I am a new home owner that recently bought a 1912 house in Canada with my wife. We are doing renovation in one of the rooms where we just finished removing 5 layers (!) of wallpaper over the original plaster walls. However, while removing the wallpaper on the exterior wall, we notice that there were some mild moldy smell (as if one of the old layers of wall paper had gotten a bit moldy). Most importantly, at the juncture between the ceiling and that particular wall, the plaster seemed a little crumblier and some of the nails that I removed from the wood trims are a little rusty. Otherwise, the plaster on this wall and on all other walls seem to be in very good shape and does not show any sign of water damage. (Except for the ceiling: the plaster has quite a lot of cracks, but does not show any water marks or stains). My guess is that this would be the result of poor insulation and condensation (these old houses don't have vapor barriers).

Now, I was hoping to be able to finish these reno without having the deal with the extra-messy job of removing the plaster wall and replacing it with boring dry wall. Plus, I want to keep the integrity of the old house as much as possible and I would prefer to keep the plaster. But of course, I do not want to do renovations over an existing problem. So I am not sure what would be the best course of action here. Any suggestions? That would be much appreciated. Thank you!

 

I would also like to add that the most recent layer of wallpaper that was covering all the other layers was a type of vinyl wallpaper. Could that have anything to do with the moisture issue underneath? (wall not "breathing"? etc.)