Creaky Floor Fix ?

If it's a carpeted room one thing you can do is take the carpet up, and run wood screws through the floor, the sub floor and into the floor joists. If you're going with that method remember to coat the screws in wood glue, or some other adhesive to keep them from backing out over time under the carpet. If it's a wood floor, you can pull up the floor to expose the sub floor, do basically the same thing, and then use stuff called "leveling compound" over the top of the sub floor. Once that is dry, re-lay your wood flooring. If neither of these options sound good, and the joists are exposed on the underside, you can use screws up from the joists at an angle to tighten the gap between the joists and the sub floor, just make sure that your screws don't go more than 1/2 and inch vertically into the subfloor. Also, reinforce the joists to ensure that the joints aern't squeeking. For toung and groove wood flooring sometimes the floor settles and forms a gap between the floor and the sub floor. If you're not willing to take up the floor to fix the squeek, you can drill tiny holes in the flooring, and then inject self leveling compound or wood filler underneith the floor boards. Personally I've never done that one and don't know all the intricate details of it, but I've seen where it has been done and it is quite effective. the best way to know if you have a seperation of the floor and subfloor is to roll a golf ball across the floor. When it goes from a normal golf ball rolling sound to kind of a hollow sound, you know where your voids are. (and the pros actually use that too... I laughed quite a lot when a golf ball was a tool of the trade.)