I live in an old 1910s house and it turns out my walls aren't drywall. It is constructed of rock or some type of masonry. Over it, there is a really, really old wallpaper, which also have over itself, something covering it. It's 1½ feet wide paper-like sheet vertically pasted on walls and finaly, covered by many, many paint layers.
Yesterday, I went into a room in order to put some plaster patch on a damaged area. There was a spot, on the paper layers which I mentioned previously, which doesn't seems to stick anymore. So I simply tear it and it came off pretty easily, without too much effort (this is how I discovered the old, old wallpaper). So I applied some plaster patch on it to level it correctly. But once it has dried, some weird yellow stains appeared through the plaster patch. I'm guessing that at some point in the past, water damage or something may occurred at that location. However, when I touch it I don't feel any moisture.
- What should I do?
- Is this normal?
- Is it moisture or something like glue behind the paper-like sheets?
- Should I consider putting «placoplâte» in french (Plasterboard in english I guess or draywall) to cover all over these walls?
- Is there anything I must do to ensure my walls are really dry?
- Are these yellow spots appear on the paint too?
Thanks in advance. I must specify that it will be a new born child's room so I don't want to take any risks but I really want to do it on my own without paying for an expensive professional service.