Hello; An old house can have lumber that is larger in dimensions than the finished that you can buy now. It could well be stronger than a modern house. Also being old, the wood can be compromised to the point of near failure. Dry rot, insects, someone cutting structure and such are all possible. It is also possible that the builder did not put it together well or even built it better than good. The only way to know is for someone with the know how to actually have a look.
Here is a link I often post about the subject.
Hello; here is the web address of an article that talks about the issue.
http://badmanstropicalfish.com/articles/article28.html