We recently moved in to a 20 yr old house having minimum maintenance during it's life. The caulk in the tub in the second floor bath starting dropping off in strips. I recaulked the area. There are a few loose floor tiles (1" size). After being away for 3 weeks the floor in the bathroom has a definite sag - covering a one foot square of floor surface. So...I figure that alot of "moisture" has probably rotted the subfloor? Perhaps the 3 weeks of no use did something? I am BROKE and I need help. What can I do to ascertain repair prior to calling someone to come in? Can I do anything? I am willing to try anything, but I have to hold the book open while I do it! Thanks!