Only been in the house a few months. While decorating an upstairs bedroom I found quite a few nail heads raised a mm or 2 so tapped them down. Also put in quite a few 4 x 40mm screws where floorboards seemed a bit loose or squeaky. Now I have a different problem in that a whole quadrant of the floor produces a noise not individual boards. I reckon the joists had dropped in some places and I've now lifted them up to the boards with the screws so the joists aren't sitting on the wall anymore. I'm going to lift some boards and try and find the problem but has anyone got any thoughts on whether I might be on the right track or miles off. And if I am how I fill the gap between the joist and wall please? Thanks.