Loud creaking noise + uneven floor - should I be concerned?
I have an 1857 home that is in quite good shape structurally. There's only two areas downstairs where the floor is uneven, and the plaster walls don't have many cracks at all. However, I'm starting to become concerned with one area of the house. I hear one or two very loud creaks in it every day, so loud that for a while I thought someone was outside throwing something against our house. It's actually more like a single banging noise than a creak.
The area where the creaks are coming from is one of the areas where the floor is sloping a fair amount. No one is walking anywhere in the house when the creaks occur. I have noticed these noises since this spring (we only moved in in December 2009. The house inspector cleared the house of any major problems at that time, but still...)
The basement under the creaky part of the house looks okay, not saggy that I can tell. There are a couple large cracks in the plaster walls in the uneven floor/creaking area, but nothing worse than what is found in the rest of the house.
I know old houses have uneven floors and I know old houses creak, but I'm not sure how much creaking I should be hearing or how loud it should be! Should I be concerned? If I wanted to call a professional in to take a look, what kind of professional would I call?
Thanks in advance!