In one of my 1st floor bedrooms, there is a gap between the floor and the drywall of about 1 inch which was conveniently covered up by installed carpet by the previous owners. It runs the full length of the outside wall. The problem is the gap extend down between 4-6 inches and opens up into a cavity running under the drywall. It is a fairly large cavity. What prompted me to take action is there is air coming from the space and with my heating bills soaring over $400.00, I need to fill gaps etc. I bought some of that expanding foam stuff and to test I sprayed it in a small section of the "void" to see if it works.
My question is, why is that gap there? A bit of background. My house is approx 80 yrs old. There are some sagging floors but not so much with this bedroom. The floor is level in this area. The general slope of the sagging tends to the center of the house. Can this be the reason for the gap? Did the previous owners screw up when they remodled and installed all new drywall? (removed plaster walls). What sort of things cause gaps?