Hi, all - this is my first post here (be nice). I have a 1921 "jumbo" Chicago style bungalow in Oak Park, Illinois. The dining and living rooms have the original plaster walls and (what I believe to be) original trim and molding.

My terminology on this is lacking (I lived in a new build condo until 2 years ago), but there is crown molding that starts very high on the wall and extends into the ceiling, giving a similar effect to that of a tray ceiling. I believe that part is original. Below that, on the wall, however, they then added another trip of molding about 4 inches tall. I think this was added later and I have no idea why. It seems to have been there for a very long time, I just don't think it's been there since 1921. Around most of the rooms, a gap has opened between these two moldings. In some spots, it's negligible, in others it's wide enough to slide my fingers in. I can see that behind the gap, the plaster is mostly crumbled and gone.

So that was a lot of words to ask - how do I fill this gap?? I think it's too big for a simple caulk job. And the lack of plaster behind it, makes it seem like it would be difficult to fill.