Eliminate squeaks in flooring
Depending on what flooring is used, the subfloor needs to be properly secured. Older homes (60+ years old which I am all too familiar with) tend to have flooring which may have settled over the decades. Overtime, the nails used to secure the flooring to the floor joists separate and create squeaks when walking on them. Same can happen with "newer" homes where the nails can pop out of the OSB/plywood over years of expansion and contraction.
If you have NOT installed any finished flooring and have access to the subfloor:
Step 1: Screw the subfloor to the floor joists.
Grab a box of wood deck screws and find where the original nails are nailed down to the floor joists. DO NOT use drywall screws as the expansion and contraction of the floor to subfloor can shear the screw and create more noise. 1-3/4" to 2" long deck screws that are partially threaded are preferable. The partial thread allows the head of the screw to compress the subfloor together. Pre-drill the holes where you plan to screw down the subfloor. For this part I would recommend the Hillman Group Deck Screw:
For homes with tongue and groove subflooring you'll need a lot more screws as there are a lot of narrow boards. Predrill holes in each board before screwing so you do not split the wood. Screw down along the nail lines where there are squeaks and continue stepping all over the floor to identify any additional squeaks. Screw until the squeaks are gone.
Step 2: Glue down wood underlayment
You'll want to install 3/16" - 1/4" wood underlayment or thicker. You can grab 4'x8' sheets at your local big box store. Next you will need to apply a generous amount of subfloor adhesive to the underlayment such as Liquid Nails LNP902.
Once the adhesive is applied, begin laying down the sheets glue side down over the subfloor.
Step 3: Staple down the underlayment
To complete this job, you will need a crown staple gun. Metabo makes a great pneumatic stapler and you'll need an air compressor such as the Craftsman 6 gallon air compressor kit with air hose and attachments. If you're looking for an electric cordless, Dewalt has you covered. Both options use 18 gauge crown staples.
Begin stapling down the underlayment and be very generous with the staples, especially around the edges where the underlayment butts up against another piece. I tend to staple with a 1-2" spacing around the perimeter of each sheet and 3-6" all around the center. Make sure when you butt up the edges of the underlayment are flush and level to each other. Once everything is stapled down install your finished flooring of choice.
If you have finished flooring installed and do not plan on removing the flooring to eliminate the squeaks:
You have a few options to eliminate squeaks with preinstalled flooring:
The O'Berry Enterprises kit provides depth tools and special screws which are scored to break the heads off leaving a clean and invisible fix. Using the kit is easy and is for hardwoods and carpeted floors. Locate the squeak and the floor joist location to screw into. Place the screw through the depth tool and screw until the head of the screw snaps off. If you're screwing through hardwood flooring, you can use a little wood putty to fill in the small hole that you drilled through.
Screwing through carpet requires no additional work and will not be visible.
Fix-A-Floor is a unique solution where you drill small holes in the target area, and squeeze the polyurethane adhesive into the drilled holes. 1 tube covers approximately 4 square feet. You can use this on tile, marble, stone, and wood flooring. For tiles, drill holes in the grout lines.
Floating Floors (laminate, vinyl plank, etc)
If you have installed floating flooring, the only way to use the above products is to remove the flooring (unless you want to core holes and screw through it!). While you can disassemble the flooring which could be an option, your next best solution is to see if you have access to the floor joists via a basement, crawlspace, or drop ceiling.
If you have access to the floor joists from the underside (basement or crawl space):
Install Shims using cedar shims
If there is a gap between the subflooring and the top of the floor joist, try wedging a shim into there with some construction adhesive. Just tap it into place softly until it is snug and trim the excess shims off with a utility knife. Do not hammer aggressively or you risk lifting the other floorboards causing more squeaking.
Sister wood to the floor joist
For this option, you are going to use adhesive between the subfloor and the floor joist and smear it into the gap. Next find a 1-2' long scrap piece of wood like a 2x4 and predrill holes on the wider side of the board Every 6-8". Make sure the screw holes go in on an slight angle pointing towards the floor and not perpendicular to the board. These screws will secure to the floor joist not the flooring. Apply a generous amount of adhesive to the top and side of your wood piece and place the board below where the squeak is and secure in place with construction or deck screws.
Finding a floor squeak can drive you mad. Follow these tips to get back your sanity!