intact as it is still very strong? 

Yes, but get a scraper behind the edges to make sure none of what you’re leaving behind is loose. 
 

Your plasterer should assess this and will be using either PVA or SBR as the bonding agent. SBR is a like PVA but it doesn’t skin over. You need to plaster on to neat, wet PVA and never over PVA that has gone dry or lost its tackiness. 
 

SBR remains tacky for a long time, even when dry.

[Dodbiz]

Thanks, Nick, the DDragon