I’m just a homeowner that is trying to solve a floor problem. The person I had check out a squeak in my floor said the only way to try to fix was to tear up the tile (my tile was installed in 1962 -Armstrong all-the-way-through color, at least 1/8 inch thick, chipped marble pattern). To do what he suggested would mean I would probably have to replace a 15 x 36 room with something that is not nearly as good as what I have. The inspector did crawl under the house and said that he had never seen a house as solid as mine. We have the 1 x 6 subflooring with 3/4″ plywood and then the tile. He said that the 1 by 6’s seemed to be tight against the floor joists so the assumption is the plywood has become loose. In the kitchen area where the squeak is you can see a ridge as if the corner of a sheet of ply is raised. Is there someway to fix this from the bottom with maybe extra cross pieces between the joists and screws through the subfloor up into the plywood? ANY SUGGESTIONS ON HOW TO FIX THIS PROBLEM?
Here's an idea- Take a 1 1/2" Forstner or hole bore bit, not a paddle. With me so far. Go under the floor along the seem,(best guess) and drill several holes along this line. It will probably be along a joist and you might see the tips of flooring nails that just missed the joist. After the plug you just cut in the 1 x's falls out revealing the plywood underlayment your good to go.
Span the hole with a 1x2 or rip of plywood. Carefully screw through the 1x2 ,that's spaning the hole , into the subfloor plywood. Use a short enough screw but deep threads to grip. About 2 " long. Don't draw tight yet till all screws are set then tighten each one a little until you've pulled the plywood down. Ideally if possible squirt some subfloor adhesive into the edges of the holes first especially if there's a gap.
If the screws fail to pull the subfloor at least the adhesive might set up enough to fix the plywood in place.
All this hoping movement hasn't been caused by a combination of moisture and poor nailing. Especially if the plywood is yellow pine. This stuff is tough to unwarp.
Similar to Bob's idea...do you have acloset where you could cut some plugs? Get a set of countersink bits and plug cutting bits like those used in woodworking. Carefully drill through the face of the tile where you see the loose edge of the plywood. Squirt in some adhesive and run in some good screws, then cut a plug from the closet and fill the hole in the tile. The advantage to this method is that you can see where the ply is bowed up, and you can use long enough screws to get good purchase into the joists. The down side is the plugs.
Do it right, or do it twice.