We recently moved some furniture around in our 100+ year old house, and it's drawn attention to the fact that some of our floors aren't 100% level. I can't really tell if this is something that's new, or if it's always been a problem but I've never noticed.
Are there tools available for me to track the sagging over a period of time to see if it's getting worse? I have a level but there's no great way (for me) to track whether the bubble's moved more or less during over a period of time. My mobile phone as a level app, but I assume that's more for fun that an accurate tool.
Also, if the problem is getting what sort of professional would I want to bring in the assess the problem, and what sort of professional might I need to fix the problem?