Pieces of the wall came off when I removed the trim, how do I fix this?

[Mattias_Eson]

Yes, plaster and longer screws are also a good option. That's what we did on 2 of the walls the last time we renovated a room with this type of wall. But then there was a bit more work with the moldings around the windows.

Claiming that it's a huge task to knock down the plaster and drywall, I think is an exaggeration. I myself tore down 2 walls, drywalled, and cleaned up in one workday, a good air purifier helps a lot.

 

[gaia]

It is best to use the same type of plaster already on your wall for repairs. In old houses with wooden planks and reed underneath, it is usually a question of lime plaster. If you use gypsum or cement plaster, there is a risk that it will crack where the two materials meet. Different materials move differently with humidity changes in the air, which can cause cracks.