Squeaky floors occur when the subfloor separates from the floor joists and moves up and down when walked on. Older subfloors were made from planks that ran diagonally across the floor joists. Modern subfloors are made from plywood or oriented strand board. The cure for a squeaky floor is to reunite it with the floor joists. You can fix a squeaky subfloor from above or below the floor using any of several techniques.
Press the bottom of the stud finder against the floor, depress the find button and move the stud finder in a straight line until it beeps or lights up. If you move it more than 24 inches without the indicator lighting, you are moving it in the wrong direction. Move it in a line perpendicular to the first.
Place the carpeting screw guide from the kit directly over the stud. Drive the screw into the floor with the battery drill. The guide will stop the screw at the correct depth.
Remove the screw guide from the screw and place the screw head notch on the guide on the head of the screw. Bend the screw to one side to snap it off. The screw is designed to break inside the subfloor and won't protrude into carpeting.
Place additional screws through the subfloor into the joist at intervals as necessary. An extra screw six to eight inches on either side of the squeak will help prevent the squeak from reoccurring.
Pinpoint the squeaky location as near as possible on a hardwood floor. Find the joist as described earlier on a carpeted floor. Old homes with hardwood floors tend to squeak above a joist, while squeaks occur in newer homes between the joists. Vinyl floors always squeak at a joist.
Drill a 1/8-inch pilot hole at the squeak location in a hardwood floor. Do not drill pilot holes in vinyl floors.
Place the hardwood/vinyl screw guide over the pilot hole on a hardwood floor or over the floor joist on a vinyl floor. Place a screw in the guide and drive the screw into the floor using the supplied screwdriver bit. The screw will snap off when it meets the top of the drill guide.
Fill the hole in the floor with colour-matched putty. You may also use a colour-matched caulk on vinyl floors. Wax pencils are another good option for wood floors.
Have someone else walk across the floor where it squeaks while you watch from below. You will be able to pinpoint the location by watching the subfloor for movement. If you can't see the subfloor move, have them knock on the floor to help you find the squeaky location.
Spread yellow wood glue on a shim and tap it into the space between the subfloor and the joist. Don't push it in to far or you will raise the floor. You only want to fill the space between the subfloor and the joist.
Drill a 3/32 pilot hole beginning 1 1/4 inches below the subfloor at a 45-degree angle through the joist, the shim and into the subfloor.
Drive a #10 wood screw into the pilot hole at a 45-degree angle through the joist, the wooden shim and into the subfloor. The screw helps keep the subfloor anchored to the joist and prevents the shim from working its way out.
Space additional shims, pilot holes and screws six to eight inches apart as necessary to help hold the subfloor against the joist. If a gap exists eight inches from the first shim, add another. Be sure not to the shims in so far you create more gaps.
If a squeak continues and you've hit the joists, it is possible you have a subfloor with a plywood underlayment above it. The squeak could occur between the joists and you'll have to add some screws there to stop it.
When screwing into the floor from below, make sure you don't use screws that are too long or start the screw too close to the subfloor. If your subfloor is only 1/2-inch thick, use 2 1/4-inch screws instead of 2 1/2-inch screws.