Creaking floorboards is a sign that the subfloor has separated slightly from the floor joists. The wood is rubbing together, causing the creaking noise. If your carpeted stairs are creaking, you don't have to remove the carpet to repair the creak. The best repair for creaking floorboards is to locate the nearby floor joists and drive a screw or nail through the carpet into each joist near the creak. This can be accomplished with a few simple tools.
Tap the floor very gently with a hammer, listening for the difference between a hollow sound and a firm sound. The firm sound indicates the location of a floor joist. The joist should be centred on the step. Start tapping from the edges of the creaky step and move toward the centre until the joist is located.
Drive a joist-finding drill bit into the floor above the joist with a drill. This drill bit is a long smooth pole with a few threads on the tip. Continue to drive the drill bit into the floor until the drill bit sticks in the floor joist. The drill bit will slide in and out of the floor easily if you miss the joist. Stretch a piece of tape straight from the back of the step to the front, covering the location in which the drill bit is positioned. This tape indicates the position of the joist. Remove the drill bit.
Position the tripod directly over the tape near the back of the step and attach the specialised drill bit to the drill. The drill bit and tripod are included with the purchase of scored screws designed for this application. Insert a scored screw into the drill bit, stand over the tripod, and drive the screw into the floor and joist through the tape. The tripod will stop the screw when approximately one inch of the screw is still exposed above the carpet.
Repeat Step 3 closer to the front of the step along the tape line to drive a second screw into the joist.
Insert the head of each screw into the T-shaped groove on the side of the tripod. Bend the screw to the side to snap the head off the screw. This leaves nothing exposed above the carpet.
Repeat the entire process for any additional creaking steps. If the creaking step is wide, it may have multiple joists running beneath it. If so, repeat the process for each joist.